Fireproof composite material for fireproof door and preparation method thereof

Abstract

The invention relates to the technical field of fireproof polymer composite materials, in particular to a fireproof composite material for a fireproof door and a preparation method of the fireproof composite material. A fireproof composite material for a fireproof door is prepared from the following raw materials in parts by mass: 55-60 parts of polyvinyl chloride, 15-20 parts of a flame retardant, 40-50 parts of wood flour, 120-130 parts of modified sepiolite mineral powder, 26-32 parts of reinforced fibers, 2.5-3 parts of a coupling agent, 5-6 parts of a foaming agent, 1-1.3 parts of a lubricant and 3-3.5 parts of a toughening agent. According to the fireproof composite material for the fireproof door, a four-effect synergistic system of smoke suppression, charring, oxygen isolation and heat conduction is constructed through three major technologies of'alkali-silane-organic 'triple modification of sepiolite, 'diamino coupling-nitrogen and phosphorus grafting' modification of alumina fibers and'interface coating 'coating modification of cyclotriphosphazene-silicon nitride; the flame retardant property and the mechanical property of the fireproof composite material are obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of fireproof polymer composite materials, and in particular to a fireproof composite material for fireproof doors and a preparation method thereof. Background Art

[0002] Wood-plastic composites are composite materials made primarily of mineral powder and wood fiber / wood powder, supplemented by polymers such as polyvinyl chloride and processing aids. Mineral powder accounts for a high proportion of the raw material system, and the resulting wood-plastic composites have the advantages of being natural and environmentally friendly, formaldehyde-free, moisture-resistant, and highly impact-resistant. Therefore, they can be used in door panels, door frames, or fire-resistant door core panels. When wood-plastic composites are used in the home, such as as raw materials for door panels, door frames, or fire-resistant door core panels, high fire-retardant properties are required to reduce the likelihood of fire during daily use and, in the unfortunate event of a fire, significantly slow the spread of fire and suppress combustion.

[0003] The existing technology usually directly adds flame retardant additives to the wood-plastic composite material system to improve its fire retardant properties. The flame retardant additives are usually inorganic additives such as magnesium hydroxide or aluminum hydroxide. However, in actual production and use, the addition of the above additives has limited effect on improving the flame retardancy of the wood-plastic composite material. Therefore, there is a need for a wood-plastic composite material with better fire retardancy and mechanical properties to improve its daily fire safety performance when used in home fields such as door panels, door frames or fire-resistant door core panels, as well as its flame retardant / fireproof performance in the event of a fire accident. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present application provides a fireproof composite material for fire doors and a preparation method thereof. The fireproof composite material prepared in the present application has excellent flame retardant properties and mechanical properties.

[0005] In a first aspect, the present application provides a fireproof composite material for fireproof doors, which adopts the following technical solution:

[0006] A fireproof composite material for fireproof doors comprises the following raw materials, calculated by weight: 55-60 parts of polyvinyl chloride, 15-20 parts of a flame retardant, 40-50 parts of wood flour, 120-130 parts of modified sea foam mineral powder, 26-32 parts of reinforcing fiber, 2.5-3 parts of a coupling agent, 5-6 parts of a foaming agent, 1-1.3 parts of a lubricant, and 3-3.5 parts of a toughening agent; wherein the reinforcing fiber is modified alumina fiber; the flame retardant is a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant; and the modified sea foam mineral powder is prepared by modifying sea foam mineral powder with phytic acid, polyglutamic acid, and melamine cyanurate.

[0007] By adopting the above technical solution, polyvinyl chloride (PVC) serves as the matrix material, providing basic mechanical properties and processability, while its flame retardancy is synergistically enhanced through the composite system. Wood flour, a natural filler, reduces costs and, after carbonization, forms a char layer during combustion, slowing the spread of fire. Modified sea foam mineral powder improves brittleness by replacing magnesium with phytic acid. The long-chain structure of polyglutamic acid enhances flexibility, and combined with melamine cyanurate, it forms a synergistic flame retardant. This improves dispersibility and smoke suppression, forming a loosely cross-linked structure with the matrix, extending flame retardancy. A modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant: cyclotriphosphazene introduces iminophosphine groups to enhance flame retardancy, while silicon nitride nanosheets protect the internal materials through thermal anisotropy. Esterification coating technology reduces flame retardant precipitation and improves system stability. Modified alumina fiber is surface-grafted with N,N,N-trimethylglycine and aluminum diethylphosphinate, creating a nitrogen-phosphorus synergistic flame retardant and improving compatibility with the matrix. Toughening agents improve the impact resistance of materials and synergize with reinforcing fibers to enhance mechanical properties. Coupling agents enhance the interfacial bonding between inorganic fillers and organic matrices. Foaming agents foam to form a porous structure, reducing material density while slowing down heat conduction. Lubricants optimize processing fluidity. In summary, NP synergistically flame retards: phytic acid (P), polyglutamic acid / melamine cyanurate (N) and modified cyclotriphosphazene (NP) form a multi-level flame retardant network. Thermal conductivity-smoke suppression synergy: Silicon nitride nanosheets rapidly conduct heat laterally to disperse heat, and sea foam mineral powder inhibits smoke generation. Reinforcement-toughening synergy: Modified alumina fibers enhance strength, toughening agents improve impact resistance, and coupling agents optimize interfacial bonding. Through the above synergistic effects, the flame retardant and mechanical properties of fireproof composite materials are significantly improved.

[0008] Preferably, the method for preparing the modified alumina fiber comprises the following steps:

[0009] S21. Place 100 parts by mass of alumina fibers having a length of 5-6 mm and a diameter of 3 μm in 500 parts of tetrahydrofuran, and ultrasonically disperse the mixture for 50-90 min. Then, add 30-40 parts of N,N,N-trimethylglycine, reflux for 14-16 h, filter, wash with acetone three times, and vacuum dry at 80°C for 8-10 h to obtain an intermediate.

[0010] S22. Place 100 parts of the intermediate in 300 parts of tetrahydrofuran according to the mass fraction, ultrasonically disperse for 20-30 minutes, ice-bath at 3-5°C, add 50-60 parts of diethyl aluminum phosphinate and 2-3 parts of diethylenetriamine, stir well for 4-5 hours, filter, wash with acetone three times, and vacuum dry at 80°C for 8-10 hours to obtain modified alumina fiber.

[0011] By adopting the above technical solution, S21: Hydrophilic-nitrogen source pre-grafting, N,N,N-trimethylglycine (zwitterion) binds to the Al-OH groups on the alumina fiber surface through hydrogen bonds, introducing quaternary ammonium cations and long-chain alkyl groups. This achieves: improving the fiber's wettability and dispersibility in the PVC / wood powder polar matrix; providing a nitrogen source skeleton for the subsequent phosphorus component; S22: Phosphorus-nitrogen synergistic final grafting, aluminum diethylphosphinate coordinates and grafts to the fiber surface hydroxyl groups through Al-OP bonds, forming a nanoscale phosphorus-nitrogen coating. During combustion, the phosphorus component generates an Al(PO3)3 glassy barrier, inhibiting PVC chain segment breakage; the nitrogen component releases NH3 / N2 to dilute the combustible gas and promote the formation of an intumescent char layer. In summary, the modified alumina fiber improves its dispersibility and compatibility. Furthermore, the N,N,N-trimethylglycine and aluminum diethylphosphinate grafted onto the modified alumina fiber surface form a nitrogen-phosphorus synergistic flame retardant system, significantly improving the flame retardancy and mechanical properties of the fire-resistant composite material.

[0012] Preferably, the preparation method of the modified sea foam mineral powder comprises the following steps:

[0013] S31, according to the mass parts, 100 parts of sea foam mineral powder were added to 300 parts of 50-55% sodium hydroxide aqueous solution, ultrasonically stirred for 10-12 hours, filtered, washed, and vacuum dried at 120 ° C for 8-10 hours to obtain pretreated sea foam mineral powder;

[0014] S32, dispersing 100 parts of pretreated sea foam mineral powder in a solution consisting of 300 parts of ethanol and 50 parts of water, then adding 3-4 parts of vinyltriethoxysilane, adjusting the pH of the solution to 5-6, stirring for 5-6 hours, filtering, washing three times, and vacuum drying at 100°C for 8-10 hours to obtain silanized sea foam mineral powder;

[0015] S33. Disperse 100 parts of silanized sea foam mineral powder in 200 parts of deionized water according to mass fractions, stir for 30-40 minutes, then add 100-120 parts of phytic acid, 30-35 parts of polyglutamic acid and 12-15 parts of melamine cyanurate, raise the temperature to 80-86°C, stir for 10-12 hours, filter and wash 3 times, vacuum dry at 100°C for 8-10 hours, grind and sieve to obtain modified sea foam mineral powder with an average particle size of 2-5 microns.

[0016] By employing the above technical solutions, S31: Alkaline Etching - Interlayer Spacing Control: Interlayer Spacing Expansion: Na⁺ replaces Mg²⁺, increasing the interlayer spacing and exposing more Si-OH active sites. Defect Introduction: Alkaline etching creates mesopores, increasing surface area and enhancing adsorption and smoke suppression capabilities. S32: Silane Coupling - Interfacial Bridging: Hydrophobicization: Si-OH condenses with silane hydrolysis products, improving compatibility with PVC. Double Bond Introduction: Vinyl groups provide anchor points for subsequent free radical grafting of phytic acid / polyglutamic acid. S33: Organic Hybridization - Nitrogen-Phosphorus Synergy: Brittleness Improvement: Phytic acid H⁺ replaces the interlayer Mg²⁺ of sepiolite, forming PO-Al / Si covalent bonds. Lattice defects are filled with polyglutamic acid flexible segments (γ-PGA), reducing Young's modulus. NP Synergistic Flame Retardancy: Phytic acid (P source): catalyzes the crosslinking of PVC to form carbon. Polyglutamic acid (N source): Thermal decomposition generates NH⁃ to dilute the combustible gas, which reacts with P to form a PNC expanded carbon layer. Melamine cyanurate: Sublimation absorbs heat and releases nitrogen, suppressing droplets. Loosely cross-linked structure: The γ-carboxyl groups of polyglutamic acid form hydrogen bonds with the Si-OH groups of sepiolite, creating a "flexible buffer layer" that prevents cracking of the char layer during combustion. The prepared modified sepiolite mineral powder functions in fire-resistant composite materials: 1) Smoke suppression-charring core, porous adsorption: The mesoporous structure after alkaline etching adsorbs benzene volatiles produced by PVC thermal decomposition. Catalytic charring: Phytic acid and PVC form an Al-OP cross-linked structure (POC bond verified by XPS), with sepiolite serving as a rigid skeleton supporting the char layer and inhibiting shrinkage. 2) Mechanical-flame retardant balance, toughening mechanism: The flexible polyglutamic acid chains disperse stress and form an "interpenetrating network" with wood powder, improving impact strength. Interfacial synergy: The silane coupling agent forms covalent-hydrogen double crosslinks with sepiolite and PVC to prevent phase separation. In summary, the modified sea foam mineral powder prepared in this application is upgraded from a traditional inorganic filler to a multifunctional micro-nano center for smoke suppression, carbonization and toughening through a three-step modification of "alkaline etching-silane bridging-organic hybridization". It forms a "rigid skeleton + flexible network + expansion barrier" synergistic system with modified alumina fiber and cyclotriphosphazene-silicon nitride, thereby significantly improving the flame retardant and mechanical properties of the fire-proof composite material.

[0017] Preferably, the preparation method of the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant comprises the following steps:

[0018] S41. Add hexaphenoxy cyclotriphosphazene to acetone in parts by mass, stir and dissolve, ice-bathe at 3-5° C. for 20-30 min, add tris(dimethylamino)phosphine imide, and heat to 83-88° C. at a stirring speed of 200 r / min under a nitrogen atmosphere. Stir and react for 15-18 h. After the reaction is completed, cool to room temperature, separate the precipitate, wash the separated precipitate with tetrahydrofuran solvent, dry it, and dissolve it in methanol solvent. Add sodium ethoxide under a nitrogen atmosphere, stir and react for 3-4 h. After vacuum concentration, remove the methanol solvent by rotary evaporation to obtain a modified cyclotriphosphazene.

[0019] S42, dispersing 25 parts by mass of silicon nitride nanosheets having an average particle size of 200-300 nm in 150 parts by mass of a mixed solution of 30% hydrochloric acid and 70% nitric acid in a volume ratio of 2:5, stirring for 10-12 hours, centrifuging, rinsing three times with a 5% ammonia aqueous solution, then washing with deionized water until neutral, and drying in a vacuum oven at 100° C. for 8-10 hours to obtain modified silicon nitride nanosheets;

[0020] S43. Dissolve 10 parts of modified cyclotriphosphazene in 70 parts of methanol solvent according to their mass fractions, then add 20-25 parts of modified silicon nitride nanosheets, raise the temperature to 50-56°C, keep stirring for 10-12 hours, filter and wash 3 times, and vacuum dry at 80°C for 8-10 hours to obtain a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant.

[0021] By employing the aforementioned technical solutions, S41: Molecularly modified cyclotriphosphazene (CPC) was synthesized, where phosphine imide groups (P=N-) replaced some phenoxy groups to increase the phosphorus content, thereby enhancing the efficiency of gas-phase free radical quenching. Sodium ethoxide enhanced hydrogen bonding and electrostatic adsorption with hydroxyl groups on the silicon nitride surface, improving coating stability. S42: Nanoscale silicon nitride (Si3N4) surface activation, with carboxylation providing esterification sites for CPC, increased coating efficiency. S43: Micro-nano composite coating, silicon nitride nanosheets are respectively grafted with carboxyl groups through surface modification, and esterified and coated in a solution of modified cyclotriphosphazene, and the carboxyl groups on the surface of the modified silicon nitride react with the iminophosphazene groups of the modified cyclotriphosphazene to coat the modified cyclotriphosphazene in the gaps between the silicon nitride nanosheets, thereby reducing the precipitation of the modified cyclotriphosphazene. At the same time, based on the characteristic that the in-plane thermal conductivity of the silicon nitride nanosheets is higher than that in the vertical direction when the silicon nitride nanosheets are oriented in the composite material, it can quickly conduct heat to the edge, thereby protecting the internal material and improving its flame retardant effect. In short, the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant prepared in this application is constructed through the three steps of "molecular modification-nano coating-interface bridging". CPC-Si3N4 becomes the core synergistic unit of flame retardancy-smoke suppression-enhancement in the composite material, achieving the simultaneous optimization of high-efficiency flame retardancy and mechanical properties.

[0022] Preferably, in step S41, the mass ratio of the hexaphenoxycyclotriphosphazene, tris(dimethylamino)phosphineimide and sodium ethoxide is 10:75-85:3-4.

[0023] Preferably, the foaming agent is melamine, and the toughening agent is chlorinated polyethylene.

[0024] Preferably, the average particle size of the wood powder is 8-15 microns.

[0025] Preferably, the coupling agent is prepared by mixing N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 3:2.

[0026] By employing this technical solution, the coupling agent acts as an interfacial bridge in this formulation, addressing the following key issues through chemical bonding and physical adsorption: 1) Enhanced inorganic-organic compatibility. Modified inorganic fillers such as seafoam mineral powder, alumina fiber, and silicon nitride have significant polarity differences with the polyvinyl chloride (PVC) matrix, making phase separation more likely. The coupling agent forms a molecular bridge through its amphiphilic groups (siloxane groups with affinity for inorganics and amine groups with affinity for organics), improving dispersibility. 2) Enhanced mechanical properties: By strengthening the interfacial bonding between the filler and the resin, stress concentration is reduced, and the tensile strength and impact toughness of the composite material are increased. 3) Synergistic flame retardancy is achieved: the amine groups (—NH2) form hydrogen bonds or coordination interactions with the phosphorus and nitrogen elements in the flame retardant, promoting uniform dispersion of the flame retardant component and preventing localized failure. N-(β-Aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602): The bisamino group (-NH-(CH2)2-NH2) provides multi-stage reaction sites (primary amines graft to the inorganic phase, secondary amines bond to the organic phase). Methoxy groups hydrolyze to form Si-OH groups, which condense with the Al-OH / Si-OH groups of sepiolite and alumina fiber, forming covalent and hydrogen-bonded dual crosslinks. γ-Aminopropyltriethoxysilane (KH-550): The monoamino group (-NH2) forms hydrogen bonds and quaternary ammonium salt bonds with the Cl atoms of PVC, improving compatibility. Hydrolysis of the triethoxy group produces more Si-OH groups, enhancing the inorganic coating density. KH-602 preferentially anchors to polar inorganic phases (sepiolite and alumina fiber), while KH-550 preferentially bonds to non-polar organic phases (PVC and wood flour), achieving gradient interface matching. Through a precise ratio of 3:2, KH-602 and KH-550 construct a gradient interface. The two work synergistically to improve the flame retardant and mechanical properties of the fire-resistant composite material.

[0027] Preferably, the lubricant is prepared by mixing zinc stearate and polyethylene wax in a mass ratio of 1:2.

[0028] In a second aspect, the present application provides a method for preparing a fireproof composite material for fireproof doors, using the following technical solution:

[0029] As a general technical concept, the present application also provides a method for preparing the fireproof composite material for fireproof doors, comprising the following steps:

[0030] Polyvinyl chloride, flame retardant, wood flour, modified sea foam mineral powder, reinforcing fiber, coupling agent, foaming agent, lubricant and toughening agent are placed in a high-speed mixer according to their mass proportions, the speed is set to 350 r / min, the temperature is raised to 150-156° C. and mixed for 20-30 minutes, and the mixture is cooled to room temperature to obtain a mixed material; the mixed material is then melt-extruded at an extrusion temperature of 160-166° C. through a twin-screw extruder, and then cooled and granulated to obtain a fire-resistant composite material for fire doors.

[0031] In summary, this application includes at least one of the following beneficial technical effects:

[0032] 1. Excellent flame retardant properties

[0033] By subjecting sea foam mineral powder to multiple modifications with phytic acid, polyglutamic acid and melamine cyanurate, not only its dispersibility and stability are improved, but also a synergistic flame retardant mechanism of NP is introduced; at the same time, the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant works together with the nitrogen-phosphorus synergistic system in the modified alumina fiber to form a multi-layered flame retardant protection, enabling the material to have more efficient charring, heat insulation and smoke suppression capabilities at high temperatures, thereby significantly improving the overall flame retardancy level.

[0034] 2. Good mechanical properties

[0035] The addition of modified seafoam mineral powder and reinforcing fibers (such as modified alumina fiber) effectively improves the tensile strength, impact resistance, and dimensional stability of the composite material. The rational proportion of the coupling agent further enhances the interfacial bonding between the inorganic filler and the organic matrix, thereby improving the overall structural strength and durability of the material.

[0036] 3. Excellent processing performance and compatibility

[0037] By pre-treating the sea foam mineral powder with vinyl triethoxysilane and using it in combination with a coupling agent in a specific proportion, the dispersion and compatibility of the filler in the polyvinyl chloride matrix are significantly improved, agglomeration is avoided, and good fluidity and formability of the material are ensured during processing.

[0038] 4. Environmental protection and sustainability

[0039] This application uses natural wood powder as part of the filling material, combined with renewable or low-toxicity modification additives, to reduce the risk of release of harmful substances that may exist in traditional fireproof materials, which is in line with the development trend of green building materials.

[0040] 5. Long-term stability and durability

[0041] Multiple modification methods (such as the flexible cross-linked structure of sea foam mineral powder and the coating protection of silicon nitride nanosheets) effectively improve the thermal stability and chemical stability of the material in complex environments, and extend the service life of fire doors in practical applications. DETAILED DESCRIPTION

[0042] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0043] In the following examples and preparation examples, 1 part represents 100 g, and the average particle size of the wood powder is 11 μm.

[0044] Preparation Example 1 Preparation of modified alumina fiber

[0045] The preparation method of modified alumina fiber comprises the following steps:

[0046] S21. Place 100 parts by mass of alumina fibers having a length of 5-6 mm and a diameter of 3 μm in 500 parts of tetrahydrofuran, and ultrasonically disperse them for 70 minutes. Then, add 36 parts of N,N,N-trimethylglycine, reflux for 15 hours, filter, wash with acetone three times, and vacuum dry at 80°C for 9 hours to obtain an intermediate.

[0047] S22. According to the mass fraction, 100 parts of the intermediate were placed in 300 parts of tetrahydrofuran, ultrasonically dispersed for 25 minutes, ice-bathed at 4°C, added with 55 parts of aluminum diethylphosphinate and 2.3 parts of diethylenetriamine, stirred thoroughly for 4.5 hours, filtered, washed with acetone three times, and vacuum-dried at 80°C for 9 hours to obtain modified alumina fiber.

[0048] Preparation Example 2 Preparation of modified sea foam mineral powder

[0049] The preparation method of modified sea foam mineral powder comprises the following steps:

[0050] S31, according to the mass parts, 100 parts of sea foam mineral powder were added to 300 parts of 53% sodium hydroxide aqueous solution, ultrasonically stirred for 11 hours, filtered, washed, and vacuum dried at 120 ° C for 9 hours to obtain pretreated sea foam mineral powder;

[0051] S32, dispersing 100 parts of pretreated sea foam mineral powder in a solution consisting of 300 parts of ethanol and 50 parts of water, and then adding 3.5 parts of vinyltriethoxysilane, adjusting the pH of the solution to 5.4, stirring for 5.6 hours, filtering, washing three times, and vacuum drying at 100°C for 9 hours to obtain silanized sea foam mineral powder;

[0052] S33. Disperse 100 parts of silanized sea foam mineral powder in 200 parts of deionized water according to mass fractions, stir for 35 minutes, then add 110 parts of phytic acid, 33 parts of polyglutamic acid and 14 parts of melamine cyanurate, raise the temperature to 85°C, stir for 11 hours, filter and wash 3 times, vacuum dry at 100°C for 9 hours, grind and sieve to obtain modified sea foam mineral powder with an average particle size of 3 microns.

[0053] Preparation Example 3 Modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant

[0054] The preparation method of the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant comprises the following steps:

[0055] S41. According to the mass ratio, 10 parts of hexaphenoxy cyclotriphosphazene were added to 180 parts of acetone, stirred and dissolved, and then ice-bathed at 4°C for 25 minutes. Then, 78 parts of tris(dimethylamino)phosphine imide were added. Under a nitrogen atmosphere, the temperature was raised to 85°C at a stirring speed of 200 r / min, and the mixture was stirred and reacted for 17 hours. After the reaction was completed, the mixture was cooled to room temperature, the precipitate was separated, and the separated precipitate was washed with tetrahydrofuran solvent, dried, and dissolved in 60 parts of methanol solvent. 3.5 parts of sodium ethoxide were added under a nitrogen atmosphere, and the reaction was stirred for 3.4 hours. After vacuum concentration, the methanol solvent was removed by rotary evaporation to obtain a modified cyclotriphosphazene.

[0056] S42, dispersing 25 parts by mass of silicon nitride nanosheets having an average particle size of 260 nm in 150 parts by mass of a mixed solution consisting of 30% hydrochloric acid and 70% nitric acid in a volume ratio of 2:5, stirring for 11 hours, centrifuging, rinsing three times with a 5% ammonia aqueous solution, and then washing with deionized water until neutral, and drying in vacuo at 100° C. for 9 hours to obtain modified silicon nitride nanosheets;

[0057] S43. Dissolve 10 parts of modified cyclotriphosphazene in 70 parts of methanol solvent according to their mass fractions, add 23 parts of modified silicon nitride nanosheets, raise the temperature to 53°C, keep stirring for 11 hours, filter and wash 3 times, and vacuum dry at 80°C for 9 hours to obtain a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant.

[0058] Example 1

[0059] A fireproof composite material for fireproof doors comprises the following raw materials, calculated by weight: 55 parts of polyvinyl chloride, 15 parts of a flame retardant, 40 parts of wood flour, 120 parts of modified sea foam mineral powder, 26 parts of reinforcing fiber, 2.5 parts of a coupling agent, 5 parts of melamine, 1 part of a lubricant, and 3 parts of chlorinated polyethylene; wherein the reinforcing fiber is modified alumina fiber; the flame retardant is a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant; the coupling agent is prepared by mixing N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and γ-aminopropyltriethoxysilane in a weight ratio of 3:2; and the lubricant is prepared by mixing zinc stearate and polyethylene wax in a weight ratio of 1:2.

[0060] The method for preparing the fireproof composite material for fireproof doors comprises the following steps:

[0061] Polyvinyl chloride, flame retardant, wood flour, modified sea foam mineral powder, reinforcing fiber, coupling agent, melamine, lubricant and chlorinated polyethylene are placed in a high-speed mixer according to their mass proportions, the speed is set to 350 r / min, the temperature is raised to 150° C. and mixed for 30 minutes, and the mixture is cooled to room temperature to obtain a mixed material; the mixed material is then melt-extruded at an extrusion temperature of 160° C. through a twin-screw extruder, and then cooled and granulated to obtain a fire-resistant composite material for fire doors.

[0062] Example 2

[0063] A fireproof composite material for fireproof doors comprises the following raw materials, calculated by weight: 60 parts of polyvinyl chloride, 20 parts of a flame retardant, 50 parts of wood flour, 130 parts of modified sea foam mineral powder, 32 parts of reinforcing fiber, 3 parts of a coupling agent, 6 parts of melamine, 1.3 parts of a lubricant, and 3.5 parts of chlorinated polyethylene; wherein the reinforcing fiber is modified alumina fiber; the flame retardant is a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant; the coupling agent is prepared by mixing N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and γ-aminopropyltriethoxysilane in a weight ratio of 3:2; and the lubricant is prepared by mixing zinc stearate and polyethylene wax in a weight ratio of 1:2.

[0064] The method for preparing the fireproof composite material for fireproof doors comprises the following steps:

[0065] Polyvinyl chloride, flame retardant, wood flour, modified sea foam mineral powder, reinforcing fiber, coupling agent, melamine, lubricant and chlorinated polyethylene are placed in a high-speed mixer according to their mass proportions, the speed is set to 350 r / min, the temperature is raised to 153°C and mixed for 30 minutes, and the mixture is cooled to room temperature to obtain a mixed material; the mixed material is then melt-extruded at an extrusion temperature of 163°C through a twin-screw extruder, cooled and granulated to obtain a fire-resistant composite material for fire doors.

[0066] Example 3

[0067] A fireproof composite material for fireproof doors comprises the following raw materials, calculated by weight: 58 parts of polyvinyl chloride, 17 parts of a flame retardant, 45 parts of wood flour, 126 parts of modified sea foam mineral powder, 29 parts of reinforcing fiber, 2.7 parts of a coupling agent, 5.6 parts of melamine, 1.2 parts of a lubricant, and 3.3 parts of chlorinated polyethylene; wherein the reinforcing fiber is modified alumina fiber; the flame retardant is a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant; the coupling agent is prepared by mixing N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and γ-aminopropyltriethoxysilane in a weight ratio of 3:2; and the lubricant is prepared by mixing zinc stearate and polyethylene wax in a weight ratio of 1:2.

[0068] The method for preparing the fireproof composite material for fireproof doors comprises the following steps:

[0069] Polyvinyl chloride, flame retardant, wood flour, modified sea foam mineral powder, reinforcing fiber, coupling agent, melamine, lubricant and chlorinated polyethylene are placed in a high-speed mixer according to their mass proportions, the speed is set to 350 r / min, the temperature is raised to 156°C and mixed for 25 minutes, and the mixture is cooled to room temperature to obtain a mixed material; the mixed material is then melt-extruded at an extrusion temperature of 166°C through a twin-screw extruder, cooled and granulated to obtain a fire-resistant composite material for fire doors.

[0070] Comparative Example 1

[0071] The same as Example 3, except that: unmodified sefoam mineral powder with an average particle size of 3 μm is used in equal parts by mass instead of the modified sefoam mineral powder.

[0072] Comparative Example 2

[0073] The same as Example 3, except that: an equal mass fraction of unmodified alumina fibers with a length of 5-6 mm and a diameter of 3 μm is used instead of the modified alumina fibers.

[0074] Comparative Example 3

[0075] The same as Example 3, except that: a mixture of equal mass parts (hexaphenoxycyclotriphosphazene and silicon nitride nanosheets with an average particle size of 260 nanometers mixed in a mass ratio of 10:23) is used instead of the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant.

[0076] Comparative Example 4

[0077] The same as Example 3, except that the coupling agent is N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0078] Comparative Example 5

[0079] The same as Example 3, except that the coupling agent is γ-aminopropyltriethoxysilane.

[0080] Performance testing

[0081] The fire-resistant composite materials for fire doors prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were sampled and pressed into shape using a mold to obtain test strips. The following tests were performed, with each group tested three times. The results were averaged and shown in Table 1.

[0082] Tensile strength: tested according to GB / T1040-2006 standard, tensile rate is 50mm / min; sample size is 150mm×10mm×3mm;

[0083] Impact strength: tested in accordance with GB / T1843-2008 standard, sample size is 150mm×10mm×3mm;

[0084] Flame retardant performance (limiting oxygen index): tested according to GB / T2406.2-2009 standard, using an oxygen index meter to measure the limiting oxygen index of the sample. The sample size is 150mm×6.5mm×3mm.

[0085] Heat release rate: tested according to ISO 5660-1:2015 standard; sample size is 100mm×100mm×9mm;

[0086] Table 1 Performance test

[0087] project Tensile strength / MPa <![CDATA[Impact strength / kJ / m 2 > Limiting oxygen index / % Heat release rate / kW / m² Example 1 63.6 28.7 48.6 121 Example 2 64.4 28.2 47.9 130 Example 3 66.7 29.6 49.0 116 Comparative Example 1 57.2 22.4 38.3 187 Comparative Example 2 51.3 21.3 37.4 198 Comparative Example 3 59.8 22.6 41.2 171 Comparative Example 4 61.4 26.3 45.6 129 Comparative Example 5 61.8 26.7 46.1 135

[0088] Analyzing the data in Table 1, we can see that:

[0089] 1) The fireproof composite materials for fire doors prepared in Examples 1 to 3 have excellent flame retardant properties and mechanical properties.

[0090] 2) The performance comparison analysis of the fireproof composite material for fire doors prepared in Example 3 and Comparative Example 1 shows that the modified sepiolite mineral powder prepared in this application first uses high-concentration strong base sodium hydroxide to adjust the interlayer spacing of sepiolite, and vinyltriethoxysilane to jointly modify sepiolite, thereby improving the dispersion performance of sepiolite and the adsorption performance of sepiolite, thereby improving the smoke suppression performance of sepiolite; on the other hand, this application uses phytic acid, polyglutamic acid and melamine cyanurate to further modify the organic-inorganic combined modified sepiolite, and the H in the phytic acid structure is further modified. + Can replace Mg in the sepiolite structure 2+, which improves the brittleness of the modified sepiolite. Polyglutamic acid, as an amino acid polymer, has a long-chain structure, fewer branches and a methylene chain structure, and has good flexibility. Phytic acid, polyglutamic acid and sepiolite can form a looser cross-linking structure, which improves the brittleness of sepiolite and enhances the stability of the synthesized modified sepiolite, and can have a more lasting flame retardant and smoke suppression effect. Furthermore, phytic acid contains P element, polyglutamic acid and melamine cyanurate contain N element, which can play a synergistic flame retardant role of N and P, thereby improving the flame retardant properties of the modified sepiolite, and thus significantly improving the flame retardant properties and mechanical properties of the fire-proof composite material.

[0091] 3) A comparative analysis of the performance of the fire-resistant composite materials for fire doors prepared in Example 3 and Comparative Example 2 demonstrates that modified alumina fibers improve their dispersibility and compatibility. Furthermore, the N,N,N-trimethylglycine and aluminum diethylphosphinate grafted onto the surface of the modified alumina fibers form a nitrogen-phosphorus synergistic flame-retardant system, significantly enhancing the flame retardancy and mechanical properties of the fire-resistant composite materials.

[0092] 4) A comparative analysis of the performance of the fire-resistant composite materials for fire doors prepared in Example 3 and Comparative Example 3 shows that the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant prepared in the present application uses hexaphenoxycyclotriphosphazene as a raw material to react with tris(dimethylamino)phosphine imide, and further introduces phosphine imide groups into the cyclotriphosphazene molecule to improve its flame retardant properties to obtain modified cyclotriphosphazene; in addition, using silicon nitride nanosheets as raw materials, carboxyl groups are grafted separately through surface modification, and esterification and coating are performed in a solution of modified cyclotriphosphazene, and the modified cyclotriphosphazene is coated in the gaps between the silicon nitride nanosheets, thereby reducing the precipitation of the modified cyclotriphosphazene. At the same time, based on the characteristic that the in-plane thermal conductivity of the silicon nitride nanosheets is higher than that in the vertical direction when the silicon nitride nanosheets are oriented in the composite material, it can quickly conduct heat to the edge, thereby protecting the internal material, thereby improving its flame retardant effect, and thus improving the flame retardant properties and mechanical properties of the fire-resistant composite material.

[0093] 4) A comparative analysis of the properties of the fire-resistant composite materials for fire doors prepared in Example 3 and Comparative Examples 4 and 5 shows that the coupling agent, prepared by mixing N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 3:2, leverages their synergistic effect to achieve: 1) enhanced inorganic-organic compatibility. The polarity difference between inorganic fillers such as modified seafoam mineral powder, alumina fiber, and silicon nitride and the polyvinyl chloride (PVC) matrix is ​​significant, making phase separation more likely. The coupling agent's amphiphilic groups (siloxane groups with an affinity for inorganics and amine groups with an affinity for organics) form molecular bridges, improving dispersibility. 2) enhanced mechanical properties by strengthening the interfacial bonding between the filler and the resin, reducing stress concentration, and increasing the tensile strength and impact toughness of the composite material. 3) synergistic flame retardancy is achieved. The amine groups can form hydrogen bonds or coordination interactions with the phosphorus and nitrogen elements in the flame retardant, promoting uniform dispersion of the flame retardant component and preventing localized failure.

[0094] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the above embodiments provide a detailed description of the present application, relevant technical personnel should understand that the specific implementation methods of the present application may still be modified or replaced by equivalents. Any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A fireproof composite material for fireproof doors, characterized in that: The preparation comprises the following raw materials, calculated by weight: 55-60 parts of polyvinyl chloride, 15-20 parts of flame retardant, 40-50 parts of wood flour, 120-130 parts of modified sea foam mineral powder, 26-32 parts of reinforcing fiber, 2.5-3 parts of coupling agent, 5-6 parts of foaming agent, 1-1.3 parts of lubricant, and 3-3.5 parts of toughening agent; wherein the reinforcing fiber is modified alumina fiber; the flame retardant is a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant; and the modified sea foam mineral powder is prepared by modifying sea foam mineral powder with phytic acid, polyglutamic acid, and melamine cyanurate. The preparation method of the modified alumina fiber comprises the following steps: S21. Place 100 parts by mass of alumina fibers having a length of 5-6 mm and a diameter of 3 μm in 500 parts of tetrahydrofuran, and ultrasonically disperse the mixture for 50-90 min. Then, add 30-40 parts of N,N,N-trimethylglycine, reflux for 14-16 h, filter, wash with acetone three times, and vacuum dry at 80°C for 8-10 h to obtain an intermediate. S22. Place 100 parts of the intermediate in 300 parts of tetrahydrofuran according to the mass fraction, ultrasonically disperse for 20-30 minutes, ice-bath at 3-5°C, add 50-60 parts of diethyl aluminum phosphinate and 2-3 parts of diethylenetriamine, stir well for 4-5 hours, filter, wash with acetone three times, and vacuum dry at 80°C for 8-10 hours to obtain modified alumina fiber.

2. The fireproof composite material for fireproof doors according to claim 1, characterized in that: The preparation method of the modified sea foam mineral powder comprises the following steps: S31, according to the mass parts, 100 parts of sea foam mineral powder were added to 300 parts of 50-55% sodium hydroxide aqueous solution, ultrasonically stirred for 10-12 hours, filtered, washed, and vacuum dried at 120 ° C for 8-10 hours to obtain pretreated sea foam mineral powder; S32, dispersing 100 parts of pretreated sea foam mineral powder in a solution consisting of 300 parts of ethanol and 50 parts of water, then adding 3-4 parts of vinyltriethoxysilane, adjusting the pH of the solution to 5-6, stirring for 5-6 hours, filtering, washing three times, and vacuum drying at 100°C for 8-10 hours to obtain silanized sea foam mineral powder; S33. Disperse 100 parts of silanized sea foam mineral powder in 200 parts of deionized water according to mass fractions, stir for 30-40 minutes, then add 100-120 parts of phytic acid, 30-35 parts of polyglutamic acid and 12-15 parts of melamine cyanurate, raise the temperature to 80-86°C, stir for 10-12 hours, filter and wash 3 times, vacuum dry at 100°C for 8-10 hours, grind and sieve to obtain modified sea foam mineral powder with an average particle size of 2-5 microns.

3. The fireproof composite material for fireproof doors according to claim 1, characterized in that: The preparation method of the modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant comprises the following steps: S41. Add hexaphenoxy cyclotriphosphazene to acetone in parts by mass, stir and dissolve, ice-bathe at 3-5° C. for 20-30 min, add tris(dimethylamino)phosphine imide, and heat to 83-88° C. at a stirring speed of 200 r / min under a nitrogen atmosphere. Stir and react for 15-18 h. After the reaction is completed, cool to room temperature, separate the precipitate, wash the separated precipitate with tetrahydrofuran solvent, dry it, and dissolve it in methanol solvent. Add sodium ethoxide under a nitrogen atmosphere, stir and react for 3-4 h. After vacuum concentration, remove the methanol solvent by rotary evaporation to obtain a modified cyclotriphosphazene. S42, dispersing 25 parts by mass of silicon nitride nanosheets having an average particle size of 200-300 nm in 150 parts by mass of a mixed solution of 30% hydrochloric acid and 70% nitric acid in a volume ratio of 2:5, stirring for 10-12 hours, centrifuging, rinsing three times with a 5% ammonia aqueous solution, then washing with deionized water until neutral, and drying in a vacuum oven at 100° C. for 8-10 hours to obtain modified silicon nitride nanosheets; S43. Dissolve 10 parts of modified cyclotriphosphazene in 70 parts of methanol solvent according to their mass fractions, then add 20-25 parts of modified silicon nitride nanosheets, raise the temperature to 50-56°C, keep stirring for 10-12 hours, filter and wash 3 times, and vacuum dry at 80°C for 8-10 hours to obtain a modified cyclotriphosphazene-silicon nitride nanosheet composite flame retardant.

4. The fireproof composite material for fireproof doors according to claim 3, characterized in that: In step S41, the mass ratio of the hexaphenoxycyclotriphosphazene, tris(dimethylamino)phosphineimide and sodium ethoxide is 10:75-85:3-4.

5. The fireproof composite material for fireproof doors according to claim 1, characterized in that: The foaming agent is melamine, and the toughening agent is chlorinated polyethylene.

6. The fireproof composite material for fireproof doors according to claim 1, characterized in that: The average particle size of the wood flour is 8-15 microns.

7. The fireproof composite material for fireproof doors according to claim 1, characterized in that: The coupling agent is prepared by mixing N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 3:

2.

8. The fireproof composite material for fireproof doors according to claim 1, characterized in that: The lubricant is prepared by mixing zinc stearate and polyethylene wax in a mass ratio of 1:

2.

9. A method for preparing a fireproof composite material for fireproof doors according to any one of claims 1 to 8, characterized in that: The following steps are involved: Polyvinyl chloride, flame retardant, wood flour, modified sea foam mineral powder, reinforcing fiber, coupling agent, foaming agent, lubricant and toughening agent are placed in a high-speed mixer according to their mass proportions, the speed is set to 350 r / min, the temperature is raised to 150-156° C. and mixed for 20-30 minutes, and the mixture is cooled to room temperature to obtain a mixed material; the mixed material is then melt-extruded at an extrusion temperature of 160-166° C. through a twin-screw extruder, and then cooled and granulated to obtain a fire-resistant composite material for fire doors.