Red mud-based flame-retardant material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of waste recycling, in particular to a red-mud-based flame-retardant material as well as a preparation method and application thereof. The preparation method comprises the following steps: pretreating the red mud iron dressing tailings to obtain pretreated red mud iron dressing tailings; wherein the pretreated red mud iron dressing tailings comprise iron oxide and aluminum oxide; mixing an acid source, a gas production source, an antioxidant, thermoplastic polyurethane and the pretreated red mud iron dressing tailings to obtain a mixed flame-retardant raw material; wherein the mass m1 of the pretreated red mud iron dressing tailings and the mass m2 of the thermoplastic polyurethane meet the relational expression that m1: m2 is larger than or equal to 33.33: 100 and smaller than or equal to 1: 1; and carrying out first extrusion granulation on the mixed flame-retardant raw material to obtain the red mud-based flame-retardant material. According to the preparation method, through functional modification and multi-component reaction collaborative design of the red mud iron dressing tailings, the problem of mechanical property degradation caused by a traditional inorganic filler is solved while a breakthrough in flame retardance is achieved, and a new way is provided for high-value utilization of red mud solid waste.

Description

Technical Field

[0001] This application relates to the technical field of waste recycling, and particularly to a red mud-based flame retardant material, a preparation method thereof, and an application thereof. Background Art

[0002] A large amount of red mud is inevitably generated during the production process of alumina. The composition of this red mud is relatively complex and generally contains components such as iron oxide, alumina, silica, and calcium oxide. In addition, some special red mud may contain some harmful substances (such as heavy metals and radioactive elements). The large production of red mud not only occupies a large amount of land but also causes serious environmental pollution, and even seriously threatens the safety of soil, water bodies, and ecosystems. Facing the huge pressure of red mud accumulation on environmental protection and the need for sustainable development of solid waste, how to recycle red mud resourcefully to achieve a win-win situation of economic benefits, environmental protection, and social sustainable development is an urgent problem to be solved at present. At the present stage, red mud can be used as a raw material to screen out iron products through magnetic separation or multi-stage separation. However, at present, this method only accounts for about 55% of the total utilization amount of red mud, and the average yield of iron concentrate in these iron products is only about 20%. The utilization rate of red mud is limited, which makes a large amount of red mud iron tailings formed after screening iron products from red mud. These red mud iron tailings still occupy a large amount of land and cause a series of environmental problems.

[0003] At present, most red mud iron tailings are used as filling materials, such as flame retardant fillers. However, the large addition of red mud iron tailings will instead affect the flame retardant performance of the flame retardant material and reduce the stability of these flame retardant materials, making these flame retardant materials pose a huge potential hazard to the environment. Summary of the Invention

[0004] This application provides a red mud-based flame retardant material, a preparation method thereof, and an application thereof to solve the following technical problems: how to balance the stability and flame retardant performance of the flame retardant material using red mud iron ore as a filling material.

[0005] In a first aspect, an embodiment of this application provides a preparation method of a red mud-based flame retardant material, and the preparation method includes:

[0006] Pre-treat the red mud iron tailings to obtain pre-treated red mud iron tailings; wherein, the pre-treated red mud iron tailings include iron oxide and alumina;

[0007] Mix an acid source, a gas generating source, an antioxidant, thermoplastic polyurethane, and the pre-treated red mud iron tailings to obtain a mixed flame retardant raw material; wherein, the mass m1 of the pre-treated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: 33.33:100 ≤ m1:m2 ≤ 1:1;

[0008] Carry out first extrusion granulation on the mixed flame retardant raw materials to obtain a red mud-based flame retardant material.

[0009] Optionally, the pH value of the pretreated red mud iron tailings is 8-10, and the particle size D of the pretreated red mud iron tailings satisfies: 0 mm < D ≤ 0.074 mm.

[0010] Optionally, the mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant, and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = (0.33-50.00):(0.33-33.33):(0.1-2.0):100.

[0011] Optionally, the types of the acid source include at least one of the following: phosphates, borates, sulfates, and nitrates; and / or

[0012] the types of the gas generating source include at least one of the following: amino compounds, polyols, amino resins, and carbonates; and / or

[0013] the types of the antioxidant include at least one of the following: amines, hindered phenols, sulfur antioxidants, phosphorus antioxidants, and composite antioxidants; and / or

[0014] the types of the thermoplastic polyurethane include at least one of the following: polyester-based polyurethane, polyether-based polyurethane, aliphatic polyurethane, and butadiene-based polyurethane.

[0015] Optionally, the temperature of the first extrusion granulation is 100°C - 230°C, and the feeding frequency of the first extrusion granulation is 40 Hz - 160 Hz.

[0016] In a second aspect, the present application provides a red mud-based flame retardant material, which is prepared by the preparation method described in the first aspect.

[0017] In a third aspect, the present application provides a flame retardant composite material, which includes a flammable polymer and the flame retardant material described in the second aspect. The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relationship: m6:m7 = (50 - 90):(10 - 50).

[0018] Optionally, the types of the flammable polymer include at least one of the following: polyoxymethylene, polyurethane, polypropylene, polyvinyl chloride, polyester, polyurethane, polycarbonate, and polyvinyl alcohol.

[0019] In a fourth aspect, the present application provides a method for preparing the flame retardant composite material described in the third aspect. The method includes:

[0020] Mix the flammable polymer and the flame retardant material to obtain a mixed raw material;

[0021] Perform second extrusion granulation on the mixed raw material to obtain flame retardant composite material particles;

[0022] Perform injection molding on the flame retardant composite material particles to obtain a flame retardant composite material.

[0023] Optionally, the temperature of the second extrusion granulation is 160°C to 180°C, and the feeding frequency of the second extrusion granulation is 80 Hz to 160 Hz; and / or

[0024] The injection molding includes a molding section, a holding pressure section, and a cooling section. The temperature of the molding section is 160°C to 180°C, the pressure of the molding section is 0.20 MPa to 0.60 MPa, the time of the holding pressure section is 2 s to 10 s, and the time of the cooling section is 10 s to 60 s.

[0025] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0026] An embodiment of the present application provides a preparation method of a red mud-based flame retardant material. In this preparation method, an acid source, a gas generating source, an antioxidant, thermoplastic polyurethane, and pretreated red mud iron tailings are used as mixed flame retardant raw materials for first extrusion granulation. Based on the characteristics of iron oxide and alumina in the pretreated red mud iron tailings, and the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: 33.33:100 ≤ m1:m2 ≤ 1:1. In the first extrusion granulation stage, the iron oxide in the pretreated red mud iron tailings will catalyze the carbonization reaction of the pretreated red mud iron tailings and the thermoplastic polyurethane in a high-temperature environment to form a large number of carbon layers, and the alumina will improve the thermal stability of these carbon layers to improve the stability of the flame retardant material. In addition, the acid source will react with these metal oxides in the pretreated red mud iron tailings to generate phosphate glass bodies, and these phosphate glass bodies will form a dense carbon layer on the surface of the pretreated red mud iron tailings to improve the flame retardant performance of the flame retardant material. In addition, based on the good adhesion characteristics, fluidity, high-temperature stability, high mechanical strength and other characteristics of thermoplastic polyurethane, mixing thermoplastic polyurethane and pretreated red mud iron tailings can not only bond the particles of the pretreated red mud iron tailings into shape, but also undergo a cross-linking reaction by itself in a high-temperature environment, or a cross-linking reaction with the pretreated red mud iron tailings, acid source, gas generating source and antioxidant. These cross-linking reactions will ultimately generate stable carbon layers with heat insulation and oxygen isolation functions to improve the stability of the flame retardant material. In addition, the addition of the gas generating source will cause the flame retardant material to generate non-combustible or non-flammable gases during combustion, and these gases will enter these carbon layers and expand to enhance the heat insulation performance of these carbon layers, thereby further improving the flame retardant performance of the flame retardant material. In addition, the addition of the antioxidant can inhibit the oxidation reaction that occurs during the extrusion granulation stage of flame retardant material raw materials such as the acid source, gas generating source, thermoplastic polyurethane and pretreated red mud iron tailings, and can improve the thermal stability of these raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic flowchart of a preparation method of a red mud-based flame retardant material provided by an embodiment of the present application;

[0030] Figure 2Schematic flowchart of a preparation method of a flame-retardant composite material provided by an embodiment of the present application. Detailed implementation manners

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0032] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0033] In this text, terms such as "including" mean "including but not limited to". Relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the associated relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "multiple" means two or more; "at least one kind", "at least one of the following items" or similar expressions refer to any combination of these items, including any combination of single item or plural items; for example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple respectively. "Parts representation method" such as parts by weight, parts by mass, etc. represents the proportional relationship between each component. In the proportional relationships involved in this text, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0034] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in this text can be obtained through market purchase or can be prepared by existing methods.

[0035] Figure 1 Exemplarily, a schematic flow diagram of a preparation method of a red mud-based flame retardant material provided by an embodiment of the present application is shown;

[0036] As Figure 1 shown, an embodiment of the present application provides a preparation method of a red mud-based flame retardant material, and the preparation method includes:

[0037] S1. Pretreat the red mud iron tailings to obtain pretreated red mud iron tailings; wherein, the pretreated red mud iron tailings include iron oxide and aluminum oxide;

[0038] S2. Mix an acid source, a gas generating source, an antioxidant, thermoplastic polyurethane, and the pretreated red mud iron tailings to obtain a mixed flame retardant raw material; wherein, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relational expression: 33.33:100 ≤ m1:m2 ≤ 1:1;

[0039] S3. First, extrude and pelletize the mixed flame retardant raw materials to obtain the red mud-based flame retardant material.

[0040] The mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane can satisfy the relationship: m1:m2 = 35:100, 36:100, 37:100, 38:100, 39:100, 40:100, 50:100, 60:100, 70:100, 80:100, 90:100, or 100:100.

[0041] It should be noted that the pretreatment can be grinding, washing, drying, dispersing, screening, or a sequence of grinding, washing, drying, dispersing, and screening.

[0042] It should be noted that the mixing method can be mechanical stirring or ultrasonic oscillation.

[0043] It should be noted that the first extrusion and pelletization can be carried out using a twin-screw extruder.

[0044] It should be noted that the embodiment of the present application provides a preparation method of a red mud-based flame retardant material. This preparation method realizes the dual improvement of flame retardancy and stability through multi-dimensional synergistic effects. The specific mechanism can be summarized as follows:

[0045] 1. Synergy between red mud pretreatment and components:

[0046] (1) Regulation of red mud activity: Fe2O3 and Al2O3 in the pretreated red mud iron tailings will form a bimetallic synergistic system. Fe2O3 will catalyze the process of carbonization reaction at high combustion temperatures, promoting the fracture and recombination of the molecular chains of thermoplastic polyurethane and generating a graphitized carbon layer, while Al2O3 will improve the char residue rate of the flame retardant material by enhancing the lattice stability of the graphitized carbon layer.

[0047] (2) Enhancement of interfacial reaction: The acid source will undergo an in-situ reaction with metal oxides in the red mud to generate AlPO4 and FePO4 glass bodies. These phosphates will be embedded in the pores of the graphitized carbon layer in the form of nanoparticles to form a dense composite barrier, which can improve the limiting oxygen index of the flame retardant material.

[0048] 2. Synergistic effect of the flame retardant system:

[0049] (1) Construction of an expanded carbon layer: The gas generation source will decompose to produce NH3 and H2O at a temperature of 220°C to 280°C. These gases will act together with the CO2 generated by the degradation of thermoplastic polyurethane to increase the expansion ratio of the graphitized carbon layer. The gas diffusion rate is restricted by the Al2O3 framework, forming a honeycomb-like porous structure and reducing the thermal conductivity of the flame retardant material.

[0050] (2) Dynamic crosslinked network: Thermoplastic polyurethane can bind to red mud iron tailings particles through hydrogen bonds and coordination bonds during the first extrusion granulation stage. At the same time, the terminal hydroxyl groups of thermoplastic polyurethane will undergo esterification crosslinking with the acid source, and these reactions will form a crosslinked three-dimensional network structure. This three-dimensional network structure can improve the tensile strength retention rate and elongation at break of the flame retardant material to enhance the stability of the flame retardant material.

[0051] 3. Process parameter optimization:

[0052] (1) Critical filling ratio: When m1:m2 = 33.33:100, the red mud iron tailings particles will be continuously distributed (spacing < 5 μm) in the matrix of thermoplastic polyurethane to enhance the percolation effect of the flame retardant material. After exceeding this threshold, the vertical burning of the flame retardant material will reach V-0 level and have a lower peak heat release rate (pHRR) to further improve the flame retardant performance of the flame retardant material.

[0053] (2) Extrusion process control: Adopt the first extrusion granulation process to promote the grafting reaction between the surface hydroxyl groups of red mud iron tailings and the molecular chains of thermoplastic polyurethane to improve the interfacial bonding strength of the flame retardant material, thereby enhancing the stability of the flame retardant material.

[0054] 4. Stability enhancement mechanism:

[0055] (1) Antioxidant effect: The antioxidant will preferentially adsorb on the surface of red mud iron tailings particles and increase the thermal decomposition temperature of the material by scavenging ·OH free radicals, which can inhibit the yellowing phenomenon during processing.

[0056] (2) Carbon layer self-repairing property: The isocyanate groups generated by the thermal degradation of thermoplastic polyurethane will react with CaO in red mud iron tailings to form a polyurea structure. Under high-temperature conditions, these polyurea structures will dynamically repair the cracks in the carbon layer, enabling the flame retardant material to still maintain a complete layered structure in a high-temperature environment.

[0057] In summary, the embodiment of the present application provides a preparation method of a red mud-based flame retardant material. This preparation method, through the functional modification of red mud iron tailings and the collaborative design of multi-component reactions, while achieving a breakthrough in flame retardant performance, solves the problem of deterioration of mechanical properties caused by traditional inorganic fillers, providing a new way for the high-value utilization of red mud solid waste.

[0058] In some alternative embodiments, the pH value of the pretreated red mud iron tailings is 8 - 10, and the particle size D of the pretreated red mud iron tailings satisfies: 0 mm < D ≤ 0.074 mm.

[0059] In these embodiments, since some raw materials of thermoplastic polyurethane, acid source, gas generating source or antioxidant are highly sensitive to acidity and alkalinity, when the acidity and alkalinity of the pretreated red mud iron ore tailings is 8-10, the pretreated red mud iron ore tailings are in a weakly alkaline state, avoiding the self-decomposition of these raw materials or the extrusion granulation and forming of the flame retardant material due to the excessive acidity or alkalinity of the pretreated iron ore tailings.

[0060] And the particle size D of the pretreated red mud iron ore tailings satisfies: 0mm < D ≤ 0.074mm,

[0061] In some alternative embodiments, the mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = (0.33 - 50.00):(0.33 - 33.33):(0.1 - 2.0):100.

[0062] In these embodiments, the mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = (0.33 - 50.00):(0.33 - 33.33):(0.1 - 2.0):100, so that the flame retardant material has sufficient acid source, gas generating source, antioxidant and thermoplastic polyurethane. Sufficient acid source, gas generating source, antioxidant and thermoplastic polyurethane can react fully and form a dense and stable carbon layer, thereby improving the flame retardancy and stability of the flame retardant material.

[0063] The value of the mass m3 of the acid source can be 0.33, 0.5, 1.0, 5.0, 10.0, 15.0, 20.0, 30.0, 40.0 or 50.0.

[0064] The value of the mass m4 of the gas generating source can be 0.33, 0.5, 1.0, 5.0, 10.0, 15.0, 20.0, 30.0 or 33.33.

[0065] The value of the mass m5 of the antioxidant can be 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5 or 2.0.

[0066] It should be noted that during the combustion of the flame retardant material, the acid source decomposes to produce inorganic acids. These inorganic acids can catalyze the dehydration and carbonization of red mud iron tailings, gas generating source, antioxidant, and thermoplastic polyurethane to form a protective carbon layer with sufficient thickness. These protective carbon layers can prevent the spread of combustion flames, thereby improving the flame retardancy of the flame retardant material. In addition, these inorganic acids can also increase the melting point of the protective carbon layer, enabling the flame retardant material to remain stable under high temperature conditions to prevent the melting and dripping of the flame retardant material, effectively reducing the spread of combustion flames, and thus improving the stability of the flame retardant material.

[0067] It should be noted that after combustion, the gas generating source produces non-flammable or non-combustible gases. These gases play a role in diluting flammable gases to reduce the oxygen concentration in the combustion area and inhibit the combustion process.

[0068] In some alternative embodiments, the types of the acid source include at least one of the following: phosphates, borates, sulfates, and nitrates; and / or

[0069] the types of the gas generating source include at least one of the following: amino compounds, polyols, amino resins, and carbonates; and / or

[0070] the types of the antioxidant include at least one of the following: amines, hindered phenols, sulfur antioxidants, phosphorus antioxidants, and compound antioxidants; and / or

[0071] the types of the thermoplastic polyurethane include at least one of the following: polyester-based polyurethane, polyether-based polyurethane, aliphatic polyurethane, and butadiene-based polyurethane.

[0072] In these embodiments, the types of the acid source can include at least one of the following: phosphates, borates, sulfates, and nitrates, and the types of the gas generating source can include at least one of the following: amino compounds, polyols, amino resins, and carbonates, and the types of the antioxidant can include at least one of the following: amines, hindered phenols, sulfur antioxidants, phosphorus antioxidants, and compound antioxidants, and the types of the thermoplastic polyurethane can include at least one of the following: polyester-based polyurethane, polyether-based polyurethane, aliphatic polyurethane, and butadiene-based polyurethane, which can enable the acid source, gas generating source, antioxidant, thermoplastic polyurethane, and pretreated red mud iron tailings to fully crosslink, ultimately obtaining a dense and stable carbon layer, thereby improving the flame retardancy and stability of the flame retardant material.

[0073] In some alternative embodiments, the temperature of the first extrusion granulation is 100°C to 230°C, and the feeding frequency of the first extrusion granulation is 40 Hz to 160 Hz.

[0074] In these embodiments, the temperature of the first extrusion granulation can be 100°C to 230°C, and the feeding frequency of the first extrusion granulation can be 40 Hz to 160 Hz, such that the first extrusion granulation

[0075] The temperature of the first extrusion granulation can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C or 230°C.

[0076] The feeding frequency of the first extrusion granulation can be 40 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, 90 Hz, 100 Hz, 110 Hz, 120 Hz, 130 Hz, 140 Hz, 150 Hz or 160 Hz.

[0077] It should be noted that when the temperature of the first extrusion granulation is lower than 100°C, the flow and viscosity of the thermoplastic polyurethane may decrease, making the processing of the first extrusion granulation more difficult and resulting in uneven distribution of the components of the prepared red mud-based flame retardant material, with significant differences in the flame retardant effect of the flame retardant material. When the temperature of the first extrusion granulation is higher than 230°C, the thermoplastic polyurethane and other raw materials of the flame retardant material may decompose during the first extrusion granulation.

[0078] It should be noted that when the feeding frequency of the first extrusion granulation is lower than 40 Hz, the thermoplastic polyurethane and the raw materials of the flame retardant material will be in a high-temperature environment for a long time, and being in a high-temperature environment will cause the thermoplastic polyurethane and other raw materials of the flame retardant material to decompose. When the feeding frequency of the first extrusion granulation is higher than 160 Hz, the processing difficulty of the first extrusion granulation will be increased, resulting in uneven distribution of the components of the flame retardant material and significant differences in the flame retardant effect of the flame retardant material.

[0079] Based on a general inventive concept, an embodiment of the present application provides a red mud-based flame retardant material, which is prepared by the preparation method.

[0080] The red mud-based flame retardant material is realized based on the above preparation method. The specific steps of the preparation method can refer to the above embodiments. Since the red mud-based flame retardant material adopts some or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0081] Based on a general inventive concept, an embodiment of the present application provides a flame retardant composite material, which includes a flammable polymer and the flame retardant material, and the mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relationship: m6:m7 = (50 - 90):(10 - 50).

[0082] It should be noted that adding flammable polymers to flame retardant materials has the following advantages:

[0083] 1. Synergistic optimization of flame retardancy efficiency and material properties:

[0084] (1) Flame retardant threshold control: When the proportion of flame retardant material is ≥ 10% (m7 ≥ 10%), inorganic fillers (such as Fe2O3 / Al2O3 in red mud iron ore tailings) will form a continuous phase in the flammable polymer matrix, and the limiting oxygen index (LOI) of the flame retardant composite material can be increased by catalyzing the carbonization reaction to meet the UL-94 V-1 standard. When the proportion of flame retardant material is increased to 30%, the thickness of the expanded carbon layer formed by the flame retardant material and the flammable polymer can reach a relatively high level, and the peak heat release rate (pHRR) will also be reduced.

[0085] (2) Retention of mechanical properties: When the mass of the flammable polymer m6 ≥ 50%, matrix materials such as thermoplastic polyurethane and polypropylene of the flame retardant material can still maintain relatively high tensile strength and elongation at break.

[0086] 2. Improvement of processing technology adaptability:

[0087] (1) Regulation of melt fluidity: When the proportion of flame retardant material is ≤ 50%, the melt index (MFI) of the flame retardant composite material can be maintained at a relatively high level to meet the requirements of the twin-screw extrusion process. The red mud iron ore tailings particles form hydrogen bonds with the molecular chains of the flammable polymer through surface hydroxyl groups, and these hydrogen bonds can inhibit the agglomeration of the fillers in the flame retardant composite material.

[0088] (2) Guarantee of dispersion uniformity: By controlling the critical mass fraction of the flame retardant material, the spacing of the red mud iron ore tailings particles in the matrix remains < 5 μm, avoiding the interfacial peeling of the flame retardant material caused by stress concentration. This characteristic can improve the green body forming efficiency of the flame retardant composite material in the preparation of the flame retardant composite material.

[0089] 3. Balance of functional characteristics:

[0090] (1) Coupling of lightweight and heat insulation: When the mass of the flame retardant material m7 = 20%, the density of the flame retardant composite material can be reduced, and at the same time, the thermal conductivity coefficient of the flame retardant composite material will also be reduced, and the A-level fire protection requirements in the building field can be achieved.

[0091] (2) Enhancement of environmental stability: The phosphate glass body formed by the reaction of the metal oxide (such as Al2O3) of the flame retardant material with the acid source can inhibit the thermal oxygen degradation of the polymer matrix, so that after the composite material is aged for 1000 h in an environment of 85°C / 85% RH, the attenuation of mechanical properties is at a relatively low level.

[0092] 4. Economy and Sustainability:

[0093] (1) Optimization of raw material cost: When the addition amount of solid waste of red mud iron tailings reaches 30%, the total cost of the flame retardant composite material can be reduced, and at the same time, the flame retardant composite material can meet the EN 45545-2 rail transit flame retardant standard.

[0094] (2) Recycling compatibility: Within this ratio range, the compatibility between the flame retardant material and the polymer is good, and it can be recycled multiple times through melt regranulation, and the LOI of the recycled material still remains at a relatively high level.

[0095] In summary, a flame retardant composite material provided by an embodiment of the present application. The ratio design of the flame retardant composite material breaks through the bottleneck of mechanical property deterioration caused by traditional high filling amounts while meeting the flame retardant grading requirements of GB 8624-2012 building materials through the dynamic balance of the flame retardant percolation effect and the matrix continuous phase.

[0096] The value of the mass m6 of the flammable polymer can be 50, 55, 60, 65, 70, 75, 80, 85 or 90.

[0097] The value of the mass m7 of the flame retardant material can be 10, 15, 20, 25, 30, 35, 40, 45 or 50.

[0098] The flame retardant composite material is realized based on the above flame retardant material. The specific composition of the flame retardant material can refer to the above embodiments. Since the flame retardant composite material adopts some or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated one by one here.

[0099] In some alternative embodiments, the types of the flammable polymer include at least one of the following: polyoxymethylene, polyurethane, polypropylene, polyvinyl chloride, polyester, polyurethane, polycarbonate and polyvinyl alcohol.

[0100] In these embodiments, the types of the flammable polymer can include at least one of the following: polyoxymethylene, polyurethane, polypropylene, polyvinyl chloride, polyester, polyurethane, polycarbonate and polyvinyl alcohol, so that the flammable polymer can cover most types of flammable polymers, and the flammable polymer can fully coat the flame retardant material to form a microcapsule charring agent. This microcapsule charring agent can exhibit good flame retardant performance and will not significantly reduce the mechanical properties of the flame retardant composite material.

[0101] Figure 2 Exemplarily shows a schematic flow chart of a preparation method of a flame retardant composite material provided by an embodiment of the present application;

[0102] Based on a general inventive concept, asFigure 2 As shown in the figure, an embodiment of the present application provides a method for preparing the flame retardant composite material, and the method includes:

[0103] S1. Mix the flammable polymer and the flame retardant material to obtain a mixed raw material;

[0104] S2. Perform second extrusion granulation on the mixed raw material to obtain flame retardant composite material particles;

[0105] S3. Perform injection molding on the flame retardant composite material particles to obtain a flame retardant composite material.

[0106] This method is for the preparation method of the above-mentioned flame retardant composite material. The specific composition of the flame retardant composite material can refer to the above embodiment. Since this method adopts some or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, and will not be elaborated here one by one.

[0107] It should be noted that the second extrusion granulation can be carried out using a twin-screw extruder for extrusion granulation.

[0108] In some optional embodiments, the temperature of the second extrusion granulation is 160°C to 180°C, and the feeding frequency of the second extrusion granulation is 80Hz to 160Hz; and / or

[0109] The injection molding includes a molding section, a holding pressure section and a cooling section. The temperature of the molding section is 160°C to 180°C, the pressure of the molding section is 0.20MPa to 0.60MPa, the time of the holding pressure section is 2s to 10s, and the time of the cooling section is 10s to 60s.

[0110] In these embodiments, the temperature of the second extrusion granulation can be 160°C to 180°C, and the feeding frequency of the second extrusion granulation can be 80Hz to 160Hz, so that the flammable polymer and the flame retardant material can be fully melted and mixed during the second extrusion granulation, and at the same time, the thermosensitive components of the flammable polymer are prevented from decomposing to form flame retardant composite material particles with regular particle morphology; in addition, the injection molding can include a molding section, a holding pressure section and a cooling section, and the temperature of the molding section can be 160°C to 180°C, and the pressure of the molding section can be 0.20MPa to 0.60MPa, and the time of the holding pressure section can be 2s to 10s, and the time of the cooling section can be 10s to 60s, which can increase the melt flow length of the flame retardant composite material particles to avoid the surface fiber floating defect caused by the migration of the flame retardant composite material particles. At the same time, the holding pressure and cooling stages can eliminate the internal air holes of the flame retardant composite material and improve the gradient crystallization degree of the flame retardant composite material, thereby effectively improving the mechanical properties of the flame retardant composite material.

[0111] The temperature of the second extrusion granulation can be 160°C, 165°C, 170°C, 175°C or 180°C.

[0112] The feeding frequency of the second extrusion granulation can be 80Hz, 90Hz, 100Hz, 110Hz, 120Hz, 130Hz, 140Hz, 150Hz or 160Hz.

[0113] The temperature of the shaping section can be 160°C, 165°C, 170°C, 175°C or 180°C.

[0114] The pressure of the shaping section can be 0.20MPa, 0.30MPa, 0.40MPa, 0.50MPa or 0.60MPa.

[0115] The time of the pressure holding section can be 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s or 10s.

[0116] The time of the cooling section can be 10s, 20s, 30s, 40s, 50s or 60s.

[0117] The present application will be further elaborated below in conjunction with specific embodiments. For the experimental methods without specific conditions indicated in the following embodiments, they are usually determined according to national standards / industry standards; if there are no corresponding national standards / industry standards, they are carried out according to general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0118] Example 1

[0119] As Figure 1 shown, a preparation method of a red mud-based flame retardant material, the preparation method includes:

[0120] S1. The red mud iron tailings are successively subjected to grinding, washing, drying, dispersion and 200-mesh screening to obtain pretreated red mud iron tailings; wherein, the pretreated red mud iron tailings include iron oxide and alumina;

[0121] S2. 13.47g of acid source, 0.09g of gas generating source, 0.54g of antioxidant, 26.93g of thermoplastic polyurethane and 8.98g of pretreated red mud iron tailings are mixed to obtain a mixed flame retardant raw material; wherein, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m1:m2 = 33.33:100;

[0122] S3. The mixed flame retardant raw material is subjected to the first extrusion granulation to obtain a red mud-based flame retardant material.

[0123] The pH value of the pretreated red mud iron tailings is 10, and the particle size D of the pretreated red mud iron tailings satisfies: 0mm < D ≤ 0.074mm.

[0124] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant, and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = 50:0.33:2:100.

[0125] The type of the acid source is ammonium polyphosphate;

[0126] The type of the gas generating source is melamine;

[0127] The antioxidant is antioxidant 1010 from Henan Kaifeng Longyu Chemical Co., Ltd.;

[0128] The thermoplastic polyurethane is TPU 6385A from Wanhua Chemical Group Co., Ltd.

[0129] The temperature of the first extrusion granulation is 100 °C, and the feeding frequency of the first extrusion granulation is 40 Hz.

[0130] A red mud-based flame retardant material, which is prepared by the preparation method.

[0131] A flame retardant composite material, which includes a flammable polymer and a flame retardant material. The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relationship: m6:m7 = 90:10.

[0132] The type of the flammable polymer is polyoxymethylene.

[0133] As Figure 2 shown, a method for preparing a flame retardant composite material, the method includes:

[0134] S1. Mix 450 g of the flammable polymer and the flame retardant material to obtain a mixed raw material;

[0135] S2. Perform second extrusion granulation on the mixed raw material to obtain flame retardant composite material particles;

[0136] S3. Perform injection molding on the flame retardant composite material particles to obtain a flame retardant composite material.

[0137] The temperature of the second extrusion granulation is 160 °C, and the feeding frequency of the second extrusion granulation is 80 Hz;

[0138] The injection molding includes a molding section, a pressure holding section, and a cooling section. The temperature of the molding section is 160 °C, the pressure of the molding section is 0.0 MPa, the time of the pressure holding section is 10 s, and the time of the cooling section is 10 s.

[0139] Example 2

[0140] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0141] S2. Mix 41.67 g of acid source, 7.5 g of gas generating source, 0.83 g of antioxidant, 83.33 g of thermoplastic polyurethane, and 66.67 g of pretreated red mud iron tailings to obtain a mixed flame retardant raw material; among them, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m1:m2 = 80:100.

[0142] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant, and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = 50:9:1:100.

[0143] The type of the acid source is ammonium polyphosphate;

[0144] The type of the gas generating source is melamine;

[0145] The antioxidant is antioxidant 1010 from Henan Kaifeng Longyu Chemical Co., Ltd.;

[0146] The thermoplastic polyurethane is TPU 6385A from Wanhua Chemical Group Co., Ltd.

[0147] The temperature of the first extrusion granulation is 160 °C, and the feeding frequency of the first extrusion granulation is 160 Hz.

[0148] The mass of the flammable polymer is 300 g.

[0149] The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relationship: m6:m7 = 60:40.

[0150] The temperature of the second extrusion granulation is 170 °C, and the feeding frequency of the second extrusion granulation is 160 Hz;

[0151] The temperature of the molding section is 170 °C, the pressure of the molding section is 0.30 MPa, the time of the pressure holding section is 2 s, and the time of the cooling section is 10 s.

[0152] Example 3

[0153] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0154] S2. Mix 0.35 g of acid source, 35.65 g of gas generating source, 0.1 g of antioxidant, 106.95 g of thermoplastic polyurethane, and 106.95 g of pretreated red mud iron tailings to obtain a mixed flame retardant raw material; among them, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m1:m2 = 100:100.

[0155] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant, and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = 0.33:33.33:0.1:100.

[0156] The type of the acid source is ammonium polyphosphate;

[0157] The type of the gas generating source is melamine;

[0158] The antioxidant is antioxidant 1010 from Henan Kaifeng Longyu Chemical Co., Ltd.;

[0159] The thermoplastic polyurethane is TPU 6385A from Wanhua Chemical Group Co., Ltd.

[0160] The temperature of the first extrusion granulation is 230 °C, and the feeding frequency of the first extrusion granulation is 120 Hz.

[0161] The mass of the flammable polymer is 250 g.

[0162] The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relationship: m6:m7 = 50:50.

[0163] The temperature of the second extrusion granulation is 180 °C, and the feeding frequency of the second extrusion granulation is 120 Hz;

[0164] The temperature of the molding section is 180 °C, the pressure of the molding section is 0.6 MPa, the holding time of the pressure holding section is 2 s, and the cooling time of the cooling section is 60 s.

[0165] Example 4

[0166] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0167] S2. Mix 41.67 g of the acid source, 7.5 g of the gas generating source, 0.83 g of the antioxidant, 83.33 g of the thermoplastic polyurethane, and 66.67 g of the pretreated red mud iron tailings to obtain a mixed flame retardant raw material; among them, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m1:m2 = 80:100.

[0168] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant, and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = 50:9:1:100.

[0169] The type of the acid source is ammonium dihydrogen phosphate;

[0170] The type of the gas generating source is magnesium carbonate;

[0171] The antioxidant is antioxidant 168 from Henan Kaifeng Longyu Chemical Co., Ltd.

[0172] The thermoplastic polyurethane is TPU 6385A of Wanhua Chemical Group Co., Ltd.

[0173] The temperature of the first extrusion granulation is 160 °C, and the feeding frequency of the first extrusion granulation is 80 Hz.

[0174] The mass of the flammable polymer is 300 g.

[0175] The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relation: m6:m7 = 60:40.

[0176] The temperature of the second extrusion granulation is 170 °C, and the feeding frequency of the second extrusion granulation is 160 Hz;

[0177] The injection molding includes a molding section, a holding pressure section and a cooling section. The temperature of the molding section is 170 °C, the pressure of the molding section is 0.30 MPa, the time of the holding pressure section is 2 s, and the time of the cooling section is 10 s.

[0178] Example 5

[0179] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0180] S2. Mix 41.67 g of acid source, 7.5 g of gas generating source, 0.83 g of antioxidant, 83.33 g of thermoplastic polyurethane and 66.67 g of pretreated red mud iron tailings to obtain a mixed flame retardant raw material; wherein, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relation: m1:m2 = 80:100.

[0181] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant and the mass m2 of the thermoplastic polyurethane satisfy the relation: m3:m4:m5:m2 = 50:9:1:100.

[0182] The type of the acid source is sodium pyrophosphate;

[0183] The type of the gas generating source is sodium bicarbonate;

[0184] The antioxidant is antioxidant 1076 of Henan Kaifeng Longyu Chemical Co., Ltd.;

[0185] The thermoplastic polyurethane is TPU 6385A of Wanhua Chemical Group Co., Ltd.

[0186] The temperature of the first extrusion granulation is 160 °C, and the feeding frequency of the first extrusion granulation is 80 Hz.

[0187] The mass of the flammable polymer is 300 g.

[0188] The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relation: m6:m7 = 60:40.

[0189] The temperature of the second extrusion granulation is 170 °C, and the feeding frequency of the second extrusion granulation is 160 Hz;

[0190] The injection molding includes a molding section, a pressure holding section, and a cooling section. The temperature of the molding section is 170 °C, the pressure of the molding section is 0.30 MPa, the time of the pressure holding section is 2 s, and the time of the cooling section is 10 s.

[0191] Comparative Example 1

[0192] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0193] The pretreated red mud iron tailings are not added. The specific process is as follows:

[0194] S2. Mix 41.67 g of acid source, 7.5 g of gas generating source, 0.83 g of antioxidant, and 83.33 g of thermoplastic polyurethane to obtain a mixed flame retardant raw material.

[0195] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant, and the mass m2 of the thermoplastic polyurethane satisfy the relation: m3:m4:m5:m2 = 50:9:1:100.

[0196] The type of the acid source is ammonium polyphosphate;

[0197] The type of the gas generating source is melamine;

[0198] The antioxidant is antioxidant 1010 from Henan Kaifeng Longyu Chemical Co., Ltd.;

[0199] The thermoplastic polyurethane is TPU 6385A from Wanhua Chemical Group Co., Ltd.

[0200] The temperature of the first extrusion granulation is 120 °C, and the feeding frequency of the first extrusion granulation is 80 Hz.

[0201] The mass of the flammable polymer is 366.67 g.

[0202] The mass m6 of the flammable polymer and the mass m7 of the mixed flame retardant raw material satisfy the relation: m6:m7 = 73.3:26.67.

[0203] The temperature of the second extrusion granulation is 170 °C, and the feeding frequency of the second extrusion granulation is 160 Hz;

[0204] The injection molding includes a molding section, a pressure holding section, and a cooling section. The temperature of the molding section is 170 °C, the pressure of the molding section is 0.30 MPa, the time of the pressure holding section is 2 s, and the time of the cooling section is 10 s.

[0205] Comparative Example 2

[0206] Based on the content disclosed in Example 1, the following further modifications are made:

[0207] Do not add thermoplastic polyurethane. The specific process is as follows:

[0208] S2. Mix 41.67 g of acid source, 7.5 g of gas generating source, 0.83 g of antioxidant and 66.67 g of pretreated red mud iron tailings to obtain a mixed flame retardant raw material.

[0209] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant and the mass m1 of the pretreated red mud iron tailings satisfy the relationship: m3:m4:m5:m1 = 50:9:1:80.

[0210] The mass of the flammable polymer is 383.33 g.

[0211] Comparative Example 3

[0212] Based on the content disclosed in Example 1, the following further modifications are made:

[0213] Do not perform the first extrusion granulation process. The specific process is as follows:

[0214] S2. Mix 41.67 g of acid source, 7.5 g of gas generating source, 0.83 g of antioxidant, 83.33 g of thermoplastic polyurethane and 66.67 g of pretreated red mud iron tailings to obtain a mixed flame retardant raw material; among them, the mass m1 of the pretreated red mud iron tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m1:m2 = 80:100.

[0215] The pH value of the pretreated red mud iron tailings is 10.

[0216] The mass m3 of the acid source, the mass m4 of the gas generating source, the mass m5 of the antioxidant and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2 = 50:9:1:100.

[0217] The type of the acid source is ammonium polyphosphate;

[0218] The type of the gas generating source is melamine;

[0219] The antioxidant is antioxidant 1010 from Henan Kaifeng Longyu Chemical Co., Ltd.;

[0220] The thermoplastic polyurethane is TPU 6385A from Wanhua Chemical Group Co., Ltd.

[0221] The temperature of the first extrusion granulation is 120 °C, and the feeding frequency of the first extrusion granulation is 80 Hz.

[0222] The mass of the flammable polymer is 300 g.

[0223] The mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relation: m6:m7 = 60:40.

[0224] The temperature of the second extrusion granulation is 170 °C, and the feeding frequency of the second extrusion granulation is 80 Hz;

[0225] The injection molding includes a molding section, a holding pressure section, and a cooling section. The temperature of the molding section is 170 °C, the pressure of the molding section is 0.40 MPa, the time of the holding pressure section is 2 s, and the time of the cooling section is 10 s.

[0226] Comparative Example 4

[0227] On the basis of the content disclosed in Example 2, the following further modifications are made:

[0228] The temperature of the first extrusion granulation is 50 °C, and the feeding frequency of the first extrusion granulation is 200 Hz.

[0229] Comparative Example 5

[0230] On the basis of the content disclosed in Example 2, the following further modifications are made:

[0231] The temperature of the first extrusion granulation is 300 °C, and the feeding frequency of the first extrusion granulation is 20 Hz.

[0232] Related experiments and effect data:

[0233] The performance of the flame retardant composite materials obtained in each example and comparative example is analyzed, and the results are shown in Table 1.

[0234] Table 1 Performance distribution of the flame retardant composite materials in each example and comparative example

[0235]

[0236] From the data in Table 1, it can be seen that for a flame retardant composite material provided by an embodiment of the present application, as the mass ratio of the red mud-based flame retardant material in the flame retardant composite material increases, the flame retardant effect of the flame retardant composite material shows an obvious upward trend, but the mechanical properties show a continuous downward trend. In addition, by comparing each example, it can be found that when the proportion of the pretreated red mud iron ore tailings is appropriately reduced and the proportion of the acid source is appropriately increased at the same time, the flame retardant effect of the flame retardant composite material will be improved to a certain extent, but the mechanical properties show a slightly decreasing phenomenon.

[0237] It can be found from the data comparison between Example 2 and Comparative Example 1 that the introduction of pretreated red mud iron tailings will greatly improve the flame retardant performance of the flame retardant composite material, making the vertical burning grade of the flame retardant composite material rise from no grade to the highest grade V-0, and the limiting oxygen index increase significantly from 25.2% to 43.5%. Thus, a flame retardant composite material with good flame retardant effect can be obtained. Although the introduction of red mud iron tailings causes partial loss of the mechanical properties of the flame retardant composite material, this loss of mechanical properties is within the standard range of normal flame retardant composite materials.

[0238] It can be found from the data comparison between Example 2 and Comparative Example 2 and Comparative Example 3 that the introduction of thermoplastic polyurethane 6385A into the composite material will not reduce the flame retardant performance of the flame retardant composite material itself. In addition, the introduction of thermoplastic polyurethane can effectively improve the tensile performance of the flame retardant composite material.

[0239] It can be found from the data comparison between Example 2 and Comparative Example 3 that when the flame retardant material is simply mixed with the flammable polymer and then directly subjected to the second extrusion granulation process, in the extrusion granulation process, due to the flammable polymer and other various materials being sensitive to acidity, alkalinity and temperature, in the case where the red mud iron tailings directly contact the raw materials of the flame retardant material, the directly contacted red mud iron tailings will not only affect the fluidity of the material in the second extrusion granulation stage of the flame retardant material, but also increase the difficulty of the second extrusion granulation and injection molding. In severe cases, it will even cause the decomposition of the flammable polymer. Therefore, the first extrusion granulation process used for the flame retardant material can greatly improve the convenience and stability of the flame retardant composite material in the preparation stage.

[0240] It can be found from the data comparison between Example 2 and Comparative Example 4 and Comparative Example 5 that when the base temperature is too low, the flow and viscosity of thermoplastic polyurethane are greatly reduced, making the extrusion granulation process more difficult and resulting in uneven distribution of the components of the prepared red mud-based flame retardant material, and the flame retardant effect of the flame retardant material decreases significantly. Under the condition that the temperature of the first extrusion granulation is higher than 230 °C, it may cause the decomposition of thermoplastic polyurethane and other raw materials of the flame retardant material during the first extrusion granulation, which will also greatly affect the flame retardant performance and mechanical properties of the composite material. When the feeding frequency is lower than 40 Hz, thermoplastic polyurethane and the raw materials of the flame retardant material will be in a high-temperature environment for a long time, and being in a high-temperature environment will cause the decomposition of thermoplastic polyurethane and other raw materials of the flame retardant material. When the feeding frequency is higher than 160 Hz, it will increase the processing difficulty of the first extrusion granulation, making the component distribution of the flame retardant material uneven, and the flame retardant effect and mechanical properties of the flame retardant material decrease significantly.

[0241] In summary, the preparation method of a red mud-based flame retardant material provided by the embodiments of the present application realizes a breakthrough in flame retardant performance and solves the problem of mechanical property deterioration caused by traditional inorganic fillers through the synergistic design of functional modification and multi-component reaction of red mud iron tailings, providing a new way for the high-value utilization of red mud solid waste.

[0242] In addition, the preparation method of a flame retardant composite material provided by the embodiments of the present application uses a flammable polymer and the above-mentioned flame retardant material for mixing, so that the flammable polymer can coat the flame retardant material to form a microcapsule charring agent. This microcapsule charring agent can exhibit good flame retardant performance and will not significantly reduce the mechanical properties of the flame retardant composite material.

[0243] In addition, a flame retardant composite material provided by the embodiments of the present application can effectively utilize red mud iron tailings, greatly reduce the stockpile of red mud iron tailings, reduce the waste of land resources, and increase the service life of the red mud yard. And this flame retardant composite material can also realize the green and high-value utilization of red mud iron tailings, improve the utilization rate of red mud resources, and is of great significance to the sustainable development of the alumina industry.

[0244] The above are only the specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features claimed in the present application.

Claims

1. A method for preparing a red mud-based flame retardant material, the preparation method comprising: Pre-treating the red mud iron-draining tailings to obtain pre-treated red mud iron-draining tailings; wherein the pre-treated red mud iron-draining tailings include iron oxide and aluminum oxide; The acid source, the gas source, the antioxidant, the thermoplastic polyurethane and the pretreated red mud iron-separation tailings are mixed to obtain a mixed flame-retardant raw material; wherein the mass m1 of the pretreated red mud iron-separation tailings and the mass m2 of the thermoplastic polyurethane satisfy the relationship: 33.33:100≤m1:m2≤1:1; The mixed flame retardant raw material is subjected to a first extrusion granulation to obtain a red mud-based flame retardant material.

2. The preparation method according to claim 1, wherein the pH value of the pretreated red mud iron-separation tailings is 8 to 10, and the particle size D of the pretreated red mud iron-separation tailings satisfies: 0 mm < D ≤ 0.074 mm.

3. According to the preparation method of claim 1, the mass m3 of the acid source, the mass m4 of the gas source, the mass m5 of the antioxidant and the mass m2 of the thermoplastic polyurethane satisfy the relationship: m3:m4:m5:m2=(0.33~50.00):(0.33~33.33):(0.1~2.0):

100.

4. The preparation method according to claim 1, wherein the type of the acid source comprises at least one of the following: phosphate, borate, sulfate and nitrate; and / or The gas source comprises at least one of the following: amino compounds, polyols, amino resins and carbonates; and / or The antioxidant comprises at least one of the following: amines, hindered phenols, sulfur antioxidants, phosphorus antioxidants and composite antioxidants; and / or The types of the thermoplastic polyurethane include at least one of the following: polyester polyurethane, polyether polyurethane, aliphatic polyurethane and butadiene polyurethane. 5 . The preparation method according to claim 1 , wherein the temperature of the first extrusion granulation is 100° C. to 230° C., and the feeding frequency of the first extrusion granulation is 40 Hz to 160 Hz.

6. A red mud-based flame retardant material, wherein the flame retardant material is prepared by the preparation method according to any one of claims 1 to 5.

7. A flame retardant composite material, comprising a flammable polymer and the flame retardant material according to claim 6, wherein the mass m6 of the flammable polymer and the mass m7 of the flame retardant material satisfy the relationship: m6:m7=(50-90):(10-50).

8. The flame-retardant composite material according to claim 7, wherein the type of the flammable polymer comprises at least one of the following: polyoxymethylene, polyurethane, polypropylene, polyvinyl chloride, polyester, polyurethane, polycarbonate and polyvinyl alcohol.

9. A method for preparing the flame retardant composite material according to claim 7 or 8, the method comprising: Mixing the flammable polymer and the flame retardant material to obtain a mixed raw material; The mixed raw material is subjected to a second extrusion granulation to obtain flame retardant composite material particles; The flame retardant composite material particles are injection molded to obtain a flame retardant composite material.

10. The method according to claim 9, wherein the temperature of the second extrusion granulation is 160°C to 180°C, and the feeding frequency of the second extrusion granulation is 80 Hz to 160 Hz; and / or The injection molding comprises a molding section, a pressure holding section and a cooling section. The temperature of the molding section is 160° C. to 180° C., the pressure of the molding section is 0.20 MPa to 0.60 MPa, the time of the pressure holding section is 2s to 10s, and the time of the cooling section is 10s to 60s.

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