A fire-retardant and heat-insulating polypropylene composite honeycomb board and a preparation method thereof

Abstract

The application discloses a preparation method of a flame-retardant and heat-insulating polypropylene composite honeycomb board and belongs to the technical field of high polymer materials, and is used for solving the technical problem that the flame-retardant and heat-insulating performance of the polypropylene honeycomb board needs to be further strengthened in the prior art, wherein the preparation method of the flame-retardant and heat-insulating polypropylene composite particle comprises the following steps: under a nitrogen atmosphere, polypropylene is heated and kept warm, an intermediate III and BPO are added, stirring is conducted, heating and keeping warm are conducted, cooling is conducted, ethyl acetate extraction is conducted, drying is conducted, and modified polypropylene is obtained; the modified polypropylene is heated and melted, an antioxidant, a lubricant, maleic anhydride grafted polypropylene and a flame retardant are added, uniform stirring is conducted, extrusion granulation is conducted, drying is conducted, and the flame-retardant and heat-insulating polypropylene composite particle is obtained. The flame-retardant and heat-insulating polypropylene composite honeycomb board prepared by the method has good flame-retardant and heat-insulating performance and also has good structural stability.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant and heat-insulating polypropylene composite honeycomb board and its preparation method. Background Technology

[0002] Polypropylene (PP) materials are characterized by low density, chemical resistance, good fatigue resistance, and excellent processing and molding properties, making them widely used in building decoration, transportation, packaging, and composite panels. Compared to traditional solid PP sheets, honeycomb structure sheets, through the formation of a regular honeycomb structure within the sheet, can reduce the overall weight of the sheet while increasing the specific strength and specific stiffness of the material, thus showing promising application prospects in the field of lightweight thermal insulation panels. However, PP is a flammable thermoplastic material with a low limiting oxygen index, making it prone to melting, softening, and continuous combustion upon heating, potentially accompanied by dripping during combustion. This limits its application in areas requiring high flame retardancy. Existing technologies typically improve its flame retardancy by adding flame retardants to the PP matrix, but uneven dispersion of the flame retardant with PP can affect the molding quality and performance of the honeycomb sheet.

[0003] Existing polypropylene honeycomb panels primarily utilize the honeycomb structure to reduce material weight and increase structural rigidity. However, the numerous interconnected cavities within the honeycomb cells, while reducing heat conduction to some extent, still influence thermal insulation performance due to factors such as cell size, cell wall thickness, pore structure, and the surface structure of the panel. When the bonding between the honeycomb structure and the surface layer is insufficient, or when the sides of the honeycomb cells are open, heat transfer channels can easily form at the panel edges. Furthermore, dust, moisture, or other media may enter the honeycomb cells, affecting the panel's long-term thermal insulation performance.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a flame-retardant and heat-insulating polypropylene composite honeycomb board and its preparation method, solving the technical problem that the flame-retardant and heat-insulating properties of polypropylene honeycomb boards in the prior art need to be further enhanced.

[0006] To achieve the above objectives, the present invention provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, comprising the following steps:

[0007] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0008] S2. Polypropylene particles are fed into a single-screw extruder to melt, and then extruded through a flat die to form upper and lower surface sheets.

[0009] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets and hot-press it together. Let it stand at room temperature, cut it, and seal the edges to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0010] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0011] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol are mixed, the reaction is completed, filtered, washed and dried to obtain intermediate I;

[0012] Step (2) Add intermediate I and catalyst to acetone, heat to react, and after the reaction is complete, filter under reduced pressure, wash, and dry to obtain intermediate II;

[0013] Step (3) Add intermediate II and modified hydrotalcite to anhydrous ethanol, heat to react, cool to room temperature after the reaction is complete, collect the solid by vacuum filtration under reduced pressure, wash, and vacuum dry to obtain intermediate III;

[0014] Step (4) Under a nitrogen atmosphere, polypropylene is heated and kept warm, intermediate III and BPO are added, stirred, heated and kept warm, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene;

[0015] Modified polypropylene is heated and melted, and antioxidants, lubricants, maleic anhydride-grafted polypropylene and flame retardants are added. The mixture is stirred evenly, extruded and granulated, and dried to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0016] Preferably, the melt index of the flame-retardant and heat-insulating polypropylene composite particles is 2.2-5 g / 10 min; the melt index of the polypropylene particles is 2-5.8 g / 10 min.

[0017] Preferably, in step (3), the modified hydrotalcite is prepared as follows:

[0018] Hydrotalcite was calcined at high temperature to obtain an intermediate. Under a nitrogen atmosphere, the intermediate was added to a mixed solution and heated to react. After the reaction was completed, the solution was filtered, washed, and added to distilled water to obtain an intercalated hydrotalcite slurry. Aminosilane was added, ultrasonically dispersed, and heated to react. After the reaction was completed, the solution was filtered, washed, and dried to obtain modified hydrotalcite.

[0019] Preferably, the aminosilane includes any one of γ-aminopropyltriethoxysilane, methyl(γ-aminopropyl)diethoxysilane, and γ-aminopropyltrimethoxysilane.

[0020] Preferably, in step (1), the preparation method of epoxy-modified silica is as follows:

[0021] Silica, anhydrous ethanol, and epoxy silane coupling agent are mixed evenly and heated to react. After the reaction is complete, the mixture is centrifuged and dried to obtain epoxy-modified silica.

[0022] Preferably, in step (1), the mass ratio of N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol is (2000-4000):(40-60):(80-100); the reaction temperature is 60-75℃ and the reaction time is 30-34h.

[0023] Preferably, in step (2), the mass ratio of intermediate I, catalyst and acetone is (100-140):(0.4-0.6):(1000-1600); the reaction temperature is 56-58℃ and the reaction time is 5-7h; wherein the catalyst is aluminum isopropoxide.

[0024] Preferably, in step (3), the molar ratio of intermediate II to modified hydrotalcite is 1:1; the reaction temperature is 60-70℃; and the reaction time is 6-10h.

[0025] Preferably, in step (4), the mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is (220-340):(20-40):(0.3-0.5):(2000-3200).

[0026] Preferably, in step (4), the mass ratio of modified polypropylene, antioxidant, lubricant, maleic anhydride-grafted polypropylene and flame retardant is (80-100):(0.2-0.8):(0.4-1):(4-10):(12-16).

[0027] Preferably, in step (4), the melting temperature is 170-180℃.

[0028] Preferably, the temperatures of each zone in the single-screw extruder in S1 are as follows: Zone 1 170-180℃, Zone 2 180-200℃, Zone 3 200-210℃; and the die temperature is 211-215℃.

[0029] Preferably, the temperatures of each zone in the single-screw extruder in S2 are as follows: Zone 1 180-190℃, Zone 2 200-210℃, Zone 3 210-220℃; and the die temperature 221-225℃.

[0030] Preferably, the temperature for hot pressing in S3 is 160-165℃ and the pressure is 0.3-0.5MPa.

[0031] Preferably, in step (4), the first heating temperature is 60-70℃ and the holding time is 1-2h; the second heating temperature is 85-95℃ and the holding time is 20-30min.

[0032] Preferably, the mass ratio of silica, anhydrous ethanol and epoxy silane coupling agent is (55-75):(1000-1600):(30-50); the reaction temperature is 60-80℃, and the reaction time is 5-7h.

[0033] Preferably, the epoxy silane coupling agent is any one of epoxypropoxyoctyltrimethoxysilane, epoxypropoxybutyltrimethoxysilane, and epoxypropoxypropylmethyldimethoxysilane.

[0034] Preferably, the silicon dioxide is in the micrometer size.

[0035] Preferably, the vacuum drying conditions are: -0.08 MPa and drying at 45-50°C for 4-6 hours.

[0036] Preferably, the high-temperature calcination conditions are: calcination at 400-440℃ for 4-6 hours.

[0037] Preferably, the mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is (40-50):(180-280):(18-24).

[0038] Preferably, the mass ratio of the intermediate, the mixed solution, and the distilled water is (6-8):(30-40):(20-30); the reaction conditions are 70-75℃ for 6-8 hours.

[0039] Preferably, the ultrasound conditions are: ultrasound at a frequency of 20-40 kHz for 6-10 minutes.

[0040] Preferably, the mass ratio of the intercalated hydrotalcite slurry to aminosilane is (140-180):(12-16); the reaction conditions are 50-60℃ for 2.5-4.5h.

[0041] Preferably, the flame retardant is zinc borate.

[0042] Preferably, the antioxidant is antioxidant 168.

[0043] Preferably, the lubricant is calcium stearate.

[0044] Preferably, a flame-retardant and heat-insulating polypropylene composite honeycomb board is prepared using the aforementioned method.

[0045] In this invention, the epoxy group in epoxy-modified silica undergoes a ring-opening reaction with the hydroxyl group of 3-buten-1-ol to obtain intermediate I; the hydroxyl group in intermediate I is selectively oxidized by aluminum isopropoxide catalyst to obtain intermediate II containing aldehyde group and carbon-carbon unsaturated double bond; the aldehyde group in intermediate II reacts with the amino group in modified hydrotalcite to obtain imine group (-C=N-); the carbon-carbon unsaturated double bond contained in intermediate III undergoes a solid-phase grafting reaction with polypropylene under the action of an initiator to obtain modified polypropylene.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] 1. The silica used in this invention is itself an inorganic heat-resistant particle. Epoxy-modified silica has better compatibility with polypropylene, improving its dispersibility and allowing it to be uniformly dispersed in the polypropylene matrix. This prevents structural defects caused by inorganic particle agglomeration and simultaneously improves the heat resistance of the matrix material. Modified hydrotalcite, after modification, has increased reactive sites. It forms Schiff base structures (-C=N-) through aldehyde-amine condensation and subsequently connects to polypropylene via chemical bonds, ensuring dispersion stability and avoiding mechanical and heat-resistant defects caused by agglomeration. Furthermore, during high-temperature combustion, hydrotalcite decomposes and releases non-flammable gases, diluting the concentration of combustible products generated by polypropylene pyrolysis and slowing the combustion spread rate. The resulting magnesium and aluminum oxides also serve as an inorganic framework, supporting the char layer and maintaining its structural integrity. Zinc borate is a flame retardant that also promotes char formation and glass phase construction. During heating, it gradually decomposes to generate molten B2O3, which can promote the dehydration and carbonization of the matrix, accelerate the formation of a dense char layer, and fill the pores and defects in the char layer. It reacts with silica at high temperatures to generate a more stable borosilicate glassy continuous phase, further blocking the transfer of oxygen and combustible pyrolysis gases, while also preventing heat conduction to unburned areas. Zinc borate works synergistically with the nitrogen-rich char layer constructed from Schiff bases, the inorganic framework provided by silica and magnesium aluminum oxides, and the three work together to form a composite char layer that combines structural strength and barrier function. This not only prevents the char layer from cracking and collapsing but also enhances the overall flame retardant and heat insulation effect.

[0048] 2. In this invention, by using the initiator BPO to graft intermediate III onto polypropylene, the interfacial compatibility between inorganic particles and the polypropylene matrix can be effectively improved, inhibiting the aggregation of inorganic particles and avoiding the defects of easy migration and aggregation of traditional physically blended flame retardants. The nitrogen atom in the Schiff base structure (-C=N-) can coordinate with the zinc in zinc borate, anchoring zinc borate and allowing it to be more uniformly dispersed in the matrix material. This prevents zinc borate particles from agglomerating, ensuring its stable and gradual decomposition during heating. Simultaneously, it shortens the spatial distance between zinc borate, silica, and the char-forming sites of the Schiff base, strengthening the synergistic effect among the three. This is more conducive to the rapid formation of a dense and stable composite barrier char layer, thus better protecting the integrity of the honeycomb porous structure and allowing its thermal insulation performance to continue to function, further improving the overall flame retardant and thermal insulation stability of the material. The uniform dispersion of inorganic particle components in polypropylene not only fully utilizes the synergistic flame retardant and char-forming effect of the multi-component components but also constructs a uniformly distributed inorganic particle network structure. Maleic anhydride-grafted polypropylene can also enhance the interfacial bonding force between the matrix and inorganic particles. While improving the melt strength of the system, it avoids the introduction of inorganic particles that would lead to a decrease in the mechanical properties of the composite material, thus ensuring the structural stability of the honeycomb structure for complete molding and long-term use. At the same time, it can also assist in supporting the composite carbon layer structure during combustion, further enhancing the barrier and protective effect of the carbon layer, allowing the complete honeycomb porous structure to continuously play its heat insulation role.

[0049] 3. In this invention, the melt index of the flame-retardant and heat-insulating polypropylene composite particles is 2.2-5 g / 10 min, and the melt index of the polypropylene particles is 2-5.8 g / 10 min. The melt viscosity of the core layer and the surface layer is similar. During hot-pressing at 160-165℃, the surface sheet and the honeycomb pore wall contact surface can be fully fused. The core layer pore wall has sufficient thermal creep resistance due to the inorganic particle network structure and the interface enhancement brought by maleic anhydride grafted polypropylene, and will not buckle or collapse. The honeycomb pore structure remains intact after hot pressing. A dense protective shell is formed on the surface of the honeycomb pore wall through the carbon layer, which inhibits the spread of flame along the pore wall and the dripping of melt. Even when heated, the pore wall can still maintain a certain structural integrity, allowing the internal cavity to continue to play a heat insulation role. Attached Figure Description

[0050] Figure 1 The process flow diagram for preparing flame-retardant and heat-insulating polypropylene composite particles according to the present invention is shown below.

[0051] Figure 2 The following are bar charts showing the limiting oxygen index tests of Examples 1-5 and Comparative Examples 1-3 of this invention;

[0052] Figure 3 The graphs show the thermal conductivity test results of Examples 1-5 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1

[0055] This embodiment provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, including the following steps:

[0056] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0057] The temperatures in each zone of the extruder are: Zone 1 170℃, Zone 2 180℃, Zone 3 200℃; Die head temperature 211℃.

[0058] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 50°C to obtain an upper surface sheet and a lower surface sheet.

[0059] The temperatures in each zone of the extruder are: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃; Die head temperature 221℃.

[0060] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 50 seconds at 0.3 MPa and 160°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 180°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0061] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0062] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 2000:40:80 and reacted at 60°C for 34 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 70°C for 2 h to obtain intermediate I.

[0063] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 100:0.4:1000 and reacted at 56°C for 7 hours. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 50°C for 3.5 hours to obtain intermediate II.

[0064] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 60°C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 45°C for 6 h to obtain intermediate III.

[0065] Step (4) Under a nitrogen atmosphere, polypropylene is heated to 60°C and kept at that temperature for 2 hours. Intermediate III and BPO are added, stirred, heated to 85°C and kept at that temperature for 30 minutes, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene.

[0066] The mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is 220:20:0.3:2000.

[0067] Modified polypropylene was heated to 170℃, and antioxidant 168, calcium stearate, maleic anhydride grafted polypropylene and zinc borate were added. The mixture was stirred evenly, extruded and granulated, and dried at -0.08MPa and 55℃ for 5 hours to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0068] The mass ratio of modified polypropylene, antioxidant 168, calcium stearate, maleic anhydride-grafted polypropylene, and zinc borate is 80:0.2:0.4:4:12.

[0069] Example 2

[0070] This embodiment provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, including the following steps:

[0071] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0072] The temperatures in each zone of the extruder are as follows: Zone 1: 172℃, Zone 2: 183℃, Zone 3: 202℃; Die head temperature: 212℃.

[0073] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 55°C to obtain an upper surface sheet and a lower surface sheet.

[0074] The temperatures in each zone of the extruder are as follows: Zone 1: 183℃, Zone 2: 202℃, Zone 3: 213℃; Die head temperature: 222℃.

[0075] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 45 seconds at 0.3 MPa and 162°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 185°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0076] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0077] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 2500:45:85 and reacted at 63°C for 33 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 72°C for 1.8 h to obtain intermediate I.

[0078] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 110:0.45:1150 and reacted at 56°C for 6.5 h. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 52°C for 3 h to obtain intermediate II.

[0079] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 62°C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 46°C for 5.5 hours to obtain intermediate III.

[0080] Step (4) Under a nitrogen atmosphere, polypropylene was heated to 62°C and kept at that temperature for 1.8 h. Intermediate III and BPO were added, stirred, heated to 87°C and kept at that temperature for 28 min, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene.

[0081] The mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is 250:25:0.35:2300.

[0082] Modified polypropylene was heated to 172°C, and antioxidant 168, calcium stearate, maleic anhydride grafted polypropylene and zinc borate were added. The mixture was stirred evenly, extruded and granulated, and dried at -0.08 MPa and 56°C for 4.5 h to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0083] The mass ratio of modified polypropylene, antioxidant 168, calcium stearate, maleic anhydride-grafted polypropylene, and zinc borate is 85:0.35:0.55:5.5:13.

[0084] Example 3

[0085] This embodiment provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, including the following steps:

[0086] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0087] The temperatures in each zone of the extruder are: Zone 1 175℃, Zone 2 185℃, Zone 3 205℃; and the die head temperature is 213℃.

[0088] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 60°C to obtain an upper surface sheet and a lower surface sheet.

[0089] The temperatures in each zone of the extruder are as follows: Zone 1: 185℃, Zone 2: 205℃, Zone 3: 215℃; Die head temperature: 223℃.

[0090] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 40 seconds at 0.4 MPa and 163°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 190°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0091] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0092] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 3000:50:90 and reacted at 67°C for 32 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 75°C for 1.5 h to obtain intermediate I.

[0093] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 120:0.5:1300 and reacted at 57°C for 6 hours. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 55°C for 2.5 hours to obtain intermediate II.

[0094] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 65°C for 8 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 47°C for 5 hours to obtain intermediate III.

[0095] Step (4) Under a nitrogen atmosphere, polypropylene is heated to 65°C and kept at that temperature for 1.5 h. Intermediate III and BPO are added, stirred, heated to 90°C and kept at that temperature for 25 min, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene.

[0096] The mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is 280:30:0.4:2600.

[0097] Modified polypropylene was heated to 175℃, and antioxidant 168, calcium stearate, maleic anhydride grafted polypropylene and zinc borate were added. The mixture was stirred evenly, extruded and granulated, and dried at -0.08MPa and 58℃ for 4 hours to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0098] The mass ratio of modified polypropylene, antioxidant 168, calcium stearate, maleic anhydride-grafted polypropylene, and zinc borate is 90:0.5:0.7:7:14.

[0099] Example 4

[0100] This embodiment provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, including the following steps:

[0101] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0102] The temperatures in each zone of the extruder are as follows: Zone 1: 177℃, Zone 2: 188℃, Zone 3: 208℃; Die head temperature: 214℃.

[0103] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 65°C to obtain an upper surface sheet and a lower surface sheet.

[0104] The temperatures in each zone of the extruder are as follows: Zone 1: 188℃, Zone 2: 207℃, Zone 3: 218℃; Die head temperature: 224℃.

[0105] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 35 seconds at 0.45 MPa and 164°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 195°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0106] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0107] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 3500:55:95 and reacted at 71°C for 31 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 77°C for 1.2 h to obtain intermediate I.

[0108] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 130:0.55:1450 and reacted at 58°C for 5.5 h. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 58°C for 2 h to obtain intermediate II.

[0109] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 68°C for 7 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 49°C for 4.5 hours to obtain intermediate III.

[0110] Step (4) Under a nitrogen atmosphere, polypropylene was heated to 67°C and kept at that temperature for 1.2 h. Intermediate III and BPO were added, stirred, heated to 92°C and kept at that temperature for 23 min, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene.

[0111] The mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is 310:35:0.45:2900.

[0112] Modified polypropylene was heated to 178℃, and antioxidant 168, calcium stearate, maleic anhydride grafted polypropylene and zinc borate were added. The mixture was stirred evenly, extruded and granulated, and dried at -0.08MPa and 59℃ for 3.5h to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0113] The mass ratio of modified polypropylene, antioxidant 168, calcium stearate, maleic anhydride-grafted polypropylene, and zinc borate is 95:0.65:0.85:8.5:15.

[0114] Example 5

[0115] This embodiment provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, including the following steps:

[0116] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0117] The temperatures in each zone of the extruder are: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃; Die head temperature 215℃.

[0118] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 70°C to obtain an upper surface sheet and a lower surface sheet.

[0119] The temperatures in each zone of the extruder are as follows: Zone 1: 190℃, Zone 2: 210℃, Zone 3: 220℃; Die head temperature: 225℃.

[0120] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 30 seconds at 0.5 MPa and 165°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 200°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0121] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0122] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 4000:60:100 and reacted at 75°C for 30 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 80°C for 1 h to obtain intermediate I.

[0123] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 140:0.6:1600 and reacted at 58°C for 5 hours. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 60°C for 1.5 hours to obtain intermediate II.

[0124] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 70°C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 50°C for 4 hours to obtain intermediate III.

[0125] Step (4) Under a nitrogen atmosphere, polypropylene is heated to 70°C and kept at that temperature for 1 hour. Intermediate III and BPO are added, stirred, heated to 95°C and kept at that temperature for 20 minutes, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene.

[0126] The mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is 340:40:0.5:3200.

[0127] Modified polypropylene was heated to 180℃, and antioxidant 168, calcium stearate, maleic anhydride grafted polypropylene and zinc borate were added. The mixture was stirred evenly, extruded and granulated, and dried at -0.08MPa and 60℃ for 3 hours to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0128] The mass ratio of modified polypropylene, antioxidant 168, calcium stearate, maleic anhydride-grafted polypropylene, and zinc borate is 100:0.8:1:10:16.

[0129] Example 6

[0130] This embodiment provides a method for preparing epoxy-modified silica, including the following steps:

[0131] Silica, anhydrous ethanol, and epoxypropoxyoctyltrimethoxysilane were mixed evenly at a mass ratio of 75:1000:30 and reacted at 80°C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed with deionized water, and dried at 90°C for 5 hours to obtain epoxy-modified silica.

[0132] Example 7

[0133] This embodiment provides a method for preparing modified hydrotalcite, including the following steps:

[0134] Hydrotalcite was calcined at 400°C for 6 hours to obtain an intermediate. Under a nitrogen atmosphere, the intermediate was added to a mixed solution and reacted at 75°C for 6 hours. After the reaction was completed, the solution was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry.

[0135] Intercalated hydrotalcite slurry and γ-aminopropyltriethoxysilane were mixed at a mass ratio of 140:12, ultrasonicated at 40 kHz for 6 min, reacted at 50 ℃ for 4 h, filtered, washed with deionized water, and dried at 55 ℃ for 5 h to obtain modified hydrotalcite.

[0136] The mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is 40:180:18.

[0137] The mass ratio of the intermediate, the mixed solution, and the distilled water is 6:30:20.

[0138] Comparative Example 1

[0139] This comparative example provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb panel, including the following steps:

[0140] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0141] The temperatures in each zone of the extruder are: Zone 1 170℃, Zone 2 180℃, Zone 3 200℃; Die head temperature 211℃.

[0142] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 50°C to obtain an upper surface sheet and a lower surface sheet.

[0143] The temperatures in each zone of the extruder are: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃; Die head temperature 221℃.

[0144] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 50 seconds at 0.3 MPa and 160°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 180°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0145] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0146] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 2000:40:80 and reacted at 60°C for 34 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 70°C for 2 h to obtain intermediate I.

[0147] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 100:0.4:1000 and reacted at 56°C for 7 hours. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 50°C for 3.5 hours to obtain intermediate II.

[0148] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 60°C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 45°C for 6 h to obtain intermediate III.

[0149] Step (4) Under a nitrogen atmosphere, polypropylene is heated to 60°C and kept at that temperature for 2 hours. Intermediate III and BPO are added, stirred, heated to 85°C and kept at that temperature for 30 minutes, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene.

[0150] The mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is 220:20:0.3:2000.

[0151] Modified polypropylene was heated to 170℃, and antioxidant 168, calcium stearate and maleic anhydride grafted polypropylene were added. The mixture was stirred evenly, extruded and granulated, and dried at -0.08MPa and 55℃ for 5 hours to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0152] The mass ratio of modified polypropylene, antioxidant 168, calcium stearate, and maleic anhydride grafted polypropylene is 92:0.2:0.4:4.

[0153] Comparative Example 2

[0154] This comparative example provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb panel, including the following steps:

[0155] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0156] The temperatures in each zone of the extruder are: Zone 1 170℃, Zone 2 180℃, Zone 3 200℃; Die head temperature 211℃.

[0157] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 50°C to obtain an upper surface sheet and a lower surface sheet.

[0158] The temperatures in each zone of the extruder are: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃; Die head temperature 221℃.

[0159] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 50 seconds at 0.3 MPa and 160°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 180°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0160] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0161] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 2000:40:80 and reacted at 60°C for 34 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 70°C for 2 h to obtain intermediate I.

[0162] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 100:0.4:1000 and reacted at 56°C for 7 hours. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 50°C for 3.5 hours to obtain intermediate II.

[0163] Step (3) Intermediate II and modified hydrotalcite were added to anhydrous ethanol at a molar ratio of 1:1 and reacted at 60°C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by vacuum filtration under reduced pressure. The solid was washed three times with anhydrous ethanol and dried under vacuum at -0.08 MPa and 45°C for 6 h to obtain intermediate III.

[0164] Step (4) Heat the polypropylene to 170°C, add intermediate III, antioxidant 168, calcium stearate and maleic anhydride grafted polypropylene, stir evenly, extrude and granulate, dry at -0.08MPa and 55°C for 5h to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0165] The mass ratio of polypropylene, intermediate III, antioxidant 168, calcium stearate, and maleic anhydride grafted polypropylene is 84:8:0.2:0.4:4.

[0166] Comparative Example 3

[0167] This comparative example provides a method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb panel, including the following steps:

[0168] S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board.

[0169] The temperatures in each zone of the extruder are: Zone 1 170℃, Zone 2 180℃, Zone 3 200℃; Die head temperature 211℃.

[0170] S2. Polypropylene particles are fed into a single-screw extruder to melt. The melt is extruded through a flat die and the extruded sheet is calendered and cooled by three rollers at a roller temperature of 50°C to obtain an upper surface sheet and a lower surface sheet.

[0171] The temperatures in each zone of the extruder are: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃; Die head temperature 221℃.

[0172] S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets, and hot-press it for 50 seconds at 0.3 MPa and 160°C. Then, maintain the pressure and cool to 60°C, let it stand at room temperature for 24 hours, cut it, and seal the edges at 180°C to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board.

[0173] The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps:

[0174] Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol were mixed in a mass ratio of 2000:40:80 and reacted at 60°C for 34 h. After the reaction was completed, the mixture was filtered, washed with acetone, and dried at 70°C for 2 h to obtain intermediate I.

[0175] Step (2) Intermediate I, aluminum isopropoxide and acetone are mixed in a mass ratio of 100:0.4:1000 and reacted at 56°C for 7 hours. After the reaction is completed, the mixture is filtered under reduced pressure, washed with acetone, and dried at -0.08 MPa and 50°C for 3.5 hours to obtain intermediate II.

[0176] Step (3) Physically mix intermediate II and modified hydrotalcite at a molar ratio of 1:1 to obtain the composition;

[0177] Step (4) Heat the polypropylene to 170°C, add the composition, antioxidant 168, calcium stearate and maleic anhydride grafted polypropylene, stir evenly, extrude and granulate, and dry at -0.08MPa and 55°C for 5 hours to obtain flame-retardant and heat-insulating polypropylene composite particles.

[0178] The mass ratio of polypropylene, the composition, antioxidant 168, calcium stearate, and maleic anhydride-grafted polypropylene is 84:8:0.2:0.4:4.

[0179] The epoxy-modified silica in Examples 1-5 and Comparative Examples 1-3 all used the epoxy-modified silica prepared in Example 6.

[0180] The modified hydrotalcites in Examples 1-5 and Comparative Examples 1-3 were all prepared using the modified hydrotalcites obtained in Example 7.

[0181] In this invention, maleic anhydride-grafted polypropylene was purchased from Shanghai Rizhisheng New Technology Development Co., Ltd., model CMG9801; polypropylene was from Yanshan Petrochemical Company, product grade: K8303, melt index: 2g / 10min; silica was from Shanghai Yunhe Materials Technology Co., Ltd., mesh size: 8000 mesh, content: 99.8%, brand: WACKER HDK; hydrotalcite specifically was MgAl hydrotalcite, from Jingjiang Kanggaote New Materials Technology Co., Ltd., brand: Kanggaote.

[0182] Performance testing

[0183] (1) Flame retardant performance: Flame retardant and heat-insulating polypropylene composite materials prepared from flame retardant and heat-insulating polypropylene composite particles in Examples 1-5 and Comparative Examples 1-3 were selected as samples, and their flame retardant performance was tested respectively. The limiting oxygen index was tested according to GB / T2406.2-2009 Oxygen Index Method - Test Method for Burning Performance of Plastics. Each sample was tested 5 times, and the average value was calculated. The test results are shown in Table 1.

[0184] (2) Thermal conductivity test: The flame-retardant and heat-insulating polypropylene composite particles in Examples 1-5 and Comparative Examples 1-3 were heated and melted to make 10cm×10cm×2cm samples (the samples should meet the following requirements: the sample should be a homogeneous hard material, the two surfaces should be flat, smooth and parallel, without cracks or other defects; the flatness of the sample should be within 0.5mm; the sample surface in contact with the sensor must be smooth and flat, and the sample assembly should clamp the probe). The test was carried out in accordance with GB / T 3139 2005, the hot plate temperature was 40℃, the cold plate temperature was 10℃, each group was repeated 3 times, the average value was calculated, and the test results are shown in Table 1.

[0185] Table 1

[0186] Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Limiting oxygen index (%) 28.3 28.1 27.9 27.8 27.7 27.6 27.4 26.9 Thermal conductivity (W / m·K) 0.0985 0.1069 0.1152 0.1239 0.1321 0.1082 0.1203 0.1338

[0187] Data Analysis:

[0188] As shown in Table 1, the flame-retardant and heat-insulating polypropylene composite particles prepared by this invention possess both good flame-retardant and heat-insulating properties. Compared to Comparative Examples 1-3, the limiting oxygen index of the embodiments of this invention is higher than that of the comparative examples, and the thermal conductivity of the embodiments can be reduced to as low as 0.0985 W / m·K, exhibiting excellent heat-insulating performance. In Comparative Example 1, the lack of flame retardant compared to Example 1 naturally reduces the flame-retardant performance. In Comparative Example 2, compared to Comparative Example 1, intermediate III is not chemically bonded to polypropylene, resulting in reduced dispersibility. This hinders the uniform dispersion of intermediate III, which possesses both flame-retardant and heat-insulating functions, within the polypropylene matrix. Consequently, a continuous and stable heat-insulating layer and a flame-retardant charred layer cannot be formed within the matrix, allowing heat and oxygen to penetrate the material more easily, leading to a simultaneous decrease in both flame-retardant and heat-insulating performance.

[0189] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board, characterized in that, Includes the following steps: S1. Flame-retardant and heat-insulating polypropylene composite particles are fed into a single screw extruder to melt. The melt is extruded into a honeycomb core preform through a honeycomb extrusion die. The preform is then vacuum-shaped and cooled to solidify by a vacuum shaping device to obtain a flame-retardant and heat-insulating polypropylene honeycomb core board. S2. Polypropylene particles are fed into a single-screw extruder to melt, and then extruded through a flat die to form upper and lower surface sheets. S3. Place the flame-retardant and heat-insulating polypropylene honeycomb core board between the upper and lower surface sheets and hot-press it together. Let it stand at room temperature, cut it, and seal the edges to obtain the flame-retardant and heat-insulating polypropylene composite honeycomb board. The preparation method of flame-retardant and heat-insulating polypropylene composite particles includes the following steps: Step (1) N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol are mixed, the reaction is completed, filtered, washed and dried to obtain intermediate I; Step (2) Add intermediate I and catalyst to acetone, heat to react, and after the reaction is complete, filter under reduced pressure, wash, and dry to obtain intermediate II; Step (3) Add intermediate II and modified hydrotalcite to anhydrous ethanol, heat to react, cool to room temperature after the reaction is complete, collect the solid by vacuum filtration under reduced pressure, wash, and vacuum dry to obtain intermediate III; Step (4) Under a nitrogen atmosphere, polypropylene is heated and kept warm, intermediate III and BPO are added, stirred, heated and kept warm, cooled, extracted with ethyl acetate, and dried to obtain modified polypropylene; Modified polypropylene is heated and melted, and antioxidants, lubricants, maleic anhydride-grafted polypropylene and flame retardants are added. The mixture is stirred evenly, extruded and granulated, and dried to obtain flame-retardant and heat-insulating polypropylene composite particles.

2. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, The melt index of flame-retardant and heat-insulating polypropylene composite particles is 2.2-5 g / 10 min; the melt index of polypropylene particles is 2-5.8 g / 10 min.

3. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (3), the modified hydrotalcite is prepared as follows: Hydrotalcite was calcined at high temperature to obtain an intermediate. Under a nitrogen atmosphere, the intermediate was added to a mixed solution and heated to react. After the reaction was completed, the solution was filtered, washed, and added to distilled water to obtain an intercalated hydrotalcite slurry. Aminosilane was added, ultrasonically dispersed, and heated to react. After the reaction was completed, the solution was filtered, washed, and dried to obtain modified hydrotalcite.

4. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 3, characterized in that, The aminosilane includes any one of γ-aminopropyltriethoxysilane, methyl(γ-aminopropyl)diethoxysilane, and γ-aminopropyltrimethoxysilane.

5. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (1), the preparation method of epoxy-modified silica is as follows: Silica, anhydrous ethanol, and epoxy silane coupling agent are mixed evenly and heated to react. After the reaction is complete, the mixture is centrifuged and dried to obtain epoxy-modified silica.

6. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (1), the mass ratio of N,N-dimethylformamide, epoxy-modified silica and 3-buten-1-ol is (2000-4000):(40-60):(80-100); the reaction temperature is 60-75℃ and the reaction time is 30-34h.

7. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (2), the mass ratio of intermediate I, catalyst and acetone is (100-140):(0.4-0.6):(1000-1600); the reaction temperature is 56-58℃ and the reaction time is 5-7h; the catalyst is aluminum isopropoxide.

8. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (3), the molar ratio of intermediate II to modified hydrotalcite is 1:1; the reaction temperature is 60-70℃; and the reaction time is 6-10h.

9. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (4), the mass ratio of polypropylene, intermediate III, BPO and ethyl acetate is (220-340):(20-40):(0.3-0.5):(2000-3200).

10. The method for preparing a flame-retardant and heat-insulating polypropylene composite honeycomb board according to claim 1, characterized in that, In step (4), the mass ratio of modified polypropylene, antioxidant, lubricant, maleic anhydride grafted polypropylene and flame retardant is (80-100):(0.2-0.8):(0.4-1):(4-10):(12-16).

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