Vehicle box polypropylene honeycomb core material

Abstract

The invention discloses a vehicle box polypropylene honeycomb core material, and belongs to the technical field of polypropylene honeycomb core materials, and the vehicle box polypropylene honeycomb core material is prepared by welding polypropylene round tubes. The polypropylene round tube is prepared from the following raw materials: PP particles, POE (Polyolefin Elastomer), PP-g-MAH (Polypropylene-g-Maleic Anhydride), coated modified hollow glass microspheres, polyol ester phosphate melamine salt, an antioxidant, a titanate coupling agent and stearate, the polyol ester phosphate melamine salt is formed by polymerizing phytic acid, pentaerythritol and melamine, and the antioxidant is a mixture of a coupling agent, a coupling agent and a coupling agent. The coated modified hollow glass microspheres are prepared by depositing nano calcium carbonate on the surfaces of the hollow glass microspheres through a high-pressure carbonization method; according to the polypropylene honeycomb core material, the coated modified hollow glass microspheres are used as a reinforcing phase of the polypropylene microspheres, and compared with glass fibers, the polypropylene honeycomb core material has isotropy, so that the modulus of the polypropylene honeycomb core material is prevented from being excessively influenced, the flat pressing strength and the transverse shear strength of the honeycomb core material are balanced, and the use requirement of a vehicle box body is met.

Description

Technical Field

[0001] This invention belongs to the technical field of polypropylene honeycomb core materials, specifically a polypropylene honeycomb core material for automotive bodies. Background Technology

[0002] The freight car body is the core component that directly carries goods in the logistics process. Its structure, materials, and dimensions directly determine the vehicle's transportation efficiency, fuel economy, regulatory compliance, and total life cycle cost. Therefore, the car body must be lighter, more durable, and more efficient, and conventional metal car bodies are gradually being replaced by polymer composite materials. By using honeycomb core composite materials to manufacture the car body, the car body's weight can be significantly reduced. Studies have shown that for every 10% reduction in vehicle weight, fuel consumption can be reduced by approximately 8%.

[0003] Sandwich panels for train carriages are generally made with fiberglass reinforced composite materials as the face panels and honeycomb core materials as the sandwich layers. The most common honeycomb core material is polypropylene, which is extruded into round tubes, tightly arranged, and fused together to form a honeycomb structure. Conventional fiberglass reinforced face panels generally have high strength, while the polypropylene honeycomb core material in the middle has low compressive strength. Therefore, during die extrusion, the polypropylene honeycomb core material is easily flattened, affecting the production efficiency and yield of the sandwich panels.

[0004] The face panels of honeycomb sandwich panels need to withstand bending loads, so fibers such as glass fiber can be used to improve stiffness and strength. The polypropylene honeycomb core, however, is responsible for maintaining the spacing between the two face panels and does not inherently require high modulus. Simply adding glass fiber will harden and brittle the walls of the polypropylene tubes, and it will also affect the processability of the polypropylene tubes during production. In particular, short glass fibers have a high degree of orientation along the tube axis during extrusion and traction. In actual use, the honeycomb sandwich panel must withstand not only flat pressure along the tube axis but also lateral shear from the face panels, making it prone to cracking during hot pressing. Therefore, glass fiber offers little benefit in improving the flat compressive strength of polypropylene honeycomb core materials.

[0005] Hollow glass microspheres are a lightweight filler. Compared to glass fiber, their spherical structure provides support in all directions, reducing the hindrance to molecular weight slippage and minimizing its impact on the modulus of polypropylene honeycomb core materials. Furthermore, their hollow structure can further reduce the mass of honeycomb sandwich panels. However, the surface of hollow glass microspheres is generally smooth, making them prone to interfacial debonding with the polypropylene matrix, which can affect the improvement of compressive strength. Summary of the Invention

[0006] The purpose of this invention is to provide a polypropylene honeycomb core material for automotive housings. In the preparation process, modified hollow glass microspheres coated with nano-calcium carbonate are added, and then coated with a titanate coupling agent. The interfacial strength between materials is improved by the dual effects of physical anchoring and chemical anchoring, thereby improving the flat compressive strength of the honeycomb core material.

[0007] The objective of this invention can be achieved through the following technical solutions: A polypropylene honeycomb core material for automotive bodies is made by welding polypropylene round tubes. By weight, the polypropylene round tubes comprise the following raw materials: 90-100 parts PP particles, 5-15 parts POE elastomer, 2-4 parts PP-g-MAH, 10-15 parts coated modified hollow glass microspheres, 8-12 parts melamine salt of phosphate polyol ester, 0.2-0.4 parts antioxidant, 0.2-0.3 parts titanate coupling agent, and 0.1-0.3 parts stearate.

[0008] Polypropylene round tubes are prepared through the following steps: The coated and modified hollow glass microspheres are added to a high-speed mixer and stirred for 2-3 minutes at 80-90℃ and 200-250 r / min to preheat the coated and modified hollow glass microspheres. Then, the pre-melted titanate coupling agent is added to the high-speed mixer and stirred for 8-10 minutes at 90-100℃ and 400-500 r / min. After cooling to room temperature, PP-g-MAH, melamine phosphate polyol ester, and stearate are added to the high-speed mixer and mixed at 700-900 r / min for 5-10 minutes to obtain the premix.

[0009] PP particles, POE elastomer, and antioxidants are mixed and fed into a twin-screw extruder through the main feed inlet. The premix is ​​then fed into the melting section of the twin-screw extruder through the side feed inlet. The mixture is melted and mixed at 190-210℃, and then extruded through a die. The tube is then drawn into a pipe using a traction machine. The tube blank is cooled and shaped by a cooling water spray and then cut into a ring under the traction of the traction machine to obtain a polypropylene round pipe.

[0010] After wetting the outer surface of the polypropylene round tube with a diluted surfactant solution, the tubes are laid in a mold and arranged into a rectangular honeycomb structure. A pressure plate is placed on top of the mold, and then the mold is placed in an oven and heated at 120°C for 40-50 minutes to fuse the outer surface of the polypropylene round tube. After cooling and shaping, the tubes are demolded and cut into sheets to obtain the polypropylene honeycomb core material for automotive bodies.

[0011] Furthermore, the main feed temperature of the twin-screw extruder is 160-165℃, the temperature of the melting section is 190-200℃, and the die temperature is 200-210℃.

[0012] Furthermore, the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio.

[0013] Furthermore, the stearate is calcium stearate or zinc stearate.

[0014] Furthermore, the surfactant diluent is composed of sodium dodecyl sulfonate, sodium fatty alcohol ether sulfate, alkyl alcohol amide, Tween 80 and deionized water in a mass ratio of 1:0.7-0.8:0.2-0.25:0.03-0.05:1000.

[0015] Furthermore, the melamine salt of phosphate polyol ester is polymerized from phytic acid, pentaerythritol, and melamine, and the specific preparation method is as follows: Phytic acid and deionized water were added to a flask, and pentaerythritol was added under nitrogen protection. The mixture was stirred at 300-500 rpm for 5-10 min. Then, p-toluenesulfonic acid was added as a catalyst at 120 °C, and the mixture was stirred for 10-14 h. The mixture was allowed to cool naturally to room temperature. Melamine was then dissolved in anhydrous methanol and added to the flask. The mixture was stirred for 80-85 °C for 8-10 h. The solvent was removed by rotary evaporation, and the mixture was freeze-dried and ground to obtain melamine salt of phosphate polyol ester.

[0016] The mass ratio of phytic acid, deionized water, pentaerythritol, p-toluenesulfonic acid, melamine, and anhydrous methanol is 25-30:11-12:13-14:1:12-13:240-260.

[0017] Furthermore, the coated and modified hollow glass microspheres are prepared by depositing nano-calcium carbonate on the surface of hollow glass microspheres using a high-pressure carbonization method. The specific preparation method is as follows: Hollow glass microspheres and a 1% (w / w) calcium hydroxide solution were added to a reaction vessel and stirred and dispersed for 15-30 min at 25-35℃ and 250-300 r / min. Then, carbon dioxide gas was introduced to maintain the pressure inside the vessel at 1 MPa, and the reaction was stirred for 60-90 min. The mixture was then filtered, and the filter cake was washed 2-3 times with deionized water and dried under vacuum at 60-80℃ to constant weight to obtain the coated modified hollow glass microspheres.

[0018] The ratio of hollow glass microspheres to calcium hydroxide solution is 1g:100-120mL.

[0019] The beneficial effects of this invention are: 1. The polypropylene honeycomb core material of this invention uses coated modified hollow glass microspheres as the reinforcing phase of polypropylene microspheres. Compared with glass fiber, it is isotropic, avoiding excessive influence on its modulus, balancing the compressive strength and transverse shear strength of the honeycomb core material, and meeting the requirements for use in automotive bodies.

[0020] The nano-calcium carbonate deposited on the surface of the modified hollow glass microspheres can improve the surface roughness and effectively reduce the occurrence of interfacial debonding. Furthermore, after being modified by titanate coupling agent, it has good dispersibility, which helps to improve the processing performance of polypropylene round tube extrusion and traction production processes.

[0021] 2. The raw materials for the polypropylene honeycomb core material of this invention also include PP-g-MAH, melamine phosphate polyol ester, and stearate. Stearate can improve the water resistance, compatibility, and extrusion processability of the raw materials. The phosphorus source in melamine phosphate polyol ester can chelate calcium / zinc ions in stearate to form nano-phosphate clusters, providing heterogeneous nucleation sites and further inducing β-crystal formation. The amino groups in melamine phosphate polyol ester can also undergo nucleophilic ring-opening reactions with PP-g-MAH. Through a multi-component synergistic system, this helps to improve the mechanical properties of the polypropylene material.

[0022] 3. The phosphate polyol ester melamine salt used in this invention can provide good flame retardant effect. The modified hollow glass microspheres are coated as an inorganic barrier phase, and the nano-calcium carbonate on its surface can also provide a rigid skeleton for the char layer through its rough structure, improve the stability of the char layer, and synergistically improve the flame retardant effect. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0024] Example 1: A polypropylene honeycomb core material for automotive bodies, prepared through the following steps: S1: Add 25g phytic acid and 11g deionized water to a flask, add 13g pentaerythritol under nitrogen protection, stir at 300r / min for 5min, then add 1g p-toluenesulfonic acid as a catalyst at 120℃, stir and react for 10h, cool naturally to room temperature, then dissolve 12g melamine in 240g anhydrous methanol and add to the flask, stir and react at 80℃ for 8h, remove the solvent by rotary evaporation, freeze dry, grind and refine to obtain melamine salt of phosphate polyol ester.

[0025] S2: Add 20g of hollow glass microspheres and 2L of 1% calcium hydroxide solution to the reactor. Stir and disperse at 25℃ and 250r / min for 15min. Then, introduce carbon dioxide gas to maintain the pressure inside the reactor at 1MPa and stir for 60min. Filter the mixture and wash the filter cake twice with deionized water. Dry it under vacuum at 60℃ to constant weight to obtain the coated modified hollow glass microspheres.

[0026] S3: Add 10g of coated modified hollow glass microspheres to a high-speed mixer and stir for 2 minutes at 80℃ and 200r / min to preheat the coated modified hollow glass microspheres. Then add 0.2g of pre-melted titanate coupling agent to the high-speed mixer and stir for 8 minutes at 90℃ and 400r / min. Then cool to room temperature, add 2g of PP-g-MAH, 8g of melamine phosphate polyol ester and 0.1g of calcium stearate (i.e., stearate) to the high-speed mixer and mix at 700r / min for 5 minutes to obtain the premix.

[0027] S4: Mix 90g of PP particles, 5g of POE elastomer, and 0.2g of antioxidant (the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio) and add it to the twin-screw extruder through the main feed inlet (the temperature of the main feed inlet of the twin-screw extruder is 160℃). Then, add all the premix from step S3 to the melting section of the twin-screw extruder through the side feed inlet (the temperature of the melting section is 190℃). Melt and mix, and then extrude through the die (the die temperature is 200℃). Use a traction machine to draw the tube. The tube blank is cooled and shaped by cooling water spray. Under the traction of the traction machine, it is cut into a ring to obtain a polypropylene round tube.

[0028] S5: After wetting the outer surface of the polypropylene round tube with a surfactant dilution, the tube is laid in a mold (the surfactant dilution is a mixture of sodium dodecyl sulfonate, sodium fatty alcohol ether sulfate, alkyl alcohol amide, Tween 80 and deionized water in a mass ratio of 1:0.7:0.2:0.03:1000). The surfactant dilution is rinsed on the surface of the polypropylene round tube, which can enhance the adhesion and wettability between the round tubes and facilitate the laying of the tubes. After arranging the polypropylene round tubes into a rectangular honeycomb structure, a pressure plate is placed on top of the mold, and then the mold is placed in an oven and heated at 120°C for 40 minutes to fuse the outer surface of the polypropylene round tubes. After cooling and shaping, the tubes are demolded and cut into sheets to obtain the polypropylene honeycomb core material for automotive bodies.

[0029] Example 2: A polypropylene honeycomb core material for automotive bodies, prepared through the following steps: S1: Add 27.5g phytic acid and 11.5g deionized water to a flask, add 13.5g pentaerythritol under nitrogen protection, stir at 400r / min for 7.5min, then add 1g p-toluenesulfonic acid as a catalyst at 120℃, stir and react for 12h, and cool naturally to room temperature. Then dissolve 12.5g melamine in 250g anhydrous methanol and add it to the flask, stir and react at 82.5℃ for 9h, remove the solvent by rotary evaporation, freeze dry, grind and refine to obtain melamine salt of phosphate polyol ester.

[0030] S2: 20g of hollow glass microspheres and 2.2L of 1% calcium hydroxide solution were added to the reactor and stirred and dispersed at 30℃ and 275r / min for 22.5min. Then carbon dioxide gas was introduced to maintain the pressure inside the reactor at 1MPa and the reaction was stirred for 75min. The mixture was then filtered, and the filter cake was washed twice with deionized water and dried under vacuum at 70℃ to constant weight to obtain the coated modified hollow glass microspheres.

[0031] S3: Add 12.5g of coated modified hollow glass microspheres to a high-speed mixer and stir for 2.5min at 85℃ and 225r / min to preheat the coated modified hollow glass microspheres. Then add 0.25g of pre-melted titanate coupling agent to the high-speed mixer and stir for 9min at 95℃ and 450r / min. Then cool to room temperature, add 3g of PP-g-MAH, 10g of melamine phosphate polyol ester and 0.2g of calcium stearate (i.e., stearate) to the high-speed mixer and mix at 800r / min for 7.5min to obtain the premix.

[0032] S4: Mix 95g of PP particles, 10g of POE elastomer, and 0.3g of antioxidant (the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio) and add it to the twin-screw extruder through the main feed inlet (the temperature of the main feed inlet of the twin-screw extruder is 163℃). Then, add all the premix from step S3 to the melting section of the twin-screw extruder through the side feed inlet (the temperature of the melting section is 195℃). Melt and mix, and then extrude through the die (the die temperature is 205℃). Use a traction machine to draw the tube. The tube blank is cooled and shaped by a cooling water spray. Under the traction of the traction machine, it is cut into a ring to obtain a polypropylene round tube.

[0033] S5: After wetting the outer surface of the polypropylene round tube with a surfactant dilution, lay the tube in the mold (the surfactant dilution is a mixture of sodium dodecyl sulfonate, sodium fatty alcohol ether sulfate, alkyl alcohol amide, Tween 80 and deionized water in a mass ratio of 1:0.75:0.225:0.04:1000). After arranging the polypropylene round tubes into a rectangular honeycomb structure, place a pressure plate on top of the mold, and then put it into an oven. Heat it at 120°C for 45 minutes to fuse the outer surface of the polypropylene round tubes. After cooling and shaping, demold and cut into sheets to obtain the polypropylene honeycomb core material for automotive boxes.

[0034] Example 3: A polypropylene honeycomb core material for automotive bodies, prepared through the following steps: S1: Add 30g phytic acid and 12g deionized water to a flask, add 14g pentaerythritol under nitrogen protection, stir at 500r / min for 10min, then add 1g p-toluenesulfonic acid as a catalyst at 120℃, stir and react for 14h, and cool naturally to room temperature. Then dissolve 13g melamine in 260g anhydrous methanol and add it to the flask, stir and react at 85℃ for 10h, remove the solvent by rotary evaporation, freeze dry, grind and refine to obtain melamine salt of phosphate polyol ester.

[0035] S2: Add 20g of hollow glass microspheres and 2.4L of 1% calcium hydroxide solution to a reaction vessel. Stir and disperse the mixture at 35℃ and 300r / min for 30min. Then, introduce carbon dioxide gas to maintain the pressure inside the vessel at 1MPa and stir for 90min. Filter the mixture and wash the filter cake three times with deionized water. Dry the cake under vacuum at 80℃ to constant weight to obtain the coated modified hollow glass microspheres.

[0036] S3: Add 15g of coated modified hollow glass microspheres to a high-speed mixer and stir for 3 minutes at 90℃ and 250r / min to preheat the coated modified hollow glass microspheres. Then add 0.3g of pre-melted titanate coupling agent to the high-speed mixer and stir for 10 minutes at 100℃ and 500r / min. Then cool to room temperature and add 4g of PP-g-MAH, 12g of melamine phosphate polyol ester and 0.3g of zinc stearate (i.e., stearate) to the high-speed mixer. Mix at 900r / min for 10 minutes to obtain the premix.

[0037] S4: Mix 100g of PP particles, 15g of POE elastomer, and 0.4g of antioxidant (the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio) and add it to the twin-screw extruder through the main feed inlet (the temperature of the main feed inlet of the twin-screw extruder is 165℃). Then, add all the premix from step S3 to the melting section of the twin-screw extruder through the side feed inlet (the temperature of the melting section is 200℃). Melt and mix, and then extrude through the die (the die temperature is 210℃). Use a traction machine to draw the tube. The tube blank is cooled and shaped by a cooling water spray. Under the traction of the traction machine, it is cut into a ring to obtain a polypropylene round tube.

[0038] S5: After wetting the outer surface of the polypropylene round tube with a surfactant dilution, lay the tube in the mold (the surfactant dilution is a mixture of sodium dodecyl sulfonate, sodium fatty alcohol ether sulfate, alkyl alcohol amide, Tween 80 and deionized water in a mass ratio of 1:0.8:0.25:0.05:1000). After arranging the polypropylene round tubes into a rectangular honeycomb structure, place a pressure plate on top of the mold, and then put it into an oven. Heat it at 120°C for 50 minutes to fuse the outer surface of the polypropylene round tubes. After cooling and shaping, demold and cut into sheets to obtain the polypropylene honeycomb core material for automotive bodies.

[0039] In the above embodiment, the polypropylene round tube has a pore size of 12mm, a thickness of 2mm, a size of 2.4m×1.2m on the honeycomb surface after welding, and a thickness of 20mm after cutting.

[0040] In this example, the PP particles were of type J715M, brand name Prehman, and had a density of 0.91 g / cm³. 3 The POE elastomer was grade 8450, branded by Dow Chemical (USA); the phytic acid was purchased from Xi'an Musen Bioengineering Co., Ltd., with a purity of 99%; the hollow glass microspheres were model HN32HS, branded by Hainuo, with an average particle size of 45μm and a true density of 0.30-0.34g / cm³. 3 The titanate coupling agent is designated as Titanate Coupling Agent 105, brand: Zhongjie; the PP-g-MAH grade is PO1015, brand: ExxonMobil; the calcium stearate has CAS number 1592-23-0, molecular weight 607.017, and density 1.08 g / cm³. 3 The CAS number for zinc stearate is 557-05-1, its molecular weight is 632.33, and its density is 1.095 g / cm³. 3 Sodium dodecyl sulfonate has a CAS number of 2386-53-0 and is branded by Chenqi Chemical; sodium fatty alcohol ether sulfate has a CAS number of 9004-82-4 and is branded by Huaxing; alkyl alcohol amide has a model number of 6503 and is branded by Huipeng.

[0041] Comparative Example 1: The difference from Example 1 is that in step S3, the coated modified hollow glass microspheres are replaced with raw material hollow glass microspheres of the same mass, while the other steps remain unchanged, and polypropylene honeycomb core material is prepared.

[0042] Comparative Example 2: The difference from Example 1 is that melamine salt of phosphate polyol ester is not added in step S3, while the other steps remain unchanged, and polypropylene honeycomb core material is prepared.

[0043] Comparative Example 3: The difference from Example 1 is that calcium stearate is not added in step S3, while the other steps remain unchanged, and polypropylene honeycomb core material is prepared.

[0044] Different polypropylene honeycomb core materials / polypropylene round tube raw materials were prepared into samples of corresponding specifications according to the standard, and performance tests were conducted: (1) According to ASTM C365M-16, different polypropylene honeycomb core materials were cut into 60mm×60mm×20mm specimens (without considering whether the edge tubes were intact). A compression testing machine (Shanghai Hengyi) was used. The specimens were placed in the center of the test machine indenter and pressure was applied at a speed of 2mm / min to perform a flat compression test on the specimens (the through holes of the honeycomb core material specimens were perpendicular to the plane of the indenter). When the computer collected the load through the sensor and the load began to decrease, the value of that point was recorded as the failure load. The average value of 5 results was taken to calculate its flat compression strength.

[0045] (2) In accordance with ISO 9773-2024, different polypropylene round tube raw materials were prepared into 100mm×13mm×3.2mm samples. The samples were tested for UL-94 vertical flammability using a CZF-3 vertical flammability tester (Nanjing Jiangning Analytical Instrument Co., Ltd.). The ignition flame height was kept at 2cm. The ratings were HB, V2, V1 and V0, with V0 indicating the best flame retardancy.

[0046] (3) In accordance with ISO 4589-2, different polypropylene round tube raw materials were prepared into 100mm×6.5mm×3.2mm samples. The limiting oxygen index of different samples was tested using a LOI 901 oxygen index meter (Netzsch). The average value of the results was taken as 5.

[0047] The test results are shown in Table 1: Table 1 Test Structure for Each Sample project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Compressive strength (MPa) 2.31 2.45 2.55 1.65 1.90 2.05 Flame retardant rating V0 V0 V0 V1 HB V0 Limiting oxygen index (%) 28.5 29.4 30.2 26.0 20.7 27.8 As can be seen from Table 1, the polypropylene honeycomb profile samples for vehicle bodies in Examples 1-3 have higher compressive strength and better compression resistance and flame retardant effect.

[0048] The significant decrease in compressive strength of the sample in Comparative Example 1 is due to the absence of nano-calcium carbonate deposition, resulting in premature debonding between the hollow glass microspheres and the polypropylene matrix. The decrease in compressive strength in Comparative Examples 2 and 3 may be because the phosphorus source in the melamine salt of phosphate polyol ester can chelate calcium ions in calcium stearate to form nano-calcium phosphate clusters, providing heterogeneous nucleation sites and further inducing the formation of β-crystals. The samples in Comparative Examples 2 and 3 lack this effect, thus leading to a decrease in mechanical properties.

[0049] The flame retardant effect of the sample in Comparative Example 2 was significantly reduced, indicating that the addition of melamine salt of phosphate polyol ester can provide a good flame retardant effect. The reduced flame retardant effect in Comparative Example 1 may be due to the lack of synergistic effect of nano-calcium carbonate, which leads to a decrease in char stability.

[0050] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A polypropylene honeycomb core for use in a vehicle, made by fusion of polypropylene round tubes, characterized in that, The polypropylene round pipe comprises the following raw materials in parts by mass: PP particles 90-100 parts, POE elastomer 5-15 parts, PP-g-MAH 2-4 parts, coated modified hollow glass microspheres 10-15 parts, phosphoric acid polyhydric alcohol ester melamine salt 8-12 parts, antioxidant 0.2-0.4 parts, titanate coupling agent 0.2-0.3 parts and stearate 0.1-0.3 parts; The phosphoric acid polyhydric alcohol ester melamine salt is polymerized from phytic acid, pentaerythritol and melamine. The coated modified hollow glass microspheres are prepared by depositing nano calcium carbonate on the surface of hollow glass microspheres through high-pressure carbonization.

2. The polypropylene honeycomb core for a vehicle box according to claim 1, wherein Preparation is carried out by the following steps: After the outer surface of the polypropylene round pipe is wetted with a surfactant diluent, the pipe is laid in a mold to form a rectangular honeycomb structure, an upper pressing plate is placed on the top of the mold, and then the mold is sent into an oven for heating at 120℃ for 40-50min, and then cooled and shaped, demolded and cut into pieces to obtain a polypropylene honeycomb core material for vehicle boxes; The surfactant diluent is prepared by mixing sodium dodecyl sulfonate, sodium fatty alcohol ether sulfate, alkyl alcohol amide, Tween 80 and deionized water in a mass ratio of 1:0.7-0.8:0.2-0.25:0.03-0.05:1000.

3. The polypropylene honeycomb core for a vehicle box according to claim 1, wherein The polypropylene round pipe is prepared by the following steps: After the PP particles, POE elastomer and antioxidant are mixed, they are fed into a twin-screw extruder through a main feeding port, the remaining raw materials are mixed into a premix which is then fed into the melt section of the twin-screw extruder through a side feeding port, and then melt-mixed at 190-210℃, and then extruded through a die, the pipe blank is cooled and shaped by spraying with cooling water, and then circularly cut under the traction of a traction machine to obtain the polypropylene round pipe.

4. The polypropylene honeycomb core for a vehicle box according to claim 3, wherein The temperature of the main feeding port of the twin-screw extruder is 160-165℃, the temperature of the melt section is 190-200℃, and the temperature of the die is 200-210℃.

5. The polypropylene honeycomb core for vehicle bodies according to claim 3, wherein The specific method for mixing the remaining raw materials into a premix is as follows The coated modified hollow glass microspheres are added into a high-speed mixer, preheated at 80-90℃ and 200-250r / min for 2-3min, the pre-melted titanate coupling agent is then added into the high-speed mixer, stirred at 90-100℃ and 400-500r / min for 8-10min, and then cooled to room temperature, the PP-g-MAH, phosphoric acid polyhydric alcohol ester melamine salt and stearate are added into the high-speed mixer, mixed at 700-900r / min for 5-10min to obtain the premix.

6. The polypropylene honeycomb core of claim 3, wherein the polypropylene is a propylene homopolymer. The antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

7. The polypropylene honeycomb core of claim 3, wherein the polypropylene is a propylene homopolymer. The stearate is calcium stearate or zinc stearate.

8. The polypropylene honeycomb core of claim 1 for use in a vehicle, wherein The specific preparation method of the phosphoric acid polyhydric alcohol ester melamine salt is as follows: Phytic acid and deionized water are added into a flask, under nitrogen protection, pentaerythritol is added, stirring at 300-500 r / min for 5-10 min, then p-toluenesulfonic acid as catalyst is added at a temperature of 120 DEG C, stirring reaction for 10-14 h, natural cooling to room temperature, then melamine is dissolved in anhydrous methanol and added into the flask, stirring reaction at a temperature of 80-85 DEG C for 8-10 h, rotary evaporation to remove the solvent, freeze-drying, grinding to refine, to obtain phosphoric acid polyol ester melamine salt.

9. The polypropylene honeycomb core for vehicle bodies according to claim 8, wherein The mass ratio of phytic acid, deionized water, pentaerythritol, p-toluenesulfonic acid, melamine and anhydrous methanol is 25-30:11-12:13-14:1:12-13:240-260.

10. The polypropylene honeycomb core of claim 1 for use in a vehicle, wherein The specific preparation method of the coated modified hollow glass microspheres is as follows: Hollow glass microspheres and 1wt% calcium hydroxide solution are added into a reaction kettle according to a mass ratio of 1g:100-120mL, stirring and dispersing at 25-35 DEG C and 250-300 r / min for 15-30 min, then carbon dioxide gas is introduced, maintaining the pressure in the kettle at 1MPa, stirring reaction for 60-90 min, suction filtration, washing the filter cake with deionized water for 2-3 times, vacuum drying at 60-80 DEG C until constant weight, to obtain coated modified hollow glass microspheres.