Polypropylene foam material and preparation method thereof
By modifying calcium carbonate through sol-gel coating, a silicon-containing inorganic-organic hybrid layer is constructed to prepare polypropylene foam material, which solves the problem of insufficient mechanical properties of polypropylene foam material and achieves lightweighting and performance improvement of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-13
AI Technical Summary
Existing polypropylene foam materials have insufficient mechanical properties during the lightweighting process, especially tensile strength, flexural modulus and impact toughness, which are reduced, affecting service life and reliability.
Calcium carbonate was coated and modified using the sol-gel method to construct a silicon-containing inorganic-organic hybrid coating layer. The modified calcium carbonate was then combined with polypropylene resin, and polypropylene foam material was prepared by extrusion granulation and foam injection molding.
It significantly improves the mechanical and flame-retardant properties of the material, while maintaining its lightweight advantage and improving its dispersibility and impact resistance.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials technology, specifically relating to a polypropylene foam material and its preparation method. Background Technology
[0002] Plastic cable reels are essential tools in the wire and cable, fiber optic cable, and other industries for winding, storing, and transporting cables, requiring certain structural strength, dimensional stability, and environmental resistance. Early commonly used reel materials were ABS (acrylonitrile-butadiene-styrene copolymer), which has good mechanical properties but is relatively expensive. To reduce production costs, the industry gradually shifted to polypropylene (PP) as an alternative material. PP raw materials are inexpensive and have good overall performance, but its relatively high density results in heavier reels, increasing transportation and usage costs.
[0003] To further achieve lightweighting, foamed PP has been used to manufacture spools. The foaming process creates a cellular structure within the material, significantly reducing its density and thus the overall weight of the spool. However, the foaming process often leads to a decrease in the mechanical properties of PP, such as tensile strength, flexural modulus, and impact toughness. This can cause foamed PP spools to deform or break under load, stacking, or impact, affecting their service life and reliability.
[0004] To improve the mechanical properties of foamed PP materials, existing technologies typically employ the following methods: First, by adding inorganic fillers such as calcium carbonate, talc, and glass fiber for reinforcement to enhance rigidity and strength; second, by blending PP with elastomers (such as POE and EPDM) or other plastics (such as HDPE) to improve toughness; and third, by chemically or physically modifying PP, such as increasing crystallinity or using high melt strength PP, to improve the foaming structure and stability. However, these methods still have several shortcomings: for example, while filler modification can improve strength, it often leads to increased brittleness and weight gain, and may affect foaming uniformity; blending modification may sacrifice rigidity while improving toughness, and requires high process compatibility and complex cost control; while specialized raw materials such as high melt strength PP are expensive, hindering large-scale application.
[0005] Therefore, how to effectively balance and improve the mechanical properties of PP foam while maintaining its lightweight advantages has become a pressing technical problem in this field. This invention aims to provide a new material formulation and process solution to overcome the shortcomings of the existing technology. Summary of the Invention
[0006] The purpose of this invention is to provide a polypropylene foam material and its preparation method to solve the problem of insufficient mechanical properties of polypropylene foam materials.
[0007] The objective of this invention can be achieved through the following technical solutions: The first aspect of the present invention provides a polypropylene foam material comprising the following raw materials: polypropylene resin and modified calcium carbonate, wherein the mass ratio of polypropylene resin, flame retardant and modified calcium carbonate is 72-96:0-20:4-8; wherein the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer.
[0008] In some possible implementations, the modified calcium carbonate is prepared by the following steps: Water and ethanol were mixed, and ammonia was added. Calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added while stirring. The mixture was stirred and reacted at 20-25℃ for 18-24 hours. After the reaction was completed, the mixture was washed with ethanol and dried to obtain modified calcium carbonate.
[0009] In some possible implementations, the volume ratio of water to ethanol is 1:9, the concentration of ammonia in the water-ethanol mixture is 0.1-0.5 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane is 10 mL: 1.5 g: 2-3 g: 3-4 g.
[0010] In some possible implementations, the calcium carbonate has a particle size of <20 μm.
[0011] In some possible implementations, the polypropylene resin includes virgin polypropylene resin and recycled polypropylene resin; the amount of recycled polypropylene resin added to the polypropylene resin is ≤48%. The amount of recycled polypropylene resin added should not be excessive, as excessive amounts can easily affect the overall strength of the material.
[0012] In some possible implementations, the flame retardant includes a carbon source, an acid source, and a gas source, wherein the acid source is one of ammonium polyphosphate or modified ammonium polyphosphate.
[0013] In some possible implementations, the modified ammonium polyphosphate is prepared by the following steps: Alkyltrimethoxysilane and trimethyl borate were added to an aqueous ethanol solution, and acetic acid was added to adjust the pH to 5-6. The mixture was stirred at 40°C for 2-3 hours to obtain a hydrolysate. γ-aminopropyltriethoxysilane, anhydrous ethanol and ammonium polyphosphate were mixed and stirred at 65-70℃ for 2 hours. Then, hydrolysate was added and the mixture was stirred at 70℃ for 1-2 hours. After the reaction was completed, the mixture was washed with water and dried to obtain modified ammonium polyphosphate.
[0014] In some possible implementations, the volume fraction of the aqueous ethanol solution is 20-30%, and the mass ratio of alkyltrimethoxysilane, trimethyl borate, γ-aminopropyltriethoxysilane, and ammonium polyphosphate is 5:2:3:70.
[0015] Modified ammonium polyphosphate (MPP) is a BO-Si and BOP covalent network constructed on the surface of MPP through boron-silicon synergistic modification. This network forms a low-melting-point borate glass phase in the early stages of combustion, which, together with the silicon-oxygen framework, "seals" microcracks in the expanded char layer. This transforms the char layer from a porous expander into a dense, continuous "ceramic-glass" composite barrier. This barrier significantly inhibits the diffusion of thermally decomposed volatiles from the polymer substrate into the combustion zone at high temperatures, while simultaneously blocking oxygen and heat backflow. This improves both flame retardant efficiency and fire safety, achieving the added benefit of a "thinner char layer, higher protection." The silicon-containing coating layer acts as a physical barrier and reaction regulator for the internal calcium carbonate, delaying the neutralization reaction between calcium carbonate and the acid source (MPP) of the intumescent flame retardant. This makes the consumption of the acid source more controllable, ensuring that the expansion to char reaction can still proceed effectively even with higher calcium carbonate dosages. Therefore, while maintaining or even enhancing flame retardant performance (manifested as an increased oxygen index), the amount of modified calcium carbonate added can be appropriately increased. The increased amount of calcium carbonate and the improved dispersibility directly enhanced its reinforcing and toughening effect on the material matrix, thereby further optimizing the mechanical properties of the composite foam material.
[0016] In some possible implementations, the alkyltrimethoxysilane is at least one selected from methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, and octyltrimethoxysilane. The introduction of alkyltrimethoxysilane can improve coating uniformity and can introduce alkyl segments to impart better dispersion to the material.
[0017] The second aspect of the present invention provides a method for preparing polypropylene foam material, comprising the following steps: mixing raw materials and then extruding and granulating them, followed by foaming and injection molding to obtain polypropylene foam material.
[0018] The beneficial effects of this invention are: This invention employs a sol-gel method to coat and modify calcium carbonate. Alkyltrimethoxysilane and tetraethyl orthosilicate are hydrolyzed and condensed in situ on the surface of nano-calcium carbonate particles, constructing a structurally controllable silicon-containing inorganic-organic hybrid coating layer. The introduced alkyl chains significantly enhance the compatibility between the modified calcium carbonate and the nonpolar polypropylene matrix, thereby effectively improving its dispersibility in the composite system and reducing agglomeration. This also improves the mechanical properties of the foamed polypropylene material. Detailed Implementation
[0019] 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.
[0020] The following is a detailed description of a polypropylene foam material and its preparation method according to an embodiment of this application.
[0021] The following is a detailed description with reference to specific examples.
[0022] Example 1
[0023] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin and modified calcium carbonate, wherein the mass ratio of polypropylene resin to modified calcium carbonate is 96:4; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer; the modified calcium carbonate is prepared through the following steps: Water and ethanol were mixed, and ammonia was added. While stirring, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added and mixed. The mixture was stirred and reacted at 20°C for 24 hours. After the reaction was complete, the mixture was washed with ethanol and dried to obtain modified calcium carbonate. The volume ratio of water to ethanol was 1:9, the concentration of ammonia in the water-ethanol mixture was 0.3 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane was 10 mL:1.5 g:3 g:3 g. The particle size of the calcium carbonate was <20 μm. The alkyltrimethoxysilane was propyltrimethoxysilane.
[0024] The preparation method of the above-mentioned polypropylene foam material includes the following steps: The raw materials are mixed and then fed into a twin-screw extruder for extrusion. The extruded material is cooled with cold water and then fed into a granulator for granulation to obtain composite material masterbatch. The temperature range of the extruder is 190-200℃.
[0025] After drying the composite masterbatch, it is added to the injection molding machine. Nitrogen gas is pressurized to 28-32 MPa, and supercritical nitrogen is injected into the barrel at a pressure of 16 MPa for 3 seconds. The gas is then introduced into the mold for pressure holding and cooling. The injection pressure is 80 MPa, the back pressure is 10 MPa, and the cooling time is 20 seconds. The temperature range of the injection molding machine is 190-200℃.
[0026] Example 2
[0027] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin and modified calcium carbonate, wherein the mass ratio of polypropylene resin to modified calcium carbonate is 94:6; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer; the modified calcium carbonate is prepared through the following steps: Water and ethanol were mixed, and ammonia was added. While stirring, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added and mixed. The mixture was stirred and reacted at 20°C for 24 hours. After the reaction was complete, the mixture was washed with ethanol and dried to obtain modified calcium carbonate. The volume ratio of water to ethanol was 1:9, the concentration of ammonia in the water-ethanol mixture was 0.3 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane was 10 mL:1.5 g:3 g:3 g. The particle size of the calcium carbonate was <20 μm. The alkyltrimethoxysilane was propyltrimethoxysilane.
[0028] The preparation method of the polypropylene foam material in this embodiment is the same as that in Example 1.
[0029] Example 3
[0030] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin and modified calcium carbonate, wherein the mass ratio of polypropylene resin to modified calcium carbonate is 92:8; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer; the modified calcium carbonate is prepared by the following steps: Water and ethanol were mixed, and ammonia was added. While stirring, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added and mixed. The mixture was stirred and reacted at 20°C for 24 hours. After the reaction was complete, the mixture was washed with ethanol and dried to obtain modified calcium carbonate. The volume ratio of water to ethanol was 1:9, the concentration of ammonia in the water-ethanol mixture was 0.3 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane was 10 mL:1.5 g:2 g:4 g. The particle size of the calcium carbonate was <20 μm. The alkyltrimethoxysilane was octyltrimethoxysilane.
[0031] The preparation method of the polypropylene foam material in this embodiment is the same as that in Example 1.
[0032] Example 4
[0033] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin, flame retardant, and modified calcium carbonate, wherein the mass ratio of polypropylene resin, flame retardant, and modified calcium carbonate is 76:20:4; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer; wherein the flame retardant includes a carbon source, an acid source, and a gas source, wherein the carbon source is dipentaerythritol, the acid source is ammonium polyphosphate, and the gas source is melamine. This modified calcium carbonate is prepared through the following steps: Water and ethanol were mixed, and ammonia was added. While stirring, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added and mixed. The mixture was stirred and reacted at 20°C for 24 hours. After the reaction was complete, the mixture was washed with ethanol and dried to obtain modified calcium carbonate. The volume ratio of water to ethanol was 1:9, the concentration of ammonia in the water-ethanol mixture was 0.3 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane was 10 mL:1.5 g:3 g:3 g. The particle size of the calcium carbonate was <20 μm. The alkyltrimethoxysilane was propyltrimethoxysilane.
[0034] The preparation method of the above-mentioned polypropylene foam material includes the following steps: The raw materials are mixed and then fed into a twin-screw extruder for extrusion. The extruded material is cooled with cold water and then fed into a granulator for granulation to obtain composite material masterbatch. The temperature range of the extruder is 190-200℃.
[0035] After drying the composite masterbatch, it is added to the injection molding machine. Nitrogen gas is pressurized to 28-32 MPa, and supercritical nitrogen is injected into the barrel at a pressure of 16 MPa for 3 seconds. The gas is then introduced into the mold for pressure holding and cooling. The injection pressure is 80 MPa, the back pressure is 10 MPa, and the cooling time is 20 seconds. The temperature range of the injection molding machine is 190-200℃.
[0036] Example 5
[0037] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin, flame retardant, and modified calcium carbonate, wherein the mass ratio of polypropylene resin, flame retardant, and modified calcium carbonate is 74:20:6; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer; wherein the flame retardant includes a carbon source, an acid source, and a gas source, wherein the carbon source is dipentaerythritol, the acid source is ammonium polyphosphate, and the gas source is melamine. This modified calcium carbonate is prepared through the following steps: Water and ethanol were mixed, and ammonia was added. While stirring, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added and mixed. The mixture was stirred and reacted at 20°C for 24 hours. After the reaction was complete, the mixture was washed with ethanol and dried to obtain modified calcium carbonate. The volume ratio of water to ethanol was 1:9, the concentration of ammonia in the water-ethanol mixture was 0.3 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane was 10 mL:1.5 g:3 g:3 g. The particle size of the calcium carbonate was <20 μm. The alkyltrimethoxysilane was propyltrimethoxysilane.
[0038] The preparation method of the polypropylene foam material in this embodiment is the same as that in Embodiment 4.
[0039] Example 6
[0040] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin, flame retardant, and modified calcium carbonate, wherein the mass ratio of polypropylene resin, flame retardant, and modified calcium carbonate is 72:20:8; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer; wherein the flame retardant includes a carbon source, an acid source, and a gas source, wherein the carbon source is dipentaerythritol, the acid source is ammonium polyphosphate, and the gas source is melamine. This modified calcium carbonate is prepared through the following steps: Water and ethanol were mixed, and ammonia was added. While stirring, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added and mixed. The mixture was stirred and reacted at 20°C for 24 hours. After the reaction was complete, the mixture was washed with ethanol and dried to obtain modified calcium carbonate. The volume ratio of water to ethanol was 1:9, the concentration of ammonia in the water-ethanol mixture was 0.3 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane was 10 mL:1.5 g:2 g:4 g. The particle size of the calcium carbonate was <20 μm. The alkyltrimethoxysilane was octyltrimethoxysilane.
[0041] The preparation method of the polypropylene foam material in this embodiment is the same as that in Embodiment 4.
[0042] Example 7
[0043] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin, flame retardant and modified calcium carbonate, wherein the mass ratio of polypropylene resin, flame retardant and modified calcium carbonate is 74:20:6; the difference between this embodiment and embodiment 4 is that the flame retardant used in this embodiment is modified ammonium polyphosphate, while the remaining raw materials and preparation process are the same as in embodiment 4.
[0044] The modified ammonium polyphosphate is prepared through the following steps: Alkyltrimethoxysilane and trimethyl borate were added to an aqueous ethanol solution, and acetic acid was added to adjust the pH to 5.5. The solution was stirred at 40°C for 2-3 hours to obtain a hydrolysate. γ-aminopropyltriethoxysilane, anhydrous ethanol and ammonium polyphosphate were mixed and stirred at 70°C for 2 hours. Then, hydrolysate was added and the mixture was stirred at 70°C for 2 hours. After the reaction was completed, the modified ammonium polyphosphate was obtained by washing with water and drying.
[0045] The volume fraction of the ethanol aqueous solution is 25%, and the mass ratio of alkyltrimethoxysilane, trimethyl borate, γ-aminopropyltriethoxysilane and ammonium polyphosphate is 5:2:3:70; the alkyltrimethoxysilane is propyltrimethoxysilane.
[0046] The preparation method of the polypropylene foam material in this embodiment is the same as that in Embodiment 4.
[0047] Example 8
[0048] This embodiment provides a polypropylene foam material, comprising the following raw materials: polypropylene resin, flame retardant and modified calcium carbonate. The difference between this embodiment and embodiment 4 is that the mass ratio of polypropylene resin, flame retardant and modified calcium carbonate is 72:20:8; in this embodiment, modified ammonium polyphosphate is used as the flame retardant, and the remaining raw materials and preparation process are the same as in embodiment 4.
[0049] The modified ammonium polyphosphate is prepared through the following steps: Alkyltrimethoxysilane and trimethyl borate were added to an aqueous ethanol solution, and acetic acid was added to adjust the pH to 5.5. The mixture was stirred at 40°C for 3 hours to obtain a hydrolysate. γ-aminopropyltriethoxysilane, anhydrous ethanol and ammonium polyphosphate were mixed and stirred at 70°C for 2 hours. Then, hydrolysate was added and the mixture was stirred at 70°C for 2 hours. After the reaction was completed, the modified ammonium polyphosphate was obtained by washing with water and drying.
[0050] The volume fraction of the ethanol aqueous solution is 25%, and the mass ratio of alkyltrimethoxysilane, trimethyl borate, γ-aminopropyltriethoxysilane and ammonium polyphosphate is 5:2:3:70; the alkyltrimethoxysilane is octyltrimethoxysilane.
[0051] The preparation method of the polypropylene foam material in this embodiment is the same as that in Embodiment 4.
[0052] Comparative Example 1
[0053] The difference between the comparative example and Example 2 is that the modified calcium carbonate was replaced with unmodified calcium carbonate, while the other raw materials and preparation process remained the same as in Example 2.
[0054] Comparative Example 2
[0055] The difference between this comparative example and Example 5 is that the modified calcium carbonate is replaced with unmodified calcium carbonate, while the other raw materials and preparation process remain the same as in Example 5. That is, in this comparative example, the flame retardant is ammonium polyphosphate, and modified calcium carbonate is not used.
[0056] Comparative Example 3
[0057] The difference between this comparative example and Example 7 is that the modified calcium carbonate is replaced with unmodified calcium carbonate, while the other raw materials and preparation process remain the same as in Example 7. That is, in this comparative example, the flame retardant is modified ammonium polyphosphate, and modified calcium carbonate is not used.
[0058] Test case
[0059] Performance tests were performed on Examples 1-8, Comparative Examples 1-3, and the Control Example; The cantilever beam impact strength was tested according to standard GB / T 1843-2008, with the notch on the specimen being a type A notch. A blank polypropylene sample (without calcium carbonate, flame retardant, or foaming) was used as a control. The results are shown in Table 1. Table 1
[0060] As can be seen from Table 1, by comparing Examples 1-3 with Comparative Example 1, Examples 4-6 with Comparative Example 2, and Examples 7-8, it can be seen that the introduction of modified calcium carbonate in both samples with and without flame retardants is beneficial to improving the impact resistance of the material and effectively solves the problem of poor mechanical properties of foamed polypropylene in the prior art.
[0061] Combustion performance was tested according to GB / T2406.2-2009, "Determination of Combustion Behavior by Oxygen Index Method for Plastics". The samples prepared in Examples 4-6 and Comparative Examples 1-3 were tested, and the results are shown in Table 2 below: Table 2
[0062] According to Table 2, and in conjunction with Examples 4-6 and Comparative Example 2, Examples 7-8 and Comparative Example 3, it can be seen that the modified calcium carbonate with a coating layer formed by the sol-gel method has a more complete and stable structure. This not only improves dispersion, but its silicon-containing components can also directly participate in and catalyze the formation of a denser, more insulating char layer during combustion, thus providing a superior synergistic flame-retardant enhancement effect with the flame retardant. The silicon-containing coating layer acts as a physical barrier and reaction regulator for the internal calcium carbonate, delaying the neutralization reaction between calcium carbonate and the intumescent flame retardant acid source (ammonium polyphosphate), making the consumption of the acid source more controllable, thereby ensuring that the expansion to char reaction can still proceed effectively even with a higher calcium carbonate dosage. Therefore, while maintaining or even enhancing the flame-retardant performance (manifested as an increase in the oxygen index), the amount of modified calcium carbonate added can be appropriately increased. The increased calcium carbonate dosage and improved dispersion directly enhance its reinforcing and toughening effect on the material matrix, further optimizing the mechanical properties of the composite foam material. In Examples 7 and 8, modified ammonium polyphosphate was also used. The modified ammonium polyphosphate was constructed on the surface of the ammonium polyphosphate through boron-silicon synergistic modification, forming a BO-Si and BOP covalent network. This network can form a low-melting-point borate glass phase in the early stage of combustion, which, together with the silicon-oxygen skeleton, "seals" the microcracks in the expanded carbon layer, transforming the carbon layer from a porous expander into a dense and continuous "ceramic-glass" composite barrier. This barrier can significantly inhibit the diffusion of thermal decomposition volatiles of the polymer substrate into the combustion zone at high temperatures. More importantly, the modified ammonium polyphosphate has better dispersibility in the foamed polypropylene system, which not only improves the flame retardant performance but also better enhances the mechanical properties.
[0063] In summary, as shown in Tables 1 and 2, the modified calcium carbonate coated with a silicon-containing inorganic-organic hybrid coating layer prepared by the sol-gel method can increase the amount of modified calcium titanate without reducing the flame retardant performance, thereby achieving a synergistic improvement in both flame retardant and mechanical properties.
[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "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.
[0065] 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, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A polypropylene foam material, characterized in that, The raw materials include: polypropylene resin, flame retardant and modified calcium carbonate, wherein the mass ratio of polypropylene resin, flame retardant and modified calcium carbonate is 72-96:0-20:4-8; the modified calcium carbonate contains a silicon-containing inorganic-organic hybrid coating layer.
2. The polypropylene foam material according to claim 1, characterized in that, The modified calcium carbonate is prepared by the following steps: Water and ethanol were mixed, and ammonia was added. Calcium carbonate, tetraethyl orthosilicate, and alkyltrimethoxysilane were added while stirring. The mixture was stirred and reacted at 20-25℃ for 18-24 hours. After the reaction was completed, the mixture was washed with ethanol and dried to obtain modified calcium carbonate.
3. The polypropylene foam material according to claim 1, characterized in that, The volume ratio of water to ethanol is 1:9, the concentration of ammonia in the water-ethanol mixture is 0.1-0.5 mol / L, and the ratio of water, calcium carbonate, tetraethyl orthosilicate and alkyltrimethoxysilane is 10 mL: 1.5 g: 2-3 g: 3-4 g.
4. The polypropylene foam material according to claim 1, characterized in that, The calcium carbonate has a particle size of <20 μm.
5. The polypropylene foam material according to claim 1, characterized in that, The polypropylene resin includes virgin polypropylene resin and recycled polypropylene resin; the amount of recycled polypropylene resin added to the polypropylene resin is ≤48%.
6. The polypropylene foam material according to claim 1, characterized in that, The flame retardant includes a carbon source, an acid source, and a gas source, wherein the acid source is either ammonium polyphosphate or modified ammonium polyphosphate.
7. A polypropylene foam material according to claim 6, characterized in that, The modified ammonium polyphosphate is prepared through the following steps: Alkyltrimethoxysilane and trimethyl borate were added to an aqueous ethanol solution, and acetic acid was added to adjust the pH to 5-6. The mixture was stirred at 40°C for 2-3 hours to obtain a hydrolysate. γ-aminopropyltriethoxysilane, anhydrous ethanol and ammonium polyphosphate were mixed and stirred at 65-70℃ for 2 hours. Then, hydrolysate was added and the mixture was stirred at 70℃ for 1-2 hours. After the reaction was completed, the mixture was washed with water and dried to obtain modified ammonium polyphosphate.
8. The polypropylene foam material according to claim 7, characterized in that, The volume fraction of the ethanol aqueous solution is 20-30%, and the mass ratio of alkyltrimethoxysilane, trimethyl borate, γ-aminopropyltriethoxysilane and ammonium polyphosphate is 5:2:3:
70.
9. A polypropylene foam material according to claim 2 or 7, characterized in that, The alkyltrimethoxysilane is at least one of methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, and octyltrimethoxysilane.
10. A method for preparing a polypropylene foam material, used to prepare the polypropylene foam material according to any one of claims 1-9, characterized in that, The process includes the following steps: mixing raw materials, extruding and granulating them, and then foaming and injection molding them to obtain polypropylene foam material.