Impact-resistant halogen-free flame-retardant polypropylene composite material and preparation method thereof

Abstract

This application relates to the technical field of polymer composite materials, specifically disclosing an impact-resistant halogen-free flame-retardant polypropylene composite material and its preparation method. The impact-resistant halogen-free flame-retardant polypropylene composite material comprises the following raw materials in parts by weight: 55-60 parts of block copolymer polypropylene, 10-12 parts of polyolefin elastomer, 4-6 parts of maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, 3-4 parts of liquid nitrile rubber, 10-12 parts of microencapsulated ammonium polyphosphate, 2-3 parts of organic phosphonate, 3-4 parts of dipentaerythritol, 2-3 parts of zinc borate, 4-5 parts of silane-modified attapulgite clay, 3-4 parts of core-shell structured nano-rubber particles, 0.3-0.5 parts of antioxidant, and 0.1-0.3 parts of lubricant. This application can improve the impact resistance of the halogen-free flame-retardant polypropylene composite material in low-temperature environments.

Description

Technical Field

[0001] This invention relates to the technical field of polymer composite materials, and in particular to an impact-resistant, halogen-free flame-retardant polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene is a general-purpose plastic with excellent overall performance and low price. Due to its low density, good chemical resistance, and ease of processing and molding, it is widely used in household appliances, automotive parts, electronic and electrical housings, and building materials. However, polypropylene has a limiting oxygen index (LOI) of only 17%–18%, classifying it as a flammable material. Furthermore, it easily produces molten droplets during combustion, posing a significant fire hazard. Therefore, flame-retardant modification is usually required before practical use.

[0003] In related technologies, patent CN104262778A discloses a high-impact, halogen-free, flame-retardant polypropylene composite material, which is prepared from the following components by mass percentage: 15-30% microencapsulated ammonium polyphosphate, 3-7% pentaerythritol, 2-4% zinc borate, 1-4% silane-modified attapulgite clay, and the remainder being a polypropylene matrix.

[0004] However, when the aforementioned polypropylene composite material is applied to low-temperature environments such as cold chain logistics and high-latitude cold regions, it is prone to brittle fracture and its impact resistance deteriorates. Summary of the Invention

[0005] To improve the impact resistance of halogen-free flame-retardant polypropylene composites in low-temperature environments, this application provides an impact-resistant halogen-free flame-retardant polypropylene composite material and its preparation method.

[0006] Firstly, this application provides an impact-resistant, halogen-free, flame-retardant polypropylene composite material, which adopts the following technical solution: A halogen-free flame-retardant polypropylene composite material with impact resistance comprises the following raw materials in parts by weight: 55-60 parts of block copolymer polypropylene, 10-12 parts of polyolefin elastomer, 4-6 parts of maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, 3-4 parts of liquid nitrile rubber, 10-12 parts of microencapsulated ammonium polyphosphate, 2-3 parts of organic phosphonate, 3-4 parts of dipentaerythritol, 2-3 parts of zinc borate, 4-5 parts of silane-modified attapulgite clay, 3-4 parts of core-shell structured nano-rubber particles, 0.3-0.5 parts of antioxidant, and 0.1-0.3 parts of lubricant.

[0007] In one specific implementation, the organic phosphonate includes at least one of aluminum phosphonate and calcium phosphonate.

[0008] In one specific feasible embodiment, the microencapsulated ammonium polyphosphate is prepared according to the following steps: Melamine was added to an aqueous formaldehyde solution, the pH was adjusted to 8.5-9.0, and the solution was stirred in a water bath at 70-80°C for 45-60 minutes to obtain the MF prepolymer solution. Ammonium polyphosphate and anhydrous ethanol were mixed at a weight-to-volume ratio of 1:(3-5) and ultrasonically dispersed to obtain a suspension. The MF prepolymer solution was added to the suspension, the pH was adjusted to 4.0-5.5, and the mixture was stirred in a constant temperature water bath at 75-80℃ for 2-3 hours. The mixture was then filtered, washed with anhydrous ethanol until the filtrate was clear, vacuum dried, ground, and sieved to obtain microencapsulated ammonium polyphosphate.

[0009] In one specific feasible embodiment, the silane-modified attapulgite clay is prepared according to the following steps: The attapulgite was dispersed in an aqueous ethanol solution to obtain an attapulgite suspension. The silane coupling agent was dispersed in an aqueous ethanol solution, the pH was adjusted to 3.5–4.0, and hydrolyzed at room temperature for 15–30 min to obtain a silane coupling agent solution. The silane coupling agent solution was added dropwise to an attapulgite suspension, and refluxed and condensed for 3–5 h under stirring at 300–500 rpm in a water bath at 80–85 °C. The mixture was then filtered, washed until no free silane was found, dried, ground, and sieved to obtain silane-modified attapulgite clay.

[0010] In one specific feasible embodiment, the core-shell structured nano-rubber particles are prepared according to the following steps: Mix 80-100 parts of deionized water, 0.5-1.0 parts of emulsifier, 5-10 parts of butyl acrylate and 0.1-0.2 parts of initiator, heat to 70-80℃ under nitrogen protection, and stir at a constant temperature for 30-60 minutes to obtain seed emulsion; Mix 70-80 parts of butyl acrylate, 1.0-2.0 parts of crosslinking agent, 1.5-2.5 parts of emulsifier, and 80-100 parts of deionized water, and shear at 8000-12000 rpm for 5-10 min to obtain a core layer pre-emulsion. Mix 30-40 parts of methyl methacrylate, 1.0-1.5 parts of emulsifier, and 40-60 parts of deionized water, and shear at 8000-10000 rpm for 3-5 minutes to obtain a shell pre-emulsion. The seed emulsion was heated to 70-75℃, and the pre-emulsion of the core was added dropwise to the seed emulsion under constant stirring at 200-300 rpm for 2.0-3.0 h. After the addition was completed, the mixture was kept warm for 0.5-1.0 h to obtain the butyl acrylate core emulsion. Add shell pre-emulsion dropwise to the core emulsion over a period of 1.5-2.0 h, add 0.1-0.2 parts of initiator, and continue the reaction at 70-75 °C for 1-2 h to obtain a shell-coated emulsion. Cool the shell-coated emulsion to 50-60℃, add 5-10 parts of CaCl2 solution while stirring, allow it to stand and separate into layers, filter, wash with deionized water and ethanol until no emulsifier residue remains, dry to constant weight, grind and sieve to obtain core-shell structured nano-rubber particles.

[0011] Secondly, this application provides a method for preparing an impact-resistant, halogen-free, flame-retardant polypropylene composite material, which employs the following technical solution: A method for preparing an impact-resistant, halogen-free, flame-retardant polypropylene composite material includes the following steps: Premix: Weigh each component according to the formula, and mix the block copolymer polypropylene, polyolefin elastomer, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, liquid nitrile rubber, microencapsulated ammonium polyphosphate, organic phosphonate, dipentaerythritol, zinc borate, silane-modified attapulgite clay, core-shell structured nano-rubber particles, antioxidant and lubricant. After the material temperature reaches 70-80℃, discharge the material to obtain the mixture. Extrusion granulation: The mixture is added to a twin-screw extruder for melt blending and extrusion granulation to obtain granules. The granules are dried at 80-85℃ for 2-4 hours to obtain impact-resistant halogen-free flame-retardant polypropylene composite material.

[0012] In one specific feasible implementation, the temperature of each section of the twin-screw extruder is 175-190℃, the screw speed is 350-400rpm, and the vacuum degree of the die head is ≤-0.08MPa.

[0013] In summary, this application has the following beneficial effects: 1. This application improves the impact resistance of halogen-free flame-retardant polypropylene composites in low-temperature environments by using a limited ratio of segment copolymer polypropylene, polyolefin elastomer, maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, liquid nitrile rubber, microencapsulated ammonium polyphosphate, aluminum phosphinate, dipentaerythritol, zinc borate, silane-modified attapulgite clay, core-shell structured nano-rubber particles, antioxidants, and lubricants.

[0014] 2. In this application, at least one of aluminum phosphonate and calcium phosphonate is preferred, both of which can be used to prepare impact-resistant halogen-free flame-retardant polypropylene composite materials. Detailed Implementation

[0015] Unless otherwise specified, all raw materials used in this application are commercially available. Block copolymer polypropylene, grade: J340PPB-M02. Polyolefin elastomer, grade: Saudi Basic C1055D. Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, grade: Xinrui New Materials FG03. Liquid nitrile rubber, grade: Baling Petrochemical 220. Aluminum phosphonate, CAS No. 7784-22-7, model LA2315. Dipentaerythritol, CAS No. 126-58-9, active ingredient content 99%. Zinc borate, CAS No. 10361-94-1, particle size 1000 mesh. Antioxidant, model SP-2. Lubricant is calcium stearate, CAS No. 1592-23-0, active ingredient content 99%. Melamine, CAS No. 108-78-1, active ingredient content 99%. Ammonium polyphosphate, CAS No. 68333-79-9, active ingredient content 99%. Attapulgite, 325 mesh, purchased from Shijiazhuang Borui Building Materials Co., Ltd. Emulsifier: Sodium dodecyl sulfate, CAS No. 151-21-3, active ingredient content 99%. Butyl acrylate, CAS No. 141-32-2, active ingredient content 99%. Initiator: Potassium persulfate, AR grade. Crosslinking agent: Styrene-diethylene, CAS No. 1321-74-0, active ingredient content 99%. Methyl methacrylate, CAS No. 922-67-8, active ingredient content 99%. Calcium phosphonate, CAS No. 7789-79-9, active ingredient content 99%.

[0016] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0017] Example 1

[0018] This embodiment provides an impact-resistant, halogen-free, flame-retardant polypropylene composite material comprising the following raw materials: 58 kg of block copolymer polypropylene, 11 kg of polyolefin elastomer, 5 kg of maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, 3.5 kg of liquid nitrile rubber, 11 kg of microencapsulated ammonium polyphosphate, 2.5 kg of aluminum phosphonate, 3.5 kg of dipentaerythritol, 2.5 kg of zinc borate, 4.5 kg of silane-modified attapulgite clay, 3.5 kg of core-shell structured nano-rubber particles, 0.4 kg of antioxidant, and 0.2 kg of lubricant.

[0019] Microencapsulated ammonium polyphosphate is prepared according to the following steps: Melamine and a 37% formaldehyde aqueous solution were mixed at a mass ratio of 1:3. The pH was adjusted to between 8.5 and 9.0 with a 10% Na2CO3 solution. The mixture was stirred in a 75°C water bath for 52 minutes to obtain the MF prepolymer solution.

[0020] Ammonium polyphosphate and anhydrous ethanol were mixed at a weight-to-volume ratio of 1:4 and ultrasonically dispersed to obtain a suspension. The MF prepolymer solution was added to the suspension, and the pH was adjusted to between 4.0 and 5.5 with glacial acetic acid. The mixture was stirred at 500 rpm for 2.5 h in a constant temperature water bath at 78 °C. The mixture was then filtered and washed with anhydrous ethanol until the filtrate was clear. After vacuum drying at 80 °C for 20 h, the mixture was ground and passed through a 200-mesh sieve to obtain microencapsulated ammonium polyphosphate.

[0021] Silane-modified attapulgite clay is prepared according to the following steps: Attapulgite and an 80% ethanol aqueous solution were mixed at a mass-to-volume ratio of 1:35 and ultrasonically dispersed to obtain an attapulgite suspension.

[0022] Silane coupling agent KH-550 was dispersed in an aqueous ethanol solution, and the pH was adjusted to between 3.5 and 4.0 with dilute HAc. The solution was hydrolyzed at room temperature for 22 min to obtain a KH-550 solution. The amount of silane coupling agent KH-550 used was 2% of the mass of attapulgite. The KH-550 solution was added dropwise to the attapulgite suspension, and the mixture was refluxed and condensed for 4 h under stirring at 400 rpm in an 83°C water bath. After filtration, the mixture was washed successively with anhydrous ethanol and deionized water until no free silane remained. After drying in a forced-air environment at 110°C for 5 h, the mixture was ground and passed through a 325-mesh sieve to obtain silane-modified attapulgite clay.

[0023] Core-shell structured nano-rubber particles were prepared according to the following steps: Mix 90 kg of deionized water, 0.8 kg of emulsifier, 7 kg of butyl acrylate and 0.15 kg of initiator, stir to dissolve, heat to 75 °C under nitrogen protection, and stir at a constant temperature for 45 min to obtain seed emulsion.

[0024] Mix 75 kg of butyl acrylate, 1.5 kg of crosslinking agent, 2 kg of emulsifier, and 90 kg of deionized water, and shear at 10,000 rpm for 8 minutes to obtain a core layer pre-emulsion.

[0025] Mix 35 kg of methyl methacrylate, 1.25 kg of emulsifier, and 50 kg of deionized water, and shear at 9000 rpm for 4 min to obtain a shell pre-emulsion.

[0026] The seed emulsion was heated to 72.5℃, and the pre-emulsion of the core was added dropwise to the seed emulsion at a constant speed of 250 rpm for 2.5 h. After the addition was completed, the mixture was kept warm for 0.8 h to obtain the butyl acrylate core emulsion.

[0027] The shell pre-emulsion was added dropwise to the core emulsion at a uniform rate over a period of 1.8 h. 0.15 kg of initiator was added, and the reaction was continued at a constant temperature of 72.5 °C for 1.5 h to obtain a shell-coated emulsion.

[0028] The shell-coated emulsion was cooled to 55°C, and 7.5 kg of CaCl2 solution was added while stirring. The mixture was allowed to stand and separate into layers, filtered, and washed with deionized water and ethanol until no emulsifier residue remained. It was then vacuum dried at 55°C to constant weight, ground, and passed through a 200-mesh sieve to obtain core-shell structured nano-rubber particles.

[0029] This embodiment also provides a method for preparing an impact-resistant, halogen-free, flame-retardant polypropylene composite material, comprising the following steps: Weigh each component according to the formula, and add the block copolymer polypropylene, polyolefin elastomer, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, liquid nitrile rubber, microencapsulated ammonium polyphosphate, aluminum phosphinate, dipentaerythritol, zinc borate, silane-modified attapulgite clay, core-shell structured nano-rubber particles, antioxidant and lubricant into a high-speed mixer. Mix at high speed until the material temperature reaches 75°C, and then discharge to obtain the mixture.

[0030] The mixture is added to a twin-screw extruder for melt blending, extrusion granulation to obtain granules, and the granules are dried at 83℃ for 3 hours to obtain an impact-resistant, halogen-free, flame-retardant polypropylene composite material. The temperature of each section of the twin-screw extruder is 175-190℃, the screw speed is 380 rpm, and the die head vacuum degree is ≤-0.08MPa.

[0031] Example 2

[0032] The only difference between this embodiment and Embodiment 1 is that the impact-resistant halogen-free flame-retardant polypropylene composite material includes the following raw materials: 55 kg of block copolymer polypropylene, 10 kg of polyolefin elastomer, 4 kg of maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, 3 kg of liquid nitrile rubber, 10 kg of microencapsulated ammonium polyphosphate, 2 kg of aluminum phosphonate, 3 kg of dipentaerythritol, 2 kg of zinc borate, 4 kg of silane-modified attapulgite clay, 3 kg of core-shell structured nano-rubber particles, 0.3 kg of antioxidant, and 0.1 kg of lubricant.

[0033] Example 3

[0034] The only difference between this embodiment and Embodiment 1 is that the impact-resistant halogen-free flame-retardant polypropylene composite material includes the following raw materials: 60 kg of block copolymer polypropylene, 12 kg of polyolefin elastomer, 6 kg of maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, 4 kg of liquid nitrile rubber, 12 kg of microencapsulated ammonium polyphosphate, 3 kg of aluminum phosphonate, 4 kg of dipentaerythritol, 3 kg of zinc borate, 5 kg of silane-modified attapulgite clay, 4 kg of core-shell structured nano-rubber particles, 0.5 kg of antioxidant, and 0.3 kg of lubricant.

[0035] Example 4

[0036] The only difference between this embodiment and Embodiment 1 is that an equal amount of calcium phosphonate is used instead of aluminum phosphonate.

[0037] Example 5

[0038] The only difference between this embodiment and Example 1 is that the microencapsulated ammonium polyphosphate is prepared according to the following steps: Melamine and a 37% formaldehyde aqueous solution were mixed at a mass ratio of 1:3. The pH was adjusted to between 8.5 and 9.0 with a 10% Na2CO3 solution. The mixture was stirred in a 70°C water bath for 45 minutes to obtain the MF prepolymer solution.

[0039] Ammonium polyphosphate and anhydrous ethanol were mixed at a weight-to-volume ratio of 1:3 and ultrasonically dispersed to obtain a suspension. The MF prepolymer solution was added to the suspension, and the pH was adjusted to between 4.0 and 5.5 with glacial acetic acid. The mixture was stirred at 500 rpm for 2 hours in a constant temperature water bath at 75°C. The mixture was then filtered and washed with anhydrous ethanol until the filtrate was clear. After vacuum drying at 80°C for 20 hours, the mixture was ground and passed through a 200-mesh sieve to obtain microencapsulated ammonium polyphosphate.

[0040] Example 6

[0041] The only difference between this embodiment and Example 1 is that the microencapsulated ammonium polyphosphate is prepared according to the following steps: Melamine and a 37% formaldehyde aqueous solution were mixed at a mass ratio of 1:3. The pH was adjusted to between 8.5 and 9.0 with a 10% Na2CO3 solution. The mixture was stirred in an 80°C water bath for 60 minutes to obtain the MF prepolymer solution.

[0042] Ammonium polyphosphate and anhydrous ethanol were mixed at a weight-to-volume ratio of 1:3 and ultrasonically dispersed to obtain a suspension. The MF prepolymer solution was added to the suspension, and the pH was adjusted to between 4.0 and 5.5 with glacial acetic acid. The mixture was stirred at 500 rpm for 3 hours in a constant temperature water bath at 80°C. Then, the mixture was filtered and washed with anhydrous ethanol until the filtrate was clear. After vacuum drying at 80°C for 20 hours, the mixture was ground and passed through a 200-mesh sieve to obtain microencapsulated ammonium polyphosphate.

[0043] Example 7

[0044] The only difference between this embodiment and Example 1 is that the silane-modified attapulgite clay is prepared according to the following steps: Attapulgite and an 80% ethanol aqueous solution were mixed at a mass-to-volume ratio of 1:35 and ultrasonically dispersed to obtain an attapulgite suspension.

[0045] Silane coupling agent KH-550 was dispersed in an aqueous ethanol solution, and the pH was adjusted to between 3.5 and 4.0 with dilute HAc. The solution was hydrolyzed at room temperature for 15 minutes to obtain a KH-550 solution. The amount of silane coupling agent KH-550 used was 2% of the mass of attapulgite. The KH-550 solution was added dropwise to the attapulgite suspension, and the mixture was refluxed and condensed for 3 hours at 80°C with stirring at 300 rpm. After filtration, the mixture was washed successively with anhydrous ethanol and deionized water until no free silane remained. After drying in a forced-air environment at 110°C for 5 hours, the mixture was ground and passed through a 325-mesh sieve to obtain silane-modified attapulgite clay.

[0046] Example 8

[0047] The only difference between this embodiment and Example 1 is that the silane-modified attapulgite clay is prepared according to the following steps: Attapulgite and an 80% ethanol aqueous solution were mixed at a mass-to-volume ratio of 1:35 and ultrasonically dispersed to obtain an attapulgite suspension.

[0048] Silane coupling agent KH-550 was dispersed in an aqueous ethanol solution, and the pH was adjusted to between 3.5 and 4.0 with dilute HAc. The solution was hydrolyzed at room temperature for 3 minutes to obtain a KH-550 solution. The amount of silane coupling agent KH-550 used was 2% of the mass of attapulgite. The KH-550 solution was added dropwise to the attapulgite suspension, and the mixture was refluxed and condensed for 5 hours at 85°C with stirring at 500 rpm. After filtration, the mixture was washed successively with anhydrous ethanol and deionized water until no free silane remained. After drying in a forced-air environment at 110°C for 5 hours, the mixture was ground and passed through a 325-mesh sieve to obtain silane-modified attapulgite clay.

[0049] Example 9

[0050] The only difference between this embodiment and Example 1 is that the core-shell structured nano-rubber particles are prepared according to the following steps: Mix 80 kg of deionized water, 0.5 kg of emulsifier, 5 kg of butyl acrylate and 0.1 kg of initiator, stir to dissolve, heat to 70 °C under nitrogen protection, and stir at a constant temperature for 30 min to obtain seed emulsion.

[0051] Mix 70 kg of butyl acrylate, 1.0 kg of crosslinking agent, 1.5 kg of emulsifier, and 80 kg of deionized water, and shear at 8000 rpm for 5 min to obtain a core layer pre-emulsion.

[0052] Mix 30 kg of methyl methacrylate, 1.0 kg of emulsifier, and 40 kg of deionized water, and shear at 8000 rpm for 3 min to obtain a shell pre-emulsion.

[0053] The seed emulsion was heated to 70°C, and the pre-emulsion of the core was added dropwise to the seed emulsion at a constant speed of 200 rpm for 2.0 h. After the addition was completed, the mixture was kept warm for 0.5 h to obtain the butyl acrylate core emulsion.

[0054] The shell pre-emulsion was added dropwise to the core emulsion at a uniform rate over a period of 1.5 h. 0.1 kg of initiator was added, and the reaction was continued at a constant temperature of 70 °C for 1 h to obtain a shell-coated emulsion.

[0055] The shell-coated emulsion was cooled to 50°C, and 5 kg of CaCl2 solution was added while stirring. The mixture was allowed to stand and separate into layers, filtered, and washed with deionized water and ethanol until no emulsifier residue remained. It was then vacuum dried at 55°C to constant weight, ground, and passed through a 200-mesh sieve to obtain core-shell structured nano-rubber particles.

[0056] Example 10

[0057] The only difference between this embodiment and Example 1 is that the core-shell structured nano-rubber particles are prepared according to the following steps: Mix 100 kg of deionized water, 1.0 kg of emulsifier, 10 kg of butyl acrylate and 0.2 kg of initiator, stir to dissolve, heat to 80 °C under nitrogen protection, and stir at a constant temperature for 60 min to obtain seed emulsion.

[0058] Mix 80 kg of butyl acrylate, 2.0 kg of crosslinking agent, 2.5 kg of emulsifier, and 100 kg of deionized water, and shear at 12000 rpm for 10 min to obtain a core layer pre-emulsion.

[0059] Mix 40 kg of methyl methacrylate, 1.5 kg of emulsifier, and 60 kg of deionized water, and shear at 10,000 rpm for 5 minutes to obtain a shell pre-emulsion.

[0060] The seed emulsion was heated to 75°C, and the pre-emulsion of the core was added dropwise to the seed emulsion at a constant speed of 300 rpm for 3.0 h. After the addition was completed, the mixture was kept warm for 1.0 h to obtain the butyl acrylate core emulsion.

[0061] The shell pre-emulsion was added dropwise to the core emulsion at a uniform rate over a period of 2.0 h. 0.2 kg of initiator was added, and the reaction was continued at a constant temperature of 75 °C for 2 h to obtain a shell-coated emulsion.

[0062] The shell-coated emulsion was cooled to 60°C, and 10 kg of CaCl2 solution was added while stirring. The mixture was allowed to stand and separate into layers, filtered, and washed with deionized water and ethanol until no emulsifier residue remained. It was then vacuum dried at 55°C to constant weight, ground, and passed through a 200-mesh sieve to obtain core-shell structured nano-rubber particles.

[0063] Example 11

[0064] The only difference between this embodiment and Embodiment 1 is that the preparation method of the impact-resistant halogen-free flame-retardant polypropylene composite material includes the following steps: Weigh each component according to the formula, and add the block copolymer polypropylene, polyolefin elastomer, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, liquid nitrile rubber, microencapsulated ammonium polyphosphate, aluminum phosphinate, dipentaerythritol, zinc borate, silane-modified attapulgite clay, core-shell structured nano-rubber particles, antioxidant and lubricant into a high-speed mixer. Mix at high speed until the material temperature reaches 70°C, and then discharge to obtain the mixture.

[0065] The mixture is added to a twin-screw extruder for melt blending, extrusion granulation to obtain granules, and the granules are dried at 80℃ for 2 hours to obtain an impact-resistant, halogen-free, flame-retardant polypropylene composite material. The temperature of each section of the twin-screw extruder is 175-190℃, the screw speed is 350 rpm, and the die head vacuum degree is ≤-0.08MPa.

[0066] Example 12

[0067] The only difference between this embodiment and Embodiment 1 is that the preparation method of the impact-resistant halogen-free flame-retardant polypropylene composite material includes the following steps: Weigh each component according to the formula, and add the block copolymer polypropylene, polyolefin elastomer, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, liquid nitrile rubber, microencapsulated ammonium polyphosphate, aluminum phosphinate, dipentaerythritol, zinc borate, silane-modified attapulgite clay, core-shell structured nano-rubber particles, antioxidant and lubricant into a high-speed mixer. Mix at high speed until the material temperature reaches 80°C, and then discharge to obtain the mixture.

[0068] The mixture is added to a twin-screw extruder for melt blending, extrusion granulation, and granulation to obtain granules. The granules are dried at 85°C for 4 hours to obtain an impact-resistant, halogen-free, flame-retardant polypropylene composite material. The temperature of each section of the twin-screw extruder is 175-190°C, the screw speed is 400 rpm, and the die head vacuum degree is ≤-0.08 MPa.

[0069] Comparative Example 1 The only difference between this comparative example and Example 1 is that it does not contain polyolefin elastomers.

[0070] Comparative Example 2 The only difference between this comparative example and Example 1 is that it does not contain maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer.

[0071] Comparative Example 3 The only difference between this comparative example and Example 1 is that it does not contain liquid nitrile rubber.

[0072] Comparative Example 4 The only difference between this comparative example and Example 1 is that it does not contain microencapsulated ammonium polyphosphate.

[0073] Comparative Example 5 The only difference between this comparative example and Example 1 is that it does not contain organic phosphonates.

[0074] Comparative Example 6 The only difference between this comparative example and Example 1 is that it does not contain pentaerythritol.

[0075] Comparative Example 7 The only difference between this comparative example and Example 1 is that it does not contain silane-modified attapulgite clay.

[0076] Comparative Example 8 The only difference between this comparative example and Example 1 is that it does not contain core-shell structured nano-rubber particles.

[0077] Performance testing The following performance tests were conducted on Examples 1-12 and Comparative Examples 1-8: The prepared polypropylene composite material was fabricated into Type A notched specimens (A-type notch), with dimensions of 80mm × 10mm × 4mm (length × width × thickness), notch angle of 45°, notch bottom radius r = 0.25mm, and notch depth of 2.0mm. The specimens were conditioned in an environment of 23±2℃ and 50±10% relative humidity for at least 48h to eliminate residual stress.

[0078] Room temperature impact resistance test: The specimen is mounted in the jaws of the cantilever beam impact testing machine with the notch facing away from the pendulum. The test is conducted at an impact velocity of 3.5 ± 0.2 m / s, and the impact energy E (J) absorbed by each specimen is recorded. The room temperature cantilever beam notched impact strength is calculated according to the following formula: Cantilever beam notched impact strength = corrected absorbed energy / (specimen thickness × remaining notch width).

[0079] Low-temperature impact resistance test: Place the specimen in a low-temperature test chamber and maintain the temperature at -20±1℃ for ≥4 hours. Remove the specimen and within 5 seconds, mount it to the jaws of a cantilever beam impact testing machine with the notch facing away from the pendulum. Test at an impact velocity of 3.5±0.2 m / s and record the impact energy E (J) absorbed by each specimen. Calculate the low-temperature cantilever beam notched impact strength using the following formula: Cantilever beam notched impact strength = Corrected absorbed energy / (Specimen thickness × Remaining notch width).

[0080] The test results are shown in Table 1.

[0081] Table 1

[0082] Based on Example 1 and Comparative Examples 1-8, and referring to Table 1, it can be seen that compared to Example 1, the room-temperature and low-temperature notched impact strengths of the cantilever beams in Comparative Examples 1-8 are both lower. Furthermore, the difference between the room-temperature and low-temperature notched impact strengths of the cantilever beams in Comparative Examples 1-8 is significant. This indicates that using the raw material ratio and preparation method of Example 1 helps improve the impact resistance of the halogen-free flame-retardant polypropylene composite material in low-temperature environments.

[0083] This may be because the ethylene-propylene rubber phase of block copolymer polypropylene maintains high elasticity at low temperatures, reducing the material's low-temperature brittleness. Polyolefin elastomers can synergistically work with block copolymer polypropylene, absorbing impact energy through the deformation of the rubber phase even at -20°C, thus improving low-temperature toughness. When polyolefin elastomers are combined with maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer (SEBS-g-MAH), the polyolefin elastomers can undergo large deformation to dissipate energy upon impact. The styrene hard segments of SEBS-g-MAH are compatible with the PP matrix, while the butadiene soft segments form an interpenetrating network with POE, preventing crack propagation. Liquid nitrile rubber is dispersed in the matrix in nanoscale micro-regions, absorbing localized impact energy at low temperatures through the segmental movement of its molecular chains, filling the interfacial voids between POE and the matrix. Core-shell nano-rubber particles dissipate impact energy through the plastic deformation of the core layer. By microencapsulating ammonium polyphosphate, aluminum phosphinate, dipentaerythritol, and zinc borate, flame retardant efficiency is maximized while filler content is minimized, reducing damage to toughness. The melamine-formaldehyde resin coating of microencapsulated ammonium polyphosphate reduces the polarity and hygroscopicity of APP, minimizing interfacial defects with the matrix. Aluminum phosphonate exhibits higher char density than APP, reducing the amount of APP required. Dipentaerythritol forms an expanded char layer with APP, preventing interfacial weakening caused by hygroscopicity in traditional PER. Zinc borate inhibits dripping during combustion and synergistically enhances the char layer strength with APP. Therefore, using the technical solution of Example 1, an impact-resistant, halogen-free flame-retardant polypropylene composite material can be prepared.

[0084] As can be seen from Examples 1-12 and Table 1, the room temperature and low temperature notched impact strengths of the cantilever beams in Examples 1-12 are both high. Furthermore, the difference between the room temperature and low temperature notched impact strengths of the cantilever beams in Comparative Examples 1-8 is relatively small. This indicates that using the raw material ratios and preparation methods within the range of Examples 1-12 helps improve the impact resistance of halogen-free flame-retardant polypropylene composites in low-temperature environments.

[0085] By comparing the test data of Examples 1-12, it was found that impact-resistant halogen-free flame-retardant polypropylene composite materials can be prepared by using at least one of aluminum phosphonate and calcium phosphonate.

[0086] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An impact-resistant, halogen-free, flame-retardant polypropylene composite material, characterized in that, The raw materials include the following parts by weight: 55-60 parts of block copolymer polypropylene, 10-12 parts of polyolefin elastomer, 4-6 parts of maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer, 3-4 parts of liquid nitrile rubber, 10-12 parts of microencapsulated ammonium polyphosphate, 2-3 parts of organic phosphonate, 3-4 parts of dipentaerythritol, 2-3 parts of zinc borate, 4-5 parts of silane-modified attapulgite clay, 3-4 parts of core-shell structured nano-rubber particles, 0.3-0.5 parts of antioxidant, and 0.1-0.3 parts of lubricant.

2. The impact-resistant, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that, The organic phosphonate includes at least one of aluminum phosphonate and calcium phosphonate.

3. The impact-resistant, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that, The microencapsulated ammonium polyphosphate is prepared according to the following steps: Melamine was added to an aqueous formaldehyde solution, the pH was adjusted to 8.5-9.0, and the solution was stirred in a water bath at 70-80°C for 45-60 minutes to obtain the MF prepolymer solution. Ammonium polyphosphate and anhydrous ethanol were mixed at a weight-to-volume ratio of 1:(3-5) and ultrasonically dispersed to obtain a suspension. The MF prepolymer solution was added to the suspension, the pH was adjusted to 4.0-5.5, and the mixture was stirred in a constant temperature water bath at 75-80℃ for 2-3 hours. The mixture was then filtered, washed with anhydrous ethanol until the filtrate was clear, vacuum dried, ground, and sieved to obtain microencapsulated ammonium polyphosphate.

4. The impact-resistant, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that, The silane-modified attapulgite clay is prepared according to the following steps: The attapulgite was dispersed in an aqueous ethanol solution to obtain an attapulgite suspension. The silane coupling agent was dispersed in an aqueous ethanol solution, the pH was adjusted to 3.5–4.0, and hydrolyzed at room temperature for 15–30 min to obtain a silane coupling agent solution. The silane coupling agent solution was added dropwise to an attapulgite suspension, and refluxed and condensed for 3–5 h under stirring at 300–500 rpm in a water bath at 80–85 °C. The mixture was then filtered, washed until no free silane was found, dried, ground, and sieved to obtain silane-modified attapulgite clay.

5. The impact-resistant, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that, The core-shell structured nano-rubber particles were prepared according to the following steps: Mix 80-100 parts of deionized water, 0.5-1.0 parts of emulsifier, 5-10 parts of butyl acrylate and 0.1-0.2 parts of initiator, heat to 70-80℃ under nitrogen protection, and stir at a constant temperature for 30-60 minutes to obtain seed emulsion; Mix 70-80 parts of butyl acrylate, 1.0-2.0 parts of crosslinking agent, 1.5-2.5 parts of emulsifier, and 80-100 parts of deionized water, and shear at 8000-12000 rpm for 5-10 min to obtain a core layer pre-emulsion. Mix 30-40 parts of methyl methacrylate, 1.0-1.5 parts of emulsifier, and 40-60 parts of deionized water, and shear at 8000-10000 rpm for 3-5 minutes to obtain a shell pre-emulsion. The seed emulsion was heated to 70-75℃, and the pre-emulsion of the core was added dropwise to the seed emulsion under constant stirring at 200-300 rpm for 2.0-3.0 h. After the addition was completed, the mixture was kept warm for 0.5-1.0 h to obtain the butyl acrylate core emulsion. Add shell pre-emulsion dropwise to the core emulsion over a period of 1.5-2.0 h, add 0.1-0.2 parts of initiator, and continue the reaction at 70-75 °C for 1-2 h to obtain a shell-coated emulsion. Cool the shell-coated emulsion to 50-60℃, add 5-10 parts of CaCl2 solution while stirring, allow it to stand and separate into layers, filter, wash with deionized water and ethanol until no emulsifier residue remains, dry to constant weight, grind and sieve to obtain core-shell structured nano-rubber particles.

6. A method for preparing an impact-resistant, halogen-free, flame-retardant polypropylene composite material as described in any one of claims 1-5, characterized in that, Includes the following steps: Premix: Weigh each component according to the formula, and mix the block copolymer polypropylene, polyolefin elastomer, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, liquid nitrile rubber, microencapsulated ammonium polyphosphate, organic phosphonate, dipentaerythritol, zinc borate, silane-modified attapulgite clay, core-shell structured nano-rubber particles, antioxidant and lubricant. After the material temperature reaches 70-80℃, discharge the material to obtain the mixture. Extrusion granulation: The mixture is added to a twin-screw extruder for melt blending and extrusion granulation to obtain granules. The granules are dried at 80-85℃ for 2-4 hours to obtain impact-resistant halogen-free flame-retardant polypropylene composite material.

7. The method for preparing the impact-resistant, halogen-free flame-retardant polypropylene composite material according to claim 6, characterized in that, The temperature of each section of the twin-screw extruder is 175-190℃, the screw speed is 350-400rpm, and the vacuum degree of the die head is ≤-0.08MPa.

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