A modified polypropylene recycled material and its preparation method

Abstract

The present invention discloses a modified polypropylene recycled material, and its raw materials by mass parts include: 20-40 parts of polypropylene waste, 1-5 parts of polybutylene terephthalate, 5-15 parts of sericite, 2-6 parts of piperazine pyrophosphate composite basalt fiber, 1-5 parts of flame retardant, 1-3 parts of compatibilizer, 1-2 parts of antioxidant, 1-2 parts of light stabilizer, 1-2 parts of lubricant; the piperazine pyrophosphate composite basalt fiber is obtained by activating the surface of basalt fiber by compounding potassium nitrate and imidazoline, and then synthesizing piperazine pyrophosphate on the surface of the activated basalt fiber. The present invention also discloses a preparation method of the above-mentioned modified polypropylene recycled material. The present invention not only makes full use of recycled materials and improves the environmental protection of products, but also has high mechanical strength and excellent flame retardant performance of the products, and can be effectively applied to the new energy battery casings with high requirements for flame retardancy and mechanical properties, and can completely replace the existing polypropylene resin composite materials.

Description

Technical Field

[0001] The present invention relates to the technical field of recycled polypropylene materials, in particular to a modified polypropylene recycled material and a preparation method thereof. Background Art

[0002] New energy vehicles (NEVs) are vehicles powered by unconventional fuels. The power battery is a core component of NEVs and is typically located beneath the vehicle's floorpan. The battery pack is securely attached to the vehicle through a battery housing.

[0003] As new energy vehicles become more commonplace, battery casings must be fire-resistant and mechanically strong to better protect batteries during use and minimize impact on the vehicle. Traditional battery casings come in a variety of forms. One type is welded from steel or aluminum alloys. This heavy material hinders the lightweighting of new energy vehicles and can easily pose safety risks.

[0004] Polypropylene is currently the second largest plastic in terms of production and usage, second only to polyethylene. It boasts advantages such as light weight, chemical resistance, excellent high-frequency insulation, and low price. However, with the upgrading of products, a large amount of waste polypropylene products has been generated in recent years, causing significant environmental pollution. The disposal of this waste polypropylene has become a pressing social issue.

[0005] Using recycled polypropylene as power battery casing can meet the requirements of lightweight automobiles. However, the molecular structure of polypropylene will change due to the influence of factors such as light, heat, oxygen and external force during use. At the same time, the chemical structure of polypropylene is simple, containing only two elements: carbon and hydrogen. The decomposition temperature is around 370°C, and the limiting oxygen index is 18%. It is an extremely flammable polymer. Polypropylene has obvious dripping phenomenon when burning, and it is easy to ignite again and cause secondary combustion.

[0006] After adding flame retardants to polypropylene waste for flame retardant modification, the mechanical properties of the composite material will further decline due to problems such as flame retardant dispersion. Basalt fiber, as a new type of green and environmentally friendly fiber, has strength close to that of carbon fiber, good acid and alkali resistance, high and low temperature resistance, and excellent electrical insulation properties. However, while the addition of basalt fiber can effectively improve the mechanical properties of the composite material, the heat energy is quickly transmitted along the fibers, then diverts the polypropylene melt to the "combustion zone." When the polypropylene burns, there will be a "wick effect," which makes the composite material more flammable and causes a decrease in flame retardancy.

[0007] Therefore, how to use basalt fiber in polypropylene to improve the mechanical properties of polypropylene, and then combine the advantages of flame retardants to further solve the disadvantage of poor flame retardancy of polypropylene materials, and broaden the application of polypropylene materials in the field of new energy battery casings with extremely high demand for high strength and flame retardancy has excellent prospects. Summary of the Invention

[0008] Based on the technical problems existing in the background art, the present invention proposes a modified polypropylene recycled material and a preparation method thereof.

[0009] A modified polypropylene recycled material, the raw materials of which include, by mass: 20-40 parts of polypropylene waste, 1-5 parts of polybutylene terephthalate, 5-15 parts of sericite, 2-6 parts of pyrophosphate piperazine composite basalt fiber, 1-5 parts of flame retardant, 1-3 parts of compatibilizer, 1-2 parts of antioxidant, 1-2 parts of light stabilizer, 1-2 parts of lubricant; the pyrophosphate piperazine composite basalt fiber is obtained by activating the surface of basalt fiber by compounding potassium nitrate and imidazoline, and then synthesizing pyrophosphate piperazine on the surface of the activated basalt fiber.

[0010] Preferably, the pyrophosphate piperazine composite basalt fiber is prepared by the following specific steps: soaking the basalt fiber in water and performing ultrasonic treatment for 1-2 h, adding potassium nitrate and imidazoline and continuing ultrasonic treatment for 1-2 h, filtering, washing, drying, adding to water and performing ultrasonic dispersion for 5-15 min, adding piperazine, stirring at 80-90 °C for 20-30 h, cooling to 40-50 °C, adding concentrated phosphoric acid under stirring, continuing stirring for 2-5 h, filtering, washing, drying, heating at 210-230 °C for 5-10 h under nitrogen protection, cooling to room temperature, and pulverizing to obtain the pyrophosphate piperazine composite basalt fiber.

[0011] In this application, the basalt fiber is ultrasonically treated to remove surface impurities, then the surface of the fiber is activated by compounding potassium nitrate and imidazoline, and then pyrophosphate piperazine is synthesized on its surface, so that the obtained pyrophosphate piperazine composite basalt fiber not only has good flame retardancy efficiency, but also can be coated on the surface of the basalt fiber after combustion to carbonize, which can further enhance the mechanical strength of the basalt fiber.

[0012] Preferably, the mass fraction of the concentrated phosphoric acid is 84-85.5%, and the mass ratio of the basalt fiber, potassium nitrate, imidazoline, piperazine, and concentrated phosphoric acid is 5-15:1-2:1-4:2-6:1-5.

[0013] Preferably, the melt mass flow rate of the polypropylene waste at 230 °C and a load of 2.16 kg is 10-60 g / 10 min, the initial crystallization temperature is 115-125 °C, and the crystallinity is 33.1-33.5.

[0014] Preferably, the compatibilizer is maleic anhydride grafted polypropylene.

[0015] Preferably, the light stabilizer is the ultraviolet absorber UV-P.

[0016] Preferably, the lubricant is oxidized polyethylene wax.

[0017] Preferably, the flame retardant includes: ammonium polyphosphate and melamine polyphosphate.

[0018] Preferably, the antioxidant is composed of a hindered phenol antioxidant, a phosphite antioxidant and a thioester antioxidant in a mass ratio of 1:1-2:2.

[0019] Preferably, the hindered phenol antioxidant is 2,6-di-tert-butyl-p-cresol; the phosphite antioxidant is dipentaerythritol diisodecyl diphosphite; and the thioester antioxidant is lauryl thiodipropionate.

[0020] The method for preparing the modified polypropylene recycled material includes the following steps:

[0021] (1) Melt-blend polypropylene waste, polybutylene terephthalate, sericite, piperazine pyrophosphate-coated basalt fiber and compatibilizer for 5-15 min, and then add the flame retardant, antioxidant, light stabilizer and lubricant and continue to mix for 2-6 min to obtain a premix.

[0022] (2) Extrude the premix with a twin-screw extruder. The temperatures of each zone of the extruder are 200-205 °C, 210-220 °C, 230-235 °C, 240-245 °C, and 220-230 °C respectively. After water-cooling the extruded strip, cut it into pellets to obtain the modified polypropylene recycled material.

[0023] Compared with the prior art, the present application has the following technical effects:

[0024] (1) In the present application, piperazine pyrophosphate is coated and combined on the surface of basalt fiber. Not only is the bonding strength extremely high, but also piperazine pyrophosphate can form a carbon layer on the surface of basalt fiber during the combustion process, effectively preventing the rapid conduction of heat energy along the fiber, reducing the influence of oxygen and heat. Since heat cannot be provided for the polypropylene resin, the effect of quickly extinguishing the polypropylene fire is achieved; further cooperating with the action of the flame retardant (especially ammonium polyphosphate and melamine polyphosphate), using piperazine pyrophosphate-coated basalt fiber as a charring agent, ammonium polyphosphate as a dehydrating agent, and melamine polyphosphate as a foaming agent, a dense carbon layer is formed during the combustion process, and the flame retardant performance is excellent, and the ignition temperature can reach above 960 °C.

[0025] (2) The piperazine pyrophosphate composite basalt fiber obtained in this application is melt-blended with polypropylene waste under the action of a compatibilizer. By controlling the ratio of the two, the composite basalt fiber can act as a reinforcing rib in the polypropylene waste, making the obtained recycled material have excellent flexural strength, tensile strength, high impact strength, and good mechanical property retention rate. Even in the combustion state, after the piperazine pyrophosphate is carbonized, a carbon layer is formed on the fiber surface, which can further maintain the mechanical strength of the recycled material.

[0026] (3) The present invention uses a compound of polypropylene waste and piperazine pyrophosphate composite basalt fiber, which not only makes full use of recycled materials and improves the environmental protection of products, but also has high mechanical strength and excellent flame retardant performance of the products. It can be effectively applied to the new energy battery casings with high requirements for flame retardancy and mechanical properties, and can completely replace the existing polypropylene resin composites. Description of the Drawings

[0027] Figure 1 It is a comparison chart of the mechanical properties of the polypropylene recycled materials obtained in Example 5 and Comparative Examples 1-2.

[0028] Figure 2 It is a thermogravimetric analysis chart of the polypropylene recycled materials obtained in Example 5 and Comparative Examples 1-2.

[0029] Figure 3 It is a comparison chart of the char residue rates of the polypropylene recycled materials obtained in Example 5 and Comparative Examples 1-2 at 650 °C. Detailed Embodiments

[0030] Next, the technical solutions of the present invention will be described in detail through specific examples.

[0031] Example 1

[0032] A modified polypropylene recycled material, the raw materials of which include: 20 kg of polypropylene waste [MFR (230 °C, 2.16 kg) = 10 g / 10 min], 1 kg of polybutylene terephthalate, 5 kg of sericite, 2 kg of piperazine pyrophosphate composite basalt fiber, 0.5 kg of ammonium polyphosphate, 0.5 kg of melamine polyphosphate, 1 kg of maleic anhydride grafted polypropylene, 1 kg of antioxidant, 1 kg of ultraviolet absorber UV-P, and 1 kg of oxidized polyethylene wax.

[0033] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, dipentaerythritol diisodecyl diphosphite, and lauryl thiodipropionate in a mass ratio of 1:1:2.

[0034] The piperazine pyrophosphate composite basalt fiber is prepared by the following specific steps: Soak 5 kg of basalt fiber in 30 kg of water, perform ultrasonic treatment for 1 h at an ultrasonic frequency of 5 kHz, add 1 kg of potassium nitrate and 1 kg of imidazoline, continue ultrasonic treatment for 1 h, filter, wash, dry, add it to 30 kg of water for ultrasonic dispersion for 5 min, add 2 kg of piperazine, stir at a temperature of 80 °C for 20 h, cool down to 40 °C, add 1 kg of concentrated phosphoric acid with a mass fraction of 84% under stirring, continue stirring for 2 h, filter, wash, dry, add it to a rotary furnace, heat at a temperature of 210 °C for 5 h under nitrogen protection, cool to room temperature, and crush to obtain the piperazine pyrophosphate composite basalt fiber.

[0035] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0036] (1) Melt-blend 40 kg of polypropylene waste, 5 kg of polybutylene terephthalate, 15 kg of sericite, piperazine pyrophosphate composite basalt fiber, and maleic anhydride grafted polypropylene for 5 min, add ammonium polyphosphate, melamine polyphosphate, antioxidant, ultraviolet absorber UV-P, and oxidized polyethylene wax, and continue mixing for 2 min to obtain a premix;

[0037] (2) Extrude the premix with a twin-screw extruder. The temperatures of each zone of the extruder are 200 °C, 210 °C, 230 °C, 240 °C, and 220 °C respectively. After water-cooling the extruded strand and pelletizing, the modified polypropylene recycled material is obtained.

[0038] Example 2

[0039] A modified polypropylene recycled material, the raw materials of which include: 40 kg of polypropylene waste [MFR (230 °C, 2.16 kg) = 60 g / 10 min], 5 kg of polybutylene terephthalate, 15 kg of sericite, 6 kg of piperazine pyrophosphate composite basalt fiber, 2 kg of ammonium polyphosphate, 3 kg of melamine polyphosphate, 3 kg of maleic anhydride grafted polypropylene, 2 kg of antioxidant, 2 kg of ultraviolet absorber UV-P, and 2 kg of oxidized polyethylene wax.

[0040] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, pentaerythritol diphosphite diisodecyl ester, and lauryl thiodipropionate in a mass ratio of 1:2:2.

[0041] The piperazine pyrophosphate composite basalt fiber is prepared by the following specific steps: Soak 15 kg of basalt fiber in 50 kg of water, perform ultrasonic treatment for 2 h at an ultrasonic frequency of 15 kHz, add 2 kg of potassium nitrate and 4 kg of imidazoline, continue ultrasonic treatment for 2 h, filter, wash, dry, add it to 50 kg of water for ultrasonic dispersion for 15 min, add 6 kg of piperazine, stir at a temperature of 90 °C for 30 h, cool down to 50 °C, add 5 kg of concentrated phosphoric acid with a mass fraction of 85.5% under stirring, continue stirring for 5 h, filter, wash, dry, add it to a rotary furnace, heat it at a temperature of 230 °C for 10 h under nitrogen protection, cool it to room temperature, and pulverize to obtain the piperazine pyrophosphate composite basalt fiber.

[0042] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0043] (1) Melt-blend 15 min of polypropylene waste, polybutylene terephthalate, sericite, piperazine pyrophosphate composite basalt fiber, and maleic anhydride grafted polypropylene, add ammonium polyphosphate, melamine polyphosphate, antioxidant, ultraviolet absorber UV-P, and oxidized polyethylene wax, and continue mixing for 6 min to obtain a premix;

[0044] (2) Extrude the premix with a twin-screw extruder. The temperatures of each zone of the extruder are 205 °C, 220 °C, 235 °C, 245 °C, and 230 °C respectively. After water-cooling the extruded strand, pelletize it to obtain the modified polypropylene recycled material.

[0045] Example 3

[0046] A modified polypropylene recycled material, whose raw materials include: 35 kg of polypropylene waste

MFR(230 °C, 2.16 kg) = 20 g / 10 min

[0047] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, pentaerythritol diphosphite diisodecyl ester, and lauryl thiodipropionate in a mass ratio of 1:1.2:2.

[0048] The piperazine pyrophosphate composite basalt fiber is prepared by the following specific steps: Soak 12 kg of basalt fiber in 35 kg of water and perform ultrasonic treatment for 100 min at an ultrasonic frequency of 9 kHz. Add 1.7 kg of potassium nitrate and 2 kg of imidazoline and continue ultrasonic treatment for 100 min. Filter, wash, and dry. Then add it to 35 kg of water and perform ultrasonic dispersion for 12 min. Add 3 kg of piperazine, stir at a temperature of 88 °C for 22 h, cool down to 47 °C, and add 2 kg of concentrated phosphoric acid with a mass fraction of 84.5% under stirring. Continue stirring for 3 h. Filter, wash, and dry. Add it to a rotary furnace, heat at a temperature of 225 °C for 6 h under nitrogen protection, cool to room temperature, and pulverize to obtain the piperazine pyrophosphate composite basalt fiber.

[0049] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0050] (1) Melt-blend 12 min of polypropylene waste, polybutylene terephthalate, sericite, piperazine pyrophosphate composite basalt fiber, and maleic anhydride grafted polypropylene. Add ammonium polyphosphate, melamine polyphosphate, antioxidant, ultraviolet absorber UV-P, and oxidized polyethylene wax and continue mixing for 3 min to obtain a premix;

[0051] (2) Extrude the premix with a twin-screw extruder. The temperatures of each zone of the extruder are 204 °C, 212 °C, 234 °C, 241 °C, and 228 °C respectively. Cool the extruded strip with water and pelletize to obtain the modified polypropylene recycled material.

[0052] Example 4

[0053] A modified polypropylene recycled material, whose raw materials include: 25 kg of polypropylene waste

MFR(230 °C, 2.16 kg) = 40 g / 10 min

[0054] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, pentaerythritol diphosphite diisodecyl ester, and lauryl thiodipropionate in a mass ratio of 1:1.8:2.

[0055] The piperazine pyrophosphate composite basalt fiber is prepared by the following specific steps: Soak 8 kg of basalt fiber in 45 kg of water and perform ultrasonic treatment for 80 min at an ultrasonic frequency of 12 kHz. Add 1.3 kg of potassium nitrate and 3 kg of imidazoline and continue ultrasonic treatment for 80 min. Filter, wash, and dry. Then add it to 45 kg of water and perform ultrasonic dispersion for 8 min. Add 5 kg of piperazine, stir at a temperature of 82 °C for 28 h, cool down to 43 °C, and add 4 kg of concentrated phosphoric acid with a mass fraction of 84.2% under stirring. Continue stirring for 4 h. Filter, wash, and dry. Then add it to a rotary furnace, heat it at a temperature of 215 °C for 8 h under nitrogen protection, cool it to room temperature, and pulverize to obtain the piperazine pyrophosphate composite basalt fiber.

[0056] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0057] (1) Melt-blend 30 kg of polypropylene waste, 3 kg of polybutylene terephthalate, 10 kg of sericite, 4 kg of piperazine pyrophosphate composite basalt fiber, and 2 kg of maleic anhydride grafted polypropylene for 8 min. Then add 1.5 kg of ammonium polyphosphate, 1.5 kg of melamine polyphosphate, an antioxidant, 1.5 kg of ultraviolet absorber UV-P, and 1.5 kg of oxidized polyethylene wax and continue mixing for 5 min to obtain a premix.

[0058] (2) Extrude the premix with a twin-screw extruder. The temperatures of each zone of the extruder are 202 °C, 218 °C, 232 °C, 243 °C, and 222 °C respectively. Cool the extruded strand with water and pelletize to obtain the modified polypropylene recycled material.

[0059] Example 5

[0060] A modified polypropylene recycled material, the raw materials of which include: 30 kg of polypropylene waste

MFR(230 °C, 2.16 kg) = 30 g / 10 min

[0061] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, pentaerythritol diphosphite diisodecyl ester, and lauryl thiodipropionate in a mass ratio of 1:1.5:2.

[0062] The piperazine pyrophosphate composite basalt fiber is prepared by the following specific steps: Soak 10 kg of basalt fiber in 40 kg of water and perform ultrasonic treatment for 90 min at an ultrasonic frequency of 10.5 kHz. Add 1.5 kg of potassium nitrate and 2.5 kg of imidazoline and continue ultrasonic treatment for 90 min. Filter, wash, and dry. Add it to 40 kg of water and perform ultrasonic dispersion for 10 min. Add 4 kg of piperazine, stir at a temperature of 85 °C for 25 h, cool down to 45 °C, and add 3 kg of concentrated phosphoric acid with a mass fraction of 85.2% under stirring. Continue stirring for 3.5 h. Filter, wash, and dry. Add it to a rotary furnace, heat it at a temperature of 220 °C for 7 h under nitrogen protection, cool it to room temperature, and crush to obtain the piperazine pyrophosphate composite basalt fiber.

[0063] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0064] (1) Melt-blend 30 kg of polypropylene waste, 3 kg of polybutylene terephthalate, 10 kg of sericite, the piperazine pyrophosphate composite basalt fiber, and maleic anhydride grafted polypropylene for 10 min. Add ammonium polyphosphate, melamine polyphosphate, antioxidant, ultraviolet absorber UV-P, and oxidized polyethylene wax and continue mixing for 4 min to obtain a premix.

[0065] (2) Extrude the premix with a twin-screw extruder. The temperatures of each zone of the extruder are 203 °C, 215 °C, 233 °C, 242 °C, and 225 °C respectively. Cool the extruded strand with water and pelletize to obtain the modified polypropylene recycled material.

[0066] Comparative Example 1

[0067] A modified polypropylene recycled material, whose raw materials include: 30 kg of polypropylene waste

MFR (230 °C, 2.16 kg) = 30 g / 10 min

[0068] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, pentaerythritol diphosphite diisodecyl ester, and lauryl thiodipropionate in a mass ratio of 1:1.5:2.

[0069] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0070] (1) Melt-blend 30 kg of polypropylene waste, 3 kg of polybutylene terephthalate, 10 kg of sericite, piperazine pyrophosphate, and maleic anhydride grafted polypropylene for 10 min. Add ammonium polyphosphate, melamine polyphosphate, antioxidant, ultraviolet absorber UV-P, and oxidized polyethylene wax and continue mixing for 4 min to obtain a premix.

[0071] (2) Extrude the premix using a twin-screw extruder. The temperatures of each zone of the extruder are 203 °C, 215 °C, 233 °C, 242 °C, and 225 °C respectively. After water-cooling the extruded strip, pelletize it to obtain the modified polypropylene recycled material.

[0072] Comparative Example 2

[0073] A modified polypropylene recycled material, the raw materials of which include: 30 kg of polypropylene waste [MFR (230 °C, 2.16 kg) = 30 g / 10 min], 3 kg of polybutylene terephthalate, 10 kg of sericite, 1.33 kg of piperazine pyrophosphate, 1.9 kg of basalt fiber, 1.5 kg of ammonium polyphosphate, 1.5 kg of melamine polyphosphate, 2 kg of maleic anhydride grafted polypropylene, 1.5 kg of antioxidant, 1.5 kg of ultraviolet absorber UV-P, and 1.5 kg of oxidized polyethylene wax.

[0074] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol, pentaerythritol diphosphite diisodecyl ester, and lauryl thiodipropionate in a mass ratio of 1:1.5:2.

[0075] The preparation method of the above-mentioned modified polypropylene recycled material includes the following steps:

[0076] (1) Melt-blend the polypropylene waste, polybutylene terephthalate, sericite, piperazine pyrophosphate, basalt fiber, and maleic anhydride grafted polypropylene for 10 min, and then add ammonium polyphosphate, melamine polyphosphate, antioxidant, ultraviolet absorber UV-P, and oxidized polyethylene wax and continue to mix for 4 min to obtain a premix;

[0077] (2) Extrude the premix using a twin-screw extruder. The temperatures of each zone of the extruder are 203 °C, 215 °C, 233 °C, 242 °C, and 225 °C respectively. After water-cooling the extruded strip, pelletize it to obtain the modified polypropylene recycled material.

[0078] Carry out a mechanical property comparison test on the polypropylene recycled material samples obtained in Example 5 and Comparative Examples 1-2, specifically as follows: Refer to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for moulding and extrusion plastics" to test the tensile strength of the polypropylene recycled material samples obtained in Example 5 and Comparative Examples 1-2. Refer to GB / T 9341-2008 "Determination of flexural properties of plastics" to test the flexural strength of the polypropylene recycled material samples obtained in Example 5 and Comparative Examples 1-2. Refer to GB / T 1843-2008 "Determination of Izod impact strength of plastics" to test the notched impact strength of the polypropylene recycled material samples obtained in Example 5 and Comparative Examples 1-2.

[0079] As Figure 1As shown, the mechanical properties of the polypropylene recycled material obtained in Example 5 are superior to those of Comparative Examples 1-2. The applicant believes that this is because the piperazine pyrophosphate composite basalt fiber obtained in this application is melt-blended with polypropylene waste in the presence of a compatibilizer. By controlling the ratio of the two, the composite basalt fiber acts as a reinforcement within the polypropylene waste, forming a relatively stable skeleton structure. Furthermore, the composite basalt fiber does not disrupt the continuity of the organic matrix, resulting in excellent flexural and tensile strengths and high impact strength in the resulting recycled material. Comparative Examples 1-2, on the other hand, utilize a compatibilizer to improve the interfacial strength between the inorganic and organic raw materials, resulting in mechanical properties that still surpass those of polypropylene waste.

[0080] The flame retardancy test results of the polypropylene recycled material samples obtained in Example 5 and Comparative Examples 1-2 are as follows:

[0081] Project Test method Example 5 Comparative example 1 Comparative example 2 Flame retardancy (3.2 mm) UL-94 V-0 V-1 V-1 Oxygen index ASTM D2863 35 28 30

[0082] As can be seen from the table above, the flame retardant properties of the polypropylene recycled material obtained in Example 5 are superior to those of Comparative Examples 1-2. The applicant believes that all three are flame-retardant materials because they all use piperazine pyrophosphate in combination with a flame retardant (particularly ammonium polyphosphate and melamine polyphosphate), with piperazine pyrophosphate serving as a charring agent, ammonium polyphosphate serving as a dehydrating agent, and melamine polyphosphate serving as a foaming agent. This results in the formation of a dense char layer during combustion, resulting in excellent flame retardant properties.

[0083] However, the polypropylene recycled material obtained in Example 5 is coated with piperazine pyrophosphate and bonded to the surface of the basalt fiber. Not only is the bonding strength extremely high, but during the combustion process, piperazine pyrophosphate can form a carbon layer on the surface of the basalt fiber, which can effectively prevent the rapid conduction of heat energy along the fiber and reduce the influence of oxygen and heat. Since it cannot provide heat for the polypropylene resin, the polypropylene fire extinguishing effect is quickly achieved.

[0084] The polypropylene recycled material samples obtained in Example 5 and Comparative Examples 1-2 were subjected to thermogravimetric analysis, and the test was performed with reference to GB / T27761-2011 "Test method for weight loss and residual amount by thermogravimetric analyzer", and the temperature was raised to 700°C at a constant rate of 20°C / min under a nitrogen atmosphere.

[0085] like Figure 2 As shown, the remaining mass of the three groups of samples changes with increasing temperature. The polypropylene recycled material obtained in Example 5 has the highest remaining mass, indicating that the polypropylene recycled material obtained in Example 5 has the highest thermal stability. The applicant believes that this is because the piperazine pyrophosphate composite basalt fiber and the flame retardant form a dense char layer during combustion, effectively preventing rapid heat conduction along the fibers.

[0086] At the same time, during the thermogravimetric analysis, the carbon residue rate of each group of samples was measured at 650℃. Figure 3As shown. Further confirmed: In this application, piperazine pyrophosphate is combined with basalt fiber and a flame retardant. The carbon layer formed during combustion is dense and stable enough to effectively play the role of condensed-phase flame retardancy and achieve excellent flame retardant effects.

[0087] Refer to GB / T 5169.13-2013 "Fire hazard testing for electric and electronic products - Part 13: Glow-wire / thermal-wire basic test methods - Glow-wire ignition temperature (GWIT) test for materials" for testing. At the required temperature, after applying a glow wire to the polypropylene recycled material samples (2 mm) obtained in Example 5 and Comparative Examples 1-2 for 30 s, withdraw the glow wire and observe and record.

[0088] During industrial production, the glow wire test is generally used to verify the stability of electronic and electrical materials during use, preventing fires caused by excessive temperatures due to malfunctions or overloads in electronic and electrical appliances during use. The glow-wire ignition temperature is an important indicator in the glow wire test. Using GWIT can better simulate the risks generated by overheating of the battery during the driving process of new energy vehicles and verify the flame retardant capabilities of each group of polypropylene recycled material samples.

[0089] Among them, the ignition temperature (GWIT) of Example 5 is greater than 960 °C, while those of Comparative Example 1 and Comparative Example 2 are 720 °C and 800 °C respectively. It is confirmed that in this application, piperazine pyrophosphate is coated and combined on the surface of basalt fiber. Not only is the bonding strength extremely high, but also piperazine pyrophosphate can form a carbon layer on the surface of basalt fiber during combustion, effectively preventing the rapid conduction of heat energy along the fiber, reducing the influence of oxygen and heat. At the same time, the combination of piperazine pyrophosphate composite basalt fiber and a flame retardant greatly increases the ignition temperature, reaching above 960 °C, which can effectively ensure the safety of new energy vehicles during driving.

[0090] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered by the protection scope of the present invention.

Claims

1. A modified polypropylene recycled material, characterized in that, Its raw materials by mass parts include: 20-40 parts of polypropylene waste, 1-5 parts of polybutylene terephthalate, 5-15 parts of sericite, 2-6 parts of piperazine pyrophosphate composite basalt fiber, 1-5 parts of flame retardant, 1-3 parts of compatibilizer, 1-2 parts of antioxidant, 1-2 parts of light stabilizer, 1-2 parts of lubricant; The piperazine pyrophosphate composite basalt fiber is obtained by activating the surface of basalt fiber by compounding potassium nitrate and imidazoline, and then synthesizing piperazine pyrophosphate on the surface of the activated basalt fiber; The flame retardant includes: ammonium polyphosphate, melamine polyphosphate.

2. The modified polypropylene recycled material according to claim 1, wherein, The piperazine pyrophosphate composite basalt fiber is prepared by the following specific steps: soaking the basalt fiber in water and ultrasonically treating for 1-2 h, adding potassium nitrate and imidazoline and continuing to ultrasonically treat for 1-2 h, filtering, washing, drying, adding to water and ultrasonically dispersing for 5-15 min, adding piperazine, stirring at 80-90 °C for 20-30 h, cooling to 40-50 °C, adding concentrated phosphoric acid under stirring state, continuing to stir for 2-5 h, filtering, washing, drying, heating at 210-230 °C for 5-10 h under nitrogen protection, cooling to room temperature, and pulverizing to obtain the piperazine pyrophosphate composite basalt fiber.

3. The modified polypropylene recycled material according to claim 2, wherein, The mass fraction of the concentrated phosphoric acid is 84-85.5%, and the mass ratio of the basalt fiber, potassium nitrate, imidazoline, piperazine, and concentrated phosphoric acid is 5-15:1-2:1-4:2-6:1-5.

4. The modified polypropylene recycled material according to claim 1, wherein, The compatibilizer is maleic anhydride grafted polypropylene.

5. The modified polypropylene recycled material according to claim 1, wherein The light stabilizer is ultraviolet absorber UV-P.

6. The modified polypropylene recycled material according to claim 1, wherein, The lubricant is oxidized polyethylene wax.

7. The modified polypropylene recycled material according to claim 1, wherein The antioxidant is composed of a hindered phenol antioxidant, a phosphite antioxidant, and a thioester antioxidant in a mass ratio of 1:1-2:

2.

8. The modified polypropylene recycled material according to claim 7, wherein The hindered phenol antioxidant is 2,6-di-tert-butyl-p-cresol; the phosphite antioxidant is dipentaerythritol diisodecyl diphosphite; the thioester antioxidant is lauryl thiodipropionate.

9. A preparation method of the modified polypropylene recycled material according to any one of claims 1-8, characterized in that, It includes the following steps: (1) Melting and blending the polypropylene waste, polybutylene terephthalate, sericite, piperazine pyrophosphate composite basalt fiber, and compatibilizer for 5-15 min, adding the flame retardant, antioxidant, light stabilizer, and lubricant and continuing to mix for 2-6 min to obtain a premix; (2) Extruding the premix with a twin-screw extruder, and the temperatures of each zone of the extruder are 200-205 °C, 210-220 °C, 230-235 °C, 240-245 °C, 220-230 °C respectively. After the extruded strip is water-cooled, it is pelletized to obtain the modified polypropylene recycled material.

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