A polypropylene composite plastic for the housing of new energy batteries and its preparation method

Abstract

The present invention discloses a polypropylene composite plastic for the outer shell of new energy batteries, and its raw materials include: homopolypropylene, random copolymer polypropylene, β-crystal nucleating agent, activated toughening agent, montmorillonite, sodium dodecyl sulfonate aqueous solution, boric acid, zinc oxide, KH560 coupling agent, charring agent, lubricant, antioxidant, and anti-dripping agent. The present invention discloses a preparation method of the above polypropylene composite plastic for the outer shell of new energy batteries. Through experiments, the present invention finds that compared with EPF30R polypropylene, while improving the flame retardancy performance, the present invention also improves its tensile strength and flexural strength, enhancing the service life of the lithium battery outer shell. The present invention can be realized by using an existing twin-screw extruder, with simple preparation, easy implementation and operation, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene, and particularly relates to a polypropylene composite plastic for a new energy battery housing and a preparation method thereof. Background Art

[0002] With the popularization and application of new energy vehicles, the development of battery technology has also received increasing attention. As a core component of new energy vehicles, the safe use of lithium batteries is very important, and the housing of lithium batteries plays a crucial role in protecting the battery module. The housing of lithium batteries has relatively high requirements for impact resistance, and the combination between the battery trough and the battery cover is through thermal sealing, requiring the housing material to have good thermal sealing performance. At the same time, the housing material of lithium batteries needs to have excellent flame retardant performance and good mechanical properties, especially low-temperature impact resistance.

[0003] Polypropylene (PP) is a thermoplastic plastic with a light specific gravity, a large surface hardness of the finished product, high elasticity, good heat resistance, chemical stability, and insulation. It is widely used in many fields of production and life. However, due to the fact that polypropylene is extremely easy to burn, with a limiting oxygen index of only 17.4 - 18.5, and there are serious melt drops during combustion, which easily spreads the flame and causes a fire, making its application have unsafe factors. At the same time, the quality is unstable and the quality fluctuation is too large, and it cannot be mass-produced, all of which limit the use of polypropylene materials with high impact strength for manufacturing new energy battery housings.

[0004] Among the current flame retardants used for flame-retardant polypropylene materials, zinc borate, a halogen-free flame retardant, is favored due to its advantages of low smoke and environmental protection. However, zinc borate is hydrophilic and oleophobic, and it is difficult to be evenly dispersed in the material when blended with polypropylene, which has an obvious negative impact on the low-temperature impact resistance of polypropylene, making the parts prepared from this material prone to cracking under impact at low temperatures, affecting the safe use of lithium batteries at low temperatures and deteriorating the use performance of the material. Summary of the Invention

[0005] Based on the technical problems existing in the background art, the present invention proposes a polypropylene composite plastic for a new energy battery housing and a preparation method thereof.

[0006] A polypropylene composite plastic for the housing of new energy batteries, the raw materials of which include: homopolypropylene, random copolymer polypropylene, β-crystal nucleating agent, activated toughening agent, montmorillonite, sodium dodecyl sulfonate aqueous solution, boric acid, zinc oxide, KH560 coupling agent, charring agent, lubricant, antioxidant, and anti-dripping agent. The mass ratio of homopolypropylene, random copolymer polypropylene, β-crystal nucleating agent, activated toughening agent, montmorillonite, sodium dodecyl sulfonate aqueous solution, boric acid, zinc oxide, KH560 coupling agent, charring agent, lubricant, antioxidant, and anti-dripping agent is 40-60:10-20:0.1-1:2-7:5-10:0.15-0.6:4-6:1-3:0.1-1:1-2:1-2:1-2:1-2.

[0007] Preferably, the activated toughening agent is prepared by the following specific steps: adding methoxypolyethylene glycol chloride to acetonitrile and stirring evenly, adding potassium carbonate and potassium iodide and continuing to stir for 10-20 min, dropping ethanolamine into it under stirring, refluxing and stirring at 80-100 °C in the dark for 10-20 h under nitrogen protection, cooling to room temperature, filtering by suction, and then rotary evaporation to obtain the activated toughening agent.

[0008] In this application, with ethanolamine as the core, methoxypolyethylene glycol chloride grafts with the amino group on ethanolamine, and the two hydrogen atoms on the amino group are replaced by polyethylene glycol long chains, so that the side chain of the obtained activated toughening agent not only has a large steric hindrance and is not easy to entangle, but also has a good toughening effect on homopolypropylene and random copolymer polypropylene, can fully absorb impact energy, and enhance toughness.

[0009] Preferably, the molecular weight of methoxypolyethylene glycol chloride is 500-1000, and the molar ratio of methoxypolyethylene glycol chloride, potassium carbonate, potassium iodide, and ethanolamine is 1-2:4-6:10-30:0.1-0.5.

[0010] Preferably, the melt flow rate of homopolypropylene at a temperature of 230 °C and a load of 2.16 kg is 2-10 g / 10 min.

[0011] Preferably, the melt flow rate of random copolymer polypropylene at a temperature of 230 °C and a load of 2.16 kg is 0.2-0.4 g / 10 min.

[0012] Preferably, the charring agent is a pentaerythritol-based charring agent and / or a triazine-based charring agent.

[0013] Preferably, the charring agent includes: pentaerythritol, dipentaerythritol, tripentaerythritol, and 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine.

[0014] Preferably, the antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant DSTP, and hindered amine 3853.

[0015] Preferably, the lubricant is ethylene bisstearamide, zinc stearate or / and erucamide.

[0016] Preferably, the anti-dripping agent is a polytetrafluoroethylene-based anti-dripping agent, with an average particle size of 200 - 400 μm and a density of 2.0 - 2.5 g / cm 3 .

[0017] The preparation method of the polypropylene composite plastic for the new energy battery shell described above includes the following steps:

[0018] S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant at 180 - 210 °C for 10 - 30 min, add a β-crystal nucleating agent and an activation toughening agent thereto, and stir for 5 - 15 min to obtain a preform;

[0019] S2. Add montmorillonite to an aqueous solution of sodium dodecyl sulfonate, stir at 100 - 120 °C for 10 - 30 min, cool down to 50 - 60 °C, perform homogenization treatment for 1 - 3 min, with a homogenization pressure of 5 - 15 MPa, add boric acid thereto and stir for 5 - 15 min, add zinc oxide and stir for 20 - 40 min, add KH560 coupling agent and stir for 1 - 4 h, add an activation toughening agent and stir for 1 - 2 h, filter, wash with water, dry, and pulverize to obtain dispersed zinc borate;

[0020] S3. Add dispersed zinc borate, charring agent, lubricant, and anti-dripping agent to the preform and stir evenly, melt-blend and extrude pellets with a twin-screw extruder, and injection-mold to obtain the polypropylene composite plastic for the new energy battery shell.

[0021] The present invention has the following technical effects:

[0022] 1. In the present invention, montmorillonite swells and intercalates in an aqueous solution of sodium dodecyl sulfonate, and then through homogenization treatment, the montmorillonite lamellae are promoted to exfoliate. Boric acid combines with zinc oxide and deposits in the montmorillonite lamellar structure. The KH560 coupling agent hydrolyzes to form silanol, which combines with the hydroxyl groups on the surface of zinc borate to form a covalent bond, and the epoxy group at the other end combines with the active hydroxyl groups of the activation toughening agent. Due to the large steric hindrance of the side chain of the active toughening agent, it is not only difficult to cover the surface of zinc borate, but can be fully dispersed in the polypropylene matrix and form a structure similar to a reinforcing rib, making the combination of zinc borate and polypropylene more compact and having excellent impact resistance, which is difficult to achieve by using KH560 coupling agent alone.

[0023] 2. Since zinc borate nanoparticles are uniformly deposited within the montmorillonite lamellar structure in this application, and the two act synergistically, the flame retardant performance is excellent. Compared with montmorillonite without deposited zinc borate, the initial thermal degradation temperature of the dispersed zinc borate obtained in this application is 190 - 195 °C, which is more than 25% higher than that without deposited zinc borate. Moreover, the montmorillonite lamellae can effectively prevent the dehydration of zinc borate. Due to the synergistic effect of the two, the thermal degradation temperature of montmorillonite can be increased from 300 °C to 345 - 368 °C. Therefore, when the dispersed zinc borate with a lamellar structure is fully dispersed in the polypropylene substrate, it can effectively play a heat insulation role in the substrate structure, effectively prevent the spread of flames. As the temperature rises, the outer-layer montmorillonite first undergoes high-temperature decomposition to form a heat insulation layer to prevent the spread of flames. At the same time, its lamellar structure forms a foam-like structure to coat the surface of the zinc borate nanoparticles, further enhancing the flame retardant and heat insulation performance of the zinc borate nanoparticles. As the temperature further increases, the thermal decomposition products of zinc borate adhere to the surface of the polymer, which can not only inhibit the generation of combustible gases but also prevent oxidation reactions and thermal decomposition, further enhancing the flame retardant performance.

[0024] 3. The present invention found through experiments that compared with EPF30R polypropylene, on the basis of improving the flame retardant performance, the present invention also improves its tensile strength and flexural strength.

[0025] 4. The present invention can effectively improve the impact resistance and flame retardant performance of the lithium battery casing for new energy vehicles, while taking into account and enhancing its thermal stability and corrosion resistance, thereby enhancing the service life of the lithium battery casing and providing good technical support for the use of new energy vehicles.

[0026] 5. The present invention can be realized by using an existing twin-screw extruder, with simple preparation, easy implementation and operation, and easy industrial production, having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a thermogravimetric analysis diagram of the dispersed zinc borate obtained in Example 5 and Comparative Examples 1 - 2.

[0028] Figure 2 It is a comparison diagram of the mechanical properties of the plastic specimens obtained in Example 5 and Comparative Examples 1 - 3.

[0029] Figure 3 It is a comparison diagram of the change rate of the mechanical properties of the plastic specimens obtained in Example 5 and Comparative Examples 1 - 3 after thermal aging treatment. DETAILED DESCRIPTION OF THE INVENTION

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

[0031] Example 1

[0032] A polypropylene composite plastic for the shell of new energy batteries, the raw materials of which include: 40 kg of homopolypropylene (MFR(230°C, 2.16 kg)=2 g / 10 min), 10 kg of random copolymer polypropylene (MFR(230°C, 2.16 kg)=0.2 g / 10 min), 0.1 kg of β-crystal nucleating agent, 2 kg of activated toughening agent, 5 kg of montmorillonite, 0.15 kg of sodium dodecyl sulfonate, 4 kg of boric acid, 1 kg of zinc oxide, 0.1 kg of KH560 coupling agent, 1 kg of pentaerythritol, 1 kg of erucamide, 1 kg of antioxidant DSTP, and 1 kg of polytetrafluoroethylene anti-dripping agent (particle size is 200 - 400 μm, density is 2.0 g / cm 3 )

[0033] The activated toughening agent is prepared by the following specific steps: Add 1 mol of methoxypolyethylene glycol chloride with a molecular weight of 500 to acetonitrile and stir evenly, add 4 mol of potassium carbonate and 10 mol of potassium iodide and continue to stir for 10 min, the stirring speed is 100 r / min, and 0.1 mol of ethanolamine is added dropwise thereto under stirring. Under nitrogen protection, stir and reflux at 80°C for 10 h in the dark, cool to room temperature, and after filtration, the solvent in the filtrate is removed by rotary evaporation to obtain the activated toughening agent.

[0034] The preparation method of the above polypropylene composite plastic for the shell of new energy batteries includes the following steps:

[0035] S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant DSTP at a temperature of 180°C for 10 min, add β-crystal nucleating agent and 1 kg of activated toughening agent thereto, and stir at a speed of 100 r / min for 5 min to obtain a prefabricated material;

[0036] S2. Add montmorillonite to 30 kg of an aqueous solution of sodium dodecyl sulfonate with a mass fraction of 0.5%, stir at a temperature of 100°C for 10 min, cool to 50°C, perform homogenization treatment for 1 min, the homogenization pressure is 5 MPa, add boric acid and stir for 5 min, add zinc oxide and stir for 20 min, add KH560 coupling agent and stir for 1 h, add 1 kg of activated toughening agent and stir for 1 h, filter, wash the product with water, dry, and pulverize to obtain dispersed zinc borate;

[0037] S3. Add dispersed zinc borate, pentaerythritol, erucamide, and polytetrafluoroethylene anti-dripping agent to the prefabricated material and stir evenly, feed it into a twin-screw extruder from the main feed port for melt blending and extrusion granulation. The processing temperature of the twin-screw extruder is 180°C, the vacuum degree ≤ -0.06 MPa, and it is formed by an injection molding machine to obtain the polypropylene composite plastic for the shell of new energy batteries.

[0038] Example 2

[0039] A polypropylene composite plastic for the housing of new energy batteries, the raw materials of which include: 60 kg of homopolypropylene (MFR (230 °C, 2.16 kg) = 10 g / 10 min), 20 kg of random copolymer polypropylene (MFR (230 °C, 2.16 kg) = 0.4 g / 10 min), 1 kg of β-crystal nucleating agent, 7 kg of activation toughening agent, 10 kg of montmorillonite, 0.6 kg of sodium dodecyl sulfonate, 6 kg of boric acid, 3 kg of zinc oxide, 1 kg of KH560 coupling agent, 2 kg of pentaerythritol, 2 kg of erucamide, 2 kg of antioxidant 168, and 2 kg of polytetrafluoroethylene anti-dripping agent (particle size 200 - 400 μm, density 2.5 g / cm 3 )

[0040] The activation toughening agent is prepared by the following specific steps: Add 2 mol of methoxypolyethylene glycol chloride with a molecular weight of 1000 to acetonitrile and stir evenly, add 6 mol of potassium carbonate and 30 mol of potassium iodide and continue to stir for 20 min, with a stirring speed of 500 r / min. While stirring, add 0.5 mol of ethanolamine dropwise thereto. Under nitrogen protection, stir and reflux at 100 °C in the dark for 20 h. Cool to room temperature, filter by suction, and then rotary evaporate the filtrate to remove the solvent to obtain the activation toughening agent.

[0041] The preparation method of the above polypropylene composite plastic for the housing of new energy batteries includes the following steps:

[0042] S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant 168 at 210 °C for 30 min, add the β-crystal nucleating agent and 5 kg of activation toughening agent thereto, and stir at a speed of 500 r / min for 15 min to obtain a prefabricated material;

[0043] S2. Add montmorillonite to 50 kg of an aqueous solution of sodium dodecyl sulfonate with a mass fraction of 1.2%, stir at 120 °C for 30 min, cool to 60 °C, perform homogenization treatment for 3 min, with a homogenization pressure of 15 MPa. Add boric acid thereto and stir for 15 min, add zinc oxide and stir for 40 min, add KH560 coupling agent and stir for 4 h, add 2 kg of activation toughening agent and stir for 2 h, filter, wash the product with water, dry, and pulverize to obtain dispersed zinc borate;

[0044] S3. Add dispersed zinc borate, pentaerythritol, erucamide, and polytetrafluoroethylene anti-dripping agent to the prefabricated material and stir evenly, feed it into a twin-screw extruder from the main feeding port for melt blending and extrusion granulation. The processing temperature of the twin-screw extruder is 210 °C, and the vacuum degree ≤ -0.06 MPa. Mold it through an injection molding machine to obtain the polypropylene composite plastic for the housing of new energy batteries.

[0045] Example 3

[0046] A polypropylene composite plastic for the shell of new energy batteries, the raw materials of which include: 55 kg of homopolypropylene (MFR(230°C, 2.16 kg)=4 g / 10 min), 18 kg of random copolymer polypropylene (MFR(230°C, 2.16 kg)=0.25 g / 10 min), 0.2 kg of β-crystalline nucleating agent, 3.7 kg of activated toughening agent, 9 kg of montmorillonite, 0.27 kg of sodium dodecyl sulfonate, 5.5 kg of boric acid, 1.5 kg of zinc oxide, 0.7 kg of KH560 coupling agent, 0.2 kg of pentaerythritol, 0.2 kg of dipentaerythritol, 0.2 kg of tripentaerythritol, 0.6 kg of 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, 1.7 kg of zinc stearate, 0.6 kg of antioxidant 1010, 0.6 kg of antioxidant 168, and 1.3 kg of polytetrafluoroethylene-based anti-dripping agent (particle size is 200 - 400 μm, density is 2.3 g / cm 3 )

[0047] The activated toughening agent is prepared by the following specific steps: Add 1.7 mol of methoxypolyethylene glycol chloride with a molecular weight of 700 to acetonitrile and stir evenly. Add 5.5 mol of potassium carbonate and 15 mol of potassium iodide and continue to stir for 18 min. The stirring speed is 200 r / min. Dropwise add 0.4 mol of ethanolamine under stirring. Under nitrogen protection, stir and reflux at 85°C in the dark for 17 h. Cool to room temperature, filter, and then rotary evaporate the filtrate to remove the solvent to obtain the activated toughening agent.

[0048] The preparation method of the above polypropylene composite plastic for the shell of new energy batteries includes the following steps:

[0049] S1. Mix and stir homopolypropylene, random copolymer polypropylene, antioxidant 1010, and antioxidant 168 at 190°C for 25 min. Add β-crystalline nucleating agent and 2 kg of activated toughening agent thereto, and stir at a speed of 400 r / min for 8 min to obtain a prefabricated material;

[0050] S2. Add montmorillonite to 45 kg of an aqueous solution of sodium dodecyl sulfonate with a mass fraction of 0.6%, stir at 115°C for 15 min, cool to 57°C, perform homogenization treatment for 1.5 min, and the homogenization pressure is 12 MPa. Add boric acid thereto and stir for 8 min, add zinc oxide and stir for 35 min, add KH560 coupling agent and stir for 2 h, add 1.7 kg of activated toughening agent and stir for 80 min, filter, wash the product with water, dry, and pulverize to obtain dispersed zinc borate;

[0051] S3. Add zinc borate, pentaerythritol, dipentaerythritol, tripentaerythritol, 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, zinc stearate, and polytetrafluoroethylene anti-dripping agent to the prefabricated material, stir evenly, feed it into a twin-screw extruder from the main feeding port, melt and blend, and extrude into pellets. The processing temperature of the twin-screw extruder is 200°C, the vacuum degree is ≤ -0.06 MPa, and it is formed by an injection molding machine to obtain polypropylene composite plastic for the outer shell of new energy batteries.

[0052] Example 4

[0053] A polypropylene composite plastic for the outer shell of new energy batteries, the raw materials of which include: 45 kg of homopolypropylene (MFR(230°C, 2.16 kg) = 8 g / 10 min), 12 kg of random copolymer polypropylene (MFR(230°C, 2.16 kg) = 0.35 g / 10 min), 0.8 kg of β-crystalline nucleating agent, 5.3 kg of activated toughening agent, 7 kg of montmorillonite, 0.35 kg of sodium dodecyl sulfonate, 4.5 kg of boric acid, 2.5 kg of zinc oxide, 0.3 kg of KH560 coupling agent, 0.8 kg of pentaerythritol, 1 kg of dipentaerythritol, 1.3 kg of zinc stearate, 1.8 kg of antioxidant 1010, and 1.7 kg of polytetrafluoroethylene anti-dripping agent (particle size is 200 - 400 μm, density is 2.1 g / cm 3 )

[0054] The activated toughening agent is prepared by the following specific steps: Add 1.3 mol of methoxypolyethylene glycol chloride with a molecular weight of 900 to acetonitrile, stir evenly, add 4.5 mol of potassium carbonate and 25 mol of potassium iodide, continue to stir for 12 min, the stirring speed is 400 r / min, dropwise add 0.2 mol of ethanolamine while stirring, under nitrogen protection, stir and reflux at 95°C in the dark for 13 h, cool to room temperature, filter by suction, and rotary evaporate the filtrate to remove the solvent to obtain the activated toughening agent.

[0055] The preparation method of the above polypropylene composite plastic for the outer shell of new energy batteries includes the following steps:

[0056] S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant 1010 at 200°C for 15 min, add β-crystalline nucleating agent and 4 kg of activated toughening agent thereto, and stir at a speed of 200 r / min for 12 min to obtain a prefabricated material;

[0057] S2. Add montmorillonite to 35 kg of an aqueous solution of sodium dodecyl sulfonate with a mass fraction of 1%, stir at a temperature of 105 °C for 25 min, cool down to 53 °C, perform homogenization treatment for 2.5 min with a homogenization pressure of 8 MPa, add boric acid and stir for 12 min, add zinc oxide and stir for 25 min, add KH560 coupling agent and stir for 3 h, add 1.3 kg of activation toughening agent and stir for 100 min, filter, wash the product with water, dry, and pulverize to obtain dispersed zinc borate;

[0058] S3. Add dispersed zinc borate, pentaerythritol, dipentaerythritol, zinc stearate, and polytetrafluoroethylene anti-dripping agent to the prefabricated material and stir evenly, feed it into a twin-screw extruder from the main feeding port for melt blending and pelletizing. The processing temperature of the twin-screw extruder is 190 °C, and the vacuum degree is ≤ -0.06 MPa. It is formed by an injection molding machine to obtain polypropylene composite plastic for the outer shell of new energy batteries.

[0059] Example 5

[0060] A polypropylene composite plastic for the outer shell of new energy batteries, whose raw materials include: 5 kg of homopolypropylene (MFR (230 °C, 2.16 kg) = 6 g / 10 min), 15 kg of random copolymer polypropylene (MFR (230 °C, 2.16 kg) = 0.3 g / 10 min), 0.5 kg of β-crystalline nucleating agent, 4.5 kg of activation toughening agent, 8 kg of montmorillonite, 0.32 kg of sodium dodecyl sulfonate, 5 kg of boric acid, 2 kg of zinc oxide, 0.5 kg of KH560 coupling agent, 0.5 kg of pentaerythritol, 1 kg of 2,4,6-tris (ethoxy-phenylphosphinyl)-1,3,5-triazine, 1.5 kg of ethylene bis-stearamide, 1.5 kg of antioxidant 1010, and 1.5 kg of polytetrafluoroethylene anti-dripping agent (particle size is 200 - 400 μm, density is 2.2 g / cm 3 )

[0061] The activation toughening agent is prepared by the following specific steps: Add 1.5 mol of methoxypolyethylene glycol chloride with a molecular weight of 800 to acetonitrile and stir evenly, add 5 mol of potassium carbonate and 20 mol of potassium iodide and continue to stir for 15 min with a stirring speed of 300 r / min. While stirring, dropwise add 0.3 mol of ethanolamine, under nitrogen protection, reflux and stir at a temperature of 90 °C for 15 h in the dark, cool to room temperature, filter by suction, and then rotary evaporate the filtrate to remove the solvent to obtain the activation toughening agent.

[0062] The preparation method of the above polypropylene composite plastic for the outer shell of new energy batteries includes the following steps:

[0063] S1. Homopolypropylene, random copolymer polypropylene, and antioxidant 1010 are mixed and stirred at a temperature of 195°C for 20 min. Then, a β-crystal nucleating agent and 3 kg of an activated toughening agent are added thereto, and the mixture is stirred at a speed of 300 r / min for 10 min to obtain a preform;

[0064] S2. Montmorillonite is added to 40 kg of an aqueous solution of sodium dodecyl sulfonate with a mass fraction of 0.8%, and the mixture is stirred at a temperature of 110°C for 20 min. Then, the temperature is lowered to 55°C, and homogenization treatment is carried out for 2 min with a homogenization pressure of 10 MPa. Boric acid is added thereto and stirred for 10 min, zinc oxide is added and stirred for 30 min, KH560 coupling agent is added and stirred for 2.5 h, 1.5 kg of an activated toughening agent is added and stirred for 90 min, and then filtered. The product is washed with water, dried, and pulverized to obtain dispersed zinc borate;

[0065] S3. Dispersed zinc borate, pentaerythritol, 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, ethylene bisstearamide, and a polytetrafluoroethylene-based anti-dripping agent are added to the preform and stirred evenly, and then fed into a twin-screw extruder through the main feed port for melt blending and extrusion granulation. The processing temperature of the twin-screw extruder is 195°C, and the vacuum degree is ≤ -0.06 MPa. It is molded by an injection molding machine to obtain a polypropylene composite plastic for the outer shell of a new energy battery.

[0066] Comparative Example 1

[0067] A polypropylene composite plastic for the outer shell of a new energy battery, the raw materials of which include: 5 kg of homopolypropylene (MFR (230°C, 2.16 kg) = 6 g / 10 min), 15 kg of random copolymer polypropylene (MFR (230°C, 2.16 kg) = 0.3 g / 10 min), 0.5 kg of β-crystal nucleating agent, 4.5 kg of activated toughening agent, 8 kg of montmorillonite, 5 kg of boric acid, 2 kg of zinc oxide, 0.5 kg of KH560 coupling agent, 0.5 kg of pentaerythritol, 1 kg of 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, 1.5 kg of ethylene bisstearamide, 1.5 kg of antioxidant 1010, and 1.5 kg of a polytetrafluoroethylene-based anti-dripping agent (particle size is 200 - 400 μm, density is 2.2 g / cm 3 ) 1.5 kg.

[0068] The activated toughening agent is prepared by the following specific steps: 1.5 mol of methoxypolyethylene glycol chloride with a molecular weight of 800 is added to acetonitrile and stirred evenly, 5 mol of potassium carbonate and 20 mol of potassium iodide are added and stirred for another 15 min at a stirring speed of 300 r / min. Under stirring, 0.3 mol of ethanolamine is added dropwise thereto. Under nitrogen protection, it is refluxed and stirred at a temperature of 90°C for 15 h in the dark. After cooling to room temperature, the solvent is removed by rotary evaporation of the filtrate after suction filtration to obtain the activated toughening agent.

[0069] The preparation method of the polypropylene composite plastic for the new energy battery shell is as follows:

[0070] S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant 1010 at a temperature of 195°C for 20 min. Add β-crystal nucleating agent and 3 kg of activated toughening agent thereto, and stir at a speed of 300 r / min for 10 min to obtain a prefabricated material;

[0071] S2. Stir boric acid and zinc oxide for 30 min, then add KH560 coupling agent and montmorillonite and stir for 2.5 h. Then add 1.5 kg of activated toughening agent and stir for 90 min. Filter, wash the product with water, dry, and pulverize to obtain dispersed zinc borate;

[0072] S3. Add dispersed zinc borate, pentaerythritol, 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, ethylene bisstearamide, and polytetrafluoroethylene anti-dripping agent to the prefabricated material and stir evenly. Feed it into a twin-screw extruder from the main feeding port for melt blending and pelletizing. The processing temperature of the twin-screw extruder is 195°C, and the vacuum degree is ≤ -0.06 MPa. Molding is carried out through an injection molding machine to obtain the polypropylene composite plastic for the new energy battery shell.

[0073] Comparative Example 2

[0074] A polypropylene composite plastic for the new energy battery shell, the raw materials thereof include: 5 kg of homopolypropylene (MFR(230°C, 2.16 kg) = 6 g / 10 min), 15 kg of random copolymer polypropylene (MFR(230°C, 2.16 kg) = 0.3 g / 10 min), 0.5 kg of β-crystal nucleating agent, 4.5 kg of multi-component blended and dual-grafted PS539, 8 kg of montmorillonite, 0.32 kg of sodium dodecyl sulfonate, 5 kg of boric acid, 2 kg of zinc oxide, 0.5 kg of KH560 coupling agent, 0.5 kg of pentaerythritol, 1 kg of 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, 1.5 kg of ethylene bisstearamide, 1.5 kg of antioxidant 1010, and 1.5 kg of polytetrafluoroethylene anti-dripping agent (particle size is 200 - 400 μm, density is 2.2 g / cm 3 )

[0075] The preparation method of the polypropylene composite plastic for the new energy battery shell is as follows:

[0076] S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant 1010 at a temperature of 195°C for 20 min. Add β-crystal nucleating agent and 3 kg of multi-component blended and dual-grafted PS539 thereto, and stir at a speed of 300 r / min for 10 min to obtain a prefabricated material;

[0077] S2. Add montmorillonite to 40 kg of an aqueous solution of sodium dodecyl sulfonate with a mass fraction of 0.8%, stir at 110 °C for 20 min, cool down to 55 °C, perform homogenization treatment for 2 min with a homogenization pressure of 10 MPa, add boric acid and stir for 10 min, add zinc oxide and stir for 30 min, add KH560 coupling agent and stir for 2.5 h, add 1.5 kg of polyblend bi-directional graft PS539 and stir for 90 min, filter, wash the product with water, dry, and pulverize to obtain dispersed zinc borate.

[0078] S3. Add dispersed zinc borate, pentaerythritol, 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine, ethylene bisstearamide, and polytetrafluoroethylene anti-dripping agent to the prefabricated material, stir evenly, feed it into a twin-screw extruder from the main feeding port for melt blending and extrusion granulation. The processing temperature of the twin-screw extruder is 195 °C, and the vacuum degree is ≤ -0.06 MPa. Molding is carried out through an injection molding machine to obtain polypropylene composite plastic for the outer shell of new energy batteries.

[0079] Perform thermogravimetric analysis on the dispersed zinc borate obtained in Example 5 and Comparative Examples 1-2: Take about 10 mg of the sample, in a nitrogen atmosphere with a nitrogen flow rate of 20 mL / min, heat from 30 °C to 600 °C at a heating rate of 20 °C / min, keep constant temperature for 2 min, and cool down to 40 °C.

[0080] As Figure 1 shown, due to the uniform deposition of zinc borate nanoparticles in the montmorillonite lamellar structure of this application, the two act synergistically, and the flame retardancy performance is excellent; compared with the montmorillonite without deposited zinc borate, the starting temperature of thermal degradation of the dispersed zinc borate obtained in this application is 190 - 195 °C; and the lamellae of montmorillonite can effectively prevent the dehydration phenomenon of zinc borate. The two act synergistically, and the thermal degradation temperature of montmorillonite can be increased from 300 °C to 345 - 368 °C.

[0081] Comparative Example 3

[0082] Molding is carried out using an EPF30R polypropylene injection molding machine.

[0083] Conduct a comparative test on the mechanical properties of the plastic specimens obtained in Example 5 and Comparative Examples 1-3 as follows: Refer to GB / T 1040.2-2022 "Plastics - Determination of tensile properties - Part 2: Test conditions for moulded and extruded plastics" to test the tensile strength of the plastic specimens obtained in Example 5 and Comparative Examples 1-3. Refer to GB / T9341-2008 "Plastics - Determination of flexural properties" to test the flexural strength of the plastic specimens obtained in Example 5 and Comparative Examples 1-3. Refer to GB / T 1843-2008 "Plastics - Determination of Izod impact strength" to test the notched impact strength of the plastic specimens obtained in Example 5 and Comparative Examples 1-3.

[0084] As Figure 2 shown, the indexes of the composite plastics obtained in Example 5 and Comparative Examples 1-2 are superior to those of the plastic products obtained in Comparative Example 3, and the tensile strength, flexural strength and notched impact strength of the composite plastic obtained in Example 5 are the highest.

[0085] The applicant believes that this is because montmorillonite is expanded and intercalated in an aqueous solution of sodium dodecyl sulfate in the present invention, and then the montmorillonite lamellae are exfoliated by homogenization treatment, while boric acid combines with zinc oxide and deposits in the montmorillonite lamellar structure; and the KH560 coupling agent is hydrolyzed to form silanol, which combines with the hydroxyl groups on the surface of zinc borate to form covalent bonds, and the epoxy groups at the other end combine with the active hydroxyl groups of the activation toughening agent, and can be fully dispersed in the polypropylene base material and form a structure similar to a reinforcing rib, improving its tensile strength and flexural strength, and at the same time having excellent impact resistance.

[0086] The plastic specimens obtained in Example 5 and Comparative Examples 1-3 were placed in a constant temperature blast drying oven, and the change rate of mechanical properties after thermal aging of the materials was tested at 150 °C for 300 h.

[0087] As Figure 3 shown, the tensile strength and flexural strength of each group increased. This is because secondary crystallization occurred during the thermal oxidation treatment of polypropylene at 150 °C, improving the crystallinity of the material, and the defects of the crystals gradually decreased, so the strength of the material was significantly improved. However, the absolute value of the change rate of each index of the composite plastic obtained in Example 5 is the smallest. The applicant believes that this is because the dispersed zinc borate can be fully dispersed in the polypropylene base material and form a structure similar to a reinforcing rib, which reversely restricts the performance growth of the composite plastic obtained in this application.

[0088] The plastic specimens obtained in Example 5 and Comparative Examples 1-3 were tested for flame retardancy performance as follows:

[0089] Item Flammability resistance (3.2 mm) Oxygen index Smoke density Test method UL-94 ASTM D2863 ASTM E84 Example 5 V-0 34.5 Grade A Comparative example 1 V-1 30.5 Grade B Comparative example 2 V-1 32 Grade A Comparative example 3 HB 18 Grade C

[0090] It can be seen from the above table that the composite plastic obtained in Example 5 has the most excellent flame retardancy performance and can inhibit smoke generation. The applicant believes that this is because the dispersed zinc borate in the form of a lamellar structure is fully dispersed in the polypropylene substrate, which can effectively play a heat insulation role in the substrate structure, effectively prevent the spread of fire. As the temperature rises, the outer montmorillonite first decomposes at high temperature to form a heat insulation layer to prevent the spread of fire. At the same time, its lamellar structure forms a structure similar to a foam structure to coat the surface of the zinc borate nanoparticles, further enhancing the flame retardancy and heat insulation performance of the zinc borate nanoparticles; as the temperature further rises, the thermal decomposition products of zinc borate adhere to the surface of the polymer, which can not only inhibit the generation of combustible gases, but also prevent oxidation reactions and thermal decomposition, further enhancing the flame retardancy performance.

[0091] The above are only the preferred specific embodiments 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, shall be covered by the protection scope of the present invention.

Claims

1. A polypropylene composite plastic for the shell of new energy batteries, characterized in that, its raw materials include: homopolypropylene, random copolymer polypropylene, β-crystal nucleating agent, activated toughening agent, montmorillonite, sodium dodecyl sulfonate aqueous solution, boric acid, zinc oxide, KH560 coupling agent, charring agent, lubricant, antioxidant, anti-dripping agent, and the mass ratio of homopolypropylene, random copolymer polypropylene, β-crystal nucleating agent, activated toughening agent, montmorillonite, sodium dodecyl sulfonate aqueous solution, boric acid, zinc oxide, KH560 coupling agent, charring agent, lubricant, antioxidant, anti-dripping agent is 40 - 60:10 - 20:0.1 - 1:2 - 7:5 - 10:0.15 - 0.6:4 - 6:1 - 3:0.1 - 1:1 - 2:1 - 2:1 - 2:1 - 2; The activated toughening agent is prepared by the following specific steps: Add methoxypolyethylene glycol chloride to acetonitrile and stir evenly, add potassium carbonate and potassium iodide and continue to stir for 10 - 20 min, dropwise add ethanolamine under stirring, under nitrogen protection, reflux and stir at 80 - 100 °C in the dark for 10 - 20 h, cool to room temperature, filter by suction and then rotary evaporate to obtain the activated toughening agent; The molecular weight of methoxypolyethylene glycol chloride is 500 - 1000; and is prepared by the following steps: S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant at 180 - 210 °C for 10 - 30 min, add β-crystal nucleating agent and activated toughening agent thereto, and stir for 5 - 15 min to obtain a prefabricated material; S2. Add montmorillonite to the sodium dodecyl sulfonate aqueous solution, stir at 100 - 120 °C for 10 - 30 min, cool to 50 - 60 °C, perform homogenization treatment for 1 - 3 min, the homogenization pressure is 5 - 15 MPa, add boric acid thereto and stir for 5 - 15 min, add zinc oxide and stir for 20 - 40 min, add KH560 coupling agent and stir for 1 - 4 h, add activated toughening agent and stir for 1 - 2 h, filter, wash with water, dry, and pulverize to obtain dispersed zinc borate; S3. Add dispersed zinc borate, charring agent, lubricant, and anti-dripping agent to the prefabricated material and stir evenly, melt-blend and extrude and pelletize with a twin-screw extruder, and injection mold to obtain the polypropylene composite plastic for the shell of new energy batteries.

2. The polypropylene composite plastic for the shell of new energy batteries according to claim 1, characterized in that, the molar ratio of methoxypolyethylene glycol chloride, potassium carbonate, potassium iodide, and ethanolamine is 1 - 2:4 - 6:10 - 30:0.1 - 0.

5.

3. The polypropylene composite plastic for the shell of new energy batteries according to claim 1, characterized in that, the melt flow rate of homopolypropylene at a temperature of 230 °C and a load of 2.16 kg is 2 - 10 g / 10 min.

4. The polypropylene composite plastic for the shell of new energy batteries according to claim 1, characterized in that, the melt flow rate of random copolymer polypropylene at a temperature of 230 °C and a load of 2.16 kg is 0.2 - 0.4 g / 10 min.

5. The polypropylene composite plastic for the shell of new energy batteries according to claim 1, characterized in that, The charring agent is a pentaerythritol-based charring agent and / or a triazine-based charring agent.

6. The polypropylene composite plastic for a new energy battery housing according to claim 5, wherein, the charring agent includes: pentaerythritol, dipentaerythritol, tripentaerythritol, and 2,4,6-tris(ethoxy-phenylphosphinyl)-1,3,5-triazine.

7. The polypropylene composite plastic for a new energy battery housing according to claim 1, wherein, the antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant DSTP, and hindered amine 3853; the lubricant is ethylene bisstearamide, zinc stearate, and / or erucamide.

8. The polypropylene composite plastic for a new energy battery housing according to claim 1, wherein, The anti-dripping agent is a polytetrafluoroethylene-based anti-dripping agent, with an average particle size of 200 - 400 μm and a density of 2.0 - 2.5 g / cm 3 .

9. A method for preparing a polypropylene composite plastic for a new energy battery housing according to any one of claims 1-8, wherein, it includes the following steps: S1. Mix and stir homopolypropylene, random copolymer polypropylene, and antioxidant at 180-210°C for 10-30 min, add a β-crystal nucleating agent and an activation toughening agent thereto, and stir for 5-15 min to obtain a preform; S2. Add montmorillonite to an aqueous solution of sodium dodecylsulfonate, stir at 100-120°C for 10-30 min, cool to 50-60°C, perform homogenization treatment for 1-3 min, with a homogenization pressure of 5-15 MPa, add boric acid thereto and stir for 5-15 min, add zinc oxide and stir for 20-40 min, add KH560 coupling agent and stir for 1-4 h, add an activation toughening agent and stir for 1-2 h, filter, wash with water, dry, and pulverize to obtain dispersed zinc borate; S3. Add dispersed zinc borate, a charring agent, a lubricant, and a drip inhibitor to the preform, stir evenly, melt-blend and extrude pellets with a twin-screw extruder, and injection mold to obtain a polypropylene composite plastic for a new energy battery housing.

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