Polypropylene composition, and preparation method therefor and use thereof

Abstract

A polypropylene composition, comprising the following components in parts by weight: 30-50 parts of a polypropylene resin; 15-24 parts of a piperazine flame retardant; 6-14 parts of an inorganic phosphide; 0.5-1.5 parts of a synergistic flame retardant; 20-35 parts of basalt fibers; 7-15 parts of hollow glass beads; and 2-5 parts of a compatilizer. The polypropylene composition selects a high-heat-resistance piperazine flame retardant system; by adding a combination of the basalt fibers and the hollow glass beads, the thermal insulation effect of the material can be effectively improved, and in the burning process, a good framework supporting effect can be achieved, and it is not prone to deformation and collapse, thereby achieving excellent ablation resistance, reducing the warping deformation of injection molded parts, and achieving a polypropylene composition having both characteristics of low warpage and ablation resistance; and particularly, the use requirements of large battery pack case materials on the material can be met.

Description

A polypropylene composition and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a polypropylene composition, a preparation method and an application thereof. Background Art

[0002] Compared to traditional fuel-powered vehicles, the range of new energy vehicles (NEVs) is a significant factor limiting their development. As a power source, the battery pack is a crucial core component of NEVs. Therefore, the battery pack's lightweight design, safety design, and material selection directly impact the development and adoption of electric vehicles. The battery pack's main body consists of a housing enclosing the battery module. The housing plays a critical role in the safe operation and protection of the battery module. It consists of an upper housing and a lower housing. The upper housing, or cover, primarily functions to protect, seal, and isolate the vehicle from the passenger compartment. Currently, the main materials used for NEV battery pack covers include metal, glass-fiber-reinforced thermoset plastics (SMC, PCM, etc.), and flame-retardant materials such as PPO, PPS, and PP. Metal materials are gradually being replaced by polymer composite materials due to their own shortcomings such as high specific gravity, poor insulation and corrosion resistance, and complex and time-consuming molding processes. Glass fiber-reinforced thermosetting plastics cannot be recycled and reused after use, which is not in line with the development direction of an environmentally friendly and low-carbon circular economy, and are also gradually being replaced by thermoplastic plastics. Reported reinforced flame-retardant engineering plastics such as PPO and PPS are expensive and are not suitable for large-sized battery pack covers.

[0003] Polypropylene (PP) is a widely used, abundant, and inexpensive general-purpose plastic. Its low density, excellent chemical resistance, and excellent formability combine to offer excellent overall performance and a high cost-performance ratio, making it a popular choice for battery pack cover materials. Key requirements for battery pack housing materials include passing the GB / T31467.3-2015 external fire test and avoiding the generation of significant amounts of toxic and hazardous gases during combustion. Reinforcing and flame-retardant modification of conventional polypropylene to create a new generation of low-smoke, halogen-free, ablation-resistant, and thermally insulating flame-retardant reinforced PP that meets the requirements for battery pack covers will become a technological trend. Chinese patent application CN114369303A discloses a halogen-free, thermally insulating, ablation-resistant, and flame-retardant polypropylene material. By adding long glass fiber masterbatch and ceramic fillers to a halogen-free piperazine flame retardant system, along with a fluxing agent, the material achieves a certain degree of ablation resistance. However, in actual use, the material exhibits deformation and collapse during the fire process, and injection-molded parts suffer from warping and deformation, limiting its application. Summary of the Invention

[0004] In order to overcome the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a low-warping, ablation-resistant polypropylene composition that is less likely to deform or collapse during a fire process.

[0005] Another object of the present invention is to provide a method for preparing the polypropylene composition.

[0006] The present invention is achieved through the following technical solutions:

[0007] A polypropylene composition comprising the following components in parts by weight:

[0008] 30-50 parts of polypropylene resin;

[0009] 15-24 parts of piperazine flame retardant;

[0010] 6-14 parts of inorganic phosphide;

[0011] 0.5-1.5 parts of synergistic flame retardant;

[0012] 20-35 parts of basalt fiber;

[0013] 7-15 parts of hollow glass microspheres;

[0014] 2-5 parts of compatibilizer.

[0015] The present invention has no special requirements for polypropylene resin. Both homopolymer polypropylene resin and copolymer polypropylene resin can achieve the effects of the present invention. Preferably, a polypropylene resin having a melt index of 10-200 g / 10min at 230°C and 2.16 kg is used.

[0016] In the polypropylene composition of the present invention, the content of the polypropylene resin is not less than 25 wt%.

[0017] Preferably, the diameter of the basalt fiber is 5-10 microns, and the magnesium content is greater than 5 wt %. The magnesium content of the basalt fiber can be determined by X-ray fluorescence diffraction.

[0018] Preferably, the compressive strength of the hollow glass microspheres is between 100-180 MPa and the true density is 0.4-0.9 g / cm 3 .

[0019] The true density is tested using the gas displacement method. The sample is weighed on an electronic balance, then the cup containing the sample is placed in the test chamber of a true density tester (McMerritts), the lid is tightened, and the sample weight is entered into a fully automatic true density analyzer to calculate the true density. The compressive strength can be measured using the following method: A. Set the pressure value corresponding to the product specification and place hollow glass microspheres (with measured true density) into a sealed container of a gas pressurizing device; B. Start the pressurizing device and maintain the pressure for 5 minutes after reaching the set pressure; C. Release the pressure, remove the sample, and test the true density; D. Calculate the microsphere breakage rate based on the change in true density before and after pressurization. A breakage rate of 20% is the critical pressure value, which represents the compressive strength of the hollow glass microspheres.

[0020] The crushing rate = (2.3×B-2.3×A) / (2.3×BA×B), wherein A is the true density of the hollow glass microspheres before pressurization, and B is the true density of the hollow glass microspheres after pressurization.

[0021] More preferably, the particle size D50 of the hollow glass microspheres is less than 25 μm.

[0022] Preferably, the weight content of basalt fiber in the polypropylene composition is (1.5-4):1; preferably (1.5-3.5):1.

[0023] Preferably, the piperazine flame retardant can be selected from any one or more of piperazine phosphate, piperazine pyrophosphate or piperazine polyphosphate.

[0024] Preferably, the inorganic phosphide can be selected from any one or more of melamine phosphate, melamine pyrophosphate or melamine polyphosphate.

[0025] Preferably, the synergistic flame retardant can be selected from any one or more of zinc oxide, magnesium oxide, aluminum oxide, lanthanum oxide or silicon dioxide.

[0026] Preferably, the compatibilizer is selected from PP grafted maleic anhydride.

[0027] Preferably, the polypropylene composition of the present invention further comprises 0.01-1.5 parts by weight of other additives; the other additives include any one or more of antioxidants or lubricants.

[0028] Suitable antioxidants may be selected from any one or more of hindered phenol antioxidants, phosphate antioxidants or thioether antioxidants.

[0029] Suitable lubricants may be selected from any one or more of polyethylene wax, EBS, erucamide or oleamide.

[0030] The polypropylene composition of the present invention may further contain other components such as an antistatic agent and a colorant without impairing the effects of the present invention.

[0031] The present invention also provides a method for preparing the polypropylene composition, comprising the following steps:

[0032] After mixing the components according to the ratio, a twin-screw extruder is used for melt blending, extrusion granulation, and drying to prepare a polypropylene composition; wherein the temperature of the twin-screw extruder is set to 150-200°C; the feed speed is 250-350rpm; the die temperature is 200-210°C; the main engine speed is 300-500rpm / min; and the vacuum degree is lower than -0.1MPa.

[0033] The present invention also provides the use of the above-mentioned polypropylene composition as a battery pack shell material; it is particularly suitable for large battery pack covers, for example, battery pack covers with a size of 1m×1m or more.

[0034] The present invention has the following beneficial effects:

[0035] The polypropylene composition of the present invention selects a high-heat-resistant piperazine flame retardant system and, by adding a combination of basalt fiber and hollow glass microspheres, can effectively improve the thermal insulation effect of the material, and can provide good skeleton support during the burning process without being easily deformed or collapsed, thereby obtaining excellent ablation resistance. At the same time, it can reduce the warping deformation of injection-molded parts, thereby realizing a polypropylene composition with both low warping and ablation resistance. The polypropylene composition can particularly meet the material usage requirements of large-scale battery pack shell materials. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0037] The reagents used in the examples and comparative examples of the present invention are described below, but are not limited to these materials:

[0038] Polypropylene resin 1: HP500N, CNOOC Shell;

[0039] Polypropylene resin 2: EP548R, CNOOC Shell;

[0040] Piperazine flame retardant: piperazine pyrophosphate, JNP-2, Sichuan Fine Chemical Research Institute;

[0041] Inorganic phosphide: melamine pyrophosphate, MPP, Shandong Shian Chemical;

[0042] Synergistic flame retardant: zinc oxide, commercially available;

[0043] Basalt fiber 1: 7 microns in diameter, 6 wt% magnesium content; manufactured by Shijin, brand BCF-6-307;

[0044] Basalt fiber 2: diameter 10 μm, magnesium content 2 wt%; manufacturer: Shijin, brand BCF-5-310;

[0045] Basalt fiber 3: diameter 13 microns, magnesium content 7wt%; manufacturer: Shijin, brand BCF-6-313;

[0046] Basalt fiber 4: diameter 10 μm, magnesium content 6.5 wt%; manufacturer: Shijin, brand BCF-6-410;

[0047] Glass fiber: diameter 10 microns, manufactured by Jushi, brand ECS10-03-508C;

[0048] Hollow glass microsphere 1: compressive strength 110MPa, true density 0.46g / cm 3 , particle size D50 is 20μm; manufacturer is 3M, brand is IM16k;

[0049] Hollow glass microspheres 2: compressive strength 124 MPa, true density 0.6 g / cm 3 , particle size D50 is 30μm; manufacturer is 3M, brand is S60HS;

[0050] Hollow glass microspheres 3: compressive strength 190 MPa, true density 1.1 g / cm 3 , particle size D50 is 10μm; manufacturer is Saint-Light, brand is HM15;

[0051] Hollow glass microspheres 4: compressive strength 55MPa, true density 0.42g / cm 3 , particle size D50 is 24μm, manufacturer is Saint-Light, brand is HS42;

[0052] Compatibilizer 1: PP grafted maleic anhydride, brand PC-3, commercially available;

[0053] Compatibilizer 2: POE grafted maleic anhydride, brand PC-28, commercially available;

[0054] Antioxidant: Hindered phenol antioxidant 1010 and phosphate antioxidant 168, mass ratio of 1:2, commercially available; the same antioxidant was used in both the examples and comparative examples;

[0055] Lubricant: EBS B50, erucamide, commercially available; the same lubricant was used in both the examples and the comparative examples.

[0056] Preparation methods of Examples and Comparative Examples:

[0057] After mixing the components according to the proportion, a twin-screw extruder is used for melt blending, extrusion granulation, and drying to prepare a polypropylene composition. The temperatures of the screw sections of the twin-screw extruder from the feed port to the die are: 150-160° C. for zone 1, 180-190° C. for zone 2, 180-200° C. for zone 3, 180-200° C. for zone 4, and 180-200° C. for zone 5; the feed speed is 250-350 rpm; the die temperature is 200-210° C.; the main engine speed is 300-500 rpm / min; and the vacuum degree is lower than -0.1 MPa.

[0058] Related performance test methods:

[0059] (1) Flame retardant performance: Refer to UL94-2013 to test the flame retardant grade.

[0060] (2) Injection deformation test: Injection mold a 100*100*2mm square plate specimen, press one corner, and then test the maximum height of the opposite corner (i.e. deformation). Test 3 specimens and calculate the average deformation value.

[0061] (3) Ablation resistance: Place the material sample (sample size is 100mm×100mm×2.0mm) vertically with the flat plate at an angle of 85°~95° to the horizontal plane. Use propane / butane flame to ablate the sample surface. Use a thermocouple to measure the temperature at the center of the flame on the sample. The temperature is required to be between 1000℃ and 1200℃, and the flame ablation time is 10 minutes.

[0062] ①Observe the burn-through condition: Hold the ablated sample against light to check whether there is light transmission. If there is no perforation and light transmission, the ablation resistance test has been passed;

[0063] ② Test the ablation deformation: Place the ablated sample horizontally and measure the height of the depression in the middle, which is the ablation deformation.

[0064] Table 1: Distribution ratios of each group in Examples 1-9 (by weight) and related performance test results

[0065]

[0066] Table 2: Distribution ratio of each group in comparative examples 1-5 (by weight) and related performance test results

[0067]

[0068] Table 3: Distribution ratio of each group of comparative examples 6-11 (by weight) and related performance test results

[0069]

[0070] The above results show that the polypropylene composition of the present invention can effectively improve the thermal insulation effect of the material by adding a combination of basalt fibers and hollow glass microspheres. The synergistic effect of the two can also provide a good skeleton support during the burning process and is not easy to deform and collapse, thereby obtaining excellent ablation resistance. At the same time, it can reduce the warping deformation of injection-molded parts, thereby realizing a polypropylene composition with both low warping and ablation resistance.

[0071] In Comparative Example 1, the magnesium content of the basalt fiber is too low, and the heat-resistant temperature of the material is low, which affects the deformation resistance during fire.

[0072] In Comparative Example 2, the diameter of the basalt fiber is too large, which will increase the warping deformation of the injection molded part and has poor anti-deformation effect during fire.

[0073] Comparative Example 3, using glass fiber, cannot effectively improve the deformation resistance during fire.

[0074] In comparative examples 4 and 5, the compressive strength of the hollow glass microspheres was not within the required range, and a good anti-deformation effect could not be achieved.

[0075] In comparative examples 6 and 7, no basalt fiber was added or the amount of basalt fiber added was too small, and obvious deformation and collapse problems occurred during burning.

[0076] In comparative example 8, excessive addition of basalt fiber will increase the warping deformation of the injection molded part and affect its deformation resistance during fire.

[0077] In comparative examples 9 / 10, no hollow glass microspheres were added or the amount of hollow glass microspheres added was too small, and the injection molded parts had obvious warping and deformation, and also showed obvious deformation and collapse problems during burning.

[0078] In comparative example 11, excessive addition of hollow glass microspheres will affect the combustion of the material and form a carbon layer, resulting in reduced flame retardancy of the material and failure to pass the ablation resistance test.

Claims

1. A polypropylene composition, characterized in that By weight, it includes the following components: 30-50 parts of polypropylene resin; Piperazine flame retardant 15-24 parts; 6-14 parts of inorganic phosphide; Synergistic flame retardant 0.5-1.5 parts; Basalt fiber 20-35 parts; Hollow glass microspheres 7-15 parts; Compatibilizer 2-5 parts.

2. The polypropylene composition according to claim 1, characterized in that The average diameter of the basalt fiber is 5-10 microns, and the magnesium content is greater than 5wt%.

3. The polypropylene composition according to claim 1, characterized in that The compressive strength of the hollow glass microspheres is between 100-180 MPa and the true density is 0.4-0.9 g / cm 3 .

4. The polypropylene composition according to claim 3, characterized in that The particle size D50 of the hollow glass microspheres is less than 25 μm.

5. The polypropylene composition according to claim 1, characterized in that The weight ratio of the basalt fiber to the hollow glass microspheres is (1.5-4):1; preferably (1.5-3.5):

1.

6. The polypropylene composition according to claim 1, characterized in that The piperazine flame retardant is selected from any one or more of piperazine phosphate, piperazine pyrophosphate or piperazine polyphosphate; the inorganic phosphide is selected from any one or more of melamine phosphate, melamine pyrophosphate or melamine polyphosphate; the synergistic flame retardant is selected from any one or more of zinc oxide, magnesium oxide, aluminum oxide, lanthanum oxide or silicon dioxide.

7. The polypropylene composition according to claim 1, characterized in that The compatibilizer is selected from PP grafted maleic anhydride.

8. The polypropylene composition according to claim 1, characterized in that By weight, 0.01-1.5 parts of other additives are also included; the other additives include any one or more of antioxidants or lubricants.

9. The method for preparing the polypropylene composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: After mixing the components according to the ratio, a twin-screw extruder is used for melt blending, extrusion granulation and drying to prepare a polypropylene composition; wherein the temperature of the twin-screw extruder is set to 150-200°C; the feed speed is 250-350rpm; the die temperature is 200-210°C; the main engine speed is 300-500rpm / min; and the vacuum degree is lower than -0.1MPa.

10. Use of the polypropylene composition according to any one of claims 1 to 8 as a battery pack shell material.

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