A polypropylene composition, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a polypropylene composition, which comprises the following components by weight: 30-50 parts of polypropylene resin; 15-24 parts of piperazine flame retardant; 6-14 parts of inorganic phosphide; 0.5-1.5 parts of synergistic flame retardant; 20-35 parts of basalt fiber; 7-15 parts of hollow glass microspheres; and 2-5 parts of compatibilizer. For the polypropylene composition of the present invention, a high heat-resistant piperazine flame retardant system is selected. By adding a combination of basalt fiber and hollow glass microspheres, the heat insulation effect of the material can be effectively improved, and a good skeleton support effect can be achieved during the burning process, so that it is not easy to deform and collapse. Excellent ablation resistance performance is obtained. At the same time, the warpage deformation of injection molded parts can be reduced, and a polypropylene composition with both low warpage and ablation resistance characteristics is realized, which can particularly meet the usage requirements of materials for large battery pack casings.

Description

Technical Field

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

[0002] Compared with traditional fuel vehicles, the driving range of new energy vehicles is one of the important factors restricting their development. As the power source, the battery pack is an important core component of new energy vehicles. Therefore, the lightweight design, safety design, and material selection of the battery pack directly affect the development and popularization of electric vehicles. The battery pack body is composed of a housing covering the battery module. The battery housing plays a key role in the safe operation and protection of the battery module. It is divided into an upper housing and a lower housing. The upper housing is the upper cover, and its main functions are protection, sealing, and isolation from the vehicle compartment. At present, the materials for the upper cover of new energy vehicle battery packs mainly include metal materials, glass fiber-reinforced thermosetting plastics (such as SMC and PCM), and enhanced flame-retardant PPO, PPS, PP, etc. Due to its own disadvantages such as large specific gravity, poor insulation and corrosion resistance, and complex and time-consuming molding process, metal materials are gradually being replaced by polymer composites; glass fiber-reinforced thermosetting plastics cannot be recycled and reused after use, which does not conform to the development direction of environmental protection and low-carbon circular economy, and is also gradually being replaced by thermoplastic plastics; the reported enhanced flame-retardant engineering plastics such as PPO and PPS are expensive and are not suitable for the upper cover of large-sized battery packs.

[0003] Polypropylene (PP) is a widely used, abundant, and inexpensive general-purpose plastic. It has a low density, excellent chemical resistance, and good moldability, with good comprehensive properties and high cost performance, making it one of the choices for battery pack upper cover materials. The core requirement for battery pack housing materials is to pass the external fire test of GB / T31467.3-2015, and it is required that no large amounts of toxic and harmful gases are generated during the combustion process. By enhancing the flame retardancy of ordinary polypropylene materials, obtaining a new generation of low-smoke, halogen-free, ablation-resistant, and heat-insulating flame-retardant reinforced PP that meets the usage requirements of battery pack upper covers will become the trend of technological development. Chinese Patent Application CN114369303A discloses a halogen-free heat-insulating and ablation-resistant flame-retardant polypropylene material. By adding long glass fiber masterbatch and ceramizing filler to the halogen-free piperazine flame retardant system and assisting with a flux, the material has a certain ablation resistance effect. However, it is found in actual applications that this material will have problems of deformation and collapse during the fire process, and its injection molded parts have warping deformation problems, which limit the application space of this material. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a polypropylene composition with low warpage and ablation resistance, which is not prone to deformation and collapse problems during the fire process.

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

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

[0007] A polypropylene composition, by weight, comprises the following components:

[0008] Polypropylene resin 30 - 50 parts;

[0009] Piperazine flame retardant 15 - 24 parts;

[0010] Inorganic phosphide 6 - 14 parts;

[0011] Synergistic flame retardant 0.5 - 1.5 parts;

[0012] Basalt fiber 20 - 35 parts;

[0013] Hollow glass microspheres 7 - 15 parts;

[0014] Compatibilizer 2 - 5 parts.

[0015] The present invention has no special requirements for the polypropylene resin, and both homopolypropylene resin and copolymer polypropylene resin can achieve the effects of the present invention; preferably, a polypropylene resin with 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 element content > 5 wt%. The magnesium element content of the basalt fiber can be measured by X-ray fluorescence diffraction method.

[0018] Preferably, the pressure resistance 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 measured by the gas displacement method. Specifically, the sample is weighed on an electronic balance, and then the cup containing the sample is placed into the test chamber of a true density detector (Micromeritics true density detector). The lid is tightened, and finally, the sample weight is input into the fully automatic true density analyzer to calculate the true density of the sample. The compressive strength can be measured by the following method: A. Set the pressure value corresponding to the product specification, and place the hollow glass microspheres whose true density has been measured into the sealed container of the gas pressurizing device; B. Start the pressurizing device, and hold the pressure for 5 minutes after reaching the set pressure value; C. Take out the sample after pressure relief and detect the true density; D. Calculate the crushing rate of the microspheres based on the change in true density before and after pressurization. When the crushing rate is 20%, it is the critical pressure value, that is, the compressive strength of the hollow glass microspheres is measured.

[0020] The crushing rate = (2.3×B - 2.3×A) / (2.3×B - A×B), where 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] Further preferably, the particle size D50 of the hollow glass microspheres is < 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, pyrophosphate piperazine, or polyphosphate piperazine.

[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 of other additives by weight; the other additives include any one or more of antioxidants or lubricants.

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

[0029] Suitable lubricants can 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 antistatic agents and colorants without compromising the effects of the present invention.

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

[0032] Mix the components according to the ratio, and then use a twin-screw extruder for melt blending, extrusion granulation, and drying to obtain the polypropylene composition; wherein, the temperature of the twin-screw extruder is set at 150-200 °C; the feeding speed is 250-350 rpm; the die temperature is 200-210 °C; the main machine speed is 300-500 rpm / min; the vacuum degree is lower than -0.1 MPa.

[0033] The present invention also provides the application of the above polypropylene composition as a battery pack housing material; it is particularly suitable for the upper covers of large battery packs, for example, suitable for the upper covers of battery packs with dimensions of more than 1 m × 1 m.

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

[0035] For the polypropylene composition of the present invention, a high heat-resistant piperazine flame retardant system is selected. By adding a combination of basalt fibers and hollow glass microspheres, the heat insulation effect of the material can be effectively improved, and it can play a good skeleton support role during the fire process and is not easily deformed and collapsed, obtaining excellent ablation resistance. At the same time, it can reduce the warping deformation of injection-molded parts, realizing a polypropylene composition with both low warping and ablation resistance characteristics, and particularly meeting the usage requirements of materials for large battery pack housings. Embodiment

[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 do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

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

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

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

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

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

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

[0043] Basalt fiber 1: diameter of 7 μm, magnesium element content of 6 wt%; manufacturer is Shijin, grade is BCF-6-307;

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

[0045] Basalt fiber 3: diameter of 13 μm, magnesium element content of 7 wt%; manufacturer is Shijin, grade is BCF-6-313;

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

[0047] Glass fiber: diameter of 10 μm, manufacturer is Jushi, grade is ECS10-03-508C;

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

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

[0050] Hollow glass microsphere 3: compressive strength of 190 MPa, true density of 1.1 g / cm 3 , particle size D50 of 10 μm; manufacturer is Shenglaite, grade is HM15;

[0051] Hollow glass microsphere 4: compressive strength of 55 MPa, true density of 0.42 g / cm 3 , particle size D50 of 24 μm, manufacturer is Shenglaite, grade is HS42;

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

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

[0054] Antioxidant: the mass ratio of hindered phenol antioxidant 1010 to phosphite antioxidant 168 is 1:2, commercially available; the same antioxidant is used in both the examples and the comparative examples;

[0055] Lubricant: EBS B50, erucic acid amide, commercially available; the same lubricant was used in both the example and the comparative example.

[0056] Preparation methods of embodiments 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; wherein the temperatures of the screws of the twin-screw extruder from the feed port to the die are: zone 1 150-160°C, zone 2 180-190°C, zone 3 180-200°C, zone 4 180-200°C, zone 5 180-200°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.

[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 (i.e. deformation) of the opposite corner. Test 3 specimens and calculate the average deformation value.

[0061] (3) Ablation resistance: Place the material sample (sample size is 100 mm × 100 mm × 2.0 mm) vertically with the angle between the flat plate and the horizontal plane at 85°~95°. 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 min.

[0062] ①Observe the burn-through condition: Check the sample after ablation against light to see if 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 ratios of each group in comparative examples 1-5 (by weight) and related performance test results

[0067]

[0068] Table 3: The mixing ratios of each group in Comparative Examples 6-11 (by weight parts) and the test results of related properties

[0069]

[0070] It can be seen from the above results that the polypropylene composition of the present invention can effectively improve the heat insulation effect of the material through the combination of basalt fiber and hollow glass microspheres. The synergistic effect of the two can play a good role in skeleton support during the fire process, making it not easy to deform and collapse, obtaining excellent ablation resistance performance. At the same time, it can reduce the warpage deformation of injection molded parts, realizing a polypropylene composition with both low warpage and ablation resistance characteristics.

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

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

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

[0074] In Comparative Examples 4 / 5, the pressure resistance strength of the hollow glass microspheres is not within the required range, and good anti-deformation effects cannot be achieved.

[0075] In Comparative Examples 6 / 7, without adding basalt fiber or adding too little basalt fiber, obvious deformation and collapse problems will occur during the fire.

[0076] In Comparative Example 8, adding too much basalt fiber will increase the warpage deformation of the injection molded parts and will instead affect the anti-deformation during the fire.

[0077] In Comparative Examples 9 / 10, without adding hollow glass microspheres or adding too little hollow glass microspheres, the injection molded parts have obvious warpage deformation, and obvious deformation and collapse problems will occur during the fire.

[0078] In Comparative Example 11, adding too much hollow glass microspheres will affect the formation of a carbon layer during the combustion of the material, resulting in a reduction in the flame retardant performance of the material and failing to pass the ablation resistance test.

Claims

1. A polypropylene composition, characterized in that, By weight, it comprises the following components: 30 - 50 parts of polypropylene resin; 15 - 24 parts of piperazine flame retardant; 6 - 14 parts of inorganic phosphide; 0.5 - 1.5 parts of synergistic flame retardant; 20 - 35 parts of basalt fiber; 7 - 15 parts of hollow glass microspheres; 2 - 5 parts of compatibilizer; The average diameter of the basalt fiber is 5 - 10 μm, and the magnesium element content > 5wt%; The pressure resistance of the hollow glass microspheres is between 100-180 MPa, and the true density is 0.4-0.9 g / cm 3 ; The test method for the pressure resistance of the hollow glass microspheres is as follows: Step A, set the pressure value corresponding to the product specification, and put the hollow glass microspheres with measured true density into the sealed container of the gas pressurization equipment; Step B, start the pressurization equipment, and keep the pressure for 5 minutes after reaching the set pressure value; Step C, take out the sample after pressure relief and detect the true density; Step D, calculate the microsphere breakage rate according to the change of the true density before and after pressurization. When the breakage rate is 20%, it is the critical pressure value, that is, the pressure resistance of the hollow glass microspheres is measured; Breakage rate = (2.3×B - 2.3×A) / (2.3×B - A×B), where 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.

2. The polypropylene composition according to claim 1, wherein The particle size D50 of the hollow glass microspheres < 25μm.

3. The polypropylene composition according to claim 1, wherein The weight ratio of the basalt fiber to the hollow glass microspheres is (1.5 - 4):

1.

4. The polypropylene composition according to claim 3, characterized in that, The weight ratio of the basalt fiber to the hollow glass microspheres is (1.5 - 3.5):

1.

5. 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 polyphosphoric acid piperazine; 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.

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

7. The polypropylene composition according to claim 1, characterized in that, By weight, it further comprises 0.01 - 1.5 parts of other additives; the other additives include any one or more of antioxidant or lubricant.

8. The preparation method of the polypropylene composition according to any one of claims 1-7, characterized in that, It includes the following steps: according to the ratio, after mixing each component evenly, melt blending, extrusion granulation and drying are carried out by using a twin - screw extruder to prepare a polypropylene composition; wherein, the temperature of the twin - screw extruder is set at 150 - 200°C; the feeding speed is 250 - 350 rpm; the die temperature is 200 - 210°C; the main machine speed is 300 - 500 rpm / min; the vacuum degree is lower than - 0.1 MPa.

9. Use of the polypropylene composition according to any one of claims 1 - 7 as a battery pack housing material.

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