Polypropylene composite and method for producing the same

Abstract

The application discloses a kind of polypropylene composite material and preparation method thereof, are prepared from the following weight parts components: polypropylene resin 55-70 parts, modified wet synthesis mica 10-25 parts, compatible agent 5-15 parts, internal lubricant 0.2-0.5 parts, external lubricant 0.05-0.2 parts, antioxidant 0.2-0.5 parts, light stabilizer 0.1-0.3 parts;Wherein, the surface of the modified wet synthesis mica is modified by polydopamine.The polypropylene composite material prepared by the application can still have excellent melt flow rate, high bending modulus and impact toughness, and present low gloss, excellent surface properties of scratch resistance under high content mica filling.The material achieves a good balance between rigidity and toughness, overcomes the inherent contradiction of traditional high-filled polypropylene system rigidity and toughness reduction, simultaneously meets the comprehensive requirements of processing fluidity, appearance quality and long-term heat aging of automotive interior parts, and has outstanding comprehensive performance advantages.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically a polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene (PP) has become the most widely used thermoplastic material in the automotive interior sector due to its low cost, low density, and excellent processing properties. With the trend towards lightweighting and high-end automotive products, interior components are placing increasingly stringent comprehensive performance requirements on polypropylene materials: the material needs to possess high flowability to meet the injection molding filling needs of large, thin-walled parts, while also possessing high rigidity to meet the load-bearing requirements of the components, and excellent toughness to avoid brittle fracture. However, in traditional modified polypropylene systems, there is an inherent contradiction between high flowability and high rigidity, and between high filler content and high toughness.

[0003] To improve the rigidity of polypropylene materials, the industry commonly uses the addition of inorganic fillers (such as talc and mica). However, with the increase of filler content, the impact toughness of the material often shows a significant downward trend. Especially in the higher filler content range of 15-18%, the cantilever beam notched impact strength of most traditional talc-filled systems is difficult to maintain at 20 kJ / m². 2 The above factors, to some extent, limit the application of highly filled polypropylene materials in automotive interior parts where high toughness is required. Therefore, how to simultaneously achieve rigidity, toughness, and flowability with high filler content has become a long-standing technical challenge in this field. Summary of the Invention

[0004] In view of this, the present invention provides a polypropylene composite material and its preparation method, which simultaneously achieves high fluidity, high rigidity, high toughness and excellent surface quality of polypropylene material under the condition of mica filling amount of more than 20 parts, and successfully breaks through the technical bottleneck of high filling inevitably causing embrittlement.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention discloses a polypropylene composite material prepared from the following components in parts by weight: 55-70 parts of polypropylene resin, 10-25 parts of modified wet-synthesized mica 5-15 parts compatibilizer Internal lubricant 0.2-0.5 parts, External lubricant 0.05-0.2 parts, Antioxidant 0.2-0.5 parts, Light stabilizer 0.1-0.3 parts; The surface of the modified wet-synthesized mica is modified with polydopamine.

[0006] As a further aspect of the present invention: the modified wet-synthesized mica has a particle size of 300-350 mesh and an aspect ratio greater than 50. If the mica particle size is too fine, it is prone to clumping and has poor flowability; if it is too coarse, the surface is rough and the impact strength is low. 300-350 mesh is just right to balance dispersion, flowability, and surface gloss. If the mica's aspect ratio is greater than 50, the layers can be supported, improving rigidity (modulus ≥1700MPa), while reducing shrinkage anisotropy and preventing product warping.

[0007] As a further aspect of the present invention: the polypropylene resin is compounded from high-flowability copolymer polypropylene and high-rigidity copolymer polypropylene in a weight ratio of (40-70):(30-60); the high-flowability copolymer polypropylene has a melt flow rate of 50-100 g / 10 min under the condition of 2.16 kg / 230℃; the high-rigidity copolymer polypropylene has a melt flow rate of 20-50 g / 10 min under the same conditions, and a flexural modulus ≥1400 MPa.

[0008] As a further aspect of the present invention: the compatibilizer is an ethylene-octene copolymer with a maleic anhydride grafting rate of 0.8%-1.2%.

[0009] As a further aspect of the present invention: the internal lubricant is at least one of erucamide, oleamide, or stearamide; the external lubricant is polyether-modified silicone or silicone masterbatch; the weight ratio of the internal lubricant to the external lubricant is (2-4):1. When the amount of internal lubricant is 2 to 4 times that of external lubricant, the melt flow is good and the processing window is wide; only a small amount of external lubricant is needed to form a protective film on the surface to achieve scratch resistance, but excessive amount can easily precipitate and affect spraying and adhesion. When the ratio of external lubricant to internal lubricant is less than 2:1, the surface is prone to stickiness; when it is greater than 4:1, the scratch resistance decreases. This ratio range represents an optimized balance between flowability and surface quality.

[0010] As a further aspect of the present invention: the synthesis method of the modified wet-process synthetic mica is as follows: At room temperature, wet-synthesized mica was dispersed in a buffer solution containing dopamine, allowing dopamine to self-polymerize on the mica surface to form a polydopamine coating. After washing and drying, polydopamine-modified wet-synthesized mica was obtained.

[0011] As a further aspect of the present invention: the light stabilizer is a hindered amine light stabilizer; the antioxidant is a compound of hindered phenolic antioxidants and phosphite antioxidants.

[0012] Secondly, the present invention discloses a method for preparing the polypropylene composite material as described above, comprising the following steps: The polypropylene resin, antioxidant, light stabilizer and internal lubricant are thoroughly mixed at a total mass of 60%-90% to obtain the first premix. Add a compatibilizer and the remaining internal lubricant to the first premix, and continue mixing to obtain a second premix; The second premix is ​​added from the main feed port of the twin-screw extruder, the surface-modified wet-synthesized mica is added from the side feed port of the twin-screw extruder, and the external lubricant is added in the middle and rear section of the extruder. After melt extrusion and granulation, the product is obtained. The twin-screw extruder comprises 11 temperature zones arranged sequentially, with temperatures from zone one to the die head ranging from 190-200℃, 200-210℃, 205-215℃, 210-220℃, 215-225℃, 215-225℃, 210-220℃, 210-220℃, 210-220℃, 210-220℃, 210-220℃; the screw length-to-diameter ratio is 40-48:1, and the screw speed is 400-600 rpm.

[0013] To ensure both processing fluidity and maintain the interfacial bonding between the modified mica and POE-g-MAH, the internal lubricant is added in two steps. The addition ratio was determined through repeated optimization: if the initial addition is less than 60% of the total amount, processing becomes difficult; if it is more than 90%, the interfacial bonding effect decreases. The key reason for this step-by-step addition is that the modified mica surface is pre-coated with a polydopamine (PDA) coating, and the two complement each other, forming a necessary condition for synergistic use.

[0014] As a further aspect of the present invention, the external lubricant is added in zone 7 or zone 8 of the twin-screw extruder.

[0015] Thirdly, the present invention discloses the application of the polypropylene composite material as described above in the preparation of automotive interior parts, wherein the automotive interior parts are door panels, dashboards, center consoles or pillar guards.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The polypropylene composite material prepared by this invention, even with high mica content, simultaneously possesses excellent melt flow rate, high flexural modulus, and impact toughness, while exhibiting excellent surface properties such as low gloss and scratch resistance. This material achieves a good balance between rigidity and toughness, overcoming the inherent contradiction of increased rigidity and decreased toughness in traditional high-filler polypropylene systems. It also meets the comprehensive requirements of automotive interior parts for processing fluidity, appearance quality, and long-term heat aging resistance, demonstrating outstanding comprehensive performance advantages.

[0017] By employing a gradient feeding and zoned lubrication extrusion process, polydopamine-modified mica is added via side feeding, and external lubricant is introduced in the middle and later stages of the extruder. This effectively avoids performance losses caused by excessive filler breakage and premature lubricant dispersion. The process, synergistically working with specific components of the composite material, further enhances the material's impact toughness and surface quality. Furthermore, the process is stable, easy to control, and suitable for existing twin-screw extrusion equipment, demonstrating promising prospects for industrial application. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the parts in the following embodiments refer to parts by weight.

[0021] The reagents used in the following examples and comparative examples, along with their respective suppliers, are as follows: High-flowability copolymer polypropylene (HF-PP): melt flow rate (230℃ / 2.16kg) is 58 g / 10min, grade reference: SK Chemicals, Korea, BX3900.

[0022] High-rigidity copolymer polypropylene (HR-PP): melt flow rate (230℃ / 2.16kg) is 28 g / 10min, flexural modulus is about 1480 MPa, grade reference: Sinopec Refining & Chemical Co., Ltd., EP648U.

[0023] POE-g-MAH: Grafting rate 1.0%, grade reference DuPont PTW.

[0024] Wet-process synthesized mica: 325 mesh, aspect ratio > 50, grade reference: Lingshou County Antai Mining, AT-W325.

[0025] Polydopamine-modified wet-process mica: wet-process mica was dispersed in a Tris buffer solution of dopamine hydrochloride (pH=8.5), stirred at room temperature for 18 hours, filtered, washed, and dried at 60℃ for 12 hours to obtain polydopamine-coated modified mica.

[0026] Internal lubricant: erucamide, calcium stearate.

[0027] External lubricant: polyether-modified silicone masterbatch (50% silicone content), PE wax.

[0028] Antioxidant: BASF 1076 (primary antioxidant) and 168 (secondary antioxidant) are compounded in a 1:1 weight ratio.

[0029] Light stabilizer: Hindered amine light stabilizer 770.

[0030] Talc powder, plastic grade, grade reference Liaoning Aihai Talc Co., Ltd., AH-325 (325 mesh, aspect ratio >50, whiteness ≥90%).

[0031] The reagents described above are only for illustrating the source and composition of the reagents used in the experiments of this invention, so as to provide full disclosure, and do not imply that the invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0032] Example 1 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.18 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.12 parts of erucamide for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone), and 0.1 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0033] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0034] Example 2 30 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.24 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 400 rpm for 4 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.06 parts of erucamide for 3 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 25 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone), and 0.1 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0035] The parameter settings for the twin-screw extruder are described in Example 1.

[0036] Example 3 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.27 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 400 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.03 parts of erucamide for another 5 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 16 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone), and 0.1 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0037] The parameter settings for the twin-screw extruder are described in Example 1.

[0038] Example 4 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.12 parts of calcium stearate, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.08 parts of calcium stearate for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of polydopamine surface-modified wet-process synthetic mica are added via side feeding (fifth temperature zone), and 0.1 parts of PE wax are added from the seventh temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0039] The parameter settings for the twin-screw extruder are described in Example 1.

[0040] Example 5 45 parts of high-flowability copolymer polypropylene, 25 parts of high-rigidity copolymer polypropylene, 0.15 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.05 parts of erucamide for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone), and 0.18 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0041] The parameter settings for the twin-screw extruder are described in Example 1.

[0042] Comparative Example 1 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.18 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of ordinary POE (ungrafted) compatibilizer and 0.12 parts of erucamide for 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone), and 0.1 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0043] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0044] Comparative Example 2 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.18 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.12 parts of erucamide for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of talc powder are added via side feeding (fifth temperature zone), and 0.1 parts of polyether modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0045] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0046] Comparative Example 3 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.18 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.12 parts of erucamide for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of unmodified wet-synthetic mica are added via side feeding (fifth temperature zone), and 0.1 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0047] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0048] Comparative Example 4 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.23 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.17 parts of erucamide for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, and 20 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone). After melt extrusion and granulation, the composite polypropylene is obtained.

[0049] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0050] Comparative Example 5 The entire composite material formulation of Example 1 was directly replaced with commercially available high-rigidity talc-filled PP material (brand name: Kingfa Science & Technology ABP-2020 UV, 20wt% talc filler).

[0051] Comparative Example 6 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.18 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer and 0.12 parts of erucamide for another 4 minutes to obtain the second premix. The second premix is ​​mixed evenly with 20 parts of polydopamine surface-modified wet-synthesized mica and 0.1 parts of polyether-modified silicone masterbatch, and then fed into the main feed port of a twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0052] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0053] Comparative Example 7 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.3 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain a premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer for another 4 minutes to obtain the second premix. The second premix is ​​added at the main feed port, 20 parts of polydopamine surface-modified wet-synthesized mica are added via side feeding (fifth temperature zone), and 0.1 parts of polyether-modified silicone masterbatch are added from the eighth temperature zone of the twin-screw extruder. After melt extrusion and granulation, the composite polypropylene is obtained.

[0054] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0055] Comparative Example 8 35 parts of high-flowability copolymer polypropylene, 22 parts of high-rigidity copolymer polypropylene, 0.3 parts of erucamide, 0.5 parts of antioxidant and 0.2 parts of light stabilizer were added to a high-speed mixer and mixed at 500 rpm for 3 minutes to obtain the first premix. The first premix was mixed with 10 parts of POE-g-MAH compatibilizer for another 4 minutes to obtain the second premix. The second premix was then mixed again with 20 parts of polydopamine surface-modified wet-synthesized mica and 0.1 parts of polyether-modified silicone masterbatch. The mixture was then fed into the main feed port of a twin-screw extruder and subjected to melt extrusion and granulation to obtain the composite polypropylene.

[0056] The temperature settings for each zone of the twin-screw extruder (length-to-diameter ratio 44:1) are as follows: Zone 1 195℃, Zone 2 200℃, Zone 3 205℃, Zone 4 210℃, Zone 5 215℃, Zone 6 220℃, Zone 7 220℃, Zone 8 215℃, Zone 9 215℃, Zone 10 210℃, and the die head 210℃. The screw speed is controlled at 500 rpm.

[0057] Test case The composite polypropylene materials prepared in each embodiment and comparative example were subjected to performance tests. The test items and conditions are shown below, and the test results are shown in Table 1.

[0058] Melt flow rate: Tested according to ISO 1133 standard, at a temperature of 230°C and a load of 2.16 kg.

[0059] Cantilever beam notched impact strength: According to ISO 180 standard, type A notch, test temperature is 23℃.

[0060] Flexural modulus: Tested according to ISO 178 standard, at a speed of 2 mm / min and a span of 64 mm.

[0061] 60° gloss: According to GB / T 8807 standard, the test angle is 60°.

[0062] Scratch resistance ΔL value: According to Volkswagen PV3952 standard, the change in brightness ΔL before and after scratching is measured using a wool felt scratching head with a 10N load.

[0063] Table 1

[0064] The composite polypropylene prepared in Example 1 was used in the trial production of the front door interior panel substrate of a certain car model. Its performance was compared with that of the original commercial material. The test results are shown in Table 2-3.

[0065] The assembly gap fluctuation test method is as follows: After the injection-molded door interior panel is placed in an environment of 23℃ and 50% RH for 24 hours, the gap values ​​between the door panel and the body sheet metal at 5 designated assembly points are measured using a gap gauge. The difference between the maximum and minimum values ​​is calculated as the assembly gap fluctuation (unit: mm). Each sample is measured 3 times and the average is taken.

[0066] Low-temperature (-30℃) drop ball impact test method: Refer to ISO 6603-2 standard. After freezing the sample in a -30℃ low-temperature chamber for 4 hours, remove it and immediately drop a 500g stainless steel ball from a height of 1 meter onto the central area of ​​the inner surface of the door panel. Observe whether there are visible cracks or fractures. Record the number of impacts (do not repeat impacts at the same location), and use the number of times cracks appear as the evaluation index.

[0067] TVOC, formaldehyde, and acetaldehyde testing methods: The testing shall be conducted according to the methods specified in Appendix A of GB / T 27630-2011 "Guidelines for Evaluation of Air Quality in Passenger Cars". A 1m... 3 The environmental chamber was used for testing under the following conditions: temperature 25±1℃, relative humidity 50±5%, and air exchange rate 0.5 times / hour. Samples were pretreated under standard conditions before being placed in the chamber and equilibrated for 16 hours before sampling and analysis. TVOC was detected using gas chromatography-mass spectrometry (GC-MS) (C2-C16 range), while formaldehyde and acetaldehyde were detected using high-performance liquid chromatography (HPLC). Results are expressed in µgC / g (TVOC) or µg / g (aldehydes).

[0068] Table 2

[0069] In Table 2, the brand of commercially available high-strength PP is Kingfa Science & Technology, with the brand name ABP-2020 UV.

[0070] Table 3

[0071] As can be seen from Table 1, all embodiments of the present invention, when the filler content is as high as 20-25 parts, simultaneously achieve high melt flow rate (≥26.5 g / 10min) and high notched impact strength (≥36.2 kJ / m). 2 It exhibits excellent rigidity-toughness balance and surface properties, with high flexural modulus (≥1680MPa), a 60° gloss level ≤33.5, and scratch resistance ΔL ≤0.88. In contrast, all comparative examples are significantly inferior to the examples in at least one key performance aspect.

[0072] In Comparative Example 1, replacing POE-g-MAH with ordinary POE reduced the impact strength to 21.5 kJ / m. 2The impact strength was reduced by 44% compared to Example 1, demonstrating that the chemical coupling of POE-g-MAH is the key to achieving high toughness under high filling conditions. Comparative Example 2, which replaced polydopamine-modified wet-process mica with ordinary talc, had an impact strength of only 18.2 kJ / m². 2 With a modulus of 1650 MPa, a gloss level as high as 48.0, and a scratch resistance ΔL of 1.35, it is comprehensively inferior to Example 1, confirming the necessity and superiority of high aspect ratio wet-process mica and PDA modification. Comparative Example 3 uses unmodified mica, with an impact strength of 34.4 kJ / m. 2 Compared to Example 1, the gloss and scratch resistance were reduced by approximately 10.6%, and both were slightly worse, indicating that the PDA coating can further improve performance by enhancing interfacial bonding. Comparative Example 4, without external lubricant, showed a deterioration in scratch resistance ΔL to 1.40, demonstrating that external lubricant is indispensable for surface quality. Comparative Example 5 used commercially available high-rigidity talc-filled PP, with an impact strength of only 6.5 kJ / m². 2 Although it has a high modulus, its toughness is extremely poor, failing to meet the impact performance requirements of automotive interior parts. Comparative Examples 6-8, by changing the feeding method or lubricant addition method, showed impact strengths of 30.8-34.2 kJ / m². 2 The impact modulus (1660-1740 MPa) and scratch resistance (ΔL 0.92-1.05) were all lower than those of Example 5, which used side-fed mica and step-by-step lubricant (impact 36.2 kJ / m², modulus 1720 MPa, ΔL 0.72), demonstrating the synergistic effect of gradient feeding and zoned lubrication processes.

[0073] In summary, the data in Table 1 fully demonstrate the significant advantages of the technical solution of the present invention in terms of rigidity-toughness balance, surface quality, and processing fluidity. Furthermore, the comparative examples clearly demonstrate the necessity of key technical features such as POE-g-MAH, polydopamine-modified wet mica, external lubricant, and gradient feeding process.

[0074] As shown in Table 2, the material of Example 1 was used in the trial production of the front door interior panel substrate of a certain car model and compared with commercially available high-rigidity talc-filled PP (Comparative Example 5). The results are shown in Table 2: The material of the present invention has better fluidity, allowing for thinner wall thickness design and achieving a 5.6% weight reduction in the component; the 60° gloss decreased from 55.0 to 30.2, achieving the surface texture required for high-end interiors; the scratch resistance ΔL decreased from 2.50 to 0.78, significantly improving wear resistance; the assembly gap fluctuation decreased from ±0.4 mm to ±0.15 mm, indicating that the material of the present invention has less shrinkage anisotropy and excellent dimensional stability, which is beneficial for reducing assembly noise and uneven gaps; at a low temperature of -30℃, the commercially available material cracked after 3 drop ball impacts, while the material of the present invention remained crack-free after 10 impacts, proving that the interface reinforcement of PDA-modified mica and POE-g-MAH is still effective at low temperatures, solving the engineering pain point of brittle fracture of interior parts in cold regions.

[0075] As shown in Table 3, the TVOC value of Example 1 of this invention is 42.7 µgC / g, which is 26.6% lower than that of commercially available high-rigidity PP (58.2 µgC / g) and far below the national standard limit of 60 µgC / g. This is mainly attributed to: the low impurities and low volatility of the wet-synthesized mica, the complete absence of residual monomers after the PDA coating is cured at low temperature, and the gradient feeding and zoned lubrication process avoiding early thermal decomposition of the lubricant. Formaldehyde (2.8 µg / g) and acetaldehyde (4.1 µg / g) are both significantly lower than the national standard and better than the commercially available comparative sample, proving that the interfacial chemical bonding of this invention reduces aldehyde byproducts generated by the thermal oxidative degradation of polypropylene. Benzene series compounds (benzene, toluene, xylene) were not detected, meeting the most stringent requirements for in-vehicle air quality. In summary, the material of this invention achieves excellent mechanical and surface properties while also possessing low VOC characteristics, making it particularly suitable for high-end automotive interior applications that are sensitive to in-vehicle air quality.

[0076] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0077] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A polypropylene composite material, characterized in that, It is prepared from the following components in parts by weight: 55-70 parts of polypropylene resin, 10-25 parts of modified wet-synthesized mica 5-15 parts compatibilizer Internal lubricant 0.2-0.5 parts, External lubricant 0.05-0.2 parts, Antioxidant 0.2-0.5 parts, Light stabilizer 0.1-0.3 parts; The surface of the modified wet-synthesized mica is modified with polydopamine.

2. The polypropylene composite material according to claim 1, characterized in that, The modified wet-synthesized mica has a particle size of 300-350 mesh and an aspect ratio greater than 50.

3. The polypropylene composite material according to claim 1, characterized in that, The polypropylene resin is compounded from high-flowability copolymer polypropylene and high-rigidity copolymer polypropylene in a weight ratio of (40-70):(30-60); the high-flowability copolymer polypropylene has a melt flow rate of 50-100 g / 10 min under the condition of 2.16 kg / 230℃; the high-rigidity copolymer polypropylene has a melt flow rate of 20-50 g / 10 min under the same conditions, and a flexural modulus ≥1400 MPa.

4. The polypropylene composite material according to claim 1, characterized in that, The compatibilizer is an ethylene-octene copolymer with a maleic anhydride grafting rate of 0.8%-1.2%.

5. The polypropylene composite material according to claim 1, characterized in that, The internal lubricant is at least one of erucamide, oleamide, or stearamide; the external lubricant is polyether-modified silicone or silicone masterbatch; the weight ratio of the internal lubricant to the external lubricant is (2-4):

1.

6. The polypropylene composite material according to claim 1, characterized in that, The method for synthesizing the modified wet-process mica is as follows: At room temperature, wet-synthesized mica was dispersed in a buffer solution containing dopamine, allowing dopamine to self-polymerize on the mica surface to form a polydopamine coating. After washing and drying, polydopamine-modified wet-synthesized mica was obtained.

7. The polypropylene composite material according to claim 1, characterized in that, The light stabilizer is a hindered amine light stabilizer; the antioxidant is a compound of hindered phenolic antioxidants and phosphite antioxidants.

8. The method for preparing the polypropylene composite material according to any one of claims 1-7, characterized in that, Includes the following steps: The polypropylene resin, antioxidant, light stabilizer and internal lubricant are thoroughly mixed at a total mass of 60%-90% to obtain the first premix. Add a compatibilizer and the remaining internal lubricant to the first premix, and continue mixing to obtain a second premix; The second premix is ​​added from the main feed port of the twin-screw extruder, the surface-modified wet-synthesized mica is added from the side feed port of the twin-screw extruder, and the external lubricant is added in the middle and rear section of the extruder. After melt extrusion and granulation, the product is obtained. The twin-screw extruder comprises 11 temperature zones arranged sequentially, with temperatures from zone one to the die head ranging from 190-200℃, 200-210℃, 205-215℃, 210-220℃, 215-225℃, 215-225℃, 210-220℃, 210-220℃, 210-220℃, 210-220℃, 210-220℃; the screw length-to-diameter ratio is 40-48:1, and the screw speed is 400-600 rpm.

9. The preparation method according to claim 8, characterized in that, The external lubricant is added in zone 7 or zone 8 of the twin-screw extruder.

10. The application of a polypropylene composite material as described in any one of claims 1-7 in the preparation of automotive interior parts, characterized in that, The automotive interior components include door panels, dashboards, center consoles, or pillar guards.

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