Polypropylene composite material, and preparation method and application thereof

Abstract

The application discloses a polypropylene composite material and a preparation method and application thereof, relates to the technical field of polymer materials, and discloses the polypropylene composite material, which comprises the following components in proportion by weight: 40-80 parts of high-crystalline polypropylene, 0-40 parts of a filler, 5-20 parts of linear low-density polyethylene, and 0.1-1 part of an amide scratch-resistant agent. The polypropylene composite material takes high-crystalline polypropylene material as the main resin, endows the material with basic solvent resistance and scratch resistance, and further adds specific linear low-density polyethylene, which can obviously reduce the phase separation of two phases, further improves the solvent resistance of the composite material, and is beneficial to controlling the migration rate of the amide scratch-resistant agent to the surface of a product, achieving long-acting scratch resistance, and maintaining high surface tension, the surface tension can reach more than 40, the flame spraying requirement is exempted, and the polypropylene composite material can be widely applied to the spraying of vehicle outer decoration product assemblies and the integrated design of skin and lines.

Description

Technical Field

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

[0002] In recent years, with the development of the automotive industry, more and more plastics have been used in automotive exterior parts. Among them, polypropylene, due to its excellent comprehensive performance, wide availability, and high quality and low price, occupies a large proportion of automotive plastic usage. As people's living standards continue to improve, consumers have increasingly higher requirements for automotive exterior parts. Traditionally, automotive exterior parts are generally painted. Now, with the expansion of application scenarios, integrated parts with partial painting and textured finishes have emerged, such as bumper assemblies, where the upper part is painted and the lower part is textured. Generally, painted parts require good paint adhesion, even achieving high surface tension that eliminates the need for flame treatment, while textured parts require good durability, scratch resistance, and solvent resistance. Previously, parts with these different requirements were often produced using two different materials. However, with the emergence of integrated design, automotive exterior materials are now required to simultaneously meet these performance requirements. To meet scratch resistance requirements, scratch-resistant additives are often added. However, silicone-based scratch-resistant agents tend to reduce the surface tension of the material, affecting spraying performance, while amide-based scratch-resistant agents tend to migrate rapidly and accumulate in large quantities on the surface of the part. This rapid and substantial migration and precipitation onto the surface within a short period can affect the paint finish, and the effective content is lost in a short time with vehicle washing, failing to achieve durable scratch resistance. Furthermore, the solvent resistance of automotive exterior materials is often not ideal. Unpainted automotive exterior parts are easily affected by gasoline and cleaning fluids, resulting in significant color changes that affect aesthetics and usability. Therefore, materials with good solvent resistance are required.

[0003] Existing technology discloses a polypropylene composition for bumpers, which, by weight percentage, comprises: 20%-60% copolymer polypropylene resin, 10%-40% homopolymer polypropylene resin, 10%-20% toughening agent, 1%-4% anti-aging system additives, 1%-5% scratch-resistant agent, 0.1%-0.5% nucleating agent, 0.5%-3% lubricant, 0.2%-0.5% coupling agent, 1%-15% polymeric antistatic agent, and 1%-3% color masterbatch. While the additional anti-aging system additives and silicone polymer scratch-resistant agent help improve the scratch resistance and aging resistance of the polypropylene composition, it is designed for paint-free bumper polypropylene compositions and cannot guarantee that the surface tension of the polypropylene composition meets the requirements for flame-treatment-free painting. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing polypropylene composite materials, which are difficult to achieve long-term scratch resistance and solvent resistance while also having high surface tension, making them suitable for flameless spraying. This invention provides a polypropylene composite material that, through the synergy of a highly crystalline polypropylene main resin and a specific linear low-density polyethylene resin, achieves both solvent resistance and long-term scratch resistance while ensuring high surface tension, thus meeting the requirements of flameless spraying.

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

[0006] Another object of the present invention is to provide an application of polypropylene composite material in the preparation of automotive exterior products.

[0007] Another object of the present invention is to provide an automotive exterior trim product.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] A polypropylene composite material, comprising the following components in parts by weight:

[0010] 40-80 parts of high-crystallinity polypropylene, 0-40 parts of filler, 5-20 parts of linear low-density polyethylene, and 0.1-1 parts of amide-based scratch-resistant agent;

[0011] The crystallinity of the high-crystallinity polypropylene, as determined by DSC, is ≥35%.

[0012] Furthermore, the glass transition temperature difference between the PP phase in highly crystalline polypropylene and the EPR phase in linear low-density polyethylene in polypropylene composites, Tg(PP phase)-Tg(EPR phase), is ≤48℃.

[0013] It should be noted that:

[0014] The glass transition temperature (GLT) is determined using the DSC method. DSC characterizes a material's GLT by measuring the change in its specific heat capacity with temperature. The specific heat capacity changes significantly around the GLT, and the GLT can be determined from the curve. The GLT is typically a step in the endothermic direction, and the glass transition is a region. This method usually uses the intersection of the curve with a line equidistant from two extrapolated baselines as the GLT. The test temperature range is -60℃ to 100℃, with a heating / cooling rate of 20℃ / min. The temperature is first increased from 23℃ to 100℃, then decreased from 100℃ to -60℃, and then increased again from -60℃ to 100℃.

[0015] In the polypropylene composite material of the present invention, the main resin is highly crystalline polypropylene. The higher the crystallinity of the polypropylene resin, the higher its rigidity, which is beneficial to improving the scratch resistance and solvent corrosion resistance of the composite material.

[0016] The high crystallinity polypropylene of the present invention can be copolymerized polypropylene and / or homopolymerized polypropylene. In order to achieve better processing effect and avoid underfilling, tiger stripe pattern, etc., the melt mass flow rate of high crystallinity polypropylene can be selected as 10 to 100 g / 10 min. The test standard is ISO 1133-1-2011, 230℃, 2.16Kg load.

[0017] This invention, based on the aforementioned highly crystalline polypropylene as the matrix resin, further adds linear low-density polyethylene (LLDPE). The glass transition temperature difference (Tg(PP phase) - Tg(EPR phase)) between the PP phase in the added highly crystalline polypropylene and the EPR phase in the LLDPE is ≤48℃, a relatively small difference. This LLDPE readily forms a continuous distribution phase within the polypropylene matrix resin, and the compatibility between the EPR phase of the LLDPE resin and the PP phase of the polypropylene resin is better. During processing, excessive micropores are not formed between the two phases, thereby improving the composite material's resistance to solvent intrusion corrosion. Simultaneously, the improved compatibility further refines the crystallization behavior of the highly crystalline polypropylene resin. This perfected two-phase micro-distribution creates ideally sized additive migration channels within the part, effectively controlling the migration rate of amide-based scratch-resistant additives from the core layer to the surface layer, avoiding excessive enrichment and loss of surface additives, and achieving long-lasting scratch resistance.

[0018] The amide-based scratch-resistant agent added in this invention not only improves the scratch resistance of the material, but also increases the surface tension of the material, thereby facilitating flameless spraying.

[0019] In the polypropylene composite material of this invention, the content of linear low-density polyethylene (LLDPE) is also crucial. If the amount of LLDPE used is too small, LLDPE cannot form a continuous phase within the polypropylene material, and microscopic separation easily occurs between the two phases. This leads to numerous and large gaps during processing and molding, resulting in poor solvent resistance of the finished product and excessively rapid migration of scratch-resistant additives to the surface. Over-accumulation of additives on the surface can lead to loss, failing to achieve long-term scratch resistance. Conversely, if the amount of LLDPE used is too large, the mechanical properties of the polypropylene composite material are poor, and the finished product is generally soft, failing to meet the requirements of most operating conditions.

[0020] Preferably, the product comprises the following components in parts by weight:

[0021] 50-70 parts of highly crystalline polypropylene, 10-20 parts of filler; 10-15 parts of linear low-density polyethylene, and 0.3-0.5 parts of amide-based scratch-resistant agent.

[0022] Preferably, the glass transition temperature difference between the PP phase in the highly crystalline polypropylene and the EPR phase in the linear low-density polyethylene in the polypropylene composite material, Tg(PP phase)-Tg(EPR phase), is 45-47℃.

[0023] Preferably, the crystallinity of the highly crystalline polypropylene, as determined by DSC, is 38-45%. The crystallinity of polypropylene affects the formation of effective migration channels; highly crystalline polypropylene with a crystallinity of 38-45% is more conducive to forming effective migration channels, allowing the scratch-resistant agent to migrate to the surface of the part and improving scratch resistance. Excessive crystallinity in polypropylene will result in insufficient material toughness and brittleness.

[0024] Preferably, the melt flow rate of the highly crystalline polypropylene is 30-60 g / 10 min, tested according to ISO 1133-1-2011, at 230°C and a load of 2.16 kg, and the melt flow rate of the linear low-density polyethylene is 10-25 g / 10 min, tested according to ISO 1133-1-2011, at 190°C and a load of 2.16 kg.

[0025] A low melt flow index of linear low-density polyethylene (LLDPE) is not conducive to the formation of a stable and continuous dispersed phase in the polypropylene matrix resin, and it also reduces the fluidity of the entire composite material. A high melt flow index of LLDPE often leads to a shiny appearance defect on the surface of the composite injection molded interior parts.

[0026] In specific embodiments, the filler of the present invention can be a conventional filler in the art, such as one or more of talc, calcium carbonate, wollastonite and whiskers.

[0027] In specific embodiments, the amide-based scratch-resistant agent of the present invention can be a conventional scratch-resistant agent in the art, preferably oleamide and / or erucamide.

[0028] More preferably, the amide-based scratch-resistant agent can be oleamide.

[0029] In specific embodiments, in order to meet other application requirements of polypropylene composite materials, 0.05 to 5 parts by weight of processing aids may be added to the polypropylene composite materials of the present invention, wherein the processing aids may be one or more of pigments, antioxidants, weathering agents and lubricants.

[0030] The pigments of this invention can be organic or inorganic pigments.

[0031] Inorganic pigments can include titanium dioxide, chrome yellow, cadmium yellow, molybdenum chrome red, iron red (yellow), cadmium red, ultramarine, cobalt blue, iron blue, chrome green, cobalt green, metallic powder, mica pearlescent pigments, carbon black, etc.

[0032] Organic pigments can be azo, chromidine, phthalocyanine, dyes, etc.

[0033] The antioxidants of the present invention can be hindered phenolic antioxidants, phosphite antioxidants, etc.

[0034] The weathering agent of the present invention can be a hindered amine weathering agent.

[0035] The lubricant of the present invention can be calcium stearate and zinc stearate, etc.

[0036] This invention also specifically protects a method for preparing a polypropylene composite material, comprising the following steps:

[0037] The components are mixed evenly and then added to an extruder. The mixture is then melt-blended at a temperature of 170℃ to 240℃, followed by granulation, cooling, and drying to obtain a polypropylene composite material.

[0038] The extruder of the present invention can be a twin-screw extruder or a reciprocating single-screw extruder, and the length-to-diameter ratio of the screw is not less than 32.

[0039] This invention also specifically protects the application of a polypropylene composite material in the preparation of automotive exterior products.

[0040] This invention also specifically protects an automotive exterior trim product, which is prepared by injection molding of the polypropylene composite material.

[0041] The polypropylene composite material of the present invention can be directly injection molded into automotive exterior parts, which not only have good solvent resistance and flame-free painting properties, but also have long-lasting scratch resistance, and can meet the diverse design requirements of major OEMs for exterior parts, such as automotive bumper assemblies, side skirts and fender assemblies.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] The polypropylene composite material of the present invention uses highly crystalline polypropylene as the main resin, which imparts basic solvent resistance and scratch resistance to the material. In addition, a specific linear low-density polyethylene is added. The glass transition temperature difference between the PP phase in the highly crystalline polypropylene and the EPR phase in the linear low-density polyethylene is ≤48℃, which can significantly reduce the separation of the two phases, further improve the solvent resistance of the composite material, and help control the migration rate of amide-based scratch-resistant agents to the surface of the part to achieve a long-lasting scratch resistance effect.

[0044] Meanwhile, the polypropylene composite material of the present invention can also maintain high surface tension, which can reach more than 40, meeting the requirements of flameless spraying, and can be widely used in automotive exterior component assembly spraying and integrated leather texture design. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0046] Polypropylene:

[0047] PP-1 High Crystallinity Homopolymer Polypropylene: PP H9018, crystallinity 45%, melt flow rate 60g / 10min, test standard ISO 1133-1-2011, 230℃, 2.16Kg load, manufacturer: ExxonMobil;

[0048] PP-2 high crystallinity copolymer polypropylene: PP BX3920, crystallinity 38%, melt flow rate 98g / 10min, test standard ISO 1133-1-2011, 230℃, 2.16Kg load, manufacturer: SK;

[0049] PP-3 high crystallinity copolymer polypropylene: PP BX3800, crystallinity 43%, melt flow rate 38g / 10min, test standard ISO 1133-1-2011, 230℃, 2.16Kg load, manufacturer: SK;

[0050] PP-4 high crystallinity copolymer polypropylene: PP EP648U, crystallinity 35%, melt flow rate 55g / 10min, test standard ISO 1133-1-2011, 230℃, 2.16Kg load, manufacturer: SK;

[0051] PP-5 high crystallinity copolymer polypropylene: PP HJ4045, crystallinity 48%, melt flow rate 55g / 10min, test standard ISO 1133-1-2011, 230℃, 2.16Kg load, manufacturer: Daehan Petrochemical.

[0052] PP-6 non-highly crystalline copolymer polypropylene: PP EP548R, crystallinity 20%, melt flow rate 27g / 10min, test standard ISO 1133-1-2011, 230℃, 2.16Kg load, manufacturer: CNOOC Shell;

[0053] Linear low-density polyethylene (LLDPE):

[0054] LLDPE-1: LLDPE M2320, melt flow rate of 20g / 10min, test standard ISO 1133-1-2011, test conditions 190℃, 2.16Kg, manufacturer: Maoming Petrochemical;

[0055] LLDPE-2: LLDPE DMDB-8910, melt flow rate of 10g / 10min, test standard ISO 1133-1-2011, test conditions 190℃, 2.16Kg, manufacturer: Maoming Petrochemical;

[0056] LLDPE-3: LLDPE DNDA7042, melt flow rate is 2g / 10min, test standard ISO 1133-1-2011, test conditions 190℃, 2.16Kg, manufacturer: Maoming Petrochemical;

[0057] LLDPE-4: LLDPE LL6201XR, melt flow rate of 50g / 10min, test standard ISO 1133-1-2011, test conditions 190℃, 2.16Kg, manufacturer: ExxonMobil, Saudi Arabia.

[0058] Scratch-resistant agent:

[0059] Scratch-resistant agent 1: Amide, oleamide CP, manufacturer: Akzo;

[0060] Scratch-resistant agent 2: Amide, erucamide, manufacturer: Dongli Technology;

[0061] Scratch-resistant agent 3: Silicone, BZPP301, Manufacturer: Chongqing Baozhuan;

[0062] Talc powder: commercially available; the parallel embodiments and comparative examples of this invention are all of the same kind.

[0063] Antioxidant: hindered phenolic primary antioxidant + phosphite secondary antioxidant, with a mass ratio of primary antioxidant to secondary antioxidant of 1:1, commercially available. The parallel embodiments and comparative examples of this invention are all the same commercially available products.

[0064] Examples 1-13

[0065] A polypropylene composite material, by weight, comprises the components shown in Table 1 below:

[0066] Table 1. Components and contents of polypropylene composite materials in Examples 1-13

[0067]

[0068]

[0069] The preparation method of the polypropylene composite materials in Examples 1 to 13 above specifically includes the following steps:

[0070] According to the weight parts of each component in Table 2, the components are mixed evenly in a mixing device, and then added to a twin-screw extruder with a length-to-diameter ratio of 40:1. The mixture is then melt-mixed at 200°C, granulated, cooled, and baked at 120°C for 6 hours to obtain a polypropylene composite material.

[0071] Under the conditions of injection temperature of 200℃, injection pressure of 45MPa, injection speed of 45m / s, holding pressure of 30MPa, and holding time of 5s, plastic plain sheets and textured sheets with dimensions of 100mm*100mm*3mm were obtained by injection molding.

[0072] Comparative Examples 1-4

[0073] A polypropylene composite material, by weight, comprises the components shown in Table 2 below:

[0074] Table 2. Components and contents of polypropylene composites in Comparative Examples 1–4

[0075] Comparative Example 1 2 3 4 PP-1 40 80 60 PP-6 60 Scratch-resistant agent 1 0.1 1 0.5 Scratch-resistant agent 3 0.5 talcum powder 0 40 15 15 LLDPE-1 25 3 15 15 antioxidants 0 1 1 1

[0076] The preparation methods of the polypropylene composite materials of Comparative Examples 1 to 4 mentioned above specifically include the following steps:

[0077] According to the weight parts of each component in Table 2, the components are mixed evenly in a mixing device, and then added to a twin-screw extruder with a length-to-diameter ratio of 40:1. The mixture is then melt-mixed at 200°C, granulated, cooled, and baked at 120°C for 6 hours to obtain a polypropylene composite material.

[0078] Under the conditions of injection molding temperature of 200℃, injection pressure of 45MPa, injection speed of 45m / s, holding pressure of 30MPa, and holding time of 5s, plastic smooth sheets and textured sheets with dimensions of 100mm*100mm*3mm were obtained by injection molding.

[0079] Result detection

[0080] The solvent resistance, long-term scratch resistance, and surface tension of the polypropylene composite materials of Examples 1-13 and Comparative Examples 1-4 were tested. The specific testing methods are as follows:

[0081] (1) Solvent resistance:

[0082] The solvent resistance of a plastic sheet (100mm x 100mm x 3mm) is evaluated according to standard QC / T 15-1992, section 5.5, chemical resistance test. The best grade is 6, and the worst is 1. Five professional evaluators score the sample, and the average score is rounded. Solvents used include 92# gasoline, diesel, engine oil, windshield washer fluid, acidic artificial sweat, alkaline artificial sweat, and 0.5% soapy water. 1ml of solvent is dropped onto the sample surface, left for 5 minutes, then blotted dry with a cotton cloth. The sample is then placed at 23±2℃ and 50±10% humidity for 24 hours. Colorfastness is judged by visually observing changes in the test surface area, ranging from 1 to 6. For automotive exterior materials, the requirement is ≥4.

[0083] (2) Surface tension test:

[0084] Tested according to ISO 1409-2020 standard, unit: mN / m;

[0085] (3) Scratch resistance test:

[0086] The test was conducted in accordance with Volkswagen standard PV 3952. The Volkswagen leather panel code is K3A (a leather type designation established by Volkswagen). The load was 10N, and the color difference value △L before and after scratching was tested. The scratch resistance of the sample was tested on the injection molding day (0 days) and after 90 days of exposure to light conditions on the exterior.

[0087] (4) Mechanical property testing:

[0088] The flexural modulus is used to characterize the stiffness of polypropylene composites. The testing standard is ISO 178-2010, MPa.

[0089] The specific test results are shown in Table 3.

[0090] Table 3.

[0091]

[0092]

[0093] It should be noted that:

[0094] The Tg(PP phase)-Tg(EPR phase) temperature difference in the above embodiments is the difference in glass transition temperature between the PP phase in the highly crystalline polypropylene and the EPR phase in the linear low-density polyethylene in the polypropylene composite material. Although Examples 1 to 5 all use the same PP and LLDPE, the temperature difference values ​​in the composite material are different because their contents in the composite material are different.

[0095] As can be seen from Table 3 above, the polypropylene composite material of the present invention has good solvent resistance and can achieve long-term scratch resistance for 90 days. At the same time, the polypropylene composite material of the present invention can also maintain high surface tension, reaching over 40, which meets the requirements of flameless spraying and can be widely used in automotive exterior component assembly spraying and integrated leather texture design.

[0096] In Comparative Examples 1 and 2, the amount of linear low-density polyethylene used was too high or too low, which is not within the scope of protection of this invention. Its final solvent resistance performance level can only reach level 2 and level 3, which cannot meet the requirements of level 4 or above for automotive exterior materials. Moreover, the color difference value ΔL before and after scratching at 0 days and 90 days both increased, the scratch resistance performance deteriorated, and the surface tension could not reach above 40, which could not meet the requirements of flameless spraying.

[0097] The polypropylene in Comparative Example 3 is a non-highly crystalline copolymer polypropylene with a crystallinity of 20%. The solvent resistance of the material can only reach level 1, which is poor. Furthermore, the color difference ΔL value before and after scratching at 0 days and 90 days is significantly increased, and the scratch resistance is also significantly deteriorated. All of these conditions fail to meet the requirements of this invention.

[0098] In Comparative Example 4, non-amide-based scratch-resistant agents and silicone-based scratch-resistant agents were used. Obviously, the scratch resistance performance was significantly worse and could not meet the corresponding scratch resistance performance requirements. In addition, the surface tension was low and could not meet the requirements of flameless spraying.

[0099] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A vehicle exterior trim component with integrated assembly painting and leather texture design, characterized in that, The polypropylene composite material is prepared by injection molding and, by weight, comprises the following components: 40-80 parts of high-crystallinity polypropylene, 0-40 parts of filler, 5-20 parts of linear low-density polyethylene, and 0.1-1 parts of amide-based scratch-resistant agent; The crystallinity of the highly crystalline polypropylene, as determined by DSC, is 43-45%. Furthermore, the glass transition temperature difference between the PP phase in highly crystalline polypropylene and the EPR phase in linear low-density polyethylene in polypropylene composites, Tg(PP phase)-Tg(EPR phase), is 45~46℃. The amide-based scratch-resistant agent is oleic acid amide.

2. The automotive exterior trim component with integrated assembly painting and leather texture design as described in claim 1, characterized in that, By weight, it comprises the following components: 50-70 parts of highly crystalline polypropylene, 10-20 parts of filler, 10-15 parts of linear low-density polyethylene, and 0.3-0.5 parts of amide-based scratch-resistant agent.

3. The automotive exterior trim component with integrated assembly painting and leather texture design as described in claim 1, characterized in that, The melt flow rate of the highly crystalline polypropylene is 30~60 g / 10 min, tested according to ISO 1133-1-2011, 230℃, 2.16 kg load; the melt flow rate of the linear low-density polyethylene is 10~25 g / 10 min, tested according to ISO 1133-1-2011, 190℃, 2.16 kg load.

4. The automotive exterior trim component with integrated assembly painting and leather texture design as described in claim 1, characterized in that, The filler is one or more of talc, calcium carbonate, wollastonite and whiskers.

5. A method for preparing a polypropylene composite material in an automotive exterior trim component with integrated spraying and texture design as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The components are mixed evenly and then added to an extruder. The mixture is then melt-blended at a temperature of 170℃~240℃, granulated, cooled, and dried to obtain a polypropylene composite material.

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