Spray-free polypropylene composite material, preparation method and application thereof

Abstract

The application discloses a spray-free polypropylene composite material and a preparation method and application thereof. The spray-free polypropylene composite material comprises the following components: 0.1-5% of nano pigment, the particle size of the nano pigment being 10-100 nm; 0.1-5% of a dispersing agent; 0.1-0.7% of an antioxidant; and 89.3-99.7% of polypropylene. By adding the nano pigment, the polypropylene composite material can have color and / or gloss effects, and the spray-free purpose can be achieved; the nano pigment has a small particle size, the appearance of a polypropylene composite material product can be improved, and appearance defects such as silver filaments, air lines, degradation, welding lines and / or flow marks on the surface of the product can be at least reduced or even eliminated to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of materials, and more specifically, to paint-free polypropylene composite materials, their preparation methods, and applications. Background Technology

[0002] With the rapid development of the automotive industry, new materials and processes are being used more and more widely in automobiles. Previously, plastic products used in automotive interiors and exteriors typically underwent post-treatment processes such as paint spraying or electroplating to ensure good appearance and weather resistance. However, these surface treatment processes for plastic products are complex, pollute the environment, and significantly increase manufacturing costs.

[0003] Paint-free materials are thermoplastic materials with inherent special color effects. After being formed through processes such as injection molding, extrusion, and compression molding, paint-free materials can meet the appearance requirements (including color and gloss) of decorative parts without the need for painting. The production process based on paint-free technology can reduce drying, painting or electroplating, and post-processing steps, thus effectively reducing processing steps, lowering costs, reducing energy consumption, and mitigating or even avoiding environmental pollution problems. More importantly, paint-free materials can be directly recycled and reused, reducing the need for separating thermosetting paint films or coatings during the recycling of surface-treated plastic products.

[0004] However, the surface of parts prepared using paint-free materials may have appearance defects such as silver streaks, air marks, degradation, weld lines, and flow marks. At the same time, because there is no protective coating or electroplating layer, some areas of the material surface are prone to discoloration and aging under long-term light exposure, which greatly limits the application of paint-free polypropylene composite materials.

[0005] Therefore, current spray-free polypropylene composite materials and their preparation methods still need improvement. Summary of the Invention

[0006] The present invention aims to at least alleviate or resolve at least one of the aforementioned problems to some extent.

[0007] In one aspect of the invention, a paint-free polypropylene composite material is provided. In some embodiments of the invention, the paint-free polypropylene composite material comprises: 0.1% to 5% by mass of nano-pigment, wherein the nano-pigment has a particle size of 10 nm to 100 nm; 0.1% to 5% by mass of dispersant; 0.1% to 0.7% by mass of antioxidant; and 89.3% to 99.7% by mass of polypropylene. By adding nano-pigment, the polypropylene composite material can possess color and / or gloss effects, achieving the purpose of paint-free application; the small particle size of the nano-pigment can improve the appearance of the polypropylene composite material parts, at least to a certain extent reducing or even eliminating appearance defects such as silver streaks, air bubbles, degradation, weld lines, and / or flow marks on the surface of the polypropylene composite material parts.

[0008] In some embodiments of the present invention, the nano-pigment includes at least one of aluminum powder, silver powder, copper powder, pearlescent powder, ceramic powder, and high-gloss pigment. All of the above-mentioned nano-pigments can impart color and / or gloss to polypropylene composite parts, achieving the purpose of eliminating the need for spraying.

[0009] In some embodiments of the present invention, the particle size of the nano-pigment is 40 nm to 60 nm; and / or, the mass fraction of the nano-pigment is 1.5% to 2.5%. This better ensures the dispersion effect of the nano-pigment in the polypropylene matrix, thereby contributing to further improvement in the appearance of the polypropylene composite parts.

[0010] In some embodiments of the present invention, the morphology of the nano-pigment includes at least one of flake-like, spherical, and irregular granular forms. The optical properties and / or mechanical properties of the polypropylene composite material can be adjusted by selecting the morphology of the nano-pigment to suit different application scenarios.

[0011] In some embodiments of the present invention, the polypropylene composite material satisfies at least one of the following conditions: the mass fraction of the antioxidant is 0.3% to 0.4%; the antioxidant includes antioxidant 1010 and antioxidant 168, and the mass ratio of antioxidant 1010 to antioxidant 168 is 0.4:1 to 3:1; the dispersant includes at least one of polypropylene grafted with maleic anhydride, polyacrylic acid, polycarboxylic acid, and polyvinyl alcohol; and / or, the mass ratio of the dispersant to the nano-pigment is 0.1:1 to 5:1.

[0012] In some embodiments of the present invention, the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1 to 2:1; and / or, the mass ratio of the dispersant to the nano-pigment is 1:1 to 2:1.

[0013] In another aspect of the present invention, a method for preparing the aforementioned paint-free polypropylene composite material is provided. In some embodiments of the present invention, the method for preparing the aforementioned paint-free polypropylene composite material includes: first mixing nano-pigments and a dispersant to obtain a first mixture, wherein the stirring speed during the first mixing process is 30 r / min to 100 r / min; second mixing the first mixture, polypropylene powder, and an antioxidant to obtain a second mixture, wherein the stirring speed during the second mixing process is 1200 r / min to 1700 r / min; extruding the second mixture into strands using an extruder, and then pelletizing it using a pelletizer to obtain the paint-free polypropylene composite material. Thus, the paint-free polypropylene composite material prepared by this method possesses all the characteristics and advantages of the aforementioned paint-free polypropylene composite material, which will not be repeated here. In general, the nano-pigments in this polypropylene composite material are uniformly dispersed in the polypropylene matrix, which is beneficial for improving the appearance of the polypropylene composite material parts.

[0014] In some embodiments of the present invention, the first mixing time is 0.1 min to 2 min; and / or, the second mixing time is 2 min to 6 min. This improves the dispersion uniformity and processing performance of the material, thereby facilitating further improvement of the appearance of the polypropylene composite material; the shorter mixing time also helps save production costs.

[0015] In some embodiments of the present invention, the method for preparing the aforementioned spray-free polypropylene composite material satisfies at least one of the following conditions: during the first mixing process, the speed of the mixer is 60 r / min to 70 r / min; the first mixing time is 1 min to 1.5 min; during the second mixing process, the speed of the mixer is 1450 r / min to 1650 r / min; and the second mixing time is 3 min to 4 min.

[0016] In another aspect, the present invention proposes the application of the aforementioned paint-free polypropylene composite material in automotive interior and exterior trim parts. Using the aforementioned paint-free polypropylene composite material to prepare automotive interior and exterior trim parts can yield trim parts with gloss and / or color effects without the need for additional surface treatments such as paint spraying or electroplating. Detailed Implementation

[0017] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0018] In one aspect of the invention, a paint-free polypropylene composite material is provided. In some embodiments of the invention, the paint-free polypropylene composite material may include nano-pigments, dispersants, antioxidants, and polypropylene.

[0019] In some embodiments of the present invention, based on the total mass of the paint-free polypropylene composite material, the mass fraction of the nano-pigment can be 0.1% to 5%, the mass fraction of the dispersant can be 0.1% to 5%, the mass fraction of the antioxidant can be 0.1% to 0.7%, and the mass fraction of the polypropylene can be 89.3% to 99.7%. For example, the mass fraction of the nano-pigment can be 0.1%, 0.5%, 1%, 2%, 3%, 5%, etc., the mass fraction of the dispersant can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 5%, etc., the mass fraction of the antioxidant can be 0.1%, 0.3%, 0.5%, 0.7%, etc., and the mass fraction of the polypropylene can be 89.3%, 90%, 92%, 95%, 99.7%, etc. In some embodiments of the present invention, the particle size of the nano-pigment can be 10nm to 100nm, for example, the particle size of the nano-pigment can be 10nm, 30nm, 50nm, 80nm, 100nm, etc. When the content of each component is within the above range, polypropylene composite parts can have color and / or gloss effects, achieving the purpose of eliminating the need for spraying. At the same time, polypropylene composites also have good stability, which helps to extend the service life of polypropylene composite parts.

[0020] This invention utilizes nano-pigments with particle sizes ranging from 10 nm to 100 nm, which can be uniformly dispersed within a polypropylene matrix. A dispersant further enhances this uniform dispersion. The nanoparticles form numerous interfacial domains with the polypropylene matrix, resulting in strong interfacial interactions and improving the compatibility between the polypropylene matrix and the nano-pigments. This, in turn, improves the appearance defects of the polypropylene composite parts. Simultaneously, because the nano-pigments are uniformly distributed in the polypropylene molecular chains at the nanoscale, they increase the internal friction between the polypropylene molecular chains, making it more difficult for polypropylene to relax freely at high temperatures. The same deformation requires greater stress, thus significantly improving the temperature resistance (heat resistance) of polypropylene. Furthermore, when the parts are exposed to light, the nano-pigments distributed on the polypropylene surface can absorb or reflect the light, effectively reducing the impact of sunlight on the polypropylene. This prevents the breakage and degradation of polypropylene molecules due to ultraviolet light irradiation, thus protecting the polypropylene molecules and significantly extending the service life of the polypropylene composite parts.

[0021] In some embodiments of the present invention, the nano-pigment may include at least one of aluminum powder, silver powder, copper powder, pearlescent powder, ceramic powder, and high-gloss pigment. In some embodiments of the present invention, the nano-pigment may be aluminum powder, silver powder, copper powder, pearlescent powder, ceramic powder, or high-gloss pigment. In other embodiments of the present invention, the nano-pigment may be composed of two or more of aluminum powder, silver powder, copper powder, pearlescent powder, ceramic powder, and high-gloss pigment. Aluminum powder, silver powder, and copper powder can provide good metallic luster; pearlescent powder can provide a pearly luster; ceramic powder can not only provide color and luster but also improve the wear resistance, strength, and stability of the composite material; and high-gloss pigment can provide more vibrant colors. By adding the above-mentioned types of nano-pigments to polypropylene, polypropylene composite parts can have color and / or gloss effects, achieving the purpose of eliminating the need for spraying.

[0022] In some embodiments of the present invention, the particle size of the nano pigment can be 40nm to 60nm. For example, the particle size of the nano pigment can be 40nm, 45nm, 50nm, 55nm, 60nm, etc. Nano pigments with the above particle size are not easy to agglomerate, and parts produced using polypropylene composite materials are not prone to defects such as flow marks and air marks.

[0023] In some embodiments of the present invention, the mass fraction of the nano pigment can be 1.5% to 2.5%, for example, the mass fraction of the nano pigment can be 1.5%, 1.8%, 2.0%, 2.3%, 2.5%, etc. The content of the nano pigment within the above range is beneficial to further improve the appearance and stability of the part.

[0024] In some embodiments of the present invention, the morphology of the nano-pigment may include at least one of flake-like, spherical, and irregular granular (e.g., polyhedral, rod-like, etc.) shapes. In some embodiments, the morphology of the nano-pigment may be nanosheets, spherical nanoparticles, or irregular granules. In other embodiments, the nano-pigment may include particles with the above-mentioned multiple morphologies.

[0025] In some embodiments of the present invention, the dispersant may include at least one of polypropylene grafted with maleic anhydride, polyacrylic acid, polycarboxylic acid, and polyvinyl alcohol. Adding the above-mentioned dispersant can improve the dispersion effect of nano-pigments in the polypropylene matrix, allowing the nano-pigments to be uniformly dispersed within the polypropylene molecular chains, thereby improving the appearance of polypropylene composite parts.

[0026] In some embodiments of the present invention, the mass ratio of dispersant to nanopigment can be from 0.1:1 to 5:1, for example, the mass ratio of dispersant to nanopigment can be 0.1:1, 0.5:1, 1:1, 3:1, 5:1, etc. A mass ratio of dispersant to nanopigment within the above range can at least partially improve the dispersion effect of nanopigment in the polypropylene matrix.

[0027] In some embodiments of the present invention, the mass ratio of dispersant to nano-pigment can be 1:1 to 2:1. For example, the mass ratio of dispersant to nano-pigment can be 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, etc. This is more conducive to improving the compatibility of nano-pigment with polypropylene matrix, so that nano-pigment is more uniformly dispersed in polypropylene matrix, thereby better improving the appearance of the part.

[0028] In some embodiments of the present invention, the mass fraction of the antioxidant can be 0.3% to 0.4%, for example, the mass fraction of the antioxidant can be 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, etc., thereby improving the stability of the material during processing and use, and improving the heat resistance and stability of the parts.

[0029] In some embodiments of the present invention, the antioxidant may include antioxidant 1010 and antioxidant 168, and the mass ratio of antioxidant 1010 to antioxidant 168 may be 0.4:1 to 3:1. For example, the mass ratio of antioxidant 1010 to antioxidant 168 may be 0.4:1, 0.6:1, 1:1, 1.5:1, 3:1, etc. The above-mentioned antioxidants can improve the antioxidant properties and temperature resistance of the composite material. By adjusting the proportion of the above-mentioned antioxidants, the temperature resistance and aging resistance of the part can be improved, thereby helping to extend the service life of the part.

[0030] In some embodiments of the present invention, the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1 to 2:1, for example, the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, etc.

[0031] In summary, by adding nano-pigments, this invention can effectively solve the problems of appearance defects and / or discoloration under long-term light exposure in paint-free polypropylene composite products. This is because nano-pigments have certain characteristics in the composite modification of polymers, retaining the original properties of polymers while also possessing the excellent properties of nanoparticles.

[0032] In another aspect of the present invention, a method for preparing the aforementioned spray-free polypropylene composite material is provided. In some embodiments of the present invention, the method for preparing the aforementioned spray-free polypropylene composite material may include the following steps:

[0033] S100: The nano pigment and dispersant are mixed in the first step to obtain the first mixture.

[0034] In some embodiments of the present invention, during the first mixing process, the stirring speed can be from 30 r / min to 100 r / min, for example, the stirring speed can be 30 r / min, 50 r / min, 70 r / min, 90 r / min, 100 r / min, etc. Mixing the nano-pigment and dispersant first helps improve the dispersion effect of the nano-pigment in the polypropylene matrix and avoids the agglomeration of the nano-pigment. During the first mixing process, the stirring speed is relatively low, and less heat is generated during stirring, so the nano-pigment will not be at a high temperature, thereby preventing the nano-pigment from being oxidized during stirring.

[0035] In some embodiments of the present invention, during the first mixing process, the speed of the mixer can be 60 r / min to 70 r / min. For example, the speed of the mixer can be 60 r / min, 62 r / min, 65 r / min, 68 r / min, 70 r / min, etc. The speed of the mixer within the above range is beneficial to shorten the mixing time and can better prevent the nano pigments from being oxidized during the mixing process.

[0036] In some embodiments of the present invention, the first mixing time can be 0.1 min to 2 min, for example, the first mixing time can be 0.1 min, 0.5 min, 0.8 min, 1 min, 2 min, etc., thereby enabling the nano pigments and dispersants to be mixed evenly in a shorter time, and avoiding problems such as excessive heat generated by excessive stirring time leading to oxidation of the nano pigments.

[0037] In some embodiments of the present invention, the first mixing time can be 1 min to 1.5 min, for example, the first mixing time can be 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, etc. This allows for a more uniform mixing of the nano-pigment and dispersant, and also helps to save on preparation costs.

[0038] The characteristics of nano-pigments, such as their types, particle size and morphology, types of dispersants, and the ratio of nano-pigments to dispersants, have been described in detail above and will not be repeated here.

[0039] S200: The first mixture, polypropylene powder, and antioxidant are mixed in a second mixture to obtain a second mixture.

[0040] In some embodiments of the present invention, the first mixture, polypropylene powder, and antioxidant may be mixed in a high-speed mixer.

[0041] In some embodiments of the present invention, during the second mixing process, the rotational speed of the mixer can be 1200 r / min to 1700 r / min, for example, the rotational speed of the mixer can be 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1700 r / min, etc. At the above rotational speeds, the raw materials can be mixed quickly, which is beneficial to shortening the mixing time.

[0042] In some embodiments of the present invention, during the second mixing process, the stirring speed can be from 1450 r / min to 1650 r / min, for example, the stirring speed can be 1450 r / min, 1500 r / min, 1550 r / min, 1600 r / min, 1650 r / min, etc. This allows mixing to be completed in a shorter time and avoids problems such as oxidation of raw materials due to excessively high temperatures.

[0043] In some embodiments of the present invention, the second mixing time can be 2 min to 6 min, for example, the second mixing time can be 2 min, 3 min, 5 min, 6 min, etc. This allows the raw materials to be thoroughly mixed, and the nano-pigment can be uniformly dispersed in the polypropylene matrix.

[0044] In some embodiments of the present invention, the second mixing time can be 3 to 4 minutes, for example, 3 minutes, 3.2 minutes, 3.5 minutes, 3.8 minutes, 4 minutes, etc. Performing the second mixing within the above time period can ensure that the raw materials are thoroughly mixed and can avoid generating excessive heat.

[0045] S300: The second mixture is extruded into strips using an extruder and then pelletized using a pelletizer to obtain a paint-free polypropylene composite material.

[0046] In some embodiments of the present invention, a single-screw extruder can be used to extrude the mixed raw materials into strands, and then a pelletizer can be used to pelletize them to obtain a paint-free polypropylene composite material masterbatch.

[0047] In this invention, nano-pigments and dispersants are first mixed at a low stirring speed. Then, a high-speed mixing method is used to combine the first mixture with polypropylene powder and an antioxidant. This prevents the nano-pigments from agglomerating, ensuring uniform dispersion of the nano-pigments within the polypropylene matrix. The nano-pigments can form numerous interfacial domains with the polypropylene matrix, generating strong interfacial interactions and improving the compatibility between the polypropylene matrix and the nano-pigments, thereby improving the appearance defects of the manufactured parts. Simultaneously, because the nano-pigments are uniformly distributed in nanoscale form within the polypropylene molecular chains, the internal friction between the polypropylene molecular chains is increased, making it difficult for polypropylene to relax freely at high temperatures. The same deformation requires greater stress, thus significantly improving the temperature resistance of the polypropylene composite material. Furthermore, when light irradiates the manufactured parts, the nano-pigments distributed on the polypropylene surface can absorb or reflect the light, effectively reducing the impact of sunlight on the polypropylene. This prevents the molecular chains of polypropylene from breaking and degrading due to ultraviolet light irradiation, effectively protecting the polypropylene molecules and significantly extending the service life of the polypropylene composite parts. It also avoids the problem of discoloration of polypropylene composite parts under long-term light exposure.

[0048] In another aspect, the present invention proposes the application of the aforementioned paint-free polypropylene composite material in automotive interior and exterior trim parts. After being molded through processes such as injection molding, extrusion, and compression molding, the aforementioned paint-free polypropylene composite material can be used as automotive interior and exterior trim parts, possessing color and / or gloss, without requiring further surface treatment such as paint spraying or electroplating. Automotive interior and exterior trim parts prepared using the aforementioned paint-free polypropylene composite material have a good appearance, without obvious flow marks, weld lines, air bubbles, dullness, or other appearance defects, with uniform color, and also exhibit good temperature resistance and aging resistance.

[0049] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0050] Example 1

[0051] 0.2 kg of spherical aluminum powder with a particle size of 40 nm and 0.2 kg of polypropylene grafted maleic anhydride dispersant were placed together in a mixer at a speed of 70 r / min and stirred for 1 min. Premixed nano aluminum powder, 9.56 kg of polypropylene powder, 0.02 kg of antioxidant 1010, and 0.02 kg of antioxidant 168 were placed in a high-speed mixer at a speed of 1500 r / min and stirred for 4 minutes until uniformly mixed. The mixed raw materials were extruded into strips and pelletized to prepare a paint-free polypropylene composite material masterbatch. The masterbatch was then injection molded into test samples using an injection molding machine.

[0052] Example 2

[0053] 0.2 kg of spherical aluminum powder with a particle size of 50 nm and 0.2 kg of polypropylene grafted maleic anhydride dispersant were placed together in a mixer at a speed of 70 r / min and stirred for 1 min. Premixed nano aluminum powder, 9.56 kg of polypropylene powder, 0.02 kg of antioxidant 1010, and 0.02 kg of antioxidant 168 were placed in a high-speed mixer at a speed of 1500 r / min and stirred for 4 minutes until uniformly mixed. The mixed raw materials were extruded into strips and pelletized to prepare a paint-free polypropylene composite material masterbatch. The masterbatch was then injection molded into test samples using an injection molding machine.

[0054] Example 3

[0055] 0.2 kg of spherical aluminum powder with a particle size of 90 nm and 0.2 kg of polypropylene grafted maleic anhydride dispersant were placed together in a mixer at a speed of 70 r / min and stirred for 1 min. Premixed nano aluminum powder, 9.56 kg of polypropylene powder, 0.02 kg of antioxidant 1010, and 0.02 kg of antioxidant 168 were placed in a high-speed mixer at a speed of 1500 r / min and stirred for 4 minutes until uniformly mixed. The mixed raw materials were extruded into strips and pelletized by a pelletizer to prepare a paint-free polypropylene composite material masterbatch. The masterbatch was then injection molded into test samples using an injection molding machine.

[0056] Example 4

[0057] 0.2 kg of 50 nm flake aluminum powder and 0.2 kg of polypropylene grafted maleic anhydride dispersant were placed together in a mixer at a speed of 70 r / min and stirred for 1 min. Premixed nano aluminum powder, 9.56 kg of polypropylene powder, 0.02 kg of antioxidant 1010, and 0.02 kg of antioxidant 168 were placed in a high-speed mixer at a speed of 1500 r / min and stirred for 4 minutes until uniformly mixed. The mixed raw materials were extruded into strips and pelletized to prepare a paint-free polypropylene composite material masterbatch. The masterbatch was then injection molded into test samples using an injection molding machine.

[0058] Example 5

[0059] 0.2 kg of 90 nm flake aluminum powder and 0.2 kg of polypropylene grafted maleic anhydride dispersant were placed together in a mixer at a speed of 70 r / min and stirred for 1 min. Premixed nano aluminum powder, 9.56 kg of polypropylene powder, 0.02 kg of antioxidant 1010, and 0.02 kg of antioxidant 168 were placed in a high-speed mixer at a speed of 1500 r / min and stirred for 4 minutes until uniformly mixed. The mixed raw materials were extruded into strips and pelletized to prepare a paint-free polypropylene composite material masterbatch. The masterbatch was then injection molded into test samples using an injection molding machine.

[0060] Comparative Example 1

[0061] 0.2 kg of spherical aluminum powder with a particle size of 1 μm and 0.2 kg of polypropylene grafted maleic anhydride dispersant were placed together in a mixer at a speed of 70 r / min and stirred for 1 min. Premixed aluminum powder, 9.56 kg of polypropylene powder, 0.02 kg of antioxidant 1010, and 0.02 kg of antioxidant 168 were placed in a high-speed mixer at a speed of 1500 r / min and stirred for 4 minutes until uniformly mixed. The mixed raw materials were extruded into strips and pelletized by a pelletizer to prepare a masterbatch of non-sprayed polypropylene composite material. The masterbatch was then injection molded into test samples using an injection molding machine.

[0062] The test samples prepared using spray-free polypropylene composite materials in Examples 1-5 and Comparative Example 1 were subjected to performance tests. The tensile strength was tested according to GB / T 1040.2, the flexural strength according to GB / T 9341, the impact strength according to GB / T 1043.1, the heat resistance according to GB / T 7141 (100℃ / 48h), and the color difference according to GB / T 16422.2. The test results are recorded in Table 1.

[0063] Table 1. Performance test results of the samples in Examples 1-5 and Comparative Example 1

[0064]

[0065] As shown in Table 1, the addition of nano-pigments in Examples 1-5 significantly improved the appearance, strength, and heat resistance of the parts. Compared with Examples 1, 2, and 4, the nano-pigments added in Examples 3 and 5 had slightly larger particle sizes, resulting in slight flow marks and / or slight air bubbles on the test samples, but the overall appearance was good. Comparative Example 1 used micron-sized pigments, resulting in a poor appearance of the sample with obvious color differences and more noticeable flow marks and air bubbles.

[0066] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0067] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A paint-free polypropylene composite material, characterized in that, The raw material composition of the paint-free polypropylene composite material is as follows: Nano-pigments with a mass fraction of 1.5% to 2.5%; Dispersant with a mass fraction of 0.1% to 5%; Antioxidants with a mass fraction of 0.1% to 0.7%; and Polypropylene with a mass fraction of 89.3%~99.7%, The particle size of the nano-pigment is 40nm~60nm. The nano-pigment is aluminum powder. The dispersant is polypropylene grafted with maleic anhydride. The mass ratio of the dispersant to the nano pigment is 1:1 to 2:

1.

2. The polypropylene composite material according to claim 1, characterized in that, The morphology of the nano-pigment includes at least one of flake, spherical, and irregular granular forms.

3. The polypropylene composite material according to any one of claims 1 to 2, characterized in that, At least one of the following conditions must be met: The antioxidant has a mass fraction of 0.3% to 0.4%; The antioxidants include antioxidant 1010 and antioxidant 168, and the mass ratio of antioxidant 1010 to antioxidant 168 is 0.4:1 to 3:

1.

4. The polypropylene composite material according to claim 3, characterized in that, The mass ratio of antioxidant 1010 to antioxidant 168 is 1:1 to 2:

1.

5. A method for preparing the paint-free polypropylene composite material according to any one of claims 1 to 4, characterized in that, include: The nano-pigment and dispersant are mixed in the first mixing process to obtain a first mixture. During the first mixing process, the speed of the stirrer is 30 r / min to 100 r / min. The first mixture, polypropylene powder, and antioxidant are mixed in a second mixture to obtain a second mixture. During the second mixing process, the speed of the mixer is 1200 r / min to 1700 r / min. The second mixture is extruded into strands using an extruder, and then pelletized using a pelletizer to obtain a paint-free polypropylene composite material.

6. The method according to claim 5, characterized in that, The first mixing time is 0.1 min to 2 min; And / or, the second mixing time is 2 min to 6 min.

7. The method according to claim 5 or 6, characterized in that, At least one of the following conditions must be met: During the first mixing process, the speed of the mixer is 60 r / min to 70 r / min; The first mixing time is 1 min to 1.5 min; During the second mixing process, the speed of the mixer is 1450 r / min to 1650 r / min; The second mixing time is 3 to 4 minutes.

8. The application of the paint-free polypropylene composite material according to any one of claims 1 to 4 in automotive interior and exterior trim parts.

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