A lightweight long-glass fiber reinforced polypropylene composite material with low surface floating fibers, and a preparation method and application thereof

Abstract

This invention relates to a lightweight, low-surface-fiber-floating long glass fiber reinforced polypropylene composite material, its preparation method, and its applications in the field of plastics. The lightweight, low-surface-fiber-floating long glass fiber reinforced polypropylene composite material comprises the following components: polypropylene (PP), long glass fibers (LGF), and hollow glass microspheres (HGB); wherein, based on 100 parts by weight of the total weight of the lightweight, low-surface-fiber-floating long glass fiber reinforced polypropylene composite material, the polypropylene (PP) comprises 60-70 parts by weight, the long glass fibers (LGF) comprises 25-29 parts by weight, and the hollow glass microspheres (HGB) comprises 3-15 parts by weight. The preparation method of this invention has a simple manufacturing process, low production cost, and can effectively improve the problem of fiber floating on the surface of the product, and achieve material lightweighting.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a lightweight, low-surface-float long glass fiber reinforced polypropylene composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of the plastics industry and the increasing environmental awareness of the people, thinner and lighter plastics have become the development trend of the plastics industry, which puts forward higher requirements for the performance of materials.

[0003] Polypropylene (PP) possesses excellent comprehensive mechanical properties, good chemical stability, and is easy to process and mold. It is non-toxic and odorless, making it an inexpensive and widely available general-purpose plastic. Currently, it is widely used in various fields such as automobiles, home appliances, construction, packaging, and food. Among them, glass fiber reinforced polypropylene (GFRPP) composites have broad application prospects in automotive plastics and other fields due to their higher mechanical strength, better creep resistance, weather resistance, and lower molding shrinkage.

[0004] However, during the melt processing of glass fiber reinforced polypropylene composites, especially in thin-wall injection molding, the significant difference in melt flow between the glass fiber and the resin matrix leads to extremely uneven distribution of the glass fiber within the polypropylene matrix. This can even result in very noticeable fiber floating on the product surface, causing a rough surface, poor appearance quality, and even significantly affecting the product's usability. Furthermore, the density of glass fiber is much greater than that of polypropylene, leading to a significant increase in the composite material's density, which is detrimental to material lightweighting. Therefore, how to prepare lightweight glass fiber reinforced polypropylene composites with low surface fiber floating has become an urgent problem to be solved in the industry. Currently, researchers both domestically and internationally have conducted extensive work on this issue.

[0005] Chinese patent CN103265761 A discloses a low-float glass fiber reinforced polypropylene composite and its preparation method. This method involves grafting polar monomers onto the polypropylene molecular chain during processing to improve the compatibility between glass fiber and polypropylene, thereby mitigating the fiber-float phenomenon to some extent. While this method employs common processing techniques, it requires complex raw materials, and the large-scale introduction of small-molecule processing aids can affect the mechanical properties of the material. Furthermore, the polar grafted monomers used produce unpleasant odors, which are detrimental to subsequent processing and use. Chinese patent CN 112048124 A discloses a glass fiber reinforced polypropylene material with low surface fiber float and its preparation method. This method introduces a low-molecular-weight polar wax and low-isotacticity polypropylene into the PP matrix. The polar wax can cooperate with compatibilizers to improve the bonding force between glass fiber and resin, promoting the flowability of glass fiber in polypropylene and thus reducing glass fiber exposure. Low-isotacticity polypropylene has low crystallization efficiency and good flowability, allowing it to preferentially migrate to the polymer surface during injection molding, preventing glass fiber exposure. Chinese patent CN 111087698 A discloses a method for preparing a long fiber reinforced polypropylene composite material with improved fiber floating and high surface smoothness. This method introduces a highly fluid and self-lubricating functional masterbatch into conventional long glass fiber reinforced polypropylene chips. Utilizing the self-lubricating effect of the lubricant in the masterbatch, the highly fluid functional masterbatch resin preferentially flows to the outside of the melt, coating the material surface and thus improving the fiber floating on the product surface. While these two methods can improve the fiber floating problem to some extent, the use of large amounts of low molecular weight polar wax and lubricant not only severely affects the mechanical properties of the material but also easily migrates to the surface, causing the material surface to become white and sticky, seriously affecting the appearance and performance of the product. Furthermore, these two methods do not effectively reduce the material density, and the material lightweighting effect is not significant.

[0006] In summary, existing patents addressing the fiber floating problem in glass fiber reinforced polypropylene composites mostly employ methods requiring the introduction of large amounts of low molecular weight processing aids. However, the use of large quantities of low molecular weight processing aids leads to a decrease in the mechanical properties of the composite material, and these aids readily migrate to the surface of the product, causing whitening and stickiness, thus affecting the surface appearance and usability. Furthermore, existing patents do not reduce the density of the composite material, failing to effectively meet the requirements for lightweight materials. Therefore, there is an urgent need for a simple processing method that can effectively improve the fiber floating problem on the material surface while also meeting the requirements for lightweight materials. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention proposes a lightweight, low-surface-float long glass fiber reinforced polypropylene composite material. Specifically, it relates to a lightweight, low-surface-float long glass fiber reinforced polypropylene composite material, its preparation method, and its applications.

[0008] One objective of this invention is to provide a lightweight, low-surface-float long glass fiber reinforced polypropylene composite material, which may contain the following components: polypropylene (PP), long glass fiber (LGF), and hollow glass microspheres (HGB);

[0009] In this process, taking the total weight of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material as 100 parts by weight, the polypropylene (PP) can be 60-70 parts by weight (e.g., 61, 62, 63, 64, 65, 66, 67, 68, 69, 70 parts by weight, or any value between the above), and the long glass fiber (LGF) can be 25-29 parts by weight (e.g., 25 parts by weight). The hollow glass microspheres (HGB) can be 3 to 15 parts by weight (e.g., 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, or any value between the above values). For example, the amounts of each component can be as follows: polypropylene (PP) 60 to 70 parts by weight, preferably 61 to 70 parts by weight, more preferably 61 to 69 parts by weight; long glass fiber (LGF) 25 to 29 parts by weight, preferably 25 to 29 parts by weight, more preferably 25 to 29 parts by weight; hollow glass microspheres (HGB) 3 to 15 parts by weight, preferably 3 to 10 parts by weight, more preferably 6 to 10 parts by weight.

[0010] The total amount of polypropylene (PP), long glass fiber (LGF), and hollow glass microspheres (HGB) is 100 parts by weight.

[0011] In some specific embodiments of the present invention,

[0012] The polypropylene (PP) may be selected from one or more combinations of homopolymer polypropylene, copolymer polypropylene, and impact copolymer polypropylene, preferably impact copolymer polypropylene. And / or,

[0013] The melt flow rate of the polypropylene (PP) can be 0.1 to 200 g / 10 min (230°C, 2.16 kg), (for example, 0.1 g / 10 min, 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 5 g / 10 min, 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 30 g / 10 min, 40 g / 10 min). The melt flow rate can be 50 g / 10 min, 60 g / 10 min, 70 g / 10 min, 75 g / 10 min, 80 g / 10 min, 85 g / 10 min, 90 g / 10 min, 95 g / 10 min, 100 g / 10 min, 120 g / 10 min, 140 g / 10 min, 160 g / 10 min, 180 g / 10 min, 200 g / 10 min, or any value between the above. For example, a melt flow rate of 10–150 g / 10 min (230 °C, 2.16 kg) is preferred, more preferably 30–150 g / 10 min (230 °C, 2.16 kg), and even more preferably 50–120 g / 10 min (230 °C, 2.16 kg).

[0014] In some specific embodiments of the present invention,

[0015] The length of the long glass fiber (LGF) pellets can be 6–20 mm (e.g., 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any value between the above), preferably 10–18 mm; and / or,

[0016] The diameter of the long glass fiber (LGF) can be 5 to 20 μm (e.g., 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or any value between the above), and is preferably 8 to 15 μm.

[0017] In some specific embodiments of the present invention,

[0018] The surface of the long glass fiber (LGF) can be coated with a silane-based wetting agent.

[0019] The LGF used can be a commercially available product in this field.

[0020] In some specific embodiments of the present invention,

[0021] The hollow glass microspheres (HGB) have a particle size of 12–60 μm (e.g., 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm or any value between the above values), preferably 12–30 μm, more preferably 12–25 μm, with a wall thickness of 1–3 μm and an actual density of 0.2–0.6 g / cm³. 3 (For example, it could be 0.2g / cm) 3 0.3g / cm 3 0.4g / cm 3 0.5g / cm 3 0.6g / cm 3 Or any value between the above values).

[0022] In some specific embodiments of the present invention, this application may not contain polybutene.

[0023] Furthermore, in the lightweight glass fiber reinforced polypropylene composite material with low surface fiber float described in this invention, commonly used processing aids can be added according to specific processing needs.

[0024] The components described in this application can be used for product molding through simple melt blending. The high proportion and high fluidity of polypropylene (PP) play a role in preventing glass fiber exposure. The ball bearing effect of hollow glass microspheres (HGB) can improve the dispersion and distribution of glass fibers in the matrix, thereby improving the problem of fiber floating on the product surface and enhancing the surface appearance quality. Furthermore, the closed spheres of hollow glass microspheres (HGB) are filled with a low density of nitrogen gas; when added to the matrix as a filler, they can effectively reduce the overall density of the material, achieving weight reduction and material lightweighting. This method has a simple manufacturing process, low preparation cost, effectively improves the problem of fiber floating on the product surface, and achieves material lightweighting.

[0025] The second objective of this invention is to provide a method for preparing the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material as described in the first objective of this invention, which may include the following steps:

[0026] The components, including the polypropylene and hollow glass microspheres, are melt-blended in the specified amounts to obtain a premix. The premix is ​​then melt-blended and extruded to impregnate continuous glass fibers. Following water cooling, traction, and pelletizing, a lightweight, low-surface-fiber-float long glass fiber reinforced polypropylene composite material is obtained. The melt blending can be performed using equipment commonly used in the field, such as a single-screw extruder.

[0027] Specifically, the preparation method of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material may include the following steps:

[0028] 1) Mix the polypropylene (PP), hollow glass microspheres (HGB), and other processing aids (if any) in a mixing device according to the stated content, preferably dry mixing for 3-5 minutes to obtain a premix; 2) Melt the premix and impregnate continuous glass fibers through co-extrusion, then cool it with water, draw it, and granulate it to obtain a lightweight, low-surface-float long glass fiber reinforced polypropylene composite material.

[0029] In the processing of the lightweight, low-surface-float glass fiber reinforced polypropylene composite material described in this invention, the material melt blending temperature is the same as the blending temperature typically used in polypropylene processing. It should be selected within a range that ensures complete melting of the matrix resin without causing its decomposition, generally between 190°C and 230°C, with a preferred processing temperature of 200°C to 220°C. In this invention, the glass fiber impregnation temperature can be between 230°C and 280°C, and can be adjusted according to actual conditions. In the preparation method of this invention, the material mixing equipment can be various mixing equipment used in the prior art, such as mixers and kneaders. The melt blending equipment used in the above method of this invention is a general-purpose blending equipment in the rubber and plastics processing industry, such as a single-screw extruder, a twin-screw extruder, or a BUSS mixing unit.

[0030] The third objective of this invention is to provide a polypropylene composite material prepared by the preparation method described in the second objective of this invention.

[0031] The fourth objective of this invention is to provide the application of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material described in the first objective of this invention or the polypropylene composite material described in the third objective of this invention, preferably in automotive plastics.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. Firstly, the ball bearing effect of HGB used in this invention can improve the dispersion and distribution of glass fiber in the PP matrix, thereby improving the problem of fiber floating on the product surface and enhancing the surface appearance quality of the product. Furthermore, HGB's geometric symmetry can effectively improve stress distribution, reduce the influence of glass fiber anisotropy on the polymer, and improve the dimensional stability of the product.

[0034] 2. The HGB sealed spheres used in this invention are filled with dilute nitrogen gas, which has low density and stable physical properties. When added to the PP matrix as a filler, it can effectively reduce the overall density of the material, thereby achieving weight reduction and material lightweighting.

[0035] 3. The appropriate amount of HGB added in this invention has little impact on the mechanical properties of the composite material, can well maintain the stiffness and strength of the material, and will not have any other adverse effects on the surface quality of the material.

[0036] 4. This invention only requires simple melt blending of components such as PP and HGB, followed by impregnation, coating, and pelletizing with LGF. The processing method is simple, reduces production costs, and is suitable for industrial-scale production. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] Source of raw materials

[0040] Homopolymer polypropylene (PP): YPJ-3100H, Sinopec Yangzi Petrochemical; melt flow rate (MFR) is 100g / 10min (230℃ / 2.16kg).

[0041] Copolymer polypropylene (PP): K7100, Sinopec Yanshan Petrochemical; melt flow rate (MFR) is 100g / 10min (230℃ / 2.16kg).

[0042] Impact copolymer polypropylene (PP): LA640T Hengchang Chemical; melt flow rate (MFR) is 70g / 10min (230℃ / 2.16kg).

[0043] LGF: Grade SE4805-2400, diameter 17μm, Owens Corning, USA.

[0044] Insulating glass microspheres HGB: IM30K, 3M Corporation, USA; 50% particle size 16μm, true density 0.6g / cm³ 3 The wall thickness is 1–3 μm.

[0045] Hollow glass microspheres HGB: K20, 3M Corporation, USA; 50% particle size 65μm, true density 0.2g / cm³ 3 The wall thickness is 1–3 μm.

[0046] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0047] Example 1

[0048] 68 parts by weight of PP (YPJ-3100H, produced by Sinopec Yangzi Petrochemical) with a melt flow rate of 100 g / 10 min and 3 parts by weight of HGB (IM30K, 3M, USA) were mixed evenly, specifically by dry mixing for 3-5 minutes to obtain a premix. The premix was then melt-extruded at 200°C using a single-screw extruder. Continuous LGF (E4805-2400, Owens Corning, USA) glass fibers were then introduced into the impregnation die through the glass fiber frame of a long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, the lightweight, low-surface-float glass fiber reinforced polypropylene composite particles with a glass fiber content of 29 parts by weight (i.e., 29 wt%) and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed. The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested according to GB / T 1040-92 and GB / T 9341-2008. The results are listed in Appendix 1.

[0049] Example 2

[0050] 66 parts by weight of PP (K7100, produced by Yanshan Petrochemical, Sinopec) with a melt flow rate of 100 g / 10 min and 6 parts by weight of HGB (IM30K, 3M, USA) were mixed evenly, specifically by dry mixing for 3-5 minutes, to obtain a premix. The premix was then melt-extruded at 200°C using a single-screw extruder. Continuous LGF (E4805-2400, Owens Corning, USA) glass fibers were then introduced into the impregnation die through the glass fiber frame of a long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, the lightweight, low-surface-float fiber glass fiber reinforced polypropylene composite particles with a glass fiber content of 28 parts by weight and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed.

[0051] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber condition of the sample was observed, the actual density of the sample was calculated, and the tensile and flexural strengths of the material were tested. The results are listed in Appendix 1.

[0052] Example 3

[0053] 63 parts by weight of PP (LA640T, produced by Hengchang Chemical) with a melt flow rate of 70 g / 10 min and 10 parts by weight of HGB (IM30K, 3M, USA) were mixed evenly, specifically by dry mixing for 3-5 minutes, to obtain a premix. The premix was then melt-extruded at 200°C using a single-screw extruder. Continuous LGF (E4805-2400, Owens Corning, USA) glass fibers were then introduced into the impregnation die through the glass fiber frame of a long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, the lightweight, low-surface-float glass fiber reinforced polypropylene composite particles with a glass fiber content of 27 parts by weight and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed.

[0054] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested. The results are listed in Appendix 1.

[0055] Example 4

[0056] 60 parts by weight of PP (YPJ-3100H, produced by Sinopec Yangzi Petrochemical) with a melt flow rate of 100 g / 10 min and 15 parts by weight of HGB (IM30K, 3M, USA) were mixed evenly, specifically by dry mixing for 3-5 minutes, to obtain a premix. The premix was then melt-extruded at 200°C using a single-screw extruder. Continuous LGF (E4805-2400, Owens Corning, USA) glass fibers were then introduced into the impregnation die through the glass fiber frame of a long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, the lightweight, low-surface-float glass fiber reinforced polypropylene composite particles with a glass fiber content of 25 parts by weight and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed.

[0057] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested. The results are listed in Appendix 1.

[0058] Comparative Example 1

[0059] 70 parts by weight of PP (YPJ-3100H, produced by Sinopec Yangzi Petrochemical) with a melt flow rate of 100 g / 10 min were melt-extruded at 200°C using a single-screw extruder. Then, LGF (E4805-2400 Owens Corning, USA) continuous glass fiber was introduced into the impregnation die through the glass fiber rack of the long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, glass fiber reinforced polypropylene composite particles with a glass fiber content of 30 parts by weight and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed.

[0060] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested. The results are listed in Appendix 1.

[0061] Comparative Example 2

[0062] 56 parts by weight of PP (YPJ-3100H, produced by Sinopec Yangzi Petrochemical) with a melt flow rate of 100 g / 10 min and 20 parts by weight of HGB (IM30K, 3M, USA) were mixed evenly, specifically by dry mixing for 3-5 minutes, to obtain a premix. The premix was then melt-extruded using a single-screw extruder at 200°C. Continuous glass fibers (E4805-2400, Owens Corning, USA) were then introduced into the impregnation die through the glass fiber frame of the long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, by adjusting the feed rate and traction speed, glass fiber reinforced polypropylene composite particles with a glass fiber content of 24 parts by weight and a particle length of 12 mm were obtained.

[0063] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested. The results are listed in Appendix 1.

[0064] Comparative Example 3

[0065] 63 parts by weight of PP (YPJ-3100H, produced by Sinopec Yangzi Petrochemical) with a melt flow rate of 100 g / 10 min and 10 parts by weight of HGB (K20, 3M, USA) were mixed evenly, specifically by dry mixing for 3-5 minutes, to obtain a premix. The premix was then melt-extruded at 200°C using a single-screw extruder. Continuous LGF (E4805-2400, Owens Corning, USA) glass fibers were then introduced into the impregnation die through the glass fiber frame of a long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, the glass fiber reinforced polypropylene composite particles with a glass fiber content of 27 parts by weight and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed.

[0066] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested. The results are listed in Appendix 1.

[0067] Comparative Example 4

[0068] 53 parts by weight of PP (YPJ-3100H, produced by Sinopec Yangzi Petrochemical) with a melt flow rate of 100 g / 10 min, 10 parts by weight of HGB (IM30K, 3M Corporation, USA), and 10 parts by weight of polybutene (HY-ET042, 0.48 g / 10 min, Shandong Tengzhou Ruida Chemical Co., Ltd.) were mixed evenly for 3-5 minutes to obtain a premix. The premix was then melt-extruded at 200°C using a single-screw extruder. Continuous LGF (E4805-2400, Owens Corning Corporation, USA) glass fibers were then introduced into the impregnation die through the glass fiber frame of the long fiber equipment for impregnation and coating. After water cooling, traction, and pelletizing, the glass fiber reinforced polypropylene composite particles with a glass fiber content of 27 parts by weight and a particle length of 12 mm were obtained by adjusting the feed rate and traction speed.

[0069] The composite material was prepared by injection molding at 190℃ using a micro injection molding machine, with the injection pressure controlled at 800MPa, injection time at 10s, and mold temperature at 25℃. The surface fiber presence of the samples was observed, the actual density of the samples was calculated, and the tensile and flexural strengths of the materials were tested. The results are listed in Appendix 1.

[0070] The evaluation of fiber floating grade is mainly based on the injection molding of the material into a rectangular test strip of 80mm*10mm*4mm under a specific injection molding process. The floating state of the sample surface is evaluated by visual observation combined with optical microscopy, and is mainly divided into 1 to 4 grades. Grade 1: smooth surface, no floating fibers; Grade 2: smooth surface, slight floating fibers; Grade 3: smooth surface, obvious floating fibers; Grade 4: rough surface, severe floating fibers. (For test methods, please refer to: Shen Xuqu, Chen Ruibin, He Zihao. Research on improvement of fiber floating problem in glass fiber reinforced polypropylene [J]. Guangdong Chemical Industry, 2021, 48(20):3.)

[0071] Appendix Table 1: Composition ratios and performance test results of Examples 1-4 and Comparative Examples 1-4

[0072]

[0073]

[0074] Examples 1, 2, 3, and 4 are lightweight glass fiber reinforced polypropylene composites with low surface fiber float prepared according to the method provided in this invention. Comparative Example 1 is a product obtained by melt blending 70 parts by weight of PP with a melt flow rate of 100 g / 10 min and 30 parts by weight of LGF, followed by injection molding, without the addition of HGB. Comparative Example 2 is a product obtained by melt blending 56 parts by weight of PP with a melt flow rate of 100 g / 10 min, 24 parts by weight of GF, and 20 parts by weight of HGB, followed by injection molding, wherein the amount of HGB added exceeds the amount specified in this invention. Comparative Example 3 is a product obtained by melt blending 63 parts by weight of PP with a melt flow rate of 100 g / 10 min, 10 parts by weight of HGB, and 27 parts by weight of LGF, followed by injection molding, wherein the particle size of the HGB exceeds the particle size range of this invention. Comparative Example 4 is a product made by melt blending 53 parts by weight of PP with a melt flow rate of 100 g / 10 min, 10 parts by weight of HGB, 10 parts by weight of polybutene, and 27 parts by weight of LGF, followed by injection molding. The surface fiber floating condition, density, tensile strength, and flexural strength of the above examples are shown in Table 1.

[0075] As shown in Table 1, the surface quality of the product significantly improves with increasing HGB content, and the fiber floating problem is significantly alleviated. This is because the ball bearing effect of HGB can improve the dispersion and distribution of glass fibers in the matrix, thereby improving the fiber floating problem on the product surface and enhancing the surface appearance quality. Furthermore, the density of the product significantly decreases with increasing HGB content, resulting in a significant weight reduction effect. Meanwhile, comparing Examples 1 and 2 with Comparative Example 1, it can be seen that within the content specified in this invention, the addition of HGB has a relatively small impact on the tensile strength and flexural strength of the product; a small amount of HGB can even improve the mechanical properties of the material to some extent. However, when the HGB content exceeds 15 wt%, the mechanical strength of the product decreases significantly.

[0076] Comparing Example 3 with Comparative Example 3, it can be seen that when the particle size (65 μm) of the selected HGB exceeds the range specified in this invention, the fiber floating phenomenon on the material surface cannot be resolved, nor can the purpose of reducing material weight be achieved. This is because when the particle size of HGB is too large, it is extremely easy to break during processing, failing to exert its intended effect. Comparing Example 3 with Comparative Example 4, it can be seen that the addition of polybutene reduces the mechanical properties of the material.

[0077] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A lightweight, low-surface-float fiber-reinforced polypropylene composite material, comprising the following components: polypropylene, long glass fibers, and hollow glass microspheres; in, Based on the total weight of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material as 100 parts by weight, the polypropylene is 60-70 parts by weight, the long glass fiber is 25-29 parts by weight, and the hollow glass microspheres are 3-15 parts by weight; the sum of the amounts of the polypropylene, long glass fiber, and hollow glass microspheres is 100 parts by weight. The length of the long glass fiber granules is 6–20 mm; the diameter of the long glass fiber is 5–20 μm. The hollow glass microspheres described herein have a median particle size of 12–60 μm, a wall thickness of 1–3 μm, and an actual density of 0.2–0.6 g / cm³. 3 .

2. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 1, characterized in that: in, Based on the total weight of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material as 100 parts by weight, the polypropylene is 61-70 parts by weight; and the hollow glass microspheres are 3-10 parts by weight.

3. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 2, characterized in that: in, Based on the total weight of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material as 100 parts by weight, the polypropylene comprises 61 to 69 parts by weight; and the hollow glass microspheres comprise 6 to 10 parts by weight.

4. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to any one of claims 1 to 3, characterized in that: The polypropylene is selected from one or more combinations of homopolymer polypropylene and copolymer polypropylene.

5. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 4, characterized in that: The copolymer polypropylene is selected from impact copolymer polypropylene.

6. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to any one of claims 1 to 3, characterized in that: The polypropylene exhibits a melt flow rate of 0.1–200 g / 10 min under test conditions of 230°C and 2.16 kg load.

7. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 6, characterized in that: The polypropylene exhibits a melt flow rate of 10–150 g / 10 min under test conditions of 230°C and 2.16 kg load.

8. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 7, characterized in that: The polypropylene exhibits a melt flow rate of 30–150 g / 10 min under test conditions of 230°C and 2.16 kg load.

9. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 1, characterized in that: The length of the long glass fibers cut into pellets is 10–18 mm; and / or, The diameter of the long glass fiber is 8–15 μm.

10. The lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to any one of claims 1 to 3, characterized in that: The median particle size of the hollow glass microspheres is 12–30 μm.

11. The method for preparing lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to any one of claims 1 to 10, characterized in that... Includes the following steps: The components, including the polypropylene and hollow glass microspheres, are melt-blended according to the specified amounts. Then, long glass fibers are impregnated and coated, followed by water cooling, traction, and pelletizing to obtain the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material.

12. The method for preparing lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 11, characterized in that: The melt blending temperature is 190℃~230℃.

13. The method for preparing the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 12, characterized in that: The melt blending temperature is 200℃~220℃.

14. The method for preparing lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 11, characterized in that... Includes the following steps: 1) Mix the components, including the polypropylene and hollow glass microspheres, according to the stated content to obtain a premix; 2) The premix is ​​melt-blended and extruded, the long glass fibers are impregnated and coated, and then water-cooled, drawn and pelletized to obtain a lightweight long glass fiber reinforced polypropylene composite material with low surface float.

15. The method for preparing the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 14, characterized in that: In step 1), the mixing is a dry mix for 3 to 5 minutes.

16. A polypropylene composite material prepared by the method for preparing lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to claim 11 or 14.

17. The use of the lightweight, low-surface-float long glass fiber reinforced polypropylene composite material according to any one of claims 1 to 10, or the polypropylene composite material according to claim 16.

18. The application according to claim 17, characterized in that... For applications in automotive plastics.

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