Lightweight high-strength polypropylene composite material and preparation method thereof

Abstract

The invention provides a lightweight high-strength polypropylene composite material and a preparation method thereof, and the method comprises the following steps: S1, mixing polypropylene and an engineering polymer in an extruder to form a polypropylene blend; s2, adding a filler and a processing aid into the polypropylene blend, mixing, and extruding through a mold to obtain a primary polypropylene composite material; s3, enabling the primary polypropylene composite material to pass through a shaping and traction device to obtain a polypropylene composite material parison; s4, the temperature of the polypropylene composite material parison is adjusted to be higher than the softening temperature of the polypropylene composite material parison, and the polypropylene composite material parison with the adjusted temperature is obtained; and S5, enabling the polypropylene composite material parison with the modulated temperature to pass through a drawing die, and applying drawing force by utilizing a traction machine, so that the polypropylene composite material is stretched and deformed to be oriented when passing through the drawing die, and the high-strength light-weight polypropylene composite material is prepared. The prepared polypropylene composite material has the advantages that the strength is high, the density is low, the surface of a product is smooth and uniform, and secondary treatment is not needed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer material processing, and particularly relates to a lightweight high-strength polypropylene composite material and a preparation method thereof. BACKGROUND

[0002] As a most commonly used general-purpose plastic, polypropylene is widely used in the fields of automobiles, daily necessities, household appliances, building materials, etc. due to its excellent mechanical properties and low density characteristics. The method of filling with fillers to improve the rigidity and modulus of polypropylene and reduce the cost is a commonly used simple and effective polypropylene modification method, but it will cause the toughness of the polypropylene composite material to decrease and the density to significantly increase.

[0003] In order to further improve the strength and toughness of the filled modified polypropylene composite material, the common method in the prior art is to add a toughening agent or improve the interface bonding between the filler and the polypropylene to improve the toughness and modulus, but the improvement effect of this method is limited. Through solid-state extrusion, the polymer is forced to pass through a converging die at a temperature below its melting point, so that the polymer molecular chain is highly oriented along the extrusion direction, thereby greatly improving the mechanical strength. However, the density of the solid-state extrusion product is high, and the production efficiency is low and the energy consumption is large. Solid-phase die stretching is another polymer self-reinforced high-performance process in which the polymer is stretched to form a highly oriented structure by means of external stretching force at a temperature below the melting point of the polymer. The formation of the oriented structure can significantly improve the strength, modulus and toughness of the material. Especially for the filler-filled polymer system, the stretching process not only makes the polymer highly oriented to improve the mechanical properties, but also makes the interface between the polymer and the filler debond to form a large number of cavities, thereby reducing the density of the composite material and achieving lightweight.

[0004] CN101679670B discloses a low-density oriented polymer composition containing inert inorganic fillers, which comprises 30-95wt% inert inorganic fillers, and at least one continuous phase of an orientable polymer, the oriented polymer composition contains void spaces due to cavitation, and the density of the material is less than 0.8g / cm3, the flexural modulus is greater than or equal to 1.4GPa, and the cross-sectional dimension is greater than 1.5mm. CN101687362A discloses a solid-state stretching of a filled polymer composition to a stable degree of cavitation and density, by stretching the polymer composition at a stretching rate of not less than 1.27m / min above the softening temperature of the polymer composition, to obtain an oriented filled polymer composition and form a stable cavitation structure. US6939496B discloses a method for producing a wood fiber reinforced polymer composite parison by plunger extrusion and preparing a composite material by die stretching. CN1688433A discloses an oriented polymer composite material containing active fillers and a production method thereof.

[0005] The above patents all prepare polymer composite materials with oriented structure by adopting a mouth mold stretching process and production methods thereof, but after the polymer is highly oriented along the stretching direction, micro-fiber structure is formed to cause burrs and splitting on the surface of the product, and filler powder is separated from the surface of the product, which affects direct use, so that the mouth mold stretched product needs to be subjected to subsequent heat treatment to make the surface oriented layer de-orient or melt; or the surface of the product needs to be coated with non-oriented resin, so that the production process is complicated and the production efficiency is low. SUMMARY

[0006] The present application provides a lightweight high-strength polypropylene composite material and a preparation method thereof to solve the problem of complicated production process and low production efficiency caused by the secondary treatment of the mouth mold stretched product in the prior art.

[0007] The technical scheme of the present application is as follows: According to one aspect of the present application, a lightweight high-strength polypropylene composite material is provided, comprising: 50wt%-70wt% polypropylene blend, 25wt%-45wt% filler and 2wt%-5wt% processing aid, wherein the polypropylene blend comprises polypropylene and 10wt%-30wt% engineering polymer, the engineering polymer comprises at least one of aromatic polyester and its copolymer and nylon, and the density of the lightweight high-strength polypropylene composite material is less than or equal to 0.8g / cm 3 , and the flexural modulus is greater than or equal to 3.0GPa.

[0008] Optionally, in the above lightweight high-strength polypropylene composite material, the polypropylene is a homopolymer, a copolymer or a mixture of the two, and the melt index of the polypropylene is not greater than 8g / 10min.

[0009] Optionally, in the above lightweight high-strength polypropylene composite material, the aromatic polyester and its copolymer comprise at least one of polyethylene terephthalate PET and polybutylene terephthalate PBT; the nylon comprises at least one of nylon 6, nylon 66, bio-based nylon and aromatic nylon.

[0010] Optionally, in the above lightweight high-strength polypropylene composite material, the filler comprises at least one of talc, calcium carbonate, calcium silicate, wollastonite, kaolin and fly ash; and the processing aid comprises at least one of an antioxidant, an ultraviolet light aging resistant agent, a heat stabilizer and a lubricant.

[0011] Optionally, in the above lightweight high-strength polypropylene composite material, the processing aid comprises a lubricant greater than or equal to 2wt% of the polypropylene composite material, and the lubricant comprises at least one of zinc stearate, calcium stearate, stearic acid amide, ethylene bis-stearamide, low molecular weight polyethylene wax and polyethylene glycol.

[0012] According to one aspect of the present application, a method for preparing the above-mentioned lightweight high-strength polypropylene composite material is provided, comprising: S1. mixing polypropylene and engineering polymer in an extruder at 150-230 DEG C to form a polypropylene blend; S2. adding fillers and processing aids to the polypropylene blend, mixing in an extruder and extruding through a die to obtain a primary polypropylene composite material; S3. passing the primary polypropylene composite material through a shaping and pulling device to obtain a polypropylene composite material parison; S4. modulating the temperature of the polypropylene composite material parison to above the softening temperature of the polypropylene composite material parison material to obtain a temperature-modulated polypropylene composite material parison; S5. passing the temperature-modulated polypropylene composite material parison through a stretching die and applying a stretching force using a pulling machine to cause the polypropylene composite material to be stretched and deformed when passing through the stretching die to be oriented, thereby preparing a high-strength lightweight polypropylene composite material.

[0013] Optionally, in the above preparation method, the extruder is a co-rotating twin-screw extruder or a triple-screw extruder, the extruder is provided with a main feeding port and at least one side feeding feeding port, the extruder outlet is connected in series with an extrusion molding machine and a die, the extrusion molding machine is one of a melt pump, a single-screw extrusion molding machine, an opposite-rotating twin-screw extrusion molding machine and a conical twin-screw extrusion molding machine; the polypropylene and the engineering polymer are added to the extruder through the main feeding port; and the fillers and the processing aids are added to the extruder through the side feeding feeding port.

[0014] Optionally, in the above preparation method, in step S4, the temperature of the polypropylene composite material parison is modulated to 110-155 DEG C by a temperature modulation device, and the temperature difference at each part of the cross section of the polypropylene composite material parison is less than 5 DEG C.

[0015] Optionally, in the above preparation method, in step S5, the pulling rate of the pulling machine is greater than the parison extrusion rate, and the difference between the pulling rate of the pulling machine and the parison extrusion rate is greater than or equal to 1 m / min, and the pulling rate of the pulling machine is not less than 2 m / min.

[0016] Optionally, in the above preparation method, in step S5, the stretching die is a stretching die with an axisymmetric converging structure, the stretching die is a circular die or a rectangular die, the ratio of the inlet cross-sectional area to the outlet cross-sectional area of the stretching die is between 2 and 6, and the stretching temperature of the stretching die is 130-150 DEG C.

[0017] According to the technical solution of the present application, the following beneficial effects are achieved: The polypropylene composite material prepared by the method of the present application has high strength and low density, and the product has a smooth and uniform surface without the need for secondary processing, and the production process is uniform and stable, and the production efficiency is high.

[0018] In order to better understand and illustrate the concept, working principle and inventive effect of the present application, the present application will be described in detail below with specific embodiments combined with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings required to be used in the specific embodiments or prior art description will be briefly introduced as follows.

[0020] Figure 1 is a flow chart of the preparation method of the lightweight high-strength polypropylene composite material of the present application; Figure 2 is a schematic diagram of the equipment involved in the preparation method of the lightweight high-strength polypropylene composite material of the present application; Figure 3 is an electron microscope image of the engineering polymer microfiber structure in the lightweight high-strength polypropylene composite material of the present application; Figure 4 is a corresponding relationship diagram of the die stretching rate and the stretching force; Figure 5 is a corresponding relationship diagram of the stretching rate of the polypropylene composite material and the density and the bending modulus. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical method and advantages of the present application clearer, the present application will be further described in detail below combined with the drawings and specific examples. These examples are only illustrative, and are not limiting to the present application.

[0022] The lightweight high-strength polypropylene composite material of the present application comprises: 50wt%-70wt% polypropylene blend, 25wt%-45wt% filler, and 2wt%-5wt% processing aid. The polypropylene blend comprises polypropylene and 10wt%-30wt% engineering polymer.

[0023] The density of the lightweight high-strength polypropylene composite material is less than or equal to 0.8g / cm 3 , preferably less than or equal to 0.7g / cm 3 ; the bending modulus is greater than or equal to 3.0GPa, and the bending strength is greater than or equal to 3000MPa.

[0024] The polypropylene is a homopolymer, a copolymer or a mixture of the two. Among them, the propylene content in the copolymer is greater than or equal to 90wt%; the content of the homopolymer in the polypropylene is not less than 50wt%. The melt index of the polypropylene is not greater than 8g / 10min, preferably less than or equal to 3g / 10min.

[0025] The engineering polymer includes at least one of aromatic polyester and its copolymer, and nylon. The aromatic polyester and its copolymer include at least one of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); the nylon includes at least one of nylon 6, nylon 66, bio-based nylon, and aromatic nylon. The engineering polymer can be in the form of particles or fibers, preferably, chopped fibers with a microfiber diameter less than 10 um and an aspect ratio greater than or equal to 5, and can be obtained by crushing waste recycled fabrics or yarns.

[0026] The filler is an inorganic powder, including at least one of talc, calcium carbonate, calcium silicate, wollastonite, kaolin, and fly ash; the inorganic powder can have a spherical, flaky, acicular, or porous structure, and preferably includes two fillers. The particle size of the inorganic powder is between 400 and 3000 mesh, preferably between 600 and 1500 mesh, and more preferably between 800 and 1250 mesh. The inorganic powder can be surface-treated or untreated, and preferably is surface-treated, preferably using a silane coupling agent.

[0027] The processing aid includes at least one of an antioxidant, a UV aging resistant agent, a thermal stabilizer, and a lubricant. Preferably, the processing aid includes a lubricant and the content of the lubricant is greater than or equal to 2 wt% of the total weight of the polypropylene composite material. The lubricant includes at least one of zinc stearate, calcium stearate, stearic acid amide, ethylene bis-stearamide, a low molecular weight polyethylene wax, and polyethylene glycol.

[0028] As shown in Figure 1 and Figure 2 , the preparation method of the lightweight high-strength polypropylene composite material of the present application includes the following steps: S1. mixing polypropylene and engineering polymer in an extruder to form a polypropylene blend; In step S1, the polypropylene and engineering polymer are added to the extruder through the main feeding port of the extruder, and are mixed to form a polypropylene blend at a temperature not higher than 230°C, preferably 150°C to 230°C, and more preferably 150°C to 210°C.

[0029] Referring to Figure 2 , the extruder 1 is a co-rotating twin-screw extruder or a triple-screw extruder. Preferably, it is a triple-screw extruder with three parallel or inverted triangularly arranged screws, and the screw aspect ratio is greater than or equal to 40. The extruder 1 is provided with a main feeding port 1 and at least one side feeding port 3. Preferably, two side feeding ports 3 are provided: one for adding fillers or filler master batches, and the other for adding additives or additive master batches.

[0030] The extruder 1 is provided with a vacuum vent 4 connected to a vacuum system for discharging air and low molecular volatile components introduced during the process. The temperature of the extruder is set to be not higher than 230℃. Under the process conditions, the polypropylene is melted, the engineering polymer is softened but not melted. Under the action of the screw shearing and tensile stress, the engineering polymer is extruded or stretched to form micro-fiber or fiber-like, sheet-like, rod-like dispersed phase, and the polypropylene as the continuous phase, as shown in Figure 3 With the addition of the filler or filler masterbatch and the mixing action of the screw, a three-phase structure is formed with the polypropylene as the continuous phase and the engineering polymer and the filler as the dispersed phase. The addition of the engineering polymer increases the viscosity of the polypropylene mixture, which is more conducive to the shearing force of the screw acting on the filler, so that the filler is more uniformly dispersed and distributed in the polypropylene matrix, which is conducive to improving the strength of the polypropylene composite. This allows the polypropylene composite to withstand greater tensile force during the die stretching process, which is conducive to uniform and stable production during the die stretching process and can increase the draw ratio of the final product, thereby improving the mechanical properties of the final product and reducing the density.

[0031] The extruder 1 is connected in series with an extrusion molding machine and a die. The extrusion molding machine is one of a melt pump, a single-screw extrusion molding machine, a counter-rotating twin-screw extrusion molding machine, and a conical twin-screw extrusion molding machine. The die is a circular die or a rectangular die for extruding the polypropylene composite.

[0032] S2. The filler and the processing aid are added to the polypropylene blend, mixed by the extruder, and extruded through the die to obtain a primary polypropylene composite.

[0033] In this step, the filler or filler masterbatch, the processing aid or aid masterbatch is added to the polypropylene blend through the side feeding port of the extruder, mixed by the extruder, and extruded through the extrusion molding machine and the die to obtain a primary polypropylene composite.

[0034] S3. The primary polypropylene composite is passed through a shaping and pulling device to obtain a polypropylene composite parison; In this step, the primary polypropylene composite is passed through a cooling shaping device 5 and a pulling device 6 to obtain a polypropylene composite parison.

[0035] S4. The temperature of the polypropylene composite parison is modulated to be above the softening temperature of the polypropylene composite parison material to obtain a temperature-modulated polypropylene composite parison; The temperature-modulated device is a heating device, a cooling device, or a combination of the two. Figure 2The heating device 7 in the temperature conditioning device 6) is used to heat the polypropylene composite parison to a temperature above the softening temperature of the material, i.e. to condition the polypropylene composite parison to a temperature between 110℃ and 155℃, preferably to a temperature between 130℃ and 150℃, and the temperature difference of the polypropylene composite parison at different positions of the cross section is less than 5℃, preferably less than 2℃.

[0036] S5. The temperature-conditioned polypropylene composite parison is passed through a stretching die, and the polypropylene composite is stretched and deformed to be oriented when passing through the stretching die by applying a stretching force by a traction machine, to obtain a high-strength lightweight polypropylene composite material.

[0037] The stretching die is a stretching die with a symmetrical converging structure, which is a circular die or a rectangular die, and is used to extrude the polypropylene composite. The stretching die is an axisymmetric converging die, and the size of the inlet cross section is greater than or equal to the size of the parison cross section. If the parison cross section is circular, the inlet and outlet cross sections of the stretching die are both circular, the diameter of the inlet cross section is greater than or equal to the diameter of the parison cross section, and the diameter of the outlet cross section is less than the diameter of the inlet cross section. If the parison cross section is rectangular, the stretching die is rectangular, and the thickness and width of the stretching die are both greater than or equal to the thickness and width of the parison. The ratio of the area of the inlet cross section to the area of the outlet cross section of the stretching die is between 2 and 6, preferably between 3 and 5. The stretching temperature of the stretching die is between 130℃ and 150℃.

[0038] The temperature-conditioned polypropylene composite parison is passed through the stretching die 8 and is stretched and deformed to be oriented under the action of the traction machine 9, to obtain a high-strength lightweight polypropylene composite material, which is then cut to the desired size by a cutting machine 10. The traction rate of the traction machine is greater than the extrusion rate of the parison (the rate at which the parison is extruded from the outlet of the extruder, which is usually between 0.05 and 0.1 m / min), and the difference between the traction rate of the traction machine 9 and the extrusion rate of the parison is greater than or equal to 1 m / min, preferably greater than or equal to 2 m / min, and more preferably greater than or equal to 3 m / min. The traction rate of the traction machine 9 is the same as the die stretching rate of the stretching die 8, and the traction rate of the traction machine is not less than 2 m / min, preferably not less than 3 m / min; more preferably, the traction rate of the traction machine 9 (i.e. the die stretching rate of the stretching die 8) is between 2 m / min and 3 m / min. The density of the obtained lightweight high-strength polypropylene composite material is less than or equal to 0.8 g / cm 3 , preferably less than or equal to 0.7 g / cm 3 ; the bending modulus is greater than or equal to 3.0 GPa, and the bending strength is greater than or equal to 3000 MPa.

[0039] The application enhances the strength and toughness of the polypropylene composite material matrix, so as to facilitate the realization of high die stretch rate and stable continuous production, and meanwhile, the bonding force between the polypropylene microfibers after die stretching is improved, so that the surface of the final product is smooth. Because in the stretching process, the increase of the stretching rate will increase the friction between the parison and the die, so that the stretching force is sharply increased, as shown in the attached Figure 4 The application shows that the increase of the stretching rate can increase the free stretching ratio after the die exit, so that the composite material has a higher orientation degree, thereby significantly improving the modulus of the composite material, and forming larger micropores, reducing the density of the composite material, as shown in the attached Figure 5 On the other hand, the application improves the melt viscoelasticity of the polypropylene mixture by adding the engineering polymer to form the microfiber structure, so as to facilitate the screw shearing force acting on the interface between the filler and the polypropylene mixture, enhance the dispersion and mixing effect of the filler, reduce the aggregation and shedding of the filler in the stretching process, and improve the surface quality of the polypropylene composite product.

[0040] Therefore, the polypropylene composite material prepared by the method of the application has the advantages of high strength, low density, smooth and uniform product surface without secondary processing, and uniform and stable production process, high production efficiency.

[0041] Example 1 Raw materials Polypropylene: T30S, homopolymer polypropylene, melt flow rate 3.0 g / 10 min (230℃, 2.16 kg); Nylon 66: EPR27, melting point 263℃, Pingdingshan Shenma Engineering Plastics Co., Ltd.; Calcium carbonate: 800 mesh, Quanzhou Xufeng Powder Raw Material Co., Ltd.; Antioxidant 1010, Nanjing Hualimeng Chemical Co., Ltd.; Antioxidant 168, Nanjing Hualimeng Chemical Co., Ltd.; UV stabilizer 944, Nanjing Hualimeng Chemical Co., Ltd.; Lubricant: zinc stearate, Qingdao Seno Technology Co., Ltd. The addition amount of each component is shown in Table 1.

[0042] Equipment and preparation process parameters The extruder 1 is a co-rotating twin-screw extruder with a diameter of 65 mm and a length-diameter ratio of 48, which is provided with one main feeding port 2 and two side feeding ports 3. One side feeding (first side feeding) port is located at a position 24D away from the main feeding port, and the other (second side feeding port) is located at a position 30D away from the main feeding port. The extruder 1 is provided with a vacuum vent 4 at a position 40D away from the main feeding port. Polypropylene and nylon 66 are added from the main feeding port 2 according to the set ratio, 20 wt% of calcium carbonate and all the processing aids are added from the first side feeding port, and the remaining 10 wt% of calcium carbonate is added from the second side feeding port. The twin-screw extruder has a total of 12 heating zones, and the temperatures of the respective zones are 150°C, 200°C, 210°C, 230°C, 230°C, 220°C, 220°C, 220°C, 220°C, 210°C, 210°C, and 210°C.

[0043] The twin-screw outlet is connected to a melt pump, and the melt pump is connected to a plate extruder head and a die. The die has a rectangular cross-section and can extrude polypropylene composite plates. The cross-sectional height of the die is 30 mm, and the width is 400 mm.

[0044] The extrusion output is 100 kg / h, and the rotation speed of the twin-screw extruder is 200 rpm.

[0045] The primary polypropylene composite material extruded from the die passes through a three-roll shaping device (i.e., a cooling shaping device 5) and a traction device 6 to obtain polypropylene composite plates as the polypropylene composite parison to be stretched. The plates are sequentially passed through a heating oven (i.e., a heating device 7) to modulate their temperature to 150°C, and then passed through a stretching die 8 with a stretching ratio (i.e., the ratio of the inlet cross-sectional area to the outlet cross-sectional area) of 4. The plates are then held and stretched by a traction machine 9. The stretching rate of the traction machine 9 is 2 m / min. After passing through the traction machine, the polypropylene composite material has been completely cooled, and rectangular plates with a thickness of 15 mm and a width of 100 mm are obtained. The bending strength and modulus of the polypropylene composite material are tested according to GB / T9341-2008, and the density of the polypropylene composite material is tested according to GB / T 35463-2017. The results are shown in Table 2.

[0046] Example 2 Raw materials: Polypropylene PPH2101, homopolymer polypropylene, melt flow rate 0.32 g / 10 min (230°C, 2.16 kg); nylon 6, grade B3S, BASF Company; calcium carbonate, 1250 mesh, Quanzhou Xufeng Powder Raw Material Co., Ltd. Other additives are the same as in Example 1.

[0047] Equipment and preparation process parameters: The extruder 1 is a co-rotating counter-rotating triangular three-screw extruder with a screw diameter of 65 mm and a length-diameter ratio of 40, provided with a main feeding port 2 and a side feeding port 3. The side feeding port 3 is located at a position 40D away from the main feeding port 2. In addition, a vacuum exhaust port 4 is provided at a position 40D away from the main feeding port 2. Polypropylene and nylon 60 are added from the main feeding port 2 according to the set ratio, and calcium carbonate and all the processing aids are added from the side feeding port 3. The three-screw extruder has a total of 10 heating zones, and the temperatures of the respective zones are 150℃, 200℃, 210℃, 230℃, 230℃, 220℃, 220℃, 220℃, 210℃, and 210℃, respectively.

[0048] The cooling, setting, pulling and temperature conditioning equipment, and the die stretching equipment are the same as in Example 1.

[0049] The material formula and composition, the stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0050] Example 3 Raw materials: Polypropylene PPB M02, copolymerized polypropylene with a propylene content of 90%, Yangzi Petrochemical, melt flow rate 2.0 g / 10 min (230℃, 2.16 kg); PBT, grade 1100A, Nantong Xingchen Synthetic Material Co., Ltd.; Calcium carbonate: 1250 mesh, Quanzhou Xufeng Powder Raw Material Co., Ltd. Other additives are the same as in Example 1.

[0051] The equipment and preparation process parameters are the same as in Example 2.

[0052] The material formula and composition, the stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0053] Example 4 Raw materials: Polypropylene PPB M02, copolymerized polypropylene, Yangzi Petrochemical, melt flow rate 2.0 g / 10 min (230℃, 2.16 kg); PET short fiber, average diameter 8 um, length-diameter ratio 10; calcium silicate, 1250 mesh, Quanzhou Xufeng Powder Co., Ltd.; other additives are the same as in Example 1, Equipment and preparation process parameters: The three-screw extruder, the cooling, setting, pulling and temperature conditioning equipment, and the die stretching equipment are the same as in Example 2.

[0054] The material formula and composition, the stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0055] Example 5 Raw materials: Polypropylene PPB M02, copolymerized polypropylene, Yangzi Petrochemical, melt flow rate 2.0 g / 10 min (230 °C, 2.16 kg); Nylon 66, chopped fiber, average diameter 10 um, aspect ratio 5; talc, 1250 mesh, Quanzhou Xufeng Powder Co., Ltd. Other additives are the same as in Example 1.

[0056] Equipment and process parameters: Twin-screw extruder, cooling, drawing and temperature conditioning equipment, die stretching equipment are the same as in Example 1.

[0057] The material formulation and composition, stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0058] Comparative Example 1 Raw materials: polypropylene T30s; calcium carbonate 800 mesh, Quanzhou Powder Co., Ltd.; other additives are the same as in Example 1.

[0059] Equipment and process parameters: Twin-screw extruder, cooling, drawing and temperature conditioning equipment, die stretching equipment are the same as in Example 1. The material formulation and composition, stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0060] Comparative Example 2 The raw material formulation and processing equipment are the same as in Example 2, except that the temperature of each section of the triple-screw extruder is different. In this comparative example, the temperature of each section of the triple-screw extruder is 150 °C, 210 °C, 230 °C, 260 °C, 260 °C, 260 °C, 260 °C, 260 °C, 250 °C, 250 °C.

[0061] The material formulation and composition, stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0062] Comparative Example 3 Raw materials: polypropylene PPB M02; talc, 1250 mesh, Quanzhou Xufeng Powder Co., Ltd.; other additives are the same as in Example 1.

[0063] Equipment and process parameters: Twin-screw extruder, cooling, drawing and temperature conditioning equipment, die stretching equipment are the same as in Example 1. The difference is that the temperature of sections 4-10 of the twin-screw extruder is 230 °C.

[0064] The stretching process is shown in Table 1, and the density and mechanical properties of the product are shown in Table 2.

[0065] Comparative Example 4 The raw materials, twin-screw extruder, cooling and shaping, traction and temperature conditioning equipment, and die stretching equipment were the same as in Example 3. The difference was that the 4-10 zone temperature of the triple-screw extruder was 250 DEG C, and the die stretching rate was 1 m / min.

[0066] The material formulation and composition, stretching process are shown in Table 1, and the product performance is shown in Table 2.

[0067] Table 1 Composition of polypropylene composite material and stretching process parameters in each example Table 2 Density and mechanical properties of products in each example It can be seen from Comparative Examples 1-4 that in Comparative Example 1 and Comparative Example 3, the products were broken during stretching and could not be continuously produced, and in Comparative Example 2 and Comparative Example 4, the bending strength and bending modulus of the products were less than those of the products in Example 1-5; this shows that the product prepared by the method of the application has a smaller density, is more lightweight, and has greater bending strength and bending modulus, better mechanical properties, better tensile strength, and improved strength and toughness of the polypropylene composite material matrix, thereby facilitating high die stretching rate and stable continuous production. The polypropylene composite material prepared has high strength and low density, and the product surface is smooth and uniform without the need for secondary processing.

[0068] The above description is based on the best mode of the application and working principle. The above examples should not be understood as limiting the scope of the present application, and other embodiments and combinations of implementation modes according to the concept of the application are within the scope of the present application.

Claims

1. A lightweight high-strength polypropylene composite material, characterized by, The application relates to a high-strength light-weight polypropylene composite material and a preparation method thereof. The polypropylene blend comprises 50wt%-70wt% polypropylene, 25wt%-45wt% filler and 2wt%-5wt% processing aid, wherein, The polypropylene blend comprises polypropylene and 10wt%-30wt% engineering polymer, and the engineering polymer comprises at least one of aromatic polyester and its copolymer and nylon; and the density of the lightweight high-strength polypropylene composite material is less than or equal to 0.8 g / cm 3 , and the flexural modulus is greater than or equal to 3.0 GPa.

2. The lightweight high-strength polypropylene composite material according to claim 1, characterized in that, The polypropylene is a homopolymer, a copolymer or a mixture of the two, and the melt index of the polypropylene is not greater than 8g / 10min.

3. The lightweight high-strength polypropylene composite material according to claim 1, characterized in that, The aromatic polyester and its copolymer comprise at least one of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); and the nylon comprises at least one of nylon 6, nylon 66, bio-based nylon and aromatic nylon. 4.The lightweight high-strength polypropylene composite material according to claim 1, characterized in that, The filler comprises at least one of talcum powder, calcium carbonate, calcium silicate, wollastonite, kaolin and fly ash; and the processing aid comprises at least one of antioxidant, ultraviolet light aging resistant agent, thermal stabilizer and lubricant.

5. The lightweight high-strength polypropylene composite material according to claim 1, characterized in that, The processing aid comprises lubricant which is greater than or equal to 2wt% of the polypropylene composite material, and the lubricant comprises at least one of zinc stearate, calcium stearate, stearic acid amide, ethylene bis-stearamide, low-molecular-weight polyethylene wax and polyethylene glycol.

6. The method of producing a lightweight high-strength polypropylene composite material according to any one of claims 1 to 5, characterized by, The application relates to a high-strength light-weight polypropylene composite material and a preparation method thereof. S1. mixing polypropylene and engineering polymer in an extruder at 150 DEG C-230 DEG C to form a polypropylene blend; S2. adding filler and processing aid to the polypropylene blend, mixing in the extruder and extruding through a die to obtain a primary polypropylene composite material; S3. making the primary polypropylene composite material pass through a shaping and traction device to obtain a polypropylene composite material parison; S4. modulating the temperature of the polypropylene composite material parison to be above the softening temperature of the polypropylene composite material parison material to obtain a temperature-modulated polypropylene composite material parison; S5. making the temperature-modulated polypropylene composite material parison pass through a stretching die, and applying a stretching force by a traction machine to make the polypropylene composite material be stretched and deformed to be oriented when passing through the stretching die, thereby preparing a high-strength light-weight polypropylene composite material.

7. The production method according to claim 6, wherein The extruder is a co-rotating double-screw extruder or a triple-screw extruder; the extruder is provided with a main feeding port and at least one side feeding feeding port; the extruder outlet is connected with an extrusion molding machine and a die; the extrusion molding machine is one of a melt pump, a single-screw extrusion molding machine, a counter-rotating double-screw extrusion molding machine and a conical double-screw extrusion molding machine; the polypropylene and the engineering polymer are added into the extruder through the main feeding port; and the filler and the processing aid are added into the extruder through the side feeding feeding port.

8. The preparation method according to claim 6, characterized in that, In step S4, the temperature of the polypropylene composite material parison is modulated by a temperature modulation device to be between 110 DEG C and 155 DEG C, and the temperature difference of each part of the cross section of the polypropylene composite material parison is lower than 5 DEG C.

9. The preparation method according to claim 6, characterized in that, In step S5, the pulling rate of the pulling machine is greater than the parison extrusion rate, and the difference between the pulling rate of the pulling machine and the parison extrusion rate is greater than or equal to 1 m / min, and the pulling rate of the pulling machine is not less than 2 m / min.

10. The method of claim 6, wherein, In step S5, the stretching die is a stretching die with an axisymmetric converging structure, the stretching die is a circular die or a rectangular die, the ratio of the inlet cross-sectional area to the outlet cross-sectional area of the stretching die is between 2 and 6, and the stretching temperature of the stretching die is 130 DEG C to 150 DEG C.

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