A method for preparing biomass micro-nano fiber directional modified plastic by using wet feed method

Abstract

The application discloses a method for preparing biomass micro-nano fiber directional modified plastic by using a wet feed method for extrusion, which comprises the following steps: adding plastic particles and an auxiliary agent into wet pulp containing biomass micro-nano fibers, stirring to obtain a blend; and then melt-kneading, extruding and injection molding the obtained blend. The application can effectively reduce the agglomeration of the micro-nano fibers and the plastic during the blending and melting, make the blending uniform between the two phases, and form an assembled structure with layer-by-layer embedding. The directional micro-nano fibers in the plastic matrix are realized during the extrusion and melt-kneading, the interface bonding capacity between the two phases is improved, and the obtained modified plastic has the advantages of high strength and good dimensional stability. In addition, the method has simple process, green production process and no dust pollution, can reduce the use of plastic in the composite material, reduce the cost, and the prepared composite material has excellent performances such as high strength and good dimensional stability, and can be widely applied in high-value fields such as automobile manufacturing, electronic products and building materials.

Description

Technical Field

[0001] This invention relates to a method for preparing modified plastics, and more particularly to a method for preparing biomass micro / nano fiber oriented modified plastics using wet-feed extrusion. Background Technology

[0002] Currently, research on using biomass micro / nanofibers (MNF) to reinforce polymers mainly faces the following problems: (1) chemical defiberization easily pollutes the environment; (2) MNF is prone to agglomeration after drying; (3) dried MNF fibers are fluffy and too light, making it difficult to mix evenly with plastics; (4) the interfacial bonding between the two phases is weak; and (5) the composite material has poor strength and toughness. MNF-reinforced composites are usually prepared using a compounding molding method, which involves blending and melting MNF with plastics and then processing them through mechanical methods such as extrusion, injection molding, and compression molding. In most studies, MNF is dried before composite preparation, with common methods including freeze-drying, spray drying, vacuum drying, and oven drying. Agglomeration of MNF occurs in most drying methods, directly affecting the uniform dispersion of MNF in the polymer matrix. Despite the different drying methods, the method of mixing dried MNF with polymers and then extruding (i.e., dry extrusion) has many common drawbacks: First, the drying process of MNF is time-consuming and labor-intensive, and is prone to dust pollution; second, because MNF has strong hydrophilicity, irreversible agglomeration may occur during the drying process, producing micron-sized or larger particles.

[0003] The dispersion degree of MNF in the polymer matrix and the interfacial compatibility between the two phases are key to ensuring the high performance of composite materials. Solving the problems of agglomeration and dust pollution in the production process of MNF composites, and simplifying the production process while ensuring the performance of the composite materials, is of great significance for the application of fiber composites in a wider range of fields. Summary of the Invention

[0004] Purpose of the invention: This invention aims to provide a method for preparing biomass micro-nano fiber-oriented modified plastics using wet feed extrusion. This method has the advantages of simplifying the process and improving the mechanical properties and thermal stability of the modified plastics. By achieving the orientation of biomass micro-nano fibers in the plastic matrix during extrusion melt mixing, it can effectively reduce the agglomeration of biomass micro-nano fibers and plastics during blending and melting.

[0005] Technical solution: The method for preparing biomass micro / nano fiber-oriented modified plastics using wet-feed extrusion according to the present invention includes the following steps:

[0006] Plastic particles and additives are added to a wet slurry containing biomass micro-nano fibers, and the mixture is stirred to obtain a blend. The solid content of biomass micro-nano fibers in the wet slurry is 25-40 wt%. The resulting blend is then melt-blended, extruded, and molded to obtain biomass micro-nano fiber-oriented modified plastic.

[0007] Furthermore, the method for preparing the wet pulp containing biomass micro-nano fibers includes: pre-treating the biomass raw material with alkali and washing and swelling it with water to obtain biomass fibers, then crushing, stirring and dispersing the biomass fibers to obtain biomass micro-nano fibers, and then filtering the dispersed suspension to a wet pulp state without dripping water to obtain the wet pulp containing biomass micro-nano fibers.

[0008] Furthermore, the biomass raw material is treated in an alkaline solution in a water bath for 2-6 hours, then soaked at room temperature for 10-24 hours, and then washed with water until neutral to obtain swollen biomass fiber. The concentration of the alkaline solution is 1-5 wt%.

[0009] Furthermore, the debonding process includes debonding the fibers in a high-speed mixer at a speed of 8000–12000 r / min for 3–5 minutes.

[0010] Furthermore, the diameter of the biomass micro / nano fibers is 100 nm to 100 μm.

[0011] Furthermore, in the biomass micro-nano fiber oriented modified plastic, the plastic particle content is 15-95%, the additive content is 2-10%, and the biomass micro-nano fiber content is 3-75%, wherein the additives include coupling agents and / or lubricants.

[0012] Furthermore, the extrusion process temperature is controlled at 158–165°C, the screw speed is 20–40 rpm, and the extrusion process involves simultaneous extrusion, vacuuming, and venting.

[0013] Furthermore, the plastic particles are thermoplastic plastics, including at least one of polyethylene, polypropylene, nylon, polyvinyl chloride, polyethylene terephthalate, polystyrene, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, polyetheretherketone, acrylonitrile-styrene-butadiene copolymer, polylactic acid, or polybutylene terephthalate. The raw materials for preparing the biomass micro / nano fibers include at least one of wood, bamboo, straw, rice husk, hemp, cotton, coconut shell, or sugarcane.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0015] (1) It is beneficial to enhance the mechanical properties of modified plastics; the wet feeding method is adopted, in which water can not only play a plasticizing role, but also act as a conveying medium for biomass micro-nano fibers, promoting further defiberization of biomass micro-nano fibers during the screw meshing process of the extruder, so as to improve the dispersibility of biomass micro-nano fibers in composite materials, improve the mixing effect, solve the fiber agglomeration problem in the production process of biomass micro-nano fiber reinforced plastic composites, realize the orientation of biomass micro-nano fibers in plastic matrix during extrusion melt mixing, improve the interfacial bonding ability between the two phases, and greatly enhance the mechanical properties of composite materials; unlike the traditional biomass raw materials that only serve as fillers in plastic matrix, this invention uses wet feeding method mixing and extrusion molding, the biomass micro-nano fibers are fully combined with the plastic matrix, and the fibers achieve directional flow in the barrel flow channel, the biomass micro-nano fibers have a directional reinforcing effect;

[0016] (2) The modified plastic has high strength and low coefficient of thermal expansion. Under wet conditions, with the help of the orientation arrangement of biomass micro-nano fibers, it can overcome the defects of poor stress support and poor stability of most plastics, and develop a new type of micro-nano fiber modified plastic with high strength and low coefficient of thermal expansion. It breaks through the bottleneck of traditional plastic stability limitation that prevents it from being applied on a large scale in the field of high value.

[0017] (3) Simplified process; wet extrusion eliminates the step of drying biomass micro-nano fibers, saving energy and time, and avoiding dust pollution. It can achieve green and clean production and has good industrialization prospects in high-value fields such as high-strength engineering materials and automotive body materials. Attached Figure Description

[0018] Figure 1 Transmission electron microscopy image of wood micro / nano fibers;

[0019] Figure 2 Scanning electron microscope image of polyethylene modified with 30% wood micro / nano fibers;

[0020] Figure 3 The flexural mechanical properties of polyethylene composites modified with different ratios of wood micro / nano fibers;

[0021] Figure 4 The linear thermal expansion coefficients of polyethylene modified with different ratios of wood micro / nano fibers are given. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1

[0024] (1) After mechanically crushing poplar wood shavings, they were placed in a 2wt% concentration of industrial caustic soda and treated in a 95°C water bath for 2 hours. Then, they were placed at room temperature and soaked for 10 hours. After being taken out, they were washed with deionized water until neutral to obtain swollen poplar wood fibers.

[0025] (2) Place the poplar fibers from step (1) into a high-speed fiber disintegration mixer and stir for 5 minutes. The speed of the high-speed mixer is 12000 r / min to obtain a poplar micro-nano fiber suspension with a diameter of 100 nm to 100 μm.

[0026] (3) Vacuum filter the poplar wood micro-nano fiber suspension from step (2) to a wet slurry state where no water drips, and control the solid content of the wood micro-nano fiber to be 35wt%.

[0027] (4) Mix wood micro-nano fibers, HDPE particles, maleic anhydride grafted polyethylene (MAPE) and polyethylene wax in a mass ratio of 30:63:3:4, place them in a high-speed mixer and stir at 8000r / min for 3min until they are evenly mixed to obtain a blend.

[0028] (5) The blend obtained in step (4) is placed in a twin-screw extruder for melt mixing and extrusion molding. The temperature of the extruder is set to 163°C and the screw speed is set to 30 rpm. Water vapor overflows during the extrusion process. Vacuum and exhaust are carried out while extruding. Extruded strips are obtained and granulated to obtain extruded granules.

[0029] (6) Add the extruded granules obtained in (5) to the injection molding machine for further molding. Set the heating temperature of the injection molding machine to 167°C.

[0030] Test method for bending properties of wood-based micro / nano fiber modified plastics: Injection-molded samples with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm were tested using a universal testing machine with a support span of 64 mm and a pressure bar speed of 2 mm / min. Each sample was tested six times, and the average value was taken.

[0031] Test method for linear thermal expansion coefficient of wood-based micro / nano-fiber modified plastics: A sample 25 mm long, 4.5 mm wide, and 1 mm thick was tested using a static mechanical thermal analyzer (TMA) in tensile mode under a nitrogen atmosphere. The heating rate was 5 °C / min, and the load was set to 0.03 N. Each sample was tested five times. Finally, the linear thermal expansion coefficient was calculated within the temperature range of -30 °C to 60 °C, and the average value was taken.

[0032] Through flexural mechanical testing, the average flexural modulus of the sample in Example 1 reached 2074.9 MPa, and the average flexural strength reached 43.2 MPa, representing a 102% increase in strength compared to the control group high-density polyethylene (HDPE) sample. Static thermomechanical analysis showed that the linear coefficient of thermal expansion (CTE) of the sample in Example 1 was 85 × 10⁻⁶. -6 / K, compared to the control group HDPE, the CTE value decreased by half, and the thermal stability and dimensional stability were significantly improved.

[0033] Example 2

[0034] Step (4) in Example 1 is modified as follows: wood micro-nano fibers, HDPE particles, maleic anhydride grafted polyethylene (MAPE) additive and PE wax are mixed in a mass ratio of 20:73:3:4 and placed in a high-speed mixer and stirred at 5000r / min for 3min until the mixture is uniform and a blend is obtained; the remaining steps are the same as in Example 1.

[0035] Through flexural mechanical testing, the average flexural modulus of the sample in Example 2 reached 1648.8 MPa, and the average flexural strength reached 36.0 MPa, representing a 68% increase in strength compared to the pure high-density polyethylene sample. Static thermomechanical analysis showed that the linear thermal expansion coefficient of the example sample was 96 × 10⁻⁶. -6 / K, compared to the control group, the CTE value of HDPE decreased by 74 × 10 -6 / K, greatly improving thermal stability.

[0036] Example 3

[0037] Step (4) in Example 1 is modified as follows: wood micro-nano fibers, HDPE particles, maleic anhydride grafted polyethylene (MAPE) additive and PE wax are mixed in a mass ratio of 40:53:3:4 and placed in a high-speed mixer and stirred at 5000r / min for 4min until the mixture is uniform and a blend is obtained; the remaining steps are the same as in Example 1.

[0038] Through flexural mechanical testing, the average flexural modulus of the sample in Example 3 reached 2478.5 MPa, and the average flexural strength reached 49.2 MPa, representing a 130% increase in strength compared to the pure high-density polyethylene sample. Static thermomechanical analysis showed that the linear thermal expansion coefficient of the example sample was 69 × 10⁻⁶. -6 / K, compared to the control group, the CTE value of HDPE decreased by 101 × 10 -6 / K, greatly improving thermal stability.

[0039] Example 4

[0040] Step (4) in Example 1 is modified as follows: wood micro-nano fibers, HDPE particles, maleic anhydride grafted polyethylene (MAPE) additive and PE wax are mixed in a mass ratio of 50:43:3:4 and placed in a high-speed mixer and stirred at a speed of 5000r / min for 4min until the mixture is uniform and a blend is obtained; the remaining steps are the same as in Example 1.

[0041] Through flexural mechanical testing, the average flexural modulus of the sample in Example 4 reached 3085.2 MPa, and the average flexural strength reached 53.9 MPa, representing a 152% increase in strength compared to the pure high-density polyethylene sample. Static thermomechanical analysis showed that the linear thermal expansion coefficient of the example sample was 59 × 10⁻⁶. -6 / K, compared to the control group, the CTE value of HDPE decreased by 111 × 10. -6 / K, significantly improving thermal stability.

[0042] like Figure 1 Example 1 uses poplar wood shavings as raw material. After defibering, the wood micro-nano fibers are visible. After mechanical defibering, the micron fibers are effectively disassembled and have nanofiber branches.

[0043] like Figure 2 The image shown is a scanning electron microscope (SEM) image of the surface fracture of the 30% wood-based micro / nano-fiber modified polyethylene composite material from Example 1. It is evident that the micro / nano-fibers and plastic are uniformly mixed, forming a layered, interlocking assembly structure. During the wet-feed extruder screw compounding process, the micro / nano-fibers achieve good orientation within the flowing plastic matrix, which helps improve the mechanical properties and dimensional stability of the composite material.

[0044] The composite material prepared by this invention exhibits a significant improvement in flexural strength compared to the control group polyethylene plastic, as detailed in the following figures. Figure 3 In the composite materials prepared by this invention, the composite material with 50% micro / nano fibers exhibited a flexural strength of 53.9 MPa and a flexural modulus of 3085.2 MPa, representing increases of 152% and 297% respectively compared to the control group high-density polyethylene (HDPE). Samples with 20%, 30%, and 40% micro / nano fibers showed increases in flexural strength relative to HDPE of 68%, 102%, and 130%, respectively. Within the scope of the experiments, the composite material with 50% cellulose content exhibited the best flexural performance, providing an effective preparation method for wood-based micro / nano fiber modified plastic composite materials.

[0045] The composite material prepared by this invention exhibits excellent thermal stability, and its thermal expansion properties significantly improve with increasing fiber content. Specifically, as follows... Figure 4 As shown, the linear coefficient of thermal expansion (CTE) of the composites with 30% and 50% micro / nano fibers added are 85 × 10⁻⁶ and 85 × 10⁻⁶, respectively. -6 / K、59×10 -6 / K, compared to the control group HDPE, the CTE value decreased by more than half, and the dimensional stability was greatly improved.

[0046] This invention efficiently utilizes the "wet feed method" to extrude and prepare wood micro / nano fiber modified plastics, solving the fiber agglomeration problem in the production process of wood micro / nano fiber reinforced plastics. While greatly enhancing the mechanical properties of the plastics, it also improves their dimensional stability, reduces the use of non-renewable petroleum-based plastics, and effectively saves costs. Moreover, the method is relatively simple, green, and dust-free, making it suitable for assembly line industrial production. It contributes to the research on the use of natural biomass materials to prepare novel modified plastics.

Claims

1. A method for preparing biomass micro / nano fiber-oriented modified plastics using wet-feed extrusion, characterized in that, Includes the following steps: Plastic particles and additives are added to a wet slurry containing biomass micro-nano fibers, and the mixture is stirred to obtain a blend. The solid content of biomass micro-nano fibers in the wet slurry is 25-40 wt%. The resulting blend is then melt-blended and extruded to obtain biomass micro-nano fiber oriented modified plastic. The method for preparing the wet pulp containing biomass micro-nano fibers includes: pre-treating biomass raw materials with alkali and washing and swelling them with water to obtain biomass fibers; then crushing, stirring and dispersing the biomass fibers to obtain biomass micro-nano fibers; and then filtering the dispersed suspension to a wet pulp state without dripping water to obtain the wet pulp containing biomass micro-nano fibers.

2. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, Biomass raw materials are treated in an alkaline solution for 2-6 hours, then soaked at room temperature for 10-24 hours. After being removed, they are washed with water until neutral to obtain swollen biomass fibers.

3. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 2, characterized in that, The concentration of the alkaline solution is 1~5 wt%.

4. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, The debonding process involves debonding the fibers in a high-speed mixer at a speed of 8000~12000r / min for 3~5min.

5. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, The diameter of the biomass micro-nano fibers is 100 nm to 100 μm.

6. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, The biomass micro-nano fiber oriented modified plastic has a plastic particle content of 15-95%, an additive content of 2-10%, and a biomass micro-nano fiber content of 3-75%.

7. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, The additives include coupling agents and / or lubricants.

8. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, The extrusion process is controlled at a temperature of 158~165℃ and a screw speed of 20~40rpm. The extrusion process involves simultaneous extrusion, vacuuming, and venting.

9. The method for preparing biomass micro / nano fiber-oriented modified plastics by wet-feed extrusion according to claim 1, characterized in that, The plastic particles are thermoplastic plastics, including at least one of polyethylene, polypropylene, nylon, polyvinyl chloride, polyethylene terephthalate, polystyrene, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, polyetheretherketone, acrylonitrile-styrene-butadiene copolymer, polylactic acid, or polybutylene terephthalate; the raw materials for preparing the biomass micro-nano fibers include at least one of wood, bamboo, straw, rice husk, hemp, cotton, coconut shell, or sugarcane.

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