A method for processing and manufacturing wood-plastic material

Abstract

This invention belongs to the field of bio-based composite materials technology and discloses a method for processing and manufacturing wood-plastic composite materials, including the following steps: Step 1, using coconut shell fiber, coconut coir, or short fiber as wood fiber raw materials, performing a three-stage activation pretreatment of bio-enzyme-assisted defiberization, deep alkaline activation, and coupling agent grafting modification to obtain activated coconut shell fiber powder; Step 2, synthesizing a bifunctional grafted macromolecular compatibilizer containing both epoxy groups and anhydride groups. Through the three-stage activation pretreatment in Step 1—bio-enzyme-assisted defiberization, deep alkaline activation, and coupling agent grafting modification—this invention significantly increases the surface active hydroxyl density of coconut shell fiber, enhancing the interfacial bonding ability between the fiber and the resin matrix; through the synthesis of the bifunctional grafted macromolecular compatibilizer containing both epoxy groups and anhydride groups in Step 2, a dual chemical bonding network is constructed between the fiber and the matrix, significantly improving the interfacial shear strength and the material's elongation at break.

Description

Technical Field

[0001] This invention relates to the field of bio-based composite materials technology, and in particular to a method for processing and manufacturing wood-plastic composite materials. Background Technology

[0002] Wood-plastic composites (WPC) are a type of green composite material made by melt blending and molding lignin (such as wood flour, bamboo flour, and straw flour) as the reinforcing phase and thermoplastic (such as polyethylene, polypropylene, polyvinyl chloride, or biodegradable plastics) as the matrix. WPC combines the texture and processability of wood with the water resistance and corrosion resistance of plastics, and is widely used in building decoration (outdoor flooring, wall panels, railings), landscaping, logistics packaging (pallets, crates), and automotive interiors. In recent years, with the comprehensive advancement of global "plastic ban" policies, the market demand for WPC, as a biodegradable and recyclable environmentally friendly material, has continued to grow.

[0003] However, existing wood-plastic composite materials and their manufacturing methods still face the following problems: 1. Wood fibers are hydrophilic while plastic matrices are hydrophobic, resulting in weak interfacial bonding between the two phases, which easily leads to cracking and delamination. Existing compatibilizers are mostly maleic anhydride-grafted polymers, which have limited functional groups, low grafting efficiency, and limited interfacial compatibilization effect; 2. Although coconut shell fibers are abundant, existing pretreatment methods are limited (simple alkali soaking), which fails to fully activate their surface, resulting in poor bonding between fibers and the matrix; 3. Existing wood-plastic composite materials only use micron-sized fibers and lack a nanoscale second reinforcing phase, resulting in a weak interfacial transition zone (ITZ) and difficulty in comprehensively improving mechanical properties; 4. Wood-plastic composite materials are prone to thermo-oxidative aging in environments with temperature fluctuations. Existing phase change microcapsules are mostly single-layer shells, which are prone to rupture and leakage, leading to a decline in mechanical properties. Summary of the Invention

[0004] To overcome the technical defects of the existing technology, the present invention provides a method for processing and manufacturing wood-plastic composite materials.

[0005] The technical solution adopted in this invention is: a method for processing and manufacturing wood-plastic composite materials, comprising the following steps: Step 1: Using coconut shell fiber, coconut coir or short fiber as wood fiber raw material, perform three-stage activation pretreatment in sequence: bio-enzyme-assisted defiberization treatment, alkali deep activation and coupling agent grafting modification to obtain activated coconut shell fiber powder. Step 2: Synthesize a bifunctional grafted macromolecular compatibilizer containing both epoxy groups and acid anhydride groups; Step 3: Prepare nanocellulose whiskers and modify their surface with isocyanate to obtain modified nanocellulose whiskers; Step 4: Prepare temperature phase change microcapsules with a double core-shell structure having a melamine-formaldehyde resin inner layer and a polysiloxane outer layer; Step 5: The activated coconut shell fiber powder, biodegradable resin matrix, bifunctional grafted macromolecular compatibilizer, bio-based toughening agent polybutylene succinate, modified nanocellulose whiskers, epoxy functionalized compatibilizer, bio-based plasticizer, double-layer core-shell structure temperature phase change microcapsules and processing aids are mixed in parts by weight and then melt-blended and granulated to obtain wood-plastic composite material granules. Step 6: The wood-plastic composite material granules are processed by an intelligent integrated continuous production system to obtain the finished wood-plastic material.

[0006] Preferably, in step 1, the bio-enzyme-assisted defiberization treatment is as follows: coconut shell fiber powder is placed in a composite enzyme solution containing cellulase, xylanase, and pectinase, at pH 4.5~5.5 and temperature 45~55℃, for 2~6 hours; the amount of cellulase is 0.5%~2% of the fiber mass, the amount of xylanase is 0.3%~1% of the fiber mass, and the amount of pectinase is 0.2%~0.8% of the fiber mass.

[0007] Preferably, in step 1, the alkaline deep activation is performed by placing the enzyme-treated coconut shell fiber powder in a 3%~10% NaOH solution and soaking it at 50~80°C for 1~3 hours; the coupling agent grafting modification is performed by reacting the alkaline-activated coconut shell fiber powder with γ-glycidoxypropyltrimethoxysilane in an ethanol / water mixed solvent at 60~90°C for 2~3 hours, with KH560 used at 2%~6% of the coconut shell fiber mass.

[0008] Preferably, in step 2, the bifunctional grafted macromolecular compatibilizer is synthesized by: using polylactic acid or polybutylene adipate terephthalate as the grafting skeleton, glycidyl methacrylate and maleic anhydride as grafting comonomers, and benzoyl peroxide as the initiator, through melt grafting; the mass fractions of each component are: 100 parts of polylactic acid or polybutylene adipate terephthalate, 10-20 parts of glycidyl methacrylate, 5-12 parts of maleic anhydride, and 0.3-1.0 parts of benzoyl peroxide, and the grafting reaction temperature is 170-190℃.

[0009] Preferably, in step 3, the modified nanocellulose whiskers are prepared by: placing microcrystalline cellulose or cotton linter pulp in a 64% sulfuric acid solution and hydrolyzing it at 45-55°C for 30-90 minutes, followed by centrifugation, washing, ultrasonic dispersion, dialysis, and freeze-drying to obtain nanocellulose whiskers with a diameter of 5-20 nm and a length of 100-500 nm; the surface isocyanate modification is performed by: dispersing nanocellulose whiskers in N,N-dimethylformamide, adding toluene-2,4-diisocyanate and dibutyltin dilaurate catalyst, and reacting at 60°C for 4 hours.

[0010] Preferably, in step 4, the preparation method of the double-layer core-shell structure temperature phase change microcapsules is as follows: using an organic phase change material as the core material, firstly, a first shell material is formed by in-situ polymerization of melamine-formaldehyde resin, and then a second shell material of polysiloxane formed by the hydrolysis and condensation of γ-methacryloyloxypropyltrimethoxysilane is formed by sol-gel method on the surface of the first shell material; the phase change temperature of the phase change microcapsules is 25~45℃, the particle size is 2~15 μm, and the phase change enthalpy is ≥150 J / g.

[0011] Preferably, in step 5, the components are proportioned in the following weight ratios: 25-50 parts activated coconut shell fiber powder, 35-60 parts biodegradable resin matrix, 4-12 parts bifunctional grafted macromolecular compatibilizer, 5-20 parts bio-based toughening agent polybutylene succinate, 1-8 parts modified nanocellulose whiskers, 2-6 parts epoxy functionalized compatibilizer, 2-5 parts bio-based plasticizer, 5-15 parts double-shell phase change microcapsules, and 0.5-3 parts processing aid. The biodegradable resin matrix is ​​selected from one or more of polylactic acid, polybutylene adipate-terephthalate, and polybutylene succinate-terephthalate; the epoxy functionalized compatibilizer is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer or an ethylene-butyl acrylate-glycidyl methacrylate copolymer, with an epoxy equivalent of 200~500 g / eq and a melt index of 3~10 g / 10min.

[0012] Preferably, in step 5, the melt blending granulation is carried out using a twin-screw extruder with an extrusion temperature of 150~190℃ and a screw speed of 200~400 rpm.

[0013] Preferably, in step 6, the intelligent integrated continuous production system integrates a waste heat recovery and gradient preheating module, an online melt rheology monitoring module, an adaptive molding die module, and a gradient cooling and shaping module; the waste heat recovery and gradient preheating module utilizes the waste heat generated in the extrusion section to preheat the raw material in the feeding section, reducing overall energy consumption by more than 30% compared to the traditional segmented process; the adaptive molding die module is equipped with a shape memory alloy adjustment element, which, together with the online laser thickness measuring device, forms a closed-loop control, controlling the product thickness deviation within ±1.5%.

[0014] Preferably, in step 6, the molding process is selected from one of extrusion molding, injection molding, or thermoforming.

[0015] The beneficial effects of this invention are: 1. The present invention significantly improves the surface active hydroxyl density of coconut shell fiber and enhances the interfacial bonding ability between the fiber and the resin matrix through the three-stage activation pretreatment in step 1, namely, bio-enzyme-assisted fiber disintegration, alkaline deep activation, and coupling agent grafting modification. 2. In step 2, this invention synthesizes a bifunctional grafted macromolecular compatibilizer containing both epoxy groups and anhydride groups, which constructs a dual chemical bonding network between the fiber and the matrix, significantly improving the interfacial shear strength and the elongation at break of the material. 3. In step 3, the present invention prepares surface isocyanate-modified nanocellulose whiskers as a nanoscale second reinforcing phase, which forms a multi-scale reinforcing network with micron-sized coconut shell fibers, fills the defects in the interface transition zone, and achieves simultaneous improvement of tensile strength, flexural strength and impact toughness. 4. This invention prepares a double-core-shell structure temperature phase change microcapsule with a melamine-formaldehyde resin inner layer and a polysiloxane outer layer through step 4. The outer polysiloxane is chemically bonded to the matrix resin, which solves the problems of easy breakage, easy leakage and decreased mechanical properties of traditional microcapsules, and endows the material with excellent temperature control capability and long-term durability. 5. In step 5 of this invention, 25-50 parts of activated coconut shell fiber powder, 35-60 parts of biodegradable resin matrix, 4-12 parts of bifunctional compatibilizer, 5-20 parts of PBS toughening agent, 1-8 parts of modified CNC, 2-6 parts of epoxy functionalized compatibilizer, 2-5 parts of bio-based plasticizer, 5-15 parts of double-shell phase change microcapsules, and 0.5-3 parts of processing aid are melt-blended and granulated, which optimizes the synergistic ratio of each component and ensures the balance and stability of the comprehensive performance of the composite material. 6. This invention uses an intelligent integrated continuous production system for molding and processing, which reduces overall energy consumption compared to traditional processes, controls product thickness deviation within ±1.5%, and improves production efficiency. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the various embodiments of this invention are described in detail below. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this application can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0017] Example 1 This embodiment provides a method for processing and manufacturing wood-plastic composite materials for preparing outdoor weather-resistant flooring. The specific steps are as follows: Step 1: Three-stage activation pretreatment of coconut shell fiber Coconut shell waste is crushed and sieved to obtain 120-mesh coconut shell fiber powder, which is then dried at 105℃ until the moisture content is ≤2%. (1) Bioenzyme-assisted defiber treatment: Coconut shell fiber powder was placed in a compound enzyme solution containing cellulase (1.2% of fiber mass), xylanase (0.5%), pectinase (0.3%), pH 5.0, temperature 50℃, and treated for 4 hours. After treatment, it was washed with deionized water until neutral and dried at 105℃. (2) Deep activation with alkaline solution: The enzyme-treated coconut shell fiber powder is placed in a 5% NaOH solution, soaked at 70°C for 2 hours, washed with deionized water until neutral, and dried at 105°C; (3) Coupling agent grafting modification: The alkali-activated coconut shell fiber powder and KH560 (4% of the fiber mass) were reacted in a mixed solvent of ethanol / water (volume ratio 1:1) at 80°C for 2 hours, filtered, washed and dried at 105°C to obtain activated coconut shell fiber powder.

[0018] Step 2: Synthesis of bifunctional grafted macromolecular compatibilizer Take 100 parts of PLA resin, 15 parts of GMA, 8 parts of MAH and 0.6 parts of BPO, premix them evenly in a high-speed mixer, and then melt-graft granulate them at 180°C using a twin-screw extruder to obtain PLA-g-(GMA-co-MAH) compatibilizer. The grafting rate of GMA was determined to be 5.6% and the grafting rate of MAH was 3.8% by acid-base titration.

[0019] Step 3: Preparation of modified nanocellulose whiskers Take 50g of microcrystalline cellulose, add 500mL of 64% sulfuric acid solution, hydrolyze at 50℃ for 60 minutes, centrifuge and wash until pH≈5, sonicate for 30 minutes, dialyze until pH≈6, freeze dry to obtain CNC (diameter 10~15 nm, length 200~300 nm), take 5g of CNC and disperse in 100mL of DMF, add 2g of TDI and 0.05g of dibutyltin dilaurate, react at 60℃ for 4 hours, centrifuge and wash, vacuum dry to obtain isocyanate modified CNC.

[0020] Step 4: Take 100g of n-eicosane (phase transition temperature 36.5℃) as the core material, add an emulsifier aqueous solution for high-speed emulsification, add melamine and formaldehyde (molar ratio 1:3), adjust the pH to 4.0, react at 75℃ for 2.5 hours to obtain MF-coated microcapsules. Disperse the microcapsules in an ethanol / water solution containing 5% KH570, hydrolyze and condense at 60℃ for 2 hours, centrifuge, wash, and vacuum dry to obtain MF / PDMS double-shell microcapsules. DSC test showed a phase transition enthalpy of 168 J / g, and laser particle size analyzer measured the particle size D50 to be 8.5 μm.

[0021] Step 5: Melt blending and granulation.

[0022] Weigh the following components in the indicated weight proportions: 35 parts activated coconut shell fiber powder, 40 parts PLA resin, 8 parts PLA-g-(GMA-co-MAH) compatibilizer, 12 parts PBS toughening agent, 3 parts modified CNC, 3 parts EMA-GMA (epoxy equivalent 285 g / eq, melt index 6 g / 10 min), 3 parts tributyl citrate, 10 parts double-shell phase change microcapsules, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1 part calcium stearate. The above components are put into a high-speed mixer and mixed at low speed for 3 minutes, then at high speed for 8 minutes to ensure uniform dispersion. Then, the mixture is melt-blended and extruded into granules using a twin-screw extruder. The temperature settings for each zone of the twin-screw extruder are: zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 185℃, and die head 180℃. The screw speed is 300 rpm and the feeding frequency is 15 Hz to obtain wood-plastic composite granules.

[0023] Step 6: The granules obtained in Step 5 are extruded into wood-plastic flooring profiles with a width of 300mm and a thickness of 20mm using an intelligent integrated continuous production system. Process parameters: extrusion temperature 180℃, die temperature 175℃, waste heat recovery module preheats the feed to 80℃, online laser thickness gauge sets the target thickness to 20.0mm, closed-loop control ensures thickness deviation is ±0.2mm, three-stage gradient cooling (water cooling 10℃ → air cooling 25℃ → natural cooling), traction speed 1.5 m / min. After molding, the material undergoes online cutting, grinding, and embossing. The finished product is then inspected and approved by a visual inspection system.

[0024] Performance testing The test was conducted according to GB / T 24508-2020 "Wood-Plastic Composite Flooring" and related standards, and the results are as follows:

[0025] Example 2 This embodiment provides a method for processing and manufacturing wood-plastic composite materials for use in logistics pallets. The specific steps are as follows: Step 1: Three-stage activation pretreatment of coconut shell fiber Coconut shell waste is crushed and sieved to obtain 120-mesh coconut shell fiber powder, which is then dried at 105℃ until the moisture content is ≤2%. 1) Bio-enzyme-assisted fiber debonding treatment: Place coconut shell fiber powder in a compound enzyme solution containing cellulase (1.2% of fiber mass), xylanase (0.5%), and pectinase (0.3%), pH 5.0, temperature 50℃, for 4 hours, wash with deionized water until neutral, and dry at 105℃. (2) Deep activation with alkaline solution: The enzyme-treated coconut shell fiber powder is placed in a 5% NaOH solution, soaked at 70°C for 2 hours, washed with deionized water until neutral, and dried at 105°C; (3) Coupling agent grafting modification: The alkali-activated coconut shell fiber powder and KH560 (4% of the fiber mass) were reacted in a mixed solvent of ethanol / water (volume ratio 1:1) at 80°C for 2 hours, filtered, washed and dried at 105°C to obtain activated coconut shell fiber powder.

[0026] Step 2: Synthesis of bifunctional grafted macromolecular compatibilizer Take 100 parts of PBAT resin, 15 parts of GMA, 8 parts of MAH and 0.6 parts of BPO, premix them evenly in a high-speed mixer, and then melt-graft granulate them at 180°C using a twin-screw extruder to obtain PBAT-g-(GMA-co-MAH) compatibilizer. The grafting rate of GMA was determined to be 5.2% and the grafting rate of MAH was 3.5% by acid-base titration.

[0027] Step 3: Preparation of modified nanocellulose whiskers Take 50g of microcrystalline cellulose, add 500mL of 64% sulfuric acid solution, hydrolyze at 50℃ for 60 minutes, centrifuge and wash until pH≈5, sonicate for 30 minutes, dialyze until pH≈6, freeze dry to obtain CNC (diameter 10~15 nm, length 200~300 nm), take 5g of CNC and disperse in 100mL of DMF, add 2g of TDI and 0.05g of dibutyltin dilaurate, react at 60℃ for 4 hours, centrifuge and wash, vacuum dry to obtain isocyanate modified CNC.

[0028] Step 4: Preparation of bilayer core-shell structured temperature phase change microcapsules 100g of methyl palmitate (phase transition temperature 32℃) was used as the core material. An emulsifier aqueous solution was added and emulsified at high speed. Melamine and formaldehyde (molar ratio 1:3) were added, and the pH was adjusted to 4.0. The reaction was carried out at 75℃ for 2.5 hours to obtain MF-coated microcapsules. The MF-coated microcapsules were dispersed in an ethanol / water solution containing 5% KH570 and hydrolyzed and polycondensed at 60℃ for 2 hours. After centrifugation, washing, and vacuum drying, MF / PDMS double-shell microcapsules were obtained. The phase transition enthalpy was 152 J / g by DSC test, and the particle size D50 was measured to be 7.8 μm by laser particle size analyzer.

[0029] Step 5: Melt blending and granulation Weigh the following components in the indicated weight proportions: 40 parts activated coconut shell fiber powder, 35 parts PBAT resin, 15 parts PLA resin (50 parts total for biodegradable resin matrix), 10 parts PBAT-g-(GMA-co-MAH) compatibilizer, 15 parts PBS toughening agent, 3 parts modified CNC, 3 parts EMA-GMA (epoxy equivalent 285 g / eq, melt index 6 g / 10min), 3 parts tributyl citrate, 8 parts double-shell phase change microcapsules, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1 part calcium stearate.

[0030] The above components are put into a high-speed mixer and mixed at low speed for 3 minutes, then at high speed for 8 minutes to ensure uniform dispersion. Then, the mixture is melt-blended and extruded into granules using a twin-screw extruder. The temperature settings for each zone of the twin-screw extruder are: zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 185℃, and die head 180℃. The screw speed is 300 rpm and the feeding frequency is 15 Hz to obtain wood-plastic composite granules.

[0031] Step 6: Intelligent integrated continuous forming process The granules obtained in step 5 are injection molded into logistics pallets (1200mm×1000mm×150mm, wall thickness 5mm) through an intelligent integrated continuous production system. The injection molding process parameters are: barrel temperature 185℃, mold temperature 60℃, injection pressure 80 MPa, holding pressure 60 MPa, holding time 8s, cooling time 30s, waste heat recovery module preheats the feed to 80℃, online pressure monitoring automatically adjusts the injection parameters, and after molding, the finished product is obtained after deburring, trimming and inspection.

[0032] Performance testing The tests were conducted according to GB / T 15234-1994 "Plastic Flat Pallets" and related standards, and the results are as follows:

[0033] Application Testing: The pallet was placed in a high-temperature and high-humidity environment (average daily temperature 32℃, relative humidity 85%) for continuous use for 8 months. Visual inspection showed no cracking, warping, or delamination. Static and dynamic load performance met industry standard requirements and outperformed traditional wooden pallets and injection-molded plastic pallets.

[0034] Comparative Example 1 This comparative example provides a method for processing and manufacturing wood-plastic composite materials. The difference from Example 1 is that the coconut shell fibers are only subjected to conventional alkali treatment, without enzyme treatment or silane grafting. The specific steps are as follows: Step 1: Conventional alkali treatment of coconut shell fiber Coconut shell waste was crushed and sieved to obtain 120-mesh coconut shell fiber powder. It was dried at 105℃ until the moisture content was ≤2%. The coconut shell fiber powder was placed in a 5% NaOH solution and soaked at 70℃ for 2 hours. It was washed with deionized water until neutral and dried at 105℃ to obtain alkali-treated coconut shell fiber powder (without enzyme treatment or coupling agent grafting modification).

[0035] Step 2: Synthesis of bifunctional grafted macromolecular compatibilizer Take 100 parts of PLA resin, 15 parts of GMA, 8 parts of MAH and 0.6 parts of BPO, premix them evenly in a high-speed mixer, and then melt-graft granulate them at 180°C using a twin-screw extruder to obtain PLA-g-(GMA-co-MAH) compatibilizer.

[0036] Step 3: Preparation of modified nanocellulose whiskers Take 50g of microcrystalline cellulose, add 500mL of 64% sulfuric acid solution, hydrolyze at 50℃ for 60 minutes, centrifuge and wash until pH≈5, sonicate and disperse for 30 minutes, dialyze until pH≈6, freeze dry to obtain CNC, take 5g of CNC and disperse in 100mL of DMF, add 2g of TDI and 0.05g of dibutyltin dilaurate, react at 60℃ for 4 hours, centrifuge and wash, vacuum dry to obtain isocyanate modified CNC.

[0037] Step 4: Preparation of bilayer core-shell structured temperature phase change microcapsules 100g of n-eicosane was used as the core material. An emulsifier aqueous solution was added and emulsified at high speed. Melamine and formaldehyde (molar ratio 1:3) were added, and the pH was adjusted to 4.0. The reaction was carried out at 75℃ for 2.5 hours to obtain MF-coated microcapsules. The microcapsules were dispersed in an ethanol / water solution containing 5% KH570 and hydrolyzed and polycondensed at 60℃ for 2 hours. After centrifugation and washing, the microcapsules were vacuum dried to obtain MF / PDMS double-shell microcapsules.

[0038] Step 5: Melt blending and granulation Weigh the following components in the indicated weight proportions: 35 parts alkali-treated coconut shell fiber powder, 40 parts PLA resin, 8 parts PLA-g-(GMA-co-MAH) compatibilizer, 12 parts PBS toughening agent, 3 parts modified CNC, 3 parts EMA-GMA, 3 parts tributyl citrate, 10 parts double-shell phase change microcapsules, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1 part calcium stearate.

[0039] The above components were added to a high-speed mixer and mixed evenly. Then, the mixture was melt-blended and extruded into granules using a twin-screw extruder. The temperatures of each zone of the extruder were set as follows: Zone 1 160℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and Die Head 180℃. The screw speed was 300 rpm, resulting in wood-plastic composite granules.

[0040] Step 6: Intelligent integrated continuous forming process The granules are extruded into wood-plastic flooring profiles with a width of 300mm and a thickness of 20mm through an intelligent integrated continuous production system. The process parameters are: extrusion temperature 180℃, die temperature 175℃, preheating feeding through a waste heat recovery module, online laser thickness measurement closed-loop control, three-stage gradient cooling, and after molding, the finished product is obtained by cutting, grinding and embossing.

[0041] Performance testing The same testing method was used as in Example 1, and the test results are as follows:

[0042] SEM observation of the fracture surface revealed a large number of fibers pulled out. The fiber surface was smooth and without resin adhesion, indicating extremely poor interfacial bonding. This suggests that the coconut shell fibers that were not fully activated could not form an effective interfacial bond with the matrix.

[0043] Comparative Example 2 This comparative example provides a method for processing and manufacturing wood-plastic composite materials. The difference from Example 1 is that it does not use the PLA-g-(GMA-co-MAH) bifunctional compatibilizer, but instead uses an equal amount of maleic anhydride-grafted PLA (PLA-g-MAH) as the compatibilizer. The specific steps are as follows: Step 1: Three-stage activation pretreatment of coconut shell fiber Coconut shell waste was crushed and sieved to obtain 120-mesh coconut shell fiber powder, dried at 105℃, and subjected to bio-enzyme-assisted defiberization treatment (compound enzyme solution, pH 5.0, 50℃, 4h), deep activation with alkali solution (5% NaOH, 70℃, 2h), and grafting modification with coupling agent (KH560 4%, 80℃, 2h) to obtain activated coconut shell fiber powder.

[0044] Step 2: Use a monofunctional compatibilizer This comparative example does not use the self-made PLA-g-(GMA-co-MAH) bifunctional compatibilizer from Example 1, but instead uses an equal amount of maleic anhydride grafted onto PLA.

[0045] Step 3: Preparation of modified nanocellulose whiskers Take 50g of microcrystalline cellulose, hydrolyze it with 64% sulfuric acid, centrifuge and wash it, ultrasonically disperse it, dialyze it, freeze dry it to obtain CNC, and then modify it with isocyanate.

[0046] Step 4: Preparation of bilayer core-shell structured temperature phase change microcapsules MF / PDMS bilayer shell microcapsules were prepared using n-eicosane as the core material.

[0047] Step 5: Melt blending and granulation Weigh the following components in the indicated weight proportions: 35 parts activated coconut shell fiber powder, 40 parts PLA resin, 8 parts PLA-g-MAH compatibilizer (replacing the bifunctional compatibilizer in Example 1), 12 parts PBS toughening agent, 3 parts modified CNC, 3 parts EMA-GMA, 3 parts tributyl citrate, 10 parts double-shell phase change microcapsules, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1 part calcium stearate.

[0048] The above components are put into a high-speed mixer and mixed evenly. Then, the mixture is melt-blended and extruded into granules through a twin-screw extruder. The temperature of each zone of the twin-screw extruder is set as follows: zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 185℃, and die head 180℃. The screw speed is 300 rpm to obtain wood-plastic composite granules.

[0049] Step 6: Intelligent integrated continuous forming process The granules are extruded into wood-plastic flooring profiles through an intelligent integrated continuous production system to obtain the finished product.

[0050] Performance testing The same detection method was used as in Example 1, and the results are as follows:

[0051] All performance characteristics were lower than those of Example 1, with elongation at break decreasing by 33% and impact strength decreasing by 26%. This indicates that the compatibilizing effect of the bifunctional compatibilizer (GMA+MAH) is significantly better than that of the monofunctional compatibilizer (MAH only), and the dual chemical bonding network is crucial for improving interfacial performance.

[0052] Comparative Example 3 This comparative example provides a method for processing and manufacturing wood-plastic composite materials, which differs from Example 1 in that modified nanocellulose whiskers are not added. The specific steps are as follows: Step 1: Three-stage activation pretreatment of coconut shell fiber Coconut shell waste is crushed and sieved to obtain 120-mesh coconut shell fiber powder. It is then subjected to bio-enzyme-assisted defiberization treatment, deep alkaline activation, and coupling agent grafting modification to obtain activated coconut shell fiber powder.

[0053] Step 2: Synthesis of bifunctional grafted macromolecular compatibilizer Take 100 parts of PLA resin, 15 parts of GMA, 8 parts of MAH, and 0.6 parts of BPO, and prepare PLA-g-(GMA-co-MAH) compatibilizer by melt grafting.

[0054] Step 3: Preparation of bilayer core-shell structured temperature phase change microcapsules MF / PDMS bilayer shell microcapsules were prepared using n-eicosane as the core material.

[0055] Step 4: Melt blending and granulation Weigh the following components in the indicated weight proportions: 35 parts activated coconut shell fiber powder, 40 parts PLA resin, 8 parts PLA-g-(GMA-co-MAH) compatibilizer, 12 parts PBS toughening agent, 0 parts modified CNC (not added), 3 parts EMA-GMA, 3 parts tributyl citrate, 10 parts double-shell phase change microcapsules, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1 part calcium stearate.

[0056] The above components are put into a high-speed mixer and mixed evenly. Then, the mixture is melt-blended and extruded into granules through a twin-screw extruder. The temperature of each zone of the twin-screw extruder is set as follows: zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 185℃, and die head 180℃. The screw speed of the twin-screw extruder is 300 rpm, and wood-plastic composite granules are obtained.

[0057] Step 5: Intelligent integrated continuous forming process The granules are extruded into wood-plastic flooring profiles through an intelligent integrated continuous production system to obtain the finished product.

[0058] Performance testing: The same detection method was used as in Example 1, and the results are as follows:

[0059] Compared to Example 1, the tensile strength decreased by 13%, the flexural strength decreased by 17%, and the impact strength decreased by 17%, indicating that the multi-scale reinforcement effect of nanocellulose whiskers is significant. Through chemical bonding and embedding into the interfacial transition region, it effectively improves the stress transfer efficiency.

[0060] Comparative Example 4 This comparative example provides a method for processing and manufacturing wood-plastic composite materials. The difference from Example 1 is that only MF single-layer shell microcapsules are prepared, without PDMS outer coating. The specific steps are as follows: Step 1: Three-stage activation pretreatment of coconut shell fiber Coconut shell waste is crushed and sieved to obtain 120-mesh coconut shell fiber powder. It is then subjected to bio-enzyme-assisted defiberization treatment, deep alkaline activation, and coupling agent grafting modification to obtain activated coconut shell fiber powder.

[0061] Step 2: Synthesis of bifunctional grafted macromolecular compatibilizer The process is exactly the same as step 2 in Example 1: preparing PLA-g-(GMA-co-MAH) compatibilizer.

[0062] Step 3: Preparation of modified cellulose nanofibers The procedure is exactly the same as step 3 in Example 1: prepare isocyanate-modified CNC.

[0063] Step 4: Preparation of single-layer shell phase change microcapsules 100g of n-eicosane (phase transition temperature 36.5℃) was used as the core material. An aqueous emulsifier solution was added and emulsified at high speed. Melamine and formaldehyde (molar ratio 1:3) were added, and the pH was adjusted to 4.0. The reaction was carried out at 75℃ for 2.5 hours to obtain MF-coated microcapsules. After centrifugation, washing, and vacuum drying, MF single-shell microcapsules (without KH570 hydrolysis and condensation to coat the PDMS outer layer) were obtained. DSC analysis showed a phase transition enthalpy of 165 J / g and a particle size D50 of 8.2 μm.

[0064] Step 5: Melt blending and granulation Weigh the following components in the indicated weight proportions: 35 parts activated coconut shell fiber powder, 40 parts PLA resin, 8 parts PLA-g-(GMA-co-MAH) compatibilizer, 12 parts PBS toughening agent, 3 parts modified CNC, 3 parts EMA-GMA, 3 parts tributyl citrate, 10 parts MF single-shell phase change microcapsules (replacing the double-shell microcapsules in Example 1), 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1 part calcium stearate.

[0065] The above components are put into a high-speed mixer and mixed evenly. Then, the mixture is melt-blended and extruded into granules through a twin-screw extruder. The temperature of each zone of the extruder is set as follows: Zone 1 160℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and Die Head 180℃. The screw speed is 300 rpm to obtain wood-plastic composite granules.

[0066] Step 6: Intelligent integrated continuous forming process The process is exactly the same as step 6 in Example 1: the granules are extruded into wood-plastic flooring profiles through an intelligent integrated continuous production system to obtain the finished product.

[0067] Performance testing: Initial performance testing was performed using the same testing method as in Example 1, and the results were similar to those in Example 1. Then, a thermal cycling durability test was conducted: the sample was placed at -20°C for 2 hours and then quickly transferred to 60°C for 2 hours. This was one cycle, and a total of 200 cycles were performed. After the cycle was completed, the flexural strength retention rate was tested.

[0068] SEM observation showed that in Comparative Example 4, a large number of microcapsules ruptured, the phase change core material leaked out, and voids and cracks appeared inside the matrix; while in Example 1, the microcapsule structure was intact and well bonded to the matrix, indicating that the outer layer of PDMS not only improved the shear resistance and fatigue resistance of the microcapsules, but also achieved chemical bonding with the matrix through surface reactive groups, which significantly improved long-term durability.

[0069] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0070] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for processing and manufacturing wood-plastic composite materials, characterized in that: Includes the following steps: Step 1: Using coconut shell fiber, coconut coir or short fiber as wood fiber raw material, perform three-stage activation pretreatment in sequence: bio-enzyme-assisted defiberization treatment, alkali deep activation and coupling agent grafting modification to obtain activated coconut shell fiber powder. Step 2: Synthesize a bifunctional grafted macromolecular compatibilizer containing both epoxy groups and acid anhydride groups; Step 3: Prepare nanocellulose whiskers and modify their surface with isocyanate to obtain modified nanocellulose whiskers; Step 4: Prepare temperature phase change microcapsules with a double core-shell structure having a melamine-formaldehyde resin inner layer and a polysiloxane outer layer; Step 5: The activated coconut shell fiber powder, biodegradable resin matrix, bifunctional grafted macromolecular compatibilizer, bio-based toughening agent polybutylene succinate, modified nanocellulose whiskers, epoxy functionalized compatibilizer, bio-based plasticizer, double-layer core-shell structure temperature phase change microcapsules and processing aids are mixed in parts by weight and then melt-blended and granulated to obtain wood-plastic composite material granules. Step 6: The wood-plastic composite material granules are processed by an intelligent integrated continuous production system to obtain the finished wood-plastic material.

2. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 1, the bio-enzyme-assisted defiberization treatment is as follows: coconut shell fiber powder is placed in a composite enzyme solution containing cellulase, xylanase, and pectinase at pH 4.5-5.5 and temperature 45-55℃ for 2-6 hours; the amount of cellulase used is 0.5%-2% of the fiber mass, the amount of xylanase used is 0.3%-1% of the fiber mass, and the amount of pectinase used is 0.2%-0.8% of the fiber mass.

3. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 1, the alkaline deep activation is as follows: the enzyme-treated coconut shell fiber powder is placed in a 3%~10% NaOH solution and soaked at 50~80℃ for 1~3 hours; the coupling agent grafting modification is as follows: the alkaline-activated coconut shell fiber powder is reacted with γ-glycidoxypropyltrimethoxysilane in an ethanol / water mixed solvent at 60~90℃ for 2~3 hours, and the amount of KH560 used is 2%~6% of the mass of coconut shell fiber.

4. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 2, the bifunctional grafted macromolecular compatibilizer is synthesized by using polylactic acid or polybutylene adipate terephthalate as the grafting skeleton, glycidyl methacrylate and maleic anhydride as grafting comonomers, and benzoyl peroxide as the initiator, through melt grafting. The mass fractions of each component are: 100 parts of polylactic acid or polybutylene adipate terephthalate, 10-20 parts of glycidyl methacrylate, 5-12 parts of maleic anhydride, and 0.3-1.0 parts of benzoyl peroxide. The grafting reaction temperature is 170-190℃.

5. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 3, the modified nanocellulose whiskers are prepared by placing microcrystalline cellulose or cotton linter pulp in a 64% sulfuric acid solution and hydrolyzing it at 45-55°C for 30-90 minutes. The mixture is then centrifuged, washed, ultrasonically dispersed, dialyzed, and freeze-dried to obtain nanocellulose whiskers with a diameter of 5-20 nm and a length of 100-500 nm. The surface isocyanate modification is performed by dispersing nanocellulose whiskers in N,N-dimethylformamide, adding toluene-2,4-diisocyanate and dibutyltin dilaurate catalyst, and reacting at 60°C for 4 hours.

6. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 4, the preparation method of the double-layer core-shell structure temperature phase change microcapsules is as follows: using an organic phase change material as the core material, firstly, a first shell material is formed by in-situ polymerization of melamine-formaldehyde resin, and then a second shell material of polysiloxane formed by the hydrolysis and condensation of γ-methacryloyloxypropyltrimethoxysilane is formed by sol-gel method on the surface of the first shell material; the phase change temperature of the phase change microcapsules is 25~45℃, the particle size is 2~15 μm, and the phase change enthalpy is ≥150 J / g.

7. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 5, the components are proportioned as follows by weight: 25-50 parts activated coconut shell fiber powder, 35-60 parts biodegradable resin matrix, 4-12 parts bifunctional grafted macromolecular compatibilizer, 5-20 parts bio-based toughening agent polybutylene succinate, 1-8 parts modified nanocellulose whiskers, 2-6 parts epoxy functionalized compatibilizer, 2-5 parts bio-based plasticizer, 5-15 parts double-shell phase change microcapsules, and 0.5-3 parts processing aid. The biodegradable resin matrix is ​​selected from one or more of polylactic acid, polybutylene adipate-terephthalate, and polybutylene succinate-terephthalate; the epoxy functionalized compatibilizer is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer or an ethylene-butyl acrylate-glycidyl methacrylate copolymer, with an epoxy equivalent of 200~500 g / eq and a melt index of 3~10 g / 10min.

8. The method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 5, the melt blending granulation is carried out using a twin-screw extruder with an extrusion temperature of 150~190℃ and a screw speed of 200~400 rpm.

9. A method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 6, the intelligent integrated continuous production system integrates a waste heat recovery and gradient preheating module, an online melt rheology monitoring module, an adaptive molding die module, and a gradient cooling and shaping module. The waste heat recovery and gradient preheating module utilizes the waste heat generated in the extrusion section to preheat the raw material in the feeding section, reducing overall energy consumption by more than 30% compared to the traditional segmented process. The adaptive molding die module is equipped with shape memory alloy adjustment elements, which, together with the online laser thickness measurement device, form a closed-loop control, controlling the product thickness deviation within ±1.5%.

10. A method for processing and manufacturing wood-plastic composite materials according to claim 1, characterized in that: In step 6, the molding process is selected from one of extrusion molding, injection molding, or thermoforming.

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