Mildew-proof wood-plastic board and preparation method thereof

Abstract

The application discloses a mildew-proof wood-plastic board and a preparation method thereof, and relates to the technical field of wood-plastic boards.The mildew-proof wood-plastic board is prepared from the following raw material components in parts by weight: 50-60 parts of mildew-proof modified wood powder, 35-50 parts of ultraviolet-resistant modified polypropylene, 2-5 parts of maleic anhydride grafted polypropylene, 5-8 parts of a toughening agent, 8-16 parts of modified filler, 1-2 parts of zinc stearate, 0.5-1 part of an antioxidant, 0.2-0.3 part of a hindered amine light stabilizer and 0.05-0.1 part of dicumyl peroxide; wherein the mildew-proof modified wood powder is obtained by modifying wood powder with a mildew-proof modifier; and the ultraviolet-resistant modified polypropylene is obtained by modifying polypropylene with 2-hydroxy-4-propenyloxybenzophenone.The mildew-proof wood-plastic board prepared by the application has long-term stable mildew-proof performance, and also has excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of wood-plastic composite board technology, specifically to an anti-mildew wood-plastic composite board and its preparation method. Background Technology

[0002] The core technological pain points of traditional wood-plastic composite boards (WPCs) are concentrated in three main aspects: First, wood flour, as the main plant fiber component, contains cellulose, hemicellulose, and a small amount of lignin, which easily absorb moisture. This provides abundant nutrients for molds (such as Aspergillus niger and Penicillium). In humid environments with temperatures of 25-35℃ and relative humidity >80%, mold easily grows on the surface and inside of the WPC, causing mold spots and discoloration. This not only damages the aesthetic appearance but also causes the degradation of wood flour fibers, leading to a decrease in the board's bending strength, impact resistance, and other mechanical properties, severely shortening the lifespan of the WPC. Second, thermoplastic plastics such as polypropylene are inherently susceptible to UV aging. The chemical properties are poor. When used outdoors for a long time, ultraviolet rays will cause the plastic molecular chains to break, leading to cracking and embrittlement of the board surface. The formation of cracks will further aggravate the penetration of moisture and the accumulation of dirt, forming a vicious cycle of "ultraviolet aging-cracking-mold". Most wood-plastic composite boards lose their anti-mold ability after 12 months of outdoor exposure. Thirdly, in order to balance cost and performance, traditional wood-plastic composite boards often use a single filler (such as pure glass fiber or pure calcium carbonate) or do not effectively modify the filler, resulting in poor compatibility between the filler and the plastic matrix. The mechanical properties of wood-plastic composite boards at low temperatures are relatively low and cannot meet the outdoor application requirements of cold northern regions.

[0003] In summary, to solve the above problems, this invention provides a mildew-resistant wood-plastic composite board, which not only has excellent mildew resistance but also excellent UV resistance and mechanical properties, and is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a mildew-resistant wood-plastic composite board and its preparation method to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A mildew-resistant wood-plastic composite board is prepared from the following raw material components in parts by weight: 50-60 parts of mildew-resistant modified wood powder, 35-50 parts of UV-resistant modified polypropylene, 2-5 parts of maleic anhydride grafted polypropylene, 5-8 parts of toughening agent, 8-16 parts of modified filler, 1-2 parts of zinc stearate, 0.5-1 part of antioxidant, 0.2-0.3 parts of hindered amine light stabilizer, and 0.05-0.1 parts of dicumyl peroxide; Among them, the mildew-resistant modified wood flour is obtained by modifying the wood flour with a mildew-resistant modifier; UV-resistant modified polypropylene is obtained by modifying polypropylene with 2-hydroxy-4-propenoxybenzophenone.

[0006] Furthermore, the preparation method of the mildew-resistant wood-plastic composite board includes the following steps: Step 1: Modify wood flour and filler separately using vinyl silane hydrolysate to obtain modified wood flour and modified filler; Step 2: Modify the wood flour with an anti-mildew modifier to obtain anti-mildew modified wood flour; Step 3: Modify polypropylene with 2-hydroxy-4-propenoxybenzophenone to obtain UV-resistant modified polypropylene; Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, toughening agent, modified filler, zinc stearate, antioxidant, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain mildew-resistant wood-plastic composite board.

[0007] Furthermore, the preparation method of the modified wood flour or modified filler is as follows: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 4-6. The mixture was stirred for 30-40 min to obtain a vinylsilane hydrolysate. (2) Immerse the wood powder or filler in the vinyl silane hydrolysate, sonicate for 10-30 min, filter, and vacuum dry to obtain modified wood powder or modified filler.

[0008] Furthermore, the volume ratio of the vinyltriethoxysilane to the aqueous ethanol solution is (0.04~0.08):1.

[0009] Furthermore, the filler is composed of glass fiber and nano-calcium carbonate mixed in a mass ratio of 1:1.

[0010] Further, the preparation method of the anti-mold modifier is as follows: under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one is added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution are added to it. The mixture is stirred and reacted at 0~5℃ for 4~12h. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier is obtained.

[0011] Furthermore, the ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution is 1g:(0.75~0.8)g:20mL:4mL.

[0012] Furthermore, the preparation method of the anti-mildew modified wood powder is as follows: under nitrogen protection, the anti-mildew modifier and modified wood powder are added to N,N-dimethylformamide, stirred and mixed evenly, and then azobisisobutyronitrile is added to it. The mixture is stirred and heated to 60~70℃ for 2~6 hours. After filtration, washing, and vacuum drying, the anti-mildew modified wood powder is obtained.

[0013] Furthermore, the ratio of the mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile is (0.01~0.03)g:1g:3mL:(0.0001~0.0003)g.

[0014] Furthermore, the method for preparing the UV-resistant modified polypropylene is as follows: polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant are added into a mixer and melt-blended at 170~180℃ and a rotation speed of 30~50r / min for 10~20min, then extruded and pelletized to obtain UV-resistant modified polypropylene.

[0015] Further, the mass ratio of the polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant is 1:(0.02~0.06):(0.0001~0.0003):(0.0001~0.0003).

[0016] Furthermore, the toughening agent is an ethylene-propylene-diolefin terpolymer or an ethylene-propylene binary copolymer.

[0017] Furthermore, the operating parameters of the twin-screw extruder are as follows: the main extruder speed is 100~200 r / min, the feeding speed is 50~80 r / min; the temperature of the feeding section is 150~160℃, the temperature of the melting section is 170~180℃, the temperature of the homogenization section is 165~175℃, and the temperature of the die head is 170~180℃.

[0018] Furthermore, the parameters for the extrusion molding are: extrusion pressure of 3~10MPa and extrusion time of 0.5~1.5min.

[0019] Furthermore, the mildew-resistant wood-plastic composite board prepared by the aforementioned method is a mildew-resistant wood-plastic composite board.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) Wood flour in wood-plastic composite boards is the main source of mold growth, and it is prone to mold growth when exposed to moisture and oxygen. Therefore, this invention obtains an anti-mold modifier by nucleophilically substituting the chlorine on 6-chloro-1,2-benzisothiazol-3(2H)-one and the amino group on 4-amino-1,1,1-trifluoro-3-buten-2-one. The anti-mold modifier is then used to modify the wood flour to enhance its anti-mold properties. The anti-mold modifier contains a benzisothiazolinone structure, unsaturated double bonds, and fluorinated segments. Among them, the benzisothiazolinone structure has a highly efficient antifungal and bactericidal effect. On the one hand, it can inactivate the -SH groups in the metabolic enzymes inside molds, thus hindering the normal metabolism of molds. On the other hand, it can react with peptidoglycans exposed on the mold cell wall, preventing them from transporting energy into the cell and hindering the normal physiological activities of mold cells. Furthermore, it can bind to the bases of mold DNA, altering the DNA structure within the fungus and inhibiting DNA transcription. Unsaturated double bonds can participate in the modification treatment of modified wood flour, thereby giving the wood flour stable and excellent antifungal properties while preventing the loss of effective antifungal components. Fluorine-containing segments can endow wood flour with certain hydrophobic properties, preventing water penetration and also playing a role in antifungal activity to some extent.

[0021] (2) Polypropylene itself does not mold, but its resistance to ultraviolet aging is poor. As aging intensifies, its molecular chains break, leading to defects such as cracks in the wood-plastic composite board. These defects trap dirt and grime, and also facilitate moisture penetration, thus reducing the anti-mold performance of the wood-plastic composite board. Therefore, improving the anti-ultraviolet aging performance of polypropylene can, to some extent, enhance the overall anti-mold performance of the wood-plastic composite board. Based on this, in this invention, 2-hydroxy-4-propenoxybenzophenone is used to modify polypropylene to obtain UV-modified polypropylene containing a benzophenone structure. The benzophenone structure can significantly enhance the UV resistance of polypropylene, and the wood-plastic composite board processed with it has excellent UV aging resistance. Combined with anti-mold modified wood powder, it can achieve long-term effective anti-mold effect.

[0022] (3) Polypropylene-based wood-plastic composite boards have poor resistance to low-temperature brittleness. Therefore, this invention incorporates glass fiber into the raw material components to serve as a skeleton, bearing external loads and thus improving the impact toughness and creep resistance of the wood-plastic composite board. Considering that rigidity, hardness, and wear resistance are important properties of wood-plastic composite boards, nano-calcium carbonate is further added. By using both glass fiber and nano-calcium carbonate as fillers, the relevant mechanical properties of the wood-plastic composite board are enhanced synergistically. Furthermore, nano-calcium carbonate has UV shielding properties, which can synergistically improve the UV resistance of the wood-plastic composite board. After modification with vinyltriethoxysilane, the compatibility between the filler and polypropylene is enhanced, promoting filler dispersion. Simultaneously, under the action of dicumyl peroxide, the modified filler can graft with polypropylene, further improving the interfacial bonding strength between the filler and polypropylene, resulting in a better overall modification effect on the comprehensive performance of the wood-plastic composite board.

[0023] (4) The UV-resistant modified polypropylene containing benzophenone structure prepared in this invention mainly plays a role in resisting ultraviolet radiation by absorbing ultraviolet rays. However, it cannot capture free radicals generated by photo-oxidation. Therefore, as the duration of action increases, the benzophenone structure of the UV-resistant modified polypropylene will degrade, that is, the UV resistance will gradually weaken. Therefore, this invention adds a hindered amine light stabilizer, which can capture free radicals and form a stable substance, that is, hinder the degradation of benzophenone and prolong the duration of action of the UV-resistant modified polypropylene. The two form an "absorption-capture dual ultraviolet protection system", which not only enhances the UV resistance of wood-plastic composite board, but also prolongs its UV resistance life.

[0024] (5) In this invention, maleic anhydride grafted polypropylene is added to promote compatibility of the components; toughening agent is added to synergistically modify the filler to improve the relevant mechanical properties of wood-plastic composite board; zinc stearate is added as a dispersant to promote the dispersion of anti-mildew modified wood powder and modified filler; antioxidant is added to avoid thermal oxidative degradation of polypropylene during melt blending; dicumyl peroxide is added to promote grafting to enhance the bonding of the components.

[0025] In summary, this invention modifies the main raw materials (polypropylene and wood flour) to prepare UV-resistant modified polypropylene and mildew-resistant modified wood flour, thereby giving the wood-plastic composite board (WPC) long-term stable mildew resistance. Simultaneously, based on considerations of the mechanical properties of WPC, the filler obtained by combining glass fiber and nano-calcium carbonate is modified to enhance the relevant mechanical properties of the WPC. Furthermore, a hindered amine light stabilizer is added to synergistically enhance the UV resistance of the WPC. Finally, auxiliary materials (maleic anhydride-grafted polypropylene, toughening agents, etc.) are introduced to further ensure the overall performance of the WPC. A high-strength WPC with long-term stable mildew resistance is thus obtained through comprehensive preparation. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the following quantities are by weight, and there are no special restrictions on the suppliers of all raw materials involved in this invention. Exemplary examples include: In the following examples, the wood flour has a particle size of 100 mesh; The glass fiber has a length of 3-5 mm and a diameter of 10 μm; the nano-calcium carbonate has a particle size of 60 nm; antioxidant 1010; hindered amine light stabilizer, CAS number 70624-18-9; all were purchased from Hubei Yongkuo Technology Co., Ltd. 6-Chloro-1,2-benzisothiazol-3(2H)-one, purity ≥96%, CAS No. 70-10-0; 4-amino-1,1,1-trifluoro-3-buten-2-one, purity ≥95%, CAS No. 184848-89-3; 2-hydroxy-4-propenoxybenzophenone, purity ≥97%, CAS No. 2549-87-3; all purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd. Polypropylene, grade 19T1020; maleic anhydride-grafted polypropylene, grade EP220R; both purchased from Dongguan Yili Plastics Co., Ltd. The ethylene-propylene-diolefin terpolymer, CAS No. 25038-36-2, with an ethylene content of 68%, was purchased from Shanghai Jiadeer Chemical Technology Co., Ltd.; all other raw materials were commercially available.

[0028] Preliminary preparations: Preparation of filler: Glass fiber and nano calcium carbonate are mixed in a mass ratio of 1:1 to obtain the filler; Example 1: A method for preparing a mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified filler: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and filler were immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified filler. Step 2: S21: Preparation of anti-mold modifier: Under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one was added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution were added. The mixture was stirred and reacted at 0℃ for 8 hours. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier was obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution was 1g:0.76g:20mL:4mL. S22: Preparation of mildew-resistant modified wood flour: Under nitrogen protection, mildew-resistant modifier and modified wood flour were added to N,N-dimethylformamide and stirred until homogeneous. Then, azobisisobutyronitrile was added, and the mixture was stirred and heated to 65℃ for 4 hours. After filtration, washing, and vacuum drying, mildew-resistant modified wood flour was obtained. The ratio of mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile was 0.02g:1g:3mL:0.0002g. Step 3: Preparation of UV-resistant modified polypropylene: Polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 are added to a mixer and melt-blended at 175°C and 40 r / min for 15 min. The mixture is then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 is 1:0.04:0.0002:0.0002. Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified filler, zinc stearate, antioxidant 1010, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain a mildew-resistant wood-plastic board with dimensions of 380mm (length) × 50mm (width) × 4mm (thickness). The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts of anti-mildew modified wood powder, 42 parts of UV-resistant modified polypropylene, 4 parts of maleic anhydride grafted polypropylene, 6.5 parts of ethylene-propylene-diene terpolymer, 12 parts of modified filler, 1.5 parts of zinc stearate, 0.8 parts of antioxidant 1010, 0.25 parts of hindered amine light stabilizer, and 0.08 parts of dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0029] Example 2: A method for preparing a mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified filler: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and filler were immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified filler. Step 2: S21: Preparation of anti-mold modifier: Under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one was added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution were added. The mixture was stirred and reacted at 0℃ for 8 hours. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier was obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution was 1g:0.76g:20mL:4mL. S22: Preparation of mildew-resistant modified wood flour: Under nitrogen protection, mildew-resistant modifier and modified wood flour were added to N,N-dimethylformamide and stirred until homogeneous. Then, azobisisobutyronitrile was added, and the mixture was stirred and heated to 65℃ for 4 hours. After filtration, washing, and vacuum drying, mildew-resistant modified wood flour was obtained. The ratio of mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile was 0.01g:1g:3mL:0.0001g. Step 3: Preparation of UV-resistant modified polypropylene: Polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 are added to a mixer and melt-blended at 175°C and 40 r / min for 15 min. The mixture is then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 is 1:0.02:0.0001:0.0002. Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified filler, zinc stearate, antioxidant 1010, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain a mildew-resistant wood-plastic board with dimensions of 380mm (length) × 50mm (width) × 4mm (thickness). The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts of anti-mildew modified wood powder, 42 parts of UV-resistant modified polypropylene, 4 parts of maleic anhydride grafted polypropylene, 6.5 parts of ethylene-propylene-diene terpolymer, 12 parts of modified filler, 1.5 parts of zinc stearate, 0.8 parts of antioxidant 1010, 0.25 parts of hindered amine light stabilizer, and 0.08 parts of dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0030] Example 3: A method for preparing a mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified filler: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and filler were immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified filler. Step 2: S21: Preparation of anti-mold modifier: Under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one was added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution were added. The mixture was stirred and reacted at 0℃ for 8 hours. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier was obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution was 1g:0.76g:20mL:4mL. S22: Preparation of mildew-resistant modified wood flour: Under nitrogen protection, mildew-resistant modifier and modified wood flour were added to N,N-dimethylformamide and stirred until homogeneous. Then, azobisisobutyronitrile was added, and the mixture was stirred and heated to 65℃ for 4 hours. After filtration, washing, and vacuum drying, mildew-resistant modified wood flour was obtained. The ratio of mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile was 0.03g:1g:3mL:0.0003g. Step 3: Preparation of UV-resistant modified polypropylene: Polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 are added to a mixer and melt-blended at 175°C and 40 r / min for 15 min. The mixture is then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 is 1:0.06:0.0003:0.0002. Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified filler, zinc stearate, antioxidant 1010, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain a mildew-resistant wood-plastic board with dimensions of 380mm (length) × 50mm (width) × 4mm (thickness). The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts of anti-mildew modified wood powder, 42 parts of UV-resistant modified polypropylene, 4 parts of maleic anhydride grafted polypropylene, 6.5 parts of ethylene-propylene-diene terpolymer, 12 parts of modified filler, 1.5 parts of zinc stearate, 0.8 parts of antioxidant 1010, 0.25 parts of hindered amine light stabilizer, and 0.08 parts of dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0031] A method for preparing mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified filler: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and filler were immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified filler. Step 2: Preparation of UV-resistant modified polypropylene: Polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 are added to a mixer and melt-blended at 175°C and 40 r / min for 15 min. The mixture is then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 is 1:0.04:0.0002:0.0002. Step 3: Modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified filler, zinc stearate, antioxidant 1010, hindered amine light stabilizer, and dicumyl peroxide are added to a twin-screw extruder according to the formula ratio, melt-blended, extruded into a die, extruded and cooled to obtain a 380mm (length) × 50mm (width) × 4mm (thickness) anti-mildew wood-plastic board; The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts modified wood flour, 42 parts UV-resistant modified polypropylene, 4 parts maleic anhydride grafted polypropylene, 6.5 parts ethylene-propylene-diene terpolymer, 12 parts modified filler, 1.5 parts zinc stearate, 0.8 parts antioxidant 1010, 0.25 parts hindered amine light stabilizer, and 0.08 parts dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0032] A method for preparing mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified filler: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and filler were immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified filler. Step 2: S21: Preparation of anti-mold modifier: Under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one was added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution were added. The mixture was stirred and reacted at 0℃ for 8 hours. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier was obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution was 1g:0.76g:20mL:4mL. S22: Preparation of mildew-resistant modified wood flour: Under nitrogen protection, mildew-resistant modifier and modified wood flour were added to N,N-dimethylformamide and stirred until homogeneous. Then, azobisisobutyronitrile was added, and the mixture was stirred and heated to 65℃ for 4 hours. After filtration, washing, and vacuum drying, mildew-resistant modified wood flour was obtained. The ratio of mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile was 0.02g:1g:3mL:0.0002g. Step 3: Add the mildew-resistant modified wood flour, polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified filler, zinc stearate, antioxidant 1010, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain a mildew-resistant wood-plastic board with dimensions of 380mm (length) × 50mm (width) × 4mm (thickness). The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts of anti-mildew modified wood powder, 42 parts of polypropylene, 4 parts of maleic anhydride grafted polypropylene, 6.5 parts of ethylene-propylene-diene terpolymer, 12 parts of modified filler, 1.5 parts of zinc stearate, 0.8 parts of antioxidant 1010, 0.25 parts of hindered amine light stabilizer, and 0.08 parts of dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0033] A method for preparing mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified calcium carbonate: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and calcium carbonate were respectively immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified calcium carbonate. Step 2: S21: Preparation of anti-mold modifier: Under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one was added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution were added. The mixture was stirred and reacted at 0℃ for 8 hours. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier was obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution was 1g:0.76g:20mL:4mL. S22: Preparation of mildew-resistant modified wood flour: Under nitrogen protection, mildew-resistant modifier and modified wood flour were added to N,N-dimethylformamide and stirred until homogeneous. Then, azobisisobutyronitrile was added, and the mixture was stirred and heated to 65℃ for 4 hours. After filtration, washing, and vacuum drying, mildew-resistant modified wood flour was obtained. The ratio of mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile was 0.02g:1g:3mL:0.0002g. Step 3: Preparation of UV-resistant modified polypropylene: Polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 are added to a mixer and melt-blended at 175°C and 40 r / min for 15 min. The mixture is then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 is 1:0.04:0.0002:0.0002. Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified calcium carbonate, zinc stearate, antioxidant 1010, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain a mildew-resistant wood-plastic board with dimensions of 380mm (length) × 50mm (width) × 4mm (thickness). The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts of anti-mildew modified wood powder, 42 parts of UV-resistant modified polypropylene, 4 parts of maleic anhydride grafted polypropylene, 6.5 parts of ethylene-propylene-diene terpolymer, 12 parts of modified calcium carbonate, 1.5 parts of zinc stearate, 0.8 parts of antioxidant 1010, 0.25 parts of hindered amine light stabilizer, and 0.08 parts of dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0034] A method for preparing mildew-resistant wood-plastic composite board: Step 1: Preparation of modified wood flour and modified filler: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 5. The mixture was stirred for 35 min to obtain a vinylsilane hydrolysate. The volume ratio of vinyltriethoxysilane to aqueous ethanol solution was 0.06:1. (2) Wood flour and filler were immersed in the vinylsilane hydrolysate, ultrasonically treated for 20 min, filtered, and vacuum dried to obtain modified wood flour and modified filler. Step 2: S21: Preparation of anti-mold modifier: Under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one was added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution were added. The mixture was stirred and reacted at 0℃ for 8 hours. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier was obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution was 1g:0.76g:20mL:4mL. S22: Preparation of mildew-resistant modified wood flour: Under nitrogen protection, mildew-resistant modifier and modified wood flour were added to N,N-dimethylformamide and stirred until homogeneous. Then, azobisisobutyronitrile was added, and the mixture was stirred and heated to 65℃ for 4 hours. After filtration, washing, and vacuum drying, mildew-resistant modified wood flour was obtained. The ratio of mildew-resistant modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile was 0.02g:1g:3mL:0.0002g. Step 3: Preparation of UV-resistant modified polypropylene: Polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 are added to a mixer and melt-blended at 175°C and 40 r / min for 15 min. The mixture is then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant 1010 is 1:0.04:0.0002:0.0002. Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, ethylene-propylene-diolefin terpolymer, modified filler, zinc stearate, antioxidant 1010, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, the mixture is extruded into a die, extruded and cooled to obtain a mildew-resistant wood-plastic board with dimensions of 380mm (length) × 50mm (width) × 4mm (thickness). The anti-mildew wood-plastic composite board is prepared from the following raw material components in parts by weight: 55 parts of anti-mildew modified wood powder, 42 parts of UV-resistant modified polypropylene, 4 parts of maleic anhydride grafted polypropylene, 6.5 parts of ethylene-propylene-diene terpolymer, 12 parts of modified filler, 1.5 parts of zinc stearate, 0.8 parts of antioxidant 1010, and 0.08 parts of dicumyl peroxide; The operating parameters of the twin-screw extruder are as follows: main extruder speed is 150 r / min, feeding speed is 60 r / min; feeding section temperature is 155℃, melting section temperature is 175℃, homogenization section temperature is 170℃, and die head temperature is 175℃. The parameters for extrusion molding are: extrusion pressure of 5 MPa and extrusion time of 1 min.

[0035] Performance testing: The anti-mildew wood-plastic composite boards prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to mechanical property tests, anti-mildew performance tests, and UV resistance tests. The specific test methods are as follows: 1. Mechanical performance test: Mechanical performance test shall be conducted in accordance with GB / T 29418-2023 standard; (1) Place the anti-mildew wood-plastic board in an environment of 0℃ and keep it warm for 24h. Take it out and use the three-point bending method with midpoint loading to test the bending performance of the anti-mildew wood-plastic board. The loading speed is 32.7mm / min and the test span is 280mm. Measure its bending strength; (2) Place the anti-mildew wood-plastic board in an environment of 0℃ and keep it warm for 24h. Take it out and use the drop hammer impact tester to test the impact resistance of the anti-mildew wood-plastic board. The drop hammer height is 700mm, the drop hammer head radius is 30mm, and the drop hammer mass is 1000g. If it is not damaged in 6 out of 10 tests, it is qualified; 2. Anti-mildew performance test: The anti-mildew performance test was conducted according to GB / T 35469-2017. The anti-mildew wood-plastic board was cut into samples of 50mm×50mm×4mm, and then placed in an environment of 121℃ and 50kPa for high-pressure steam sterilization for 20min. After cooling, the prepared Aspergillus niger spore solution was inoculated onto the sample and cultured at 30℃ and 85% relative humidity for 28d. The sample was then removed, and the mold growth on the sample surface was observed. The samples were graded according to the area of ​​mold growth. 3. UV resistance test: UV resistance test was conducted according to GB / T 29365-2012 standard; a Type I UVA-340 fluorescent UV lamp was used, with a power of 0.89W / m². 2 The irradiation was applied to a 50mm×50mm×4mm sample of anti-mildew wood-plastic composite board at 60℃ and 50% relative humidity for 8 hours, followed by a 4-hour irradiation treatment at 50℃ and 50% relative humidity. This was repeated as one cycle. After 100 cycles, the anti-mildew performance was tested.

[0036] The results of the above tests are shown in Table 1 below: Table 1

[0037] Results Analysis: The data in Table 1 above show that: Comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that the anti-mildew modification of wood flour can significantly improve the anti-mildew performance of wood-plastic composite board, and the UV-resistant modification of polypropylene can also significantly improve the UV resistance of wood-plastic composite board, but neither of them directly affects the mechanical properties of wood-plastic composite board. As can be seen from the comparative examples and Comparative Example 3, when calcium carbonate is used as the filler alone, the bending strength and impact resistance of the wood-plastic composite board are reduced at low temperatures. Comparative examples and Comparative Example 4 show that without the addition of hindered amine light stabilizers, the UV resistance of wood-plastic composite boards is significantly reduced.

[0038] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A mildew-resistant wood-plastic composite board, characterized in that: It is prepared from the following raw material components in parts by weight: 50-60 parts of mildew-resistant modified wood flour, 35-50 parts of UV-resistant modified polypropylene, 2-5 parts of maleic anhydride-grafted polypropylene, 5-8 parts of toughening agent, 8-16 parts of modified filler, 1-2 parts of zinc stearate, 0.5-1 part of antioxidant, 0.2-0.3 parts of hindered amine light stabilizer, and 0.05-0.1 parts of dicumyl peroxide; Among them, the mildew-resistant modified wood flour is obtained by modifying the wood flour with a mildew-resistant modifier; UV-resistant modified polypropylene is obtained by modifying polypropylene with 2-hydroxy-4-propenoxybenzophenone.

2. The method for preparing a mildew-resistant wood-plastic composite board according to claim 1, characterized in that: Includes the following steps: Step 1: Modify wood flour and filler separately using vinyl silane hydrolysate to obtain modified wood flour and modified filler; Step 2: Modify the wood flour with an anti-mildew modifier to obtain anti-mildew modified wood flour; Step 3: Modify polypropylene with 2-hydroxy-4-propenoxybenzophenone to obtain UV-resistant modified polypropylene; Step 4: Add the mildew-resistant modified wood flour, UV-resistant modified polypropylene, maleic anhydride grafted polypropylene, toughening agent, modified filler, zinc stearate, antioxidant, hindered amine light stabilizer, and dicumyl peroxide into a twin-screw extruder according to the formula ratio. After melt blending, extrude into a die, extrude to form, and cool to obtain mildew-resistant wood-plastic composite board.

3. The method for preparing a mildew-resistant wood-plastic composite board according to claim 2, characterized in that: The method for preparing the modified wood flour or modified filler is as follows: (1) Under nitrogen protection, vinyltriethoxysilane was added to a 75wt% aqueous ethanol solution, and acetic acid was added to adjust the pH to 4-6. The mixture was stirred for 30-40 min to obtain a vinylsilane hydrolysate. (2) Immerse the wood powder or filler in the vinylsilane hydrolysate, sonicate for 10-30 min, filter, and vacuum dry to obtain modified wood powder or modified filler; The volume ratio of vinyltriethoxysilane to aqueous ethanol solution is (0.04~0.08):

1. The filler is composed of glass fiber and nano-calcium carbonate mixed in a mass ratio of 1:

1.

4. The method for preparing a mildew-resistant wood-plastic composite board according to claim 2, characterized in that: The method for preparing the anti-mold modifier is as follows: under nitrogen protection, 6-chloro-1,2-benzisothiazol-3(2H)-one is added to N,N-dimethylformamide and stirred to dissolve. Then, 4-amino-1,1,1-trifluoro-3-buten-2-one and 10wt% sodium hydroxide aqueous solution are added to the mixture. The mixture is stirred and reacted at 0~5℃ for 4~12h. After vacuum distillation, washing, and vacuum drying, the anti-mold modifier is obtained. The ratio of 6-chloro-1,2-benzisothiazol-3(2H)-one, 4-amino-1,1,1-trifluoro-3-buten-2-one, N,N-dimethylformamide, and sodium hydroxide aqueous solution is 1g:(0.75~0.8)g:20mL:4mL.

5. The method for preparing a mildew-resistant wood-plastic composite board according to claim 2, characterized in that: The method for preparing the anti-mildew modified wood powder is as follows: under nitrogen protection, the anti-mildew modifier and modified wood powder are added to N,N-dimethylformamide, stirred and mixed evenly, and then azobisisobutyronitrile is added to it. The mixture is stirred and heated to 60~70℃ for 2~6 hours. After filtration, washing, and vacuum drying, the anti-mildew modified wood powder is obtained. The ratio of the anti-mildew modifier, modified wood flour, N,N-dimethylformamide, and azobisisobutyronitrile is (0.01~0.03)g:1g:3mL:(0.0001~0.0003)g.

6. The method for preparing a mildew-resistant wood-plastic composite board according to claim 2, characterized in that: The method for preparing the UV-resistant modified polypropylene is as follows: polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide and antioxidant are added into a mixer and melt-blended at 170~180℃ and a speed of 30~50r / min for 10~20min, then extruded and pelletized to obtain UV-resistant modified polypropylene. The mass ratio of polypropylene, 2-hydroxy-4-propenoxybenzophenone, dicumyl peroxide, and antioxidant is 1:(0.02~0.06):(0.0001~0.0003):(0.0001~0.0003).

7. The method for preparing a mildew-resistant wood-plastic composite board according to claim 2, characterized in that: The toughening agent is an ethylene-propylene-diolefin terpolymer or an ethylene-propylene binary copolymer.

8. The method for preparing a mildew-resistant wood-plastic composite board according to claim 2, characterized in that: The operating parameters of the twin-screw extruder are as follows: main machine speed is 100~200 r / min, feeding speed is 50~80 r / min; feeding section temperature is 150~160℃, melting section temperature is 170~180℃, homogenization section temperature is 165~175℃, and die head temperature is 170~180℃. The parameters for the extrusion molding are: extrusion pressure of 3~10MPa and extrusion time of 0.5~1.5min.

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