An antistatic co-extruded wood-plastic composite profile and its preparation method

Abstract

This invention discloses an antistatic co-extruded wood-plastic composite profile and its preparation method, belonging to the field of wood-plastic composite boards. The antistatic co-extruded wood-plastic composite profile includes a core layer and an antistatic layer; the core layer is covered with an antistatic layer. The antistatic layer comprises the following raw materials in parts by weight: 100 parts polyethylene, 30-40 parts modified graphite, 5-10 parts maleic anhydride-grafted polyethylene, and 3-5 parts antioxidant. The modified graphite surface is grafted with quaternary ammonium salt polyethylene glycol. The antistatic layer contains a large amount of graphite, which can reduce the surface resistivity of the profile, giving it a certain degree of antistatic properties. Furthermore, the graphite is modified to improve its dispersibility, solving problems such as decreased mechanical strength, brittleness, and slippage caused by excessive graphite addition, and improving interfacial bonding strength, thus maintaining the antistatic performance of the antistatic layer.

Description

Technical Field

[0001] This invention relates to the field of wood-plastic composite profiles, and particularly to an antistatic co-extruded wood-plastic composite profile and its preparation method. Background Technology

[0002] Wood-plastic composite (WPC) boards are made from wood fibers and plastics through high-temperature extrusion. The high plastic content, especially in co-extruded WPC boards where the surface coating contains over 90% plastic, makes WPC boards more resistant to decay and insects than solid wood boards. They are also less prone to water absorption, swelling, and cracking, and offer superior rigidity, creep resistance, and environmental friendliness compared to other plastic boards. The appearance and performance of WPC boards can be controlled and designed through different formulations, processes, and surface treatments. They can be used in numerous outdoor architectural and landscape applications, as well as for indoor flooring, walls, and ceilings. Co-extruded WPC boards, prepared through a co-extrusion process, not only possess the advantages of ordinary WPC boards but are also more wear-resistant, easier to clean and maintain, and offer richer colors and textures, providing greater design flexibility.

[0003] However, in practical applications, co-extruded wood-plastic composite (WPC) boards, due to their high surface plastic content, often experience peeling and charge accumulation during use due to friction. This static charge can cause electric shocks or even sparks if a sufficiently high voltage is generated. If flammable materials are present in the environment, this can lead to major fires and explosions. While static electricity generally doesn't cause direct harm, it can still cause electric shocks and attract dust, affecting the appearance of the product. Commercially available antistatic WPC boards primarily achieve this by adding antistatic agents. However, the antistatic properties of these boards are unstable, easily affected by the environment, and gradually deteriorate over time. To overcome these shortcomings, there is an urgent need to develop a co-extruded WPC composite profile with stable antistatic properties unaffected by the environment, along with its preparation method, thereby improving the safety performance of the profile and expanding its application range. Summary of the Invention

[0004] This invention provides an antistatic co-extruded wood-plastic composite profile and its preparation method, which can solve the problem of unstable antistatic properties in existing co-extruded wood-plastic boards.

[0005] In a first aspect, the present invention provides an antistatic co-extruded wood-plastic composite profile, comprising a core layer and an antistatic layer; wherein the core layer is covered with an antistatic layer.

[0006] The antistatic layer comprises the following raw materials in parts by weight:

[0007] 100 parts of polyethylene;

[0008] 30-40 parts modified graphite;

[0009] 5-10 parts of maleic anhydride-grafted polyethylene;

[0010] Antioxidant 3-5 parts;

[0011] The modified graphite surface is grafted with quaternary ammonium salt polyethylene glycol.

[0012] Preferably, the core material layer comprises the following raw materials in parts by weight: 100 parts wood flour, 50-60 parts polyethylene, 5-10 parts maleic anhydride-grafted polyethylene, 10-20 parts talc, and 1-3 parts lubricant.

[0013] Preferably, the mass ratio of the core layer to the antistatic layer is 100:(10-15).

[0014] More preferably, the polyethylene is high-density polyethylene with a degree of polymerization of 700 to 1000.

[0015] More preferably, the wood flour includes one or more combinations of poplar wood flour, eucalyptus wood flour, and bamboo wood flour; the particle size of the wood flour is 40 to 100 mesh.

[0016] More preferably, the lubricant includes one or more combinations of stearic acid, stearate, white oil, polyethylene wax, and lubricating powder.

[0017] By adopting the above technical solution, the antistatic co-extruded wood-plastic composite profile of the present invention has a core material layer containing a large amount of wood powder, which is an insulator and does not have antistatic properties. Therefore, an antistatic layer is added outside the core material layer, and a large amount of graphite is introduced into the antistatic layer. Then, through co-extrusion, the conductive graphite is uniformly dispersed on the surface of the wood-plastic composite profile, thereby reducing the surface resistivity of the profile and giving the profile a certain degree of antistatic properties.

[0018] In the antistatic layer of the present invention, in order to improve the bonding strength between the antistatic layer and the core material layer, maleic anhydride-grafted polyethylene is also added to the antistatic layer. The anhydride groups in the maleic anhydride can react and connect with the hydroxyl groups on the surface of the wood flour in the core material layer during the co-extrusion process, thereby helping to form a chemical bond bridge between the two layers. At the same time, the compatibility of the interface can be improved through molecular chain entanglement, thereby further reducing the flow difference between the antistatic layer and the core material layer.

[0019] To improve the antistatic properties of the profile, a large amount of graphite, far exceeding the typical amount of graphite added, is incorporated into the antistatic layer. This excessive graphite content leads to agglomeration of graphite particles due to van der Waals forces and π-π interactions between the graphite flakes. This agglomeration results in uneven distribution of graphite within the PE matrix, creating localized stress concentration points. Stress concentration accelerates crack initiation and propagation, significantly reducing the material's toughness. Furthermore, the high graphite content occupies a significant portion of the free volume of the PE matrix, further restricting the movement of polymer chains and decreasing the material's elongation at break. Moreover, the high graphite content also reduces the interfacial bonding strength between the graphite and polyethylene, disrupting the crystallization behavior of polyethylene. Simultaneously, while graphite, as a layered lubricant, readily forms a continuous lubricating film during friction, excessively high graphite content causes the film to cover the entire contact surface, drastically reducing the coefficient of friction and leading to slippage and other problems, thus lowering the interfacial bonding strength between the layers.

[0020] Therefore, the graphite used in this invention is modified graphite with quaternary ammonium polyethylene glycol (PEG) grafted onto its surface. The ether bonds of PEG weaken the intermolecular forces in polyethylene, improving chain segment mobility and enhancing the dispersibility of graphite within polyethylene. Furthermore, steric hindrance can interfere with graphite sheet slippage, reducing the likelihood of slippage. However, grafting only PEG can reduce conductivity and antistatic effect due to partially covering the conductive network of graphite. To further address this issue, the PEG is quaternized, utilizing cation migration to achieve ion-electron synergistic conductivity. The introduction of the quaternary ammonium salt further inhibits graphite agglomeration through electrostatic repulsion, improving dispersibility and enhancing interfacial bonding with polyethylene. This results in a structurally stable, high-performance, and well-maintained antistatic co-extruded wood-plastic composite profile.

[0021] Preferably, the raw materials for modified graphite include graphite, isocyanate and quaternary ammonium salt polyethylene glycol in a mass ratio of 1:(1.2-1.5):(2-2.6).

[0022] Preferably, the raw materials for quaternary ammonium salt polyethylene glycol include polyethylene glycol and quaternary ammonium salt in a mass ratio of 1:(6-10).

[0023] Preferably, the quaternary ammonium salt includes one or more combinations of 3-chloro-2-hydroxypropyltrimethylammonium chloride, glycidyltrimethylammonium chloride, 2-methacryloyloxyethyltrimethylammonium chloride, and acryloyloxyethyltrimethylammonium chloride; the molecular weight of the polyethylene glycol is 600 to 1500.

[0024] More preferably, the isocyanate includes one or more combinations of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.

[0025] More preferably, the graphite is powdered flake graphite with a particle size of 400 mesh to 1200 mesh.

[0026] Preferably, the modified graphite is prepared according to the following method:

[0027] Preparation of quaternary ammonium salt polyethylene glycol: Polyethylene glycol is added to water, the pH of the solution is adjusted to 10-11, the temperature is raised to 45-55℃, and the mixture is stirred and activated for 1-2 hours. Then, quaternary ammonium salt is added, the temperature is raised to 70-75℃, and the reaction is continued to be stirred for 5-7 hours. Finally, quaternary ammonium salt polyethylene glycol is obtained after neutralization, washing and dialysis.

[0028] Preparation of modified graphite: Graphite is dispersed in a solvent, isocyanate is added, and after stirring and dispersing, the temperature is raised to 70-80℃ and stirred and reacted under a nitrogen atmosphere for 12-15 hours. Then, quaternary ammonium salt polyethylene glycol is added and stirred and reacted for 8-10 hours. Finally, after washing and drying, modified graphite is obtained.

[0029] By adopting the above technical solution, in order to solve a series of problems caused by the large-scale introduction of graphite to enhance antistatic properties, such as increased material brittleness, interfacial bonding defects, and easy slippage, graphite is modified. Specifically, quaternary ammonium salt polyethylene glycol is first prepared, and then isocyanate is used as a bridging compound to graft quaternary ammonium salt polyethylene glycol onto the graphite surface.

[0030] The backbone of polyethylene glycol (PEG) consists of flexible ether bonds and methylene groups. While the ether bonds have low polarity, their helical conformation and segmental flexibility are significantly higher than those of polyethylene's linear structure. PEG segments grafted onto the graphite surface introduce additional free volume, reducing the tight packing of the PE matrix and thus decreasing van der Waals forces between molecular chains. This makes it easier for polyethylene segments to slip and rearrange under stress, thereby delaying brittle fracture. Furthermore, it improves the dispersibility of graphite within the polyethylene matrix, reducing stress concentration caused by agglomeration.

[0031] Furthermore, after polyethylene glycol segments are grafted onto the edges or surfaces of graphite sheets, their long chain structures insert into the interlayer spaces, increasing the interlayer spacing, disrupting the π-π stacking and slippage capabilities between layers, hindering continuous sliding between graphite sheets, thereby inhibiting the formation of a lubricating film and preventing excessive lubrication.

[0032] Simultaneously, polyethylene glycol (PEG) is subjected to quaternization treatment, grafting quaternary ammonium salt groups onto the ends of PEG segments. The permanent positive charge of these groups provides an ionic conductivity pathway, thereby mitigating the conductivity degradation caused by PEG. Furthermore, the cationic properties of the quaternary ammonium salts can further suppress sheet aggregation through electrostatic repulsion, improving graphite dispersibility. They can also strengthen interfacial bonding, reduce the continuity of the lubricating film, and thus further improve the performance of the antistatic layer.

[0033] Preferably, an outer surface layer is also coated on the outside of the antistatic layer;

[0034] The mass ratio of the core layer to the outer layer is 100:(8-12);

[0035] The outer layer comprises the following raw materials in parts by weight: 100 parts polyethylene, 5-10 parts pigment, 5-10 parts maleic anhydride-grafted polyethylene, 3-5 parts ultraviolet absorber, and 3-5 parts antioxidant.

[0036] More preferably, the antioxidant includes one or more combinations of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant BHT and antioxidant TNPP.

[0037] More preferably, the pigment includes one or more combinations of iron oxide red, iron oxide yellow, ultramarine, carbon black, titanium dioxide, phthalocyanine blue, and phthalocyanine green.

[0038] More preferably, the ultraviolet absorber includes one or more combinations of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, ultraviolet absorber UV-326, ultraviolet absorber UV-327, ultraviolet absorber UV-328 and ultraviolet absorber UV-531.

[0039] By adopting the above technical solution, since the antistatic layer is filled with a large amount of black graphite, which has a single color and a low coefficient of friction, an outer surface layer is set outside the antistatic layer. The outer surface layer is filled with a small amount of pigment, and the color can be adjusted in various ways. This not only makes the appearance of the profile more diverse and adjustable, but also increases the anti-slip properties of the co-extruded wood-plastic composite profile, preventing the antistatic layer from wearing out and failing. At the same time, ultraviolet absorbers are added to improve the light stability of the material, thereby enhancing the durability of the profile's antistatic performance.

[0040] Preferably, the raw material of the antistatic layer also includes 4 to 8 parts by weight of acetylated lignin; the raw material of acetylated lignin includes lignin and acetic anhydride in a mass ratio of 1:(2 to 4).

[0041] More preferably, acetylated lignin is prepared by the following method:

[0042] Lignin was added to pyridine and stirred to dissolve. Acetic anhydride was then added, and the mixture was stirred at 75–80 °C for 1–2 h. The mixture was then precipitated, washed, and dried to obtain acetylated lignin.

[0043] The addition of modified graphite can improve dispersibility to some extent and reduce material brittleness and slippage. However, when the antistatic layer is combined with the core material layer, the large amount of wood flour in the core material layer absorbs moisture and expands, which will lead to a decrease in dimensional stability. Furthermore, polyethylene glycol has strong hygroscopicity, and after modification with graphite, it will actually increase the probability of moisture absorption and expansion of the core material.

[0044] By employing the above technical solution, acetylated lignin possesses a large number of hydrophobic groups, which can significantly reduce the hydrophilicity of lignin. This hydrophobicity inhibits the penetration of moisture into the antistatic layer, reduces volume expansion and pore formation caused by moisture absorption, thereby improving overall density and reducing the possibility of moisture entering the core layer. Moreover, the uniform dispersion of acetylated lignin in the antistatic layer can effectively fill the pores between the polyethylene matrix and modified graphite, forming a dense network, thereby reducing moisture erosion.

[0045] Secondly, the present invention provides a method for preparing antistatic co-extruded wood-plastic composite profiles, comprising the following process steps:

[0046] S1. Weigh the raw materials of the antistatic layer according to the corresponding mass parts, stir and mix them at 60-80℃ for 10-20 minutes to obtain the antistatic layer mixture, and then obtain the antistatic layer masterbatch by melt plasticizing and extrusion granulation and drying.

[0047] S2. Weigh the raw materials for the outer surface layer according to the corresponding mass fractions, stir and mix them at 60-80℃ for 10-20 minutes to obtain the outer surface layer mixture, and then obtain the outer surface layer masterbatch by melt plasticizing and extrusion granulation and drying.

[0048] S3. Weigh the raw materials of the core layer according to the corresponding mass fractions, mix them evenly, and obtain the core layer masterbatch by melt extrusion and cooling crushing.

[0049] S4. The core material layer masterbatch is extruded through a mold to obtain the core material layer; the antistatic layer masterbatch and the outer layer masterbatch are co-extruded through a mold and coated on the surface of the core material layer to form the antistatic layer and the outer layer respectively. After embossing and polishing, the antistatic co-extruded wood-plastic composite profile is obtained.

[0050] Preferably, the melt plasticizing temperature in step S1 is 160–200°C, and the extrusion speed is 200–250 r / min.

[0051] Preferably, the melt plasticizing temperature in step S2 is 140–180°C and the extrusion speed is 200–250 r / min.

[0052] Preferably, the melt extrusion temperature in step S3 is 160–200°C, and the extrusion speed is 200–250 r / min.

[0053] Preferably, in step S4, the extrusion temperature is 180–200°C, the die temperature is 190–200°C, and the rotation speed is 200–250 r / min.

[0054] The beneficial effects of this invention are:

[0055] 1. The antistatic co-extruded wood-plastic composite profile of the present invention is a coated composite structure. An antistatic layer is added outside the core material layer, and a large amount of graphite is introduced into the antistatic layer, thereby reducing the surface resistivity of the profile and giving it a certain degree of antistatic properties. An outer surface layer can also be added, which allows for diverse and adjustable appearance colors of the profile, protects the antistatic layer, reduces wear, and extends its service life.

[0056] 2. The graphite in the antistatic layer of the present invention is modified graphite, and the surface of the modified graphite is grafted with quaternary ammonium salt polyethylene glycol, which can weaken the intermolecular forces of polyethylene, improve the chain segment mobility, improve the dispersibility of graphite, interfere with the sliding of graphite sheets by utilizing steric hindrance, and further inhibit graphite agglomeration by introducing quaternary ammonium salt, improve the interfacial bonding strength, and also achieve ion-electron synergistic conductivity by utilizing cation migration, thereby improving the problem of decreased antistatic properties caused by the introduction of polyethylene glycol.

[0057] 3. The antistatic layer of the present invention also contains acetylated lignin, which can improve the density of the antistatic layer and reduce moisture erosion, thereby obtaining a dimensionally stable antistatic co-extruded wood-plastic composite profile. Detailed Implementation

[0058] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0059] Preparation Example 1

[0060] Preparation Example 1-1: A modified graphite was prepared according to the following method:

[0061] Add 5g of polyethylene glycol 1000 to 200mL of water, adjust the pH of the solution to 11, raise the temperature to 50℃, stir and activate for 1h, then add 40g of 3-chloro-2-hydroxypropyltrimethylammonium chloride, raise the temperature to 70℃, continue stirring and reacting for 6h, and finally obtain quaternary ammonium salt polyethylene glycol after neutralization, washing and dialysis.

[0062] 10g of graphite (average particle size of 600 mesh) was dispersed in N,N-dimethylformamide, 14g of isocyanate was added, the mixture was stirred and dispersed, and the temperature was raised to 80℃. The mixture was stirred and reacted for 15 hours under a nitrogen atmosphere. Then, 24g of the quaternary ammonium salt polyethylene glycol obtained above was added, and the mixture was stirred and reacted for 8 hours. Finally, the modified graphite was obtained by washing and drying.

[0063] Preparation Example 1-2, a modified graphite, differs from Preparation Example 1-1 only in that the amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 30g.

[0064] Preparation Examples 1-3, a modified graphite, differs from Preparation Example 1-1 only in that the amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 50g.

[0065] Preparation Examples 1-4, a modified graphite, differs from Preparation Example 1-1 only in that the amount of isocyanate added is 12g and the amount of quaternary ammonium salt polyethylene glycol added is 20g.

[0066] Preparation Examples 1-5, a modified graphite, differ from Preparation Example 1-1 only in that the amount of isocyanate added is 15g and the amount of quaternary ammonium salt polyethylene glycol added is 26g.

[0067] Preparation Examples 1-6, a modified graphite, differs from Preparation Example 1-1 only in that the amount of quaternary ammonium salt polyethylene glycol added is 15g.

[0068] Preparation Examples 1-7, a modified graphite, differs from Preparation Example 1-1 only in that the amount of quaternary ammonium salt polyethylene glycol added is 30g.

[0069] Preparation Examples 1-8: A modified graphite was prepared according to the following method:

[0070] 10g of graphite (average particle size of 600 mesh) was dispersed in N,N-dimethylformamide, 14g of isocyanate was added, and after stirring and dispersing, the temperature was raised to 80℃ and stirred for 15 hours under a nitrogen atmosphere. Then 24g of polyethylene glycol 1000 was added and stirred for 8 hours. Finally, after washing and drying, modified graphite was obtained.

[0071] Preparation Example 2

[0072] Preparation Example 2-1: An acetylated lignin was prepared according to the following method:

[0073] 10g of lignin was added to 500mL of pyridine and stirred to dissolve. Then, 30g of acetic anhydride was added and the mixture was stirred at 80℃ for 2h. After precipitation, washing and drying, acetylated lignin was obtained.

[0074] Example

[0075] Example 1: An antistatic co-extruded wood-plastic composite profile was prepared according to the following process steps:

[0076] S1. Weigh 10 kg of polyethylene, 3.5 kg of modified graphite prepared in Example 1-1, 0.8 kg of maleic anhydride grafted polyethylene and 0.4 kg of antioxidant 1010, stir and mix at 70°C for 10 min to obtain antistatic layer mixture, then melt plasticize and extrude granulate at 160-200°C, and dry to obtain antistatic layer masterbatch;

[0077] S2. Weigh 10kg of wood flour, 5.5kg of polyethylene, 0.8kg of maleic anhydride-grafted polyethylene, 1.5kg of talc powder and 0.2kg of lubricant, mix them evenly, and then obtain the core layer masterbatch by melt extrusion and cooling crushing.

[0078] S3. The core material layer masterbatch is extruded through a die to obtain the core material layer; the antistatic layer masterbatch is co-extruded through a die to coat the surface of the core material layer, forming an antistatic layer, wherein the mass ratio of the core material layer to the antistatic layer is 100:12. After embossing and sanding, the antistatic co-extruded wood-plastic composite profile is obtained.

[0079] Examples 2 and 3 describe an antistatic co-extruded wood-plastic composite profile. The only difference between Example 1 and Example 2 is the adjustment of the raw material ratio for the antistatic layer, as shown in Table 1.

[0080] Table 1. Raw material ratio table for antistatic layers in Examples 1-3

[0081]

[0082] In both Examples 2 and 3, the modified graphite prepared in Example 1-1 was used.

[0083] Examples 4 and 5 describe an antistatic co-extruded wood-plastic composite profile, differing from Example 1 only in that the raw material ratio of the core layer is adjusted, as shown in Table 2.

[0084] Table 2. Raw material ratio table for the core layer in Examples 1, 4 and 5

[0085]

[0086] Example 6: An antistatic co-extruded wood-plastic composite profile, which differs from Example 1 only in that the mass ratio of the core layer to the antistatic layer is 100:10.

[0087] Example 7: An antistatic co-extruded wood-plastic composite profile, which differs from Example 1 only in that the mass ratio of the core layer to the antistatic layer is 100:12.

[0088] Example 8, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Example 1-2.

[0089] Example 9, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Example 1-3.

[0090] Example 10, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Example 1-4.

[0091] Example 11, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Example 1-5.

[0092] Example 12, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Examples 1-6.

[0093] Example 13, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Examples 1-7.

[0094] Example 14, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that, in step S1, 0.6 kg of acetylated lignin prepared in Preparation Example 2-1 is added to the raw material of the antistatic layer.

[0095] Example 15, an antistatic co-extruded wood-plastic composite profile, differs from Example 14 only in that the amount of acetylated lignin added in Preparation Example 2-1 is 0.4 kg.

[0096] Example 16, an antistatic co-extruded wood-plastic composite profile, differs from Example 14 only in that the amount of acetylated lignin added in Preparation Example 2-1 is 0.8 kg.

[0097] Example 17, an antistatic co-extruded wood-plastic composite profile, differs from Example 14 only in that the amount of acetylated lignin added in Preparation Example 2-1 is 0.2 kg.

[0098] Example 18, an antistatic co-extruded wood-plastic composite profile, differs from Example 14 only in that the amount of acetylated lignin added in Preparation Example 2-1 is 1 kg.

[0099] Example 19, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that an outer surface layer is coated outside the antistatic layer, and is prepared according to the following process steps:

[0100] S1. Weigh 10 kg of polyethylene, 3.5 kg of modified graphite prepared in Example 1-1, 0.8 kg of maleic anhydride grafted polyethylene and 0.4 kg of antioxidant 1010, stir and mix at 70°C for 10 min to obtain antistatic layer mixture, then melt plasticize and extrude granulate at 160-200°C, and dry to obtain antistatic layer masterbatch;

[0101] S2. Weigh 10 kg of polyethylene, 0.7 kg of titanium dioxide, 0.8 kg of maleic anhydride-grafted polyethylene, 0.4 kg of ultraviolet absorber UV-326 and 0.4 kg of antioxidant 1010, stir and mix at 60℃ for 10 min to obtain the outer layer mixture, then melt plasticize and extrude granulate at 140~180℃, and dry to obtain the outer layer masterbatch;

[0102] S3. Weigh 10kg of wood flour, 5.5kg of polyethylene, 0.8kg of maleic anhydride-grafted polyethylene, 1.5kg of talc powder and 0.2kg of lubricant, mix them evenly, and then obtain the core layer masterbatch by melt extrusion and cooling crushing.

[0103] S4. The core material layer masterbatch is extruded through a die to obtain the core material layer; the antistatic layer masterbatch and the outer layer masterbatch are co-extruded through a die and coated on the surface of the core material layer to form the antistatic layer and the outer layer, respectively, wherein the mass ratio of the core material layer, the antistatic layer and the outer layer is 100:12:10. After embossing and sanding, the antistatic co-extruded wood-plastic composite profile is obtained.

[0104] Comparative Example

[0105] Comparative Example 1, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the amount of modified graphite added in Preparation Example 1-1 is 2 kg.

[0106] Comparative Example 2, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the amount of modified graphite added in Preparation Example 1-1 is 5 kg.

[0107] Comparative Example 3, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that the modified graphite prepared in Example 1-1 is replaced with an equal amount of modified graphite prepared in Examples 1-8.

[0108] Comparative Example 4, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that an equal amount of unmodified graphite is used to replace the modified graphite prepared in Preparation Example 1-1.

[0109] Comparative Example 5, an antistatic co-extruded wood-plastic composite profile, differs from Example 1 only in that no antistatic layer masterbatch is added during the co-extrusion process in step S4.

[0110] Performance testing

[0111] 1. Antistatic performance test: According to the relevant records in GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and decorative wood-based panels", the surface resistance value of the antistatic layer of the composite profiles obtained in Examples 1 to 18 and Comparative Examples 1 to 5 was tested. At the same time, the surface resistance value of the profiles after 1000h aging treatment was compared to characterize the durability of the antistatic properties of the profiles. The test results are shown in Table 3.

[0112] 2. Peel resistance test: According to the relevant records in GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and decorative wood-based panels", the peel resistance (N) of the composite profiles obtained in the examples and comparative examples was tested, and the test results are shown in Table 4.

[0113] Table 3 Antistatic performance test results

[0114]

[0115] Table 4 Peel resistance test

[0116]

[0117] Based on Tables 3 and 4, and in conjunction with Examples 1, 12, 13, and Comparative Example 3, it can be seen that the surface resistivity values ​​of Examples 12, 13, and Comparative Example 3 decreased. This may be because Examples 12, 13, and Comparative Example 3 adjusted the degree of quaternization of the quaternary ammonium salt polyethylene glycol grafted onto the modified graphite. Less quaternary ammonium salt increases the influence of polyethylene glycol on the conductivity of graphite, leading to higher surface resistivity and decreased antistatic properties. Without quaternary ammonium salt, the performance degradation is even more pronounced. Increasing the quaternary ammonium salt content affects the improvement of graphite dispersion by polyethylene glycol segments, which is detrimental to improving antistatic properties.

[0118] Combining Examples 1 and 14, it can be seen that Example 14 has a low surface resistivity and a slightly increased peel strength, indicating that Example 14 has excellent antistatic properties. In Example 14, acetylated lignin is also added to the antistatic layer, which can improve the density of the antistatic layer, increase the internal crosslinking density, thereby improving the interlayer bonding force and peel strength.

[0119] Combining Example 1 and Comparative Example 4, it can be seen that the surface resistivity of Comparative Example 4 has increased and the peel strength has decreased. The reason is that the graphite in Comparative Example 4 has not been modified, which will cause the graphite added in the antistatic layer to agglomerate. This will not only affect the antistatic effect, but also reduce the mechanical strength of the material, increase the lubricity, reduce the interfacial bonding force, and make the interlayer easy to slide and peel off.

[0120] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An antistatic co-extruded wood composite profile, characterized in that, The core material layer and the antistatic layer are coated with each other. The antistatic layer comprises the following raw materials in mass fraction: Polyethylene 100 parts; Modified graphite 30-40 parts; Maleic anhydride grafted polyethylene 5-10 parts; Antioxidant 3-5 parts; The modified graphite is grafted with quaternary ammonium salt polyethylene glycol on the surface; The raw materials of the modified graphite comprise graphite, isocyanate and quaternary ammonium salt polyethylene glycol in a mass ratio of 1: (1.2-1.5): (2-2.6); The raw materials of the quaternary ammonium salt polyethylene glycol comprise polyethylene glycol and quaternary ammonium salt in a mass ratio of 1: (6-10); The modified graphite is prepared by the following method: Preparation of quaternary ammonium salt polyethylene glycol: add polyethylene glycol into water, adjust the pH value of the solution to 10-11, raise the temperature to 45-55℃, and stir for 1-2h for activation, then add quaternary ammonium salt, raise the temperature to 70-75℃, and continue to stir for 5-7h, finally obtain quaternary ammonium salt polyethylene glycol after neutralization, washing and dialysis; Preparation of modified graphite: disperse graphite in solvent, add isocyanate, raise the temperature to 70-80℃ after stirring and dispersion, stir for 12-15h under nitrogen atmosphere, then add quaternary ammonium salt polyethylene glycol, stir for 8-10h, and finally obtain modified graphite after washing and drying.

2. The antistatic co-extruded wood composite profile according to claim 1, characterized in that The core material layer comprises the following raw materials in mass fraction: wood powder 100 parts, polyethylene 50-60 parts, maleic anhydride grafted polyethylene 5-10 parts, talc 10-20 parts and lubricant 1-3 parts.

3. The antistatic co-extruded wood composite profile according to claim 1, characterized in that The mass ratio of the core material layer and the antistatic layer is 100: (10-15).

4. The antistatic co-extruded wood composite profile according to claim 1, characterized in that The quaternary ammonium salt comprises one or more combinations of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, epoxy propyl trimethyl ammonium chloride, 2-methacryloyloxyethyl trimethyl ammonium chloride and acryloyloxyethyl trimethyl ammonium chloride; and the molecular weight of the polyethylene glycol is 600-1500.

5. The antistatic co-extruded wood composite profile according to claim 1, characterized in that The antistatic layer is further coated with an outer surface layer; The mass ratio of the core material layer and the outer surface layer is 100: (8-12); The outer surface layer comprises the following raw materials in mass fraction: polyethylene 100 parts, pigment 5-10 parts, maleic anhydride grafted polyethylene 5-10 parts, ultraviolet absorber 3-5 parts and antioxidant 3-5 parts.

6. The antistatic co-extruded wood composite profile according to claim 1, characterized in that The raw materials of the antistatic layer further comprise acetylated lignin in a mass fraction of 4-8 parts; and the raw materials of the acetylated lignin comprise lignin and acetic anhydride in a mass ratio of 1: (2-4).

7. A method for producing an antistatic co-extruded wood composite profile according to any one of claims 1 to 6, characterized in that The following process steps are included: S1. Weigh the raw materials of the antistatic layer according to the corresponding mass fraction, stir and mix at 60-80℃ for 10-20min to obtain the antistatic layer mixture, then melt plasticize and extrude to obtain the antistatic layer master batch after drying; S2. Weigh the raw materials of the outer surface layer according to the corresponding mass fraction, stir and mix at 60-80℃ for 10-20min to obtain the outer surface layer mixture, then melt plasticize and extrude to obtain the outer surface layer master batch after drying; S3. Weigh the raw materials of the core material layer according to the corresponding mass fraction, mix uniformly, then melt extrude and cool to obtain the core material layer master batch. S4. The core material layer master batch is extruded through a mold to obtain a core material layer; the antistatic layer master batch and the outer surface layer master batch are respectively co-extruded through a mold and coated on the surface of the core material layer to respectively form an antistatic layer and an outer surface layer, and the antistatic co-extruded plastic-wood composite profile is obtained after embossing and polishing.

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