Wood-plastic composite profile and preparation method thereof

Abstract

The invention discloses a wood-plastic composite profile and a preparation method thereof. The preparation method comprises the following steps: crushing and grinding thermosetting plastic waste, and screening to obtain thermosetting powder; crushing and grinding the waste wood chips, and screening to obtain wood flour; powder in a set proportion is weighed, a core layer raw material and a surface layer raw material are obtained, the core layer raw material comprises wood powder and the following components in parts by mass: 30-50 parts of thermoplastic plastic particles, 60-120 parts of thermosetting powder and 9-12 parts of a core layer auxiliary agent, the core layer auxiliary agent comprises an interface compatilizer, and the surface layer auxiliary agent comprises a surface layer auxiliary agent and a surface layer auxiliary agent; the interface compatilizer is used for enabling wood flour and thermosetting powder to be compatible with thermoplastic plastic particles, and the surface layer raw materials comprise thermoplastic powder and a surface layer auxiliary agent; respectively mixing the core layer raw material and the surface layer raw material, and performing extrusion granulation treatment to obtain core layer particles and surface layer particles; the core layer particles and the surface layer particles are subjected to co-extrusion forming treatment to obtain the wood-plastic composite profile, the wood-plastic composite profile comprises a core layer and a surface layer, and the core layer is wrapped by the surface layer and combined with the surface layer into a whole.

Description

Technical Field

[0001] The present invention relates to the field of waste plastic recycling, and specifically, to a wood-plastic composite profile and a preparation method thereof. Background Art

[0002] At present, polymer products such as plastics and rubbers are widely used, but the recycling of these polymer materials has not kept up with the growth of production. Disposing of waste polymer materials or burning them will cause serious environmental consequences.

[0003] These polymer waste materials mainly include thermosetting materials, which belong to a highly crosslinked three-dimensional structure and are difficult to melt, soften or thermally decompose even at high temperatures, which increases the difficulty of recycling thermosetting materials. Wood-plastic composite profiles mainly refer to wood-plastic composite materials that use thermoplastic plastics as the matrix and are filled with a large amount of wood powder, and their appearance resembles wood. However, due to the fact that wood-plastic composite profiles are extremely prone to absorbing water and rotting, plastic aging is caused.

[0004] Therefore, how to effectively recycle waste thermosetting plastics to prepare wood-plastic composite materials, reduce treatment costs and environmental hazards, and at the same time improve the performance of wood-plastic composite profiles is an urgent problem to be solved in this field. Summary of the Invention

[0005] The present invention aims to solve one of the technical problems in the related art to a certain extent. For this purpose, the present invention provides a method.

[0006] To achieve the above object, as the first aspect of the present invention, a preparation method of a wood-plastic composite profile is disclosed, including:

[0007] Performing crushing and grinding treatment on waste thermosetting plastics and then screening to obtain thermosetting powder of a first set mesh number, wherein the waste thermosetting plastics include thermosetting resins;

[0008] Performing crushing and grinding treatment on waste wood chips and then screening to obtain wood powder of a second set mesh number;

[0009] Weighing set proportions of powders to obtain a core layer raw material and a surface layer raw material respectively. The core layer raw material includes the wood powder and the following components by mass parts: 30-50 parts of thermoplastic plastic particles, 60-120 parts of the thermosetting powder, and 9-12 parts of a core layer additive. Among them, the core layer additive includes an interfacial compatibilizer, and the interfacial compatibilizer is used to make the wood powder, the thermosetting powder and the thermoplastic plastic particles compatible. The surface layer raw material includes thermoplastic plastic particles and a surface layer additive;

[0010] Mixing the core layer raw material and the surface layer raw material respectively and then performing extrusion molding treatment to obtain core layer particles and surface layer particles respectively;

[0011] The core layer particles and the surface layer particles are processed by co - extrusion molding to obtain the wood - plastic composite profile. The wood - plastic composite profile includes a core layer and a surface layer, and the core layer is coated and integrated with the surface layer.

[0012] Further, in the step of performing extrusion molding treatment after mixing the core layer raw materials,

[0013] First, the thermosetting powder and the interfacial compatibilizer are mixed to obtain a modified thermosetting powder;

[0014] Then, the modified thermosetting powder, the thermoplastic plastic particles, the wood powder, and the additives are mixed for extrusion granulation treatment.

[0015] Further, in the step of first mixing the thermosetting powder and the interfacial compatibilizer to obtain a modified thermosetting powder,

[0016] The interfacial compatibilizer includes a graft compatibilizer and a coupling agent. First, the thermosetting powder and the coupling agent are mixed to obtain the modified thermosetting powder. Among them, the graft compatibilizer is used to make the wood powder and the thermoplastic plastic particles compatible, and the coupling agent is used to make the thermosetting powder and the thermoplastic plastic particles compatible. The content of the graft compatibilizer is less than or equal to the content of the coupling agent.

[0017] Further, in the core layer raw materials, by mass, the graft compatibilizer includes 0 - 3 parts, the coupling agent includes 0 - 6 parts. The graft compatibilizer includes maleic anhydride - grafted polyethylene, and the coupling agent includes at least one of silane coupling agents or titanate coupling agents. The core layer additives also include at least one of a lubricant and an antioxidant.

[0018] Further, in the step of screening the thermosetting powder with a set mesh number after crushing and grinding the thermosetting plastic waste, after crushing and grinding the thermosetting plastic waste, a pneumatic separator is used for screening, and the particle size mesh number of the thermosetting powder is between 80 mesh and 600 mesh;

[0019] In the step of screening the wood powder with a set mesh number after crushing and grinding the waste wood chips, after crushing and grinding the waste wood chips, a vibrating screen is used for screening, and the particle size of the wood powder is between 40 mesh and 100 mesh.

[0020] Further, the thermosetting plastic waste also includes at least 10wt% of glass fiber.

[0021] Further, the thermosetting resin includes at least one of phenolic resin, urea - formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, and polyurethane.

[0022] Further, in the step of separately mixing the core layer raw material and the surface layer raw material and then performing an extrusion molding process,

[0023] After mixing and stirring the core layer raw material, a first extrusion granulation process is performed to obtain the core layer particles. Among them, the stirring time is between 25 min and 35 min, and the extrusion granulation temperature is between 190 °C and 200 °C;

[0024] After mixing and stirring the surface layer raw material, a second extrusion molding process is performed to obtain the surface layer intermediate material. Among them, the stirring time is between 15 min and 25 min, and the extrusion temperature is between 160 °C and 180 °C;

[0025] The surface layer intermediate material is crushed to obtain the surface layer particles.

[0026] As a second aspect of the present invention, a wood-plastic composite profile is disclosed. The wood-plastic composite profile is obtained by using the above preparation method. The wood-plastic composite profile includes a core layer and a surface layer that are combined into one by multi-layer co-extrusion, and the core layer is coated by the surface layer.

[0027] Further, the thickness of the surface layer is less than that of the core layer.

[0028] By using the preparation method of the wood-plastic composite profile of the present invention, the thermosetting waste plastic garbage generated by industry can be effectively recycled. The thermosetting powder is used to partially or completely replace the filler or wood powder of traditional wood-plastic composite products. With the raw material components and preparation method of this application, the thermosetting waste plastic has a fine powder structure with a specific mesh number after being crushed and ground. This thermosetting powder can be evenly distributed in the thermoplastic matrix and has good interfacial compatibility with the matrix. Even if the dosage of the additives used to provide various properties of the wood-plastic composite profile in the formula is reduced, it will not have a great impact on the strength of the finally prepared wood-plastic composite profile product. Applying the thermosetting plastic powder to wood-plastic products can reduce costs and at the same time reduce the negative impact of thermosetting plastics on the environment. The wood-plastic composite profile of this application is a co-extrusion structure with the surface layer coating the core layer, which solves the problem that the color of the thermosetting plastic powder is difficult to control evenly and is not beautiful. And the wood-plastic composite material with a high filling of thermosetting plastic (waste) powder is completely adapted to the preparation process of traditional wood-plastic composite materials. Moreover, because the thermosetting plastic powder itself has a low water absorption rate and good acid and alkali resistance, it can enhance the waterproof performance and chemical stability of the wood-plastic composite material. The performance parameters such as the water absorption rate, water absorption dimensional change rate, and linear thermal expansion coefficient of the whole wood-plastic composite board can meet the requirements of the national standard for wood-plastic floors GB / T 24508-2020, and can provide better weather resistance and corrosion resistance for applications in outdoor and humid environments.

[0029] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and the accompanying drawings. The best embodiments or means of the present invention will be shown in detail in combination with the accompanying drawings, but it is not a limitation to the technical solution of the present invention. In addition, these features, elements, and components that appear in each of the following texts and drawings are multiple, and different symbols or numbers are marked for convenience of representation, but all represent components with the same or similar structures or functions. Description of the Drawings

[0030] Figure 1 is a flowchart of an embodiment of the preparation method of the wood-plastic composite profile of the present invention;

[0031] Figure 2 is a schematic structural diagram of an embodiment of the wood-plastic composite profile of the present invention.

[0032] Description of the Reference Numerals in the Drawings

[0033] 1: Wood-plastic composite profile; 10: Surface layer; 11: Core layer. Specific Embodiments

[0034] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. Based on the embodiments in the embodiments, it is intended to explain the present invention and should not be construed as a limitation to the present invention.

[0035] As used herein, the phrase "one embodiment" or "example" or "instance" means that a particular feature, structure, or characteristic described in connection with the embodiment itself may be included in at least one embodiment of the present disclosure. The appearances of the phrase "in one embodiment" in various places in the specification do not necessarily refer to the same embodiment.

[0036] The thermosetting plastic waste of the present application is industrial solid waste generated in industrial production activities. The thermosetting plastics widely used in industry at present include vulcanized rubber, polyurethane foam, unsaturated polyester, epoxy resin, and phenolic resin. The thermosetting plastic waste is mainly industrial solid waste such as defective products generated in industrial production. Therefore, it has an industrial-level cleanliness. Common thermosetting plastic wastes generally include phenolic plastics, epoxy plastics, amino plastics, unsaturated polyesters, alkyd plastics, etc. Thus, they have a dense three-dimensional network structure, are insoluble and infusible, and are difficult to be degraded. Therefore, they are not easily contaminated by other wastes. After being recycled and crushed and ground into powder, impurities and metals can be removed by screening methods such as air separation, thereby reducing the cleaning of the initial plastic and lowering the pre-treatment cost.

[0037] In addition, thermosetting plastic waste often includes glass fibers. The glass fiber content in conventional thermosetting plastic waste is at least 10wt% - 15wt%, and the glass fiber content in some thermosetting plastic waste is even higher. This makes it difficult for the plastic matrix to degrade through natural decomposition or microbial treatment. The incineration method and the dissolution method can burn the polymer matrix or dissolve the polymer matrix using chemical reagents (such as high-concentration acids or alkalis), and then reshape the glass fibers to achieve the reuse of glass fibers. However, the polymer removal process usually leads to additional greenhouse gas emissions or solvent consumption, resulting in secondary waste streams.

[0038] The waste wood chips of the present application can be crop straws or scraps from furniture making, including sawdust, planer shavings, etc. made into powder. The sources are extensive. This kind of wood powder is processed from raw ecological wood or crops during the wood processing process, without going through complex industrial processes, with high purity and no other pollutants. After screening out the appropriate particle size through a vibrating screen, the final wood powder is obtained, thus eliminating the need for special cleaning treatment and greatly reducing the treatment cost.

[0039] The production raw materials of the wood-plastic composite material of the present application can recycle waste plastics, waste wood, and crops from various industries. Therefore, the research and application of wood-plastic composite materials help to mitigate the public hazard pollution of plastic waste and also help to reduce the pollution to the environment caused by waste incineration.

[0040] As the first aspect of the present invention, a preparation method of a wood-plastic composite profile is disclosed. As Figure 1 shown, it includes:

[0041] S100. After crushing and grinding the thermosetting waste plastic and then screening, thermosetting powder with a first set mesh number is obtained. The thermosetting plastic waste includes thermosetting resin;

[0042] S110. After crushing and grinding the waste wood chips and then screening, wood powder with a second set mesh number is obtained;

[0043] S120. Weigh the powder in a set proportion to obtain the core layer raw material and the surface layer raw material respectively. The core layer raw material includes wood powder and the following components by mass parts: 30 - 50 parts of thermoplastic plastic particles, 60 - 120 parts of thermosetting powder, and 9 - 12 parts of core layer additives. Among them, the core layer additives include an interfacial compatibilizer, and the interfacial compatibilizer is used to make the wood powder, thermosetting powder, and thermoplastic plastic particles compatible. The surface layer raw material includes thermoplastic plastic particles and surface layer additives;

[0044] S130. After mixing the core layer raw material and the surface layer raw material respectively, extrusion molding treatment is carried out to obtain core layer particles and surface layer particles respectively;

[0045] S140. The core layer particles and the surface layer particles are processed by co-extrusion molding to obtain a wood-plastic composite profile. The wood-plastic composite profile includes a core layer and a surface layer. The core layer is coated and integrated with the surface layer.

[0046] In step S100, when screening the thermosetting powder with a first set number of meshes after crushing and grinding the thermosetting plastic waste, a pneumatic separator is used for screening after the crushing and grinding treatment of the thermosetting plastic waste. In order to make the thermosetting powder combine better with the thermoplastic particles and not cause stratification due to too large a density difference during mixing, preferably, the particle size number of the thermosetting powder is between 80 and 600 meshes. If the number of meshes is too large, the particle size of the thermosetting powder is too small, and the size difference from the thermoplastic particles is too large. During mixing, the thermosetting powder is likely to flow away between the thermoplastic particles, causing material stratification, thus reducing the effect of plasticizing and pelletizing. If the number of meshes is too small, the particle size of the thermosetting powder is too large, which makes the particles have defects such as holes and cracks during mixing and extrusion, affecting subsequent co-extrusion molding. In some embodiments, the particle size number of the thermosetting powder is basically greater than 80 meshes, most of the powder is between 200 and 400 meshes, and some are greater than 400 meshes.

[0047] The thermosetting resin includes at least one of phenolic resin, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, and polyurethane. These materials have heat resistance, are not easily deformed, and have high rigidity and high hardness after curing, and are not easily water-absorbent. Partially replacing wood powder can improve the water-absorption deformation problem of the wood-plastic composite board and can also increase the strength of the composite board.

[0048] In addition, the thermosetting plastic waste also includes at least 10 wt% of glass fiber. This glass fiber can be dispersed in the thermoplastic matrix after subsequent grinding and powder making to play a role in fiber reinforcement. In some embodiments, the glass fiber content of conventional thermosetting plastic waste is at least 10 wt% - 15 wt%, and the glass fiber content of some thermosetting plastic waste is higher.

[0049] In addition, in addition to the above thermosetting resin, the thermosetting plastic waste may also contain some ingredients of the industrial product itself. For example, thermoplastic materials and various functional fillers. These ingredients can be remelted at the high temperature of the extruder when ground into powder, and make the powder of the thermosetting waste combine better with the thermoplastic particles, greatly increasing the effect of uniform plasticizing and molding.

[0050] In S110, when screening wood powder of a set mesh number after crushing and grinding waste wood, after crushing and grinding the waste wood chips, a vibrating screen is used for screening. The particle size of the wood powder is between 40 mesh and 100 mesh. The size of the wood powder should not be too large. If it is too large, the wood powder particles will be obvious, which will affect the uniformity of the wood powder in the thermoplastic matrix, and will also cause the appearance of the product to be rough, reducing the aesthetic feeling and decorative property of the material. In addition, the water absorption rate of large particle wood powder is higher, and air bubble defects are likely to occur during co-extrusion.

[0051] In step S120, as an optional implementation manner, the core layer raw material comprises 30 - 50 parts of plastic, 0 - 60 parts of wood powder, 60 - 120 parts of thermosetting plastic powder, and 9 - 12 parts of core layer additives. Among them, the core layer additives include at least one of maleic anhydride grafted polyethylene (MAPE) and silane coupling agent, and the core layer additives also include at least one of lubricant and antioxidant. The surface layer raw material comprises 18 - 24 parts of plastic, 9 - 12 parts of wood powder, 1.3 - 1.5 parts of maleic anhydride grafted polyethylene (MAPE), 0.3 - 0.5 parts of lubricant, 0.8 - 1.0 parts of surface layer additives, and 0 - 0.5 parts of color powder. The surface layer additives include at least one of antioxidant and ultraviolet resistant agent. The color powder includes at least one of carbon black, titanium dioxide, iron yellow, and iron red.

[0052] In step S130, the present application does not specifically limit the mixing order. Preferably, when the core layer raw materials are mixed and extruded, specifically, the thermosetting powder is first mixed with the interfacial compatibilizer to obtain a modified thermosetting powder, and then the modified thermosetting powder is mixed with thermoplastic particles, wood powder and additives for extrusion granulation. This mixing method enables the thermosetting powder to be cross-linked with the coupling agent first, and the physical modification is obtained first. The coupling agent is a compound with amphiphilic properties, usually containing inorganic and organic groups, and the surface of the thermosetting powder usually contains hydroxyl (-OH) or other active groups. The thermosetting plastic itself is hydrophobic, which makes them less compatible with thermoplastics with strong polarity. Therefore, the inorganic groups of the coupling agent (such as the alkoxy group in the silane coupling agent) can react with the hydroxyl or other active groups on the surface of the thermosetting plastic powder to form a chemical bond. This process can significantly change the properties of the surface of thermosetting plastic powder, changing it from hydrophilic to lipophilic or improving compatibility with thermoplastic materials. The organophilic groups of the coupling agent can interact physically or chemically with thermoplastic materials. For example, organophilic groups such as long-chain alkyl or vinyl groups can be embedded in the molecular chain of thermoplastic materials, acting as a "bridge" to tightly connect thermosetting plastic powder and thermoplastic materials. Through the action of the coupling agent, the coupling agent layer formed on the surface of the thermosetting plastic powder can effectively disperse stress and reduce stress concentration at the interface. This stress dispersion effect helps prevent crack propagation and delamination of the composite material during use, thereby improving the overall mechanical properties.

[0053] As an optional embodiment, in the step of first mixing the thermosetting powder with the interface compatibilizer to obtain the modified thermosetting powder, the interface compatibilizer includes a grafted compatibilizer and a coupling agent, and the thermosetting powder is first mixed with the coupling agent to obtain the modified thermosetting powder, wherein the grafted compatibilizer is used to make the wood powder compatible with the thermoplastic plastic particles, and the coupling agent is used to make the thermosetting powder compatible with the thermoplastic plastic particles, and the content of the grafted compatibilizer is less than or equal to the content of the coupling agent. In some embodiments, the grafted compatibilizer includes maleic anhydride grafted polyethylene, and the coupling agent includes at least one of a silane coupling agent or a titanate coupling agent. If only wood powder is added, the interface compatibilizer can only use maleic anhydride grafted polyethylene MAPE. If only thermosetting powder is added, the interface compatibilizer can only use a silane coupling agent. If both wood powder and thermosetting plastic powder are present, maleic anhydride grafted polyethylene MAPE and a silane coupling agent need to exist simultaneously in the interface compatibilizer. In the core layer raw materials, by weight, the grafting compatibilizer comprises 0-3 parts, the coupling agent comprises 0-6 parts, and the core layer auxiliary agent further comprises at least one of a lubricant and an antioxidant.

[0054] This application does not make special limitations on the extrusion molding process. For example, the one-step method can be directly used for extrusion molding. For another example, the two-step method can also be used, that is, first extrusion granulation and then co-extrusion molding. In some embodiments, since the core layer contains wood powder and / or thermosetting powder, if it is directly extruded, its plasticization property will be poor, resulting in poor molding. Although the texture is more like wood, the color matching is relatively difficult, there is easy color difference, and the product quality is difficult to control. Therefore, preferably, after the core layer raw material containing wood powder and / or thermosetting powder is extruded, the core layer further includes a granulation process after extrusion to form core layer particles. The particles prevent segregation of each component due to the difference in particle size and density on the basis of the powder, and improve the uniformity of powder mixing. After the powder is extruded and granulated, the fluidity of the particles is higher, and the component contents of multiple particles are uniform. In other embodiments, if the core layer raw material does not contain wood powder, the plasticization effect during extrusion is better. Therefore, the core layer does not need to be granulated after extrusion and can be directly formed for subsequent processing.

[0055] In the step of performing extrusion molding processing after separately mixing the core layer raw material and the surface layer raw material, after mixing and stirring the core layer raw material, the first extrusion granulation process is performed to obtain core layer particles. Among them, the stirring time is between 25 min and 35 min, and the extrusion granulation temperature is between 190 °C and 200 °C. Since the core layer includes thermosetting powder and wood powder, when the above components are in the heated and molten thermoplastic material, the viscosity of the molten material increases and the fluidity weakens. In order to successfully plasticize the material, it is necessary to increase the extrusion granulation temperature, but the extrusion granulation temperature cannot exceed 200 degrees Celsius. This is because the wood powder will carbonize after exceeding 200 degrees and will be further pulverized under the high shear action of the extruder, resulting in uneven plasticization and the wood powder cannot be effectively plasticized and formed into the thermoplastic matrix.

[0056] This application does not make special limitations on the extrusion molding process of the surface layer. For example, the one-step method can be directly used for extrusion molding. For another example, the two-step method can also be used, that is, first extrusion granulation and then co-extrusion molding. In some embodiments, since the amount of thermosetting powder or wood powder in the surface layer raw material is less or almost none, the fluidity of the molten material is higher. After mixing and stirring the surface layer raw material, the second extrusion molding process is performed without granulation. The stirring time is between 15 min and 25 min, and the extrusion temperature is between 160 °C and 180 °C to obtain surface layer intermediate materials, which are multiple softer plastic masses. The surface layer intermediate materials are crushed to obtain surface layer particles.

[0057] In the current surface layer obtained by co - extrusion in wood - plastic composite boards, most of the formulations are without wood flour and are pure plastic matrices. For such components, when adding additives and masterbatch, the color is relatively easy to control and the quality is relatively stable. The wood grain or other surface effects are simulated through die design. In addition, since the surface layer is thinner than the core layer, a small amount of anti - aging and anti - ultraviolet additives (which are relatively expensive) can be added to the surface layer to achieve the required weather resistance, and the core layer does not need to consider weather resistance. For traditional wood - plastic composite boards with non - co - extruded surface layers, more weather - resistant additives need to be added to achieve the ideal weather resistance, so the cost is higher.

[0058] In some other embodiments, the surface layer raw material contains thermoplastic plastic particles and a small amount of wood flour or thermosetting powder. In order to make its plasticizing and molding better and more uniform, the surface layer is granulated after extrusion, and surface layer particles can also be obtained.

[0059] Moreover, since the wood flour content in the surface layer is generally low, there is no need to worry about the problem of high water absorption caused by wood flour in the surface layer. And if thermosetting powder is used to replace the wood flour in the surface layer, there will be no significant difference in its plasticizing performance.

[0060] In some embodiments, since the surface layer is the outer layer of the composite profile, in addition to including wood flour and / or thermosetting powder, the surface layer additives also include at least one of lubricants, antioxidants, anti - ultraviolet agents, and color powders. Among them, the anti - ultraviolet agent and antioxidant are used to prevent the aging of the wood - plastic board by ultraviolet rays and air on the outside, and the color powder is used to adjust the appearance color of the surface layer to make it more wood - textured. The color powder includes at least one of carbon black, titanium dioxide, iron yellow, and iron red.

[0061] As the second aspect of the present invention, a wood - plastic composite profile is disclosed. The wood - plastic composite profile is obtained by using the above - mentioned preparation method. The wood - plastic composite profile includes a core layer and a surface layer combined into one by multi - layer co - extrusion. The core layer is covered by the surface layer, and the thickness of the surface layer is less than that of the core layer.

[0062] Adopting the preparation method of the wood-plastic composite profile of the present invention can effectively recycle the thermosetting waste plastic garbage generated by industry, and use thermosetting powder to partially or completely replace the filler or wood powder of traditional wood-plastic composite products. With the raw material components and preparation method of this application, the thermosetting waste plastic has a fine powder structure with a specific mesh number after being crushed and ground. This thermosetting powder can be evenly distributed in the thermoplastic matrix and has good interfacial compatibility with the matrix. Even if the dosage of the additives used to provide various properties of the wood-plastic composite profile in the formula is reduced, it will not have a great impact on the strength of the finally prepared wood-plastic composite profile product. Applying thermosetting plastic powder to wood-plastic products can reduce costs and at the same time reduce the negative impact of thermosetting plastics on the environment. The wood-plastic composite profile of this application is a co-extrusion structure with a surface layer covering the core layer, which solves the problem that the color of the thermosetting plastic powder is difficult to control evenly and is not beautiful. And the wood-plastic composite material with a high filling of thermosetting plastic (waste) powder is completely adapted to the preparation process of traditional wood-plastic composite materials. Moreover, because the thermosetting plastic powder itself has a low water absorption rate and good acid and alkali resistance, it can enhance the waterproof performance and chemical stability of the wood-plastic composite material. The performance parameters such as the water absorption rate, water absorption size change rate, and linear thermal expansion coefficient of the whole wood-plastic composite board can meet the requirements of the national standard for wood-plastic floors GB / T 24508-2020, and can provide better weather resistance and corrosion resistance for applications in outdoor and humid environments.

[0063] The present invention will be further described below in conjunction with preparation examples and examples.

[0064] Example

[0065] Example 1

[0066] Provide a preparation method of a wood-plastic composite profile, including:

[0067] Step S1: Crush, grind and screen the thermosetting plastic waste to obtain thermosetting powder with a set mesh number. Specifically, mechanically grind the thermosetting plastic waste into powder with a mesh number of 60-500, so that the moisture content is lower than 0.5%. Crush and grind the waste wood and then screen to obtain wood powder with a set mesh number;

[0068] Step S2: Weigh the powder in a set ratio to obtain the core layer raw material and the surface layer raw material respectively. Among them, the core layer raw material includes, by mass: 35 parts of polyethylene, 60 parts of miscellaneous wood powder, 60 parts of thermosetting powder, 3 parts of lubricant 802, 3 parts of maleic anhydride grafted polyethylene MAPE, 3 parts of silane coupling agent A151, and 0.3 parts of antioxidant 1010. The surface layer raw material includes, by mass: 20 parts of plastic PE, 10 parts of poplar wood powder, 1.5 parts of maleic anhydride grafted polyethylene MAPE, 0.4 parts of lubricant 802, 0.4 parts of antioxidant 1010, 0.4 parts of ultraviolet absorber 531, and 0.4 parts of color powder (composed of 0.2 parts of carbon black and 0.2 parts of titanium dioxide).

[0069] Step S3: Mix the core layer raw material and the surface layer raw material respectively and then carry out extrusion granulation. Specifically, add the thermosetting powder and the coupling agent in the core layer raw material into the mixing tank for premixing, and then add the remaining raw materials in the core layer raw material and mix them at a high speed of 1000 r / min for 30 min. Add the above mixed materials into the hopper of the parallel twin-screw granulator, control the temperature at 195°C, adjust the granulation process, extrude, and granulate to obtain the core layer particles.

[0070] Mix the surface layer raw material and add it to the high-speed mixer, and mix it at a high speed of 1000 r / min for 20 min. Add the above mixed materials into the hopper of the parallel twin-screw granulator, control the temperature of the screw extruder at 170°C, the main machine speed at 300 r / min, extrude, granulate, and then crush it into particle powder by a crusher to obtain the surface layer particles.

[0071] Step S4: Obtain the wood-plastic composite profile through co-extrusion molding of the core layer particles and the surface layer particles. Specifically, add the core layer particles and the surface layer particles into two conical twin-screw co-extrusion machines respectively, and adjust the extrusion process. Among them, the main machine speed is between 8 rpm and 12 rpm, and the traction speed is between 0.5 m / min and 0.8 m / min (changing with the main machine speed). The core layer extrusion temperature has multiple temperature zones, and the extrusion temperature in multiple temperature zones is in the range of 140°C to 220°C. The surface layer extrusion temperature is adjusted between 130°C and 190°C. Finally, co-extrusion molding is carried out to obtain a co-extruded wood-plastic composite profile board. The profile board is a solid co-extruded floor with a width of 145 mm and a thickness of 25 mm, and the surface layer thickness is generally between 0.5 mm and 1.5 mm.

[0072] Example 2

[0073] Prepare the wood-plastic composite profile board by using the same preparation method as in Example 1, except that in the core layer raw material, the wood powder is 0 part, the thermosetting powder is 120 parts, and 6 parts of silane coupling agent A 151.

[0074] Example 3

[0075] The wood-plastic composite profile board was prepared by the same preparation method as in Example 1, except that in the core layer raw materials, there were 45 parts of miscellaneous wood powder, 90 parts of thermosetting plastic powder, 2 parts of maleic anhydride grafted polyethylene MAPE, and 4 parts of silane coupling agent A151.

[0076] Example 4

[0077] The wood-plastic composite profile board was prepared by the same preparation method as in Example 1, except that the wood-plastic board with the size of 22mm * 145mm * 1000mm was obtained by cutting treatment.

[0078] Comparative Example 1

[0079] The wood-plastic composite profile board was prepared by the same preparation method as in Example 1, except that no thermosetting plastic powder was added to the core layer raw materials. The core layer raw materials specifically included: 35 parts of plastic PE, 100 parts of miscellaneous wood powder, 3 parts of lubricant 802, 6 parts of maleic anhydride grafted polyethylene MAPE, 0.3 parts of antioxidant 1010, and 20 parts of calcium carbonate.

[0080] Comparative Example 2

[0081] A commercially available wood-plastic board of a certain brand A was used, which included a surface layer and a bottom layer arranged from top to bottom. The surface layer included the following raw materials in parts by weight: 50 - 70 parts of high-density polyethylene and 15 - 25 parts of additives; the bottom layer included the following raw materials in parts by weight: 70 - 80 parts of plastic resin, 10 - 20 parts of wood powder, 2 - 5 parts of flame retardant, and 10 - 30 parts of filler.

[0082] S1. Add the raw materials in each part by weight in the surface layer and the bottom layer to different mixing devices, mix and stir evenly at a temperature of 150°C - 180°C to obtain the surface layer mixture and the bottom layer mixture respectively;

[0083] S2. Extrude the surface layer mixture and the bottom layer mixture respectively by a rod extruder, and extrude and form the two-layer materials of the surface layer and the bottom layer through a co-extrusion die to obtain a wood-plastic floor blank;

[0084] S3. After the wood-plastic floor blank is cooled and solidified, cut it according to the floor size to obtain a wood-plastic floor with the size of 23mm * 140mm * 1000mm.

[0085] Comparative Example 3

[0086] Use a commercially available wood-plastic board of a certain brand B. The raw material components of its surface layer and core layer include plastic and wood powder. Among them, the plastic content is 30wt%, the wood powder content is 70wt%, the plastic is PE, and the particle sizes of the plastic and wood powder are between 60 and 160 mesh; mix the above raw materials and extrude the surface layer and core layer materials through a co-extrusion die to obtain a wood-plastic board with dimensions of 22mm * 140mm * 1000mm.

[0087] Test example

[0088] Detect the wood-plastic composite profile boards of the examples and comparative examples according to the national standard GB / T 24508-2020, and the test results are shown in Tables 1, 2, 3, and 4.

[0089] Table 1

[0090] Number Boiling water test (72h) Maximum breaking load Shore hardness Example 1 No cracking, no powdering 4450N 73 Example 2 No cracking, no powdering 4160N 76 Example 3 No cracking, no powdering 4310N 75 Comparative example 1 Cracking, no powdering 4480N 73

[0091] Table 2

[0092]

[0093]

[0094] Table 3

[0095] Number Linear thermal expansion coefficient Water absorption rate Example 1 4.70E-05 0.20％ Example 2 4.70E-05 ＜0.1％ Example 3 4.70E-05 0.10％ Comparative example 1 5.00E-05 0.80％

[0096] Table 4

[0097]

[0098] As can be seen from Tables 1 to 4 above, the wood-plastic composite profile is a solid co-extruded floor with a width of 145 mm and a thickness of 25 mm, and all tests are carried out in accordance with the national standard GB / T 24508-2020. From the above test results, it can be seen that when using thermosetting plastic powder to replace the filler and wood powder to prepare the wood-plastic composite profile, the retention rate of the flexural strength is not much different from that of the wood-plastic floor prepared with the filler and wood powder. However, the water absorption rate and the water absorption dimension change rate are lower, and its performance is much higher than the national standard. Moreover, the linear thermal expansion coefficient is less than 5×10-5, which also meets the national standard; in the boiling water test (72 h), there is no cracking or pulverization, while in Comparative Example 1, cracking will occur; in addition, in the freeze-thaw resistance test, the retention rate of the flexural strength of the wood-plastic composite profile prepared by using thermosetting plastic powder to replace the filler and wood powder is greater than or equal to 98%, indicating that its ability to resist the influence of environmental changes is very strong, which can greatly increase its service life in harsh environments, and accordingly reduce the later maintenance cost of the profile; finally, in terms of flame retardancy, the oxygen index of the wood-plastic composite profile prepared by using thermosetting plastic powder to replace the filler and wood powder is better than that of Comparative Example 1, indicating that its fire resistance performance is more excellent. Therefore, using thermosetting plastic powder to replace the filler and wood powder to prepare the wood-plastic composite profile can not only improve the performance in terms of water absorption rate, water absorption dimension change rate, boiling water test, freeze-thaw resistance and fire resistance to a certain extent, but also greatly alleviate the environmental pollution impact brought by thermosetting plastics (waste).

[0099] Table 5

[0100]

[0101] As can be seen from Table 5 above, when the wood-plastic floor of Example 4 of the present application is tested in accordance with GB / T 24508-2020 "Wood-Plastic Flooring" together with Comparative Example 2 and Comparative Example 3, the minimum concentrated load and flexural strength of the wood-plastic board prepared by the preparation method of the present application are higher, and the mechanical properties are better; in terms of the freeze-thaw resistance test, the wood-plastic board of the present application also has a higher retention rate of flexural strength, indicating that the material has the property of being able to withstand multiple freeze-thaw cycles without damage and the strength not being significantly reduced in the water-containing state, and there is no obvious damage and peeling. The wood-plastic board of the present application can better adapt to outdoor and harsh weather with large temperature differences, and has higher safety performance.

[0102] Compared with Comparative Example 2 and Comparative Example 3, since the present application uses thermosetting plastic waste to replace part of the wood powder, it is less likely to absorb water, has high dimensional stability in a humid environment, and will not easily deform; in addition, during the outdoor use process, the wood-plastic board will be affected by thermal expansion and contraction. The linear thermal expansion coefficient of the wood-plastic board of the present application is the same as that of the commercially available wood-plastic board, and it can achieve good dimensional stability of thermal expansion and contraction.

[0103] In addition, the wood-plastic board of the present application has a low soluble metal content. During the long-term use of the wood-plastic board, it is difficult to further release harmful metals, and the safety performance is higher. In addition, the wood-plastic board of the present application uses thermosetting plastic waste to replace part of the wood powder. Therefore, the material cost is lower, the performance is better, and it has a greater market competitive advantage.

[0104] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for preparing a wood-plastic composite profile, characterized in that: include: Thermosetting plastic waste is crushed, ground and then sieved to obtain thermosetting powder of a first set mesh size, wherein the thermosetting plastic waste includes thermosetting resin; The waste wood chips are crushed and ground, and then screened to obtain wood powder of a second set mesh size; Weighing powders of a set ratio to obtain a core layer raw material and a surface layer raw material respectively, the core layer raw material includes the wood powder and the following components by mass: 30-50 parts of thermoplastic plastic particles, 60-120 parts of the thermosetting powder and 9-12 parts of a core layer auxiliary agent, wherein the core layer auxiliary agent includes an interface compatibilizer, and the interface compatibilizer is used to make the wood powder and the thermosetting powder compatible with the thermoplastic plastic particles, and the surface layer raw material includes thermoplastic plastic particles and a surface layer auxiliary agent; The core layer raw material and the surface layer raw material are mixed and then subjected to extrusion molding to obtain core layer particles and surface layer particles respectively; The core layer particles and the surface layer particles are processed by co-extrusion molding to obtain the wood-plastic composite profile. The wood-plastic composite profile comprises a core layer and a surface layer, and the core layer is coated by the surface layer and combined into one.

2. The method for preparing the wood-plastic composite profile according to claim 1, characterized in that: In the step of mixing the core layer raw materials and then extruding them, Firstly, the thermosetting powder is mixed with the interface compatibilizer to obtain a modified thermosetting powder; The modified thermosetting powder is then mixed with the thermoplastic plastic particles, the wood powder and the auxiliary agent to perform extrusion granulation treatment.

3. The wood-plastic composite profile according to claim 2, characterized in that: In the step of first mixing the thermosetting powder with the interfacial compatibilizer to obtain a modified thermosetting powder, The interfacial compatibilizer includes a grafted compatibilizer and a coupling agent. The thermosetting powder is first mixed with the coupling agent to obtain the modified thermosetting powder, wherein the grafted compatibilizer is used to compatibilize the wood powder with the thermoplastic plastic particles, and the coupling agent is used to compatibilize the thermosetting powder with the thermoplastic plastic particles, and the content of the grafted compatibilizer is less than or equal to the content of the coupling agent.

4. The wood-plastic composite profile according to claim 3, characterized in that: In the core layer raw material, the grafted compatibilizer includes 0-3 parts, the coupling agent includes 0-6 parts, the grafted compatibilizer includes maleic anhydride grafted polyethylene, the coupling agent includes at least one of a silane coupling agent or a titanate coupling agent, and the core layer auxiliary agent also includes at least one of a lubricant and an antioxidant.

5. The method for preparing the wood-plastic composite profile according to claim 1, characterized in that: In the step of crushing and grinding the thermosetting plastic waste and then sieving to obtain thermosetting powder of a set mesh size, the thermosetting plastic waste is crushed and ground and then sieved using a wind separator, and the particle size of the thermosetting powder is between 80 mesh and 600 mesh; In the step of crushing and grinding the waste wood chips and then screening to obtain wood powder of a set mesh size, the waste wood chips are crushed and ground and then screened using a vibrating screen, and the particle size of the wood powder is between 40 meshes and 100 meshes.

6. The method for preparing the wood-plastic composite profile according to claim 1, characterized in that: The thermosetting plastic waste further comprises at least 10 wt % of glass fibers.

7. The method for preparing a wood-plastic composite profile according to claim 1, characterized in that: The thermosetting resin includes at least one of phenolic resin, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin and polyurethane.

8. The method for preparing a wood-plastic composite profile according to claim 1, characterized in that: In the step of mixing the core layer raw material and the surface layer raw material and then subjecting them to extrusion molding, The core layer raw materials are mixed and stirred, and then subjected to a first extrusion granulation process to obtain the core layer particles, wherein the stirring time is between 25 minutes and 35 minutes, and the extrusion granulation temperature is between 190° C. and 200° C.; The surface layer raw materials are mixed and stirred, and then subjected to a second extrusion molding process to obtain a surface layer intermediate material, wherein the stirring time is between 15 minutes and 25 minutes, and the extrusion temperature is between 160° C. and 180° C.; The surface intermediate material is crushed to obtain the surface particles.

9. The method for preparing a wood-plastic composite profile according to any one of claims 1 to 8, characterized in that: The surface layer raw material further includes the wood powder and / or the thermosetting powder, and the surface layer additive further includes at least one of a lubricant, an antioxidant, an anti-ultraviolet agent and a color powder.

10. A wood-plastic composite profile, characterized in that: The wood-plastic composite profile is obtained by the preparation method according to any one of claims 1 to 9, and the wood-plastic composite profile comprises a core layer and a surface layer integrated by multi-layer co-extrusion, and the core layer is covered by the surface layer.

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