3D Printed Polymer-Coated Wood Filaments, Preparation Methods, and 3D Parts

Abstract

This invention provides a 3D-printable polymer-coated wood filament, its preparation method, and 3D parts. The 3D-printable polymer-coated wood filament includes a core material and a coating layer covering the outer surface of the core material. The core material is a continuous linear wood, and the coating layer is made of a thermoplastic polymer. The 3D-printable polymer-coated wood filament provided in this application uses continuous linear wood as the core material and coats the surface of the continuous linear wood with thermoplastic polymer. It can be prepared by co-extrusion processing of the continuous linear wood and the coating layer material, exhibiting excellent 3D printability. 3D parts can be prepared by continuous printing, realizing continuous printing processing of 3D parts and effectively improving the mechanical properties of 3D parts. It has broad application prospects in various fields such as entertainment and education.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and more specifically, to a 3D printed polymer-coated wood filament, its preparation method, and a 3D part. Background Technology

[0002] Currently, the main material for wood-plastic composite filaments in 3D printing is thermoplastic polymer. This is produced by mixing wood powder or short fibers with thermoplastic polymers and then processing it through a hot extrusion process. While the color of this wood-plastic filament resembles wood, its properties are still similar to thermoplastic polymers, such as lower mechanical properties. This results in 3D-printed parts having significantly lower strength and modulus than wood. One important reason is that wood powder or short fibers lack the continuous long fibers found in wood, thus failing to effectively improve the mechanical properties of the structure.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The main objective of this invention is to provide a 3D printing polymer-coated wood filament, its preparation method, and 3D parts, in order to solve the problem that existing 3D printing wood-plastic filaments are made by crushing wood into wood powder or short fibers and then mixing them with thermoplastic polymers, resulting in poor mechanical properties and a significant difference in strength and modulus between the 3D printed parts and the wood itself.

[0005] To achieve the above objectives, according to one aspect of the present invention, a 3D-printed polymer-coated wood filament is provided, the 3D-printed polymer-coated wood filament comprising a core material and a coating layer covering the outer surface of the core material, wherein the core material is a continuous linear wood, and the material of the coating layer comprises a thermoplastic polymer.

[0006] Furthermore, the thermoplastic polymer includes at least one of polyamide, polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyurethane, polyacrylate, polymethacrylate, epoxy resin, polyetheretherketone, polyethyleneimine, and polyethylene terephthalate-1,4-cyclohexadiene-methylene terephthalate.

[0007] Furthermore, the mass ratio of continuous linear timber to the cladding material is 1:8 to 1:0.5, preferably 1:5 to 1:0.8.

[0008] Furthermore, the coating material also includes wood flour and optional additives.

[0009] Furthermore, the wood flour accounts for 0.5% to 5% of the mass of the coating material, preferably 1% to 3%.

[0010] Furthermore, the additives include chain extenders, which account for 0.1-1% of the mass of the coating material, preferably 0.3-0.8%.

[0011] Furthermore, the material of continuous linear timber includes at least one of linden, beech, oak, Douglas fir, spruce, ash, maple, teak, or cherry.

[0012] Furthermore, the cross-section of continuous linear timber is circular or nearly circular.

[0013] Furthermore, the width W of the continuous sheet wood satisfies 1mm≤W≤50mm, preferably 1mm≤W≤5mm; the thickness T of the continuous sheet wood satisfies 0.05mm≤T≤1mm, preferably 0.2mm≤T≤0.6mm. Furthermore, the continuous linear wood is formed by twisting and densifying the continuous sheet wood.

[0014] Furthermore, the method for preparing continuous linear wood includes: step S1, immersing continuous sheet wood in water for water filling treatment, and then performing twisting treatment to obtain continuous twisted wood; step S2, performing wire drawing treatment on the continuous twisted wood, and then drying it to obtain continuous linear wood.

[0015] Further, in step S1, the continuous sheet wood is immersed in water for a time >10s and less than 24h, preferably more than 1min and less than 10min.

[0016] Further, in step S2, the diameter of the continuous linear wood is smaller than the diameter of the continuously twisted wood, and the density difference m between the continuous linear wood and the continuously twisted wood satisfies 0.1 g / cm³. 3 ≤m≤2g / cm 3 .

[0017] Further, in step S1, before the continuous sheet wood is subjected to water filling treatment, lignin and hemicellulose removal treatment is performed. Preferably, the removal treatment includes: immersing the continuous sheet wood in an alkaline solution to remove lignin and hemicellulose.

[0018] Furthermore, the pH of the alkaline solution is ≥10.

[0019] Further, the alkaline solution is selected from at least one of 0.2-5M sodium hydroxide aqueous solution, 0.2-5M potassium hydroxide solution, or 0.05-1M sodium sulfite aqueous solution.

[0020] To achieve the above objectives, according to another aspect of the present invention, a method for preparing the above-mentioned 3D printed polymer-coated wood filament is provided, the method comprising: processing continuous linear wood and the material of the coating layer through a co-extrusion process to obtain 3D printed polymer-coated wood filament.

[0021] Furthermore, the equipment for performing the co-extrusion process includes a die assembly comprising a die core and a die sleeve, the die sleeve being fitted over the die core, continuous linear wood passing through the die core, and the covering material being extruded from the die sleeve.

[0022] Furthermore, the diameter of the mold core differs from the diameter of the continuous linear wood by 0.05~0.3mm.

[0023] Furthermore, the diameter of the mold sleeve differs from the diameter of the continuous linear timber by 0.1~1mm.

[0024] According to a third aspect of the present invention, a 3D part is provided, which is prepared by continuous printing of any of the 3D printing polymer-coated wood filaments provided in the first aspect or by continuous printing of 3D printing polymer-coated wood filaments obtained according to any of the preparation methods provided in the second aspect.

[0025] Applying the technical solution of this application, the 3D printing polymer-coated wood filament provided by this application uses continuous linear wood as the core material and wraps thermoplastic polymers on the surface of the continuous linear wood. It has excellent 3D printability and can be continuously printed to prepare 3D parts, realizing continuous printing processing of 3D parts, effectively improving the mechanical properties of 3D parts, and has broad application prospects in various fields such as entertainment and education.

[0026] The 3D-printed polymer-coated wood filament provided in this application is prepared by co-extrusion, which enables large-scale production and reduces preparation costs.

[0027] Furthermore, the 3D part provided in this application is prepared by continuous printing of 3D printed polymer-coated wood filament, realizing continuous printing processing of 3D parts. Moreover, the 3D part not only has a color closer to that of wood, but also has excellent mechanical properties, and has broad application prospects in various fields such as entertainment and education. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the structure of 3D printed polymer-coated wood filament provided in Embodiment 1 of the present invention is shown; Figure 2 A schematic diagram of the co-extrusion process of 3D printed polymer-coated wood filament provided in Embodiment 1 of the present invention is shown.

[0029] The above figures include the following reference numerals: 1. Core material; 2. Coating layer; 3. Continuous linear linden wood roll; 4. Continuous linear linden wood; 5. Guide roller; 6. Screw extruder; 7. Die assembly; 8. Cooling zone; 9. 3D printed polymer-coated wood filament; 10. Traction wheel; 11. Diameter gauge; 12. 3D printed polymer-coated wood filament roll. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] As analyzed in this application, existing 3D-printed wood-plastic composite filaments are prepared by pulverizing wood into wood powder or short fibers, mixing them with thermoplastic polymers, and then extruding them. Although the color is similar to wood, the wood powder or short fibers lack the continuous long fibers found in wood, resulting in poor mechanical properties. Consequently, the strength and modulus of the 3D-printed parts differ significantly from those of wood. To address this issue, this application provides a 3D-printed polymer-coated wood filament, its preparation method, and the resulting 3D part.

[0032] In one typical embodiment of this application, a 3D-printed polymer-coated wood filament is provided, which includes a core material and a coating layer covering the outer surface of the core material, wherein the material of the coating layer includes a thermoplastic polymer.

[0033] Applying the technical solution of this application, the 3D printing polymer-coated wood filament provided by this application uses continuous linear wood as the core material and wraps thermoplastic polymers on the surface of the continuous linear wood. It has excellent 3D printability and can be continuously printed to prepare 3D parts, realizing continuous printing processing of 3D parts, effectively improving the mechanical properties of 3D parts, and has broad application prospects in various fields such as entertainment and education.

[0034] The aforementioned 3D printability refers to meeting both the strength and toughness requirements of 3D printing while also enabling smooth continuous 3D printing.

[0035] The specific types of the aforementioned thermoplastic polymers are not limited. Any thermoplastic polymer commonly used in the 3D printing field is acceptable, including but not limited to any one or a mixture of several of the following: polyamide, polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyurethane, polyacrylate, polymethyl methacrylate, epoxy resin, polyetheretherketone, polyethyleneimine, and polyethylene terephthalate-1,4-cyclohexenedimethyl terephthalate.

[0036] To further improve the printing efficiency of 3D printing polymer-coated wood filaments, the melt flow index of the thermoplastic polymer is preferably 2~30 g / min (190℃, 2.16kg); more preferably 5~20 g / min (190℃, 2.16kg) to further improve printing efficiency.

[0037] Typical, but not limiting, melt flow indices of thermoplastic polymers include 2 g / min, 5 g / min, 8 g / min, 10 g / min, 12 g / min, 15 g / min, 18 g / min, 20 g / min, 22 g / min, 25 g / min, 28 g / min, 30 g / min, or any range of two values.

[0038] To make the color of the 3D-printed polymer-coated wood filament closer to that of wood, the coating layer material preferably also includes wood flour and optional additives. Preferably, when the mass percentage of wood flour in the coating layer material is 0.5% to 5%, the 3D-printed polymer-coated wood filament not only has a color closer to wood but also retains the processability of filament in co-extrusion processes. In particular, when the mass percentage of wood flour in the coating layer material is 1% to 3%, its process stability during co-extrusion processing is also higher.

[0039] To further promote uniform dispersion of wood flour in the coating material, a wood flour particle size of ≥300 mesh is preferred.

[0040] The specific types of additives mentioned above are not specifically limited; any additives commonly used in the field are acceptable, such as chain extenders and antioxidants. When a chain extender is added as an additive to the coating layer material, it is preferred that the chain extender be a copolymer with multiple active epoxy groups, such as the PL250 chain extender from Shangxi (Shanghai) Chemical Additives. In particular, when the mass percentage of the chain extender in the coating layer material is 0.1% to 1%, it is more beneficial to increase the viscosity of the system, thereby increasing the stability during co-extrusion and reducing the degradation of the polymer material during thermal processing. Especially when the mass percentage of the chain extender in the coating layer material is 0.3% to 0.8%, it is more beneficial to improve the processability during thermal processing.

[0041] To further improve the co-extrusion preparation efficiency and 3D printability of the aforementioned 3D printed polymer-coated wood filaments, the preferred mass ratio of continuous linear wood to the coating material is 1:8 to 1:0.5. In particular, when the mass ratio of continuous linear wood to thermoplastic polymer is 1:5 to 1:0.8, the 3D printed polymer-coated wood filaments exhibit superior co-extrusion processing stability and efficiency, as well as superior 3D printability.

[0042] When the mass ratio of continuous existing wood to the cladding material is less than 1:8, the resulting 3D printed polymer-coated wood filament has poor strength and cannot meet the strength requirements of 3D printing. When the mass ratio of continuous linear wood to the cladding material is greater than 1:0.5, the amount of cladding material used is too low, the adhesion of the 3D printed polymer-coated wood filament is poor, and it is difficult to prepare 3D parts through continuous 3D printing.

[0043] Typical, but not limiting, in 3D printed polymer-coated wood filaments, the mass ratio of continuous linear wood to the cladding material is, for example, 1:8, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 1:0.8, 1:0.5, or any range of two values.

[0044] The material of the aforementioned continuous linear timber is not specifically limited, including but not limited to composite timber made from any one or more of the following woods: linden, beech, oak, Douglas fir, spruce, ash, maple, teak, or cherry.

[0045] To further improve the smoothness of the 3D printing process of polymer-coated wood filament, it is preferable that the cross-section of the continuous linear wood is circular or nearly circular.

[0046] The specific shape of the continuous sheet wood is not limited. Preferably, the width W of the continuous sheet wood satisfies 1mm≤W≤50mm, more preferably 1mm≤W≤5mm, and the thickness T of the continuous sheet wood satisfies 0.05mm≤T≤1mm, more preferably 0.2mm≤T≤0.6mm.

[0047] To further improve the mechanical properties and printing efficiency of the aforementioned 3D printed polymer-coated wood filaments, it is preferable that the aforementioned continuous linear wood is made by densifying continuous sheet wood by twisting it into thread.

[0048] In some embodiments of this application, a preferred method for preparing continuous linear wood includes: step S1, immersing continuous sheet wood in water for water filling treatment, and then twisting it to obtain continuous twisted wood; step S2, extruding the continuous twisted wood and then drying it to obtain continuous linear wood.

[0049] In step S1 above, the continuous linear wood is first soaked in water before being twisted. Because the microstructure of the continuous linear wood contains numerous pores, the penetration of water molecules effectively expands the overall structure, thus achieving a lubricating effect and improving the material's workability. Preferably, the continuous sheet wood is immersed in water for a time greater than 10 seconds and less than 24 hours, especially for a time greater than 1 minute and less than 10 minutes, which further improves twisting efficiency.

[0050] The above twisting process can be performed in a twisting machine, which is more conducive to improving twisting efficiency.

[0051] In step S2 above, the wire drawing process compresses the diameter of the continuously twisted wood to a stable state. The wire drawing process involves passing the continuously twisted wood through a mold with a certain opening size at room temperature, during which the continuously twisted wood is compressed; or, the wood can be repeatedly passed through multiple molds with the same opening size to stabilize the diameter of the continuously twisted wood; or, the wood can be gradually compressed by passing through molds with different opening sizes (gradually decreasing). Finally, the wire-drawn wood is rolled up and dried to obtain continuous linear wood.

[0052] In step S2 above, preferably, the diameter of the continuous linear wood is smaller than the diameter of the continuously twisted wood, and the density of the continuous linear wood is greater than the density of the continuously twisted wood, with the density difference m between the two satisfying 0.1 g / cm³. 3 ≤m≤2g / cm 3 .

[0053] It should be noted that the density of the continuous linear timber mentioned above refers to the density after drying, and the diameter of the continuous linear timber mentioned above also refers to the diameter after drying.

[0054] In step S2 above, drying can be achieved naturally in the air until the humidity reaches equilibrium (the specific equilibrium value depends on the ambient humidity). Alternatively, drying can be accelerated by heating at a temperature ≥50℃ for a period of time, especially when the temperature is ≥80℃ and the time is greater than 1 minute; optionally, the heating time is 30 minutes.

[0055] To further improve the mechanical properties of the continuous linear wood, step S1 is preferred, in which the continuous sheet wood undergoes lignin and hemicellulose removal treatment before water filling treatment. The removal treatment preferably includes: immersing the continuous sheet wood in an alkaline solution to chemically remove lignin and hemicellulose; more preferably, when the pH of the alkaline solution is ≥10, it is more conducive to improving the removal efficiency of lignin and hemicellulose.

[0056] The specific type of alkaline solution mentioned above is not specifically limited, including but not limited to any one or more alkaline solutions selected from 0.2~5M sodium hydroxide aqueous solution, 0.2~5M potassium hydroxide aqueous solution, or 0.05~1M sodium sulfite aqueous solution.

[0057] The aforementioned continuous sheet timber is generally made by splicing together sheet timber. The sheet timber is cut from raw wood and its length is greater than 0.5m and less than 10m. Optionally, the length is greater than 2m.

[0058] To further extend the length of continuous sheet wood and facilitate the continuous preparation of 3D printed polymer-coated wood filaments, it is preferable to splice together multiple sheets of lignin-removed wood before the continuous sheet wood is twisted and densified.

[0059] The above splicing method is not specifically limited, and includes, but is not limited to, placing the lignin-removed sheet wood into a veneer machine for splicing, with the ends of two adjacent sheets glued together using hot melt adhesive, resulting in a continuous sheet wood length greater than 9m and less than 1000m. Optionally, the length of the continuous sheet wood after splicing is greater than 50m and less than 200m. Optionally, when two adjacent sheets of wood are spliced ​​end-to-end, the width of the joined area is greater than 0.2mm and less than 5cm. In particular, when the width of the joined area is greater than 0.6mm and less than 2mm, it is more conducive to improving splicing efficiency while ensuring splicing stability.

[0060] In a second typical embodiment of this application, a method for preparing the above-mentioned 3D printed polymer-coated wood filament is also provided. The method includes: co-extruding continuous linear wood and the material of the coating layer to obtain 3D printed polymer-coated wood filament.

[0061] The 3D-printed polymer-coated wood filament provided in this application is prepared by co-extrusion, which is easy to achieve large-scale production and reduces preparation costs.

[0062] In some embodiments of this application, the equipment for performing the above co-extrusion process includes a die head assembly, which includes a die core and a die sleeve. The die sleeve is fitted over the outside of the die core. Continuous linear wood passes through the die core, and the material of the coating layer is extruded from the die sleeve and coated on the outer surface of the continuous linear wood. After the material of the coating layer is cured, 3D printed polymer-coated wood filament is obtained.

[0063] In some embodiments of this application, the co-extrusion process includes: adding continuous linear wood and a coating material together into a co-extrusion apparatus, with the linear wood continuously passing through a die core; the coating material, including a thermoplastic polymer, is heated to its melting temperature using a single-screw extruder and injected into a die assembly, and extruded from the die sleeve to coat the outer surface of the continuous linear wood. After cooling, a 3D-printed polymer-coated wood filament is formed. Cooling methods include, but are not limited to, water cooling, oil cooling, air cooling, or natural cooling.

[0064] In some embodiments of this application, the equipment for the co-extrusion process further includes a guide roller, a screw extruder, a cooling device, a traction roller, a diameter gauge, and a winding machine. Continuous linear wood first passes through the guide roller and then exits from the die core under the traction force of the traction roller. The coating material is added to the screw extruder, mixed and heated to a molten state, and then extruded from the die under the thrust of the screw, coating the outer surface of the continuous linear wood. It is then conveyed to the cooling zone, where the molten coating material cools and solidifies under the action of the cooling device, resulting in 3D-printed polymer-coated wood filament. The 3D-printed polymer-coated wood filament is then tractioned by the traction roller, passes through the diameter gauge, and is wound into a 3D-printed polymer-coated wood filament roll.

[0065] To further improve the efficiency of co-extrusion, it is preferable that the diameter of the die core is larger than the diameter of the continuous linear wood, and the difference between the diameter of the die core and the diameter of the continuous linear wood is 0.05~0.3mm, and the difference between the diameter of the die sleeve and the diameter of the continuous linear wood is 0.1mm~1mm.

[0066] In a third typical embodiment of this application, a 3D part is also provided, which is continuously printed by any of the 3D printing polymer-coated wood filaments provided in the first typical embodiment or by continuously printing 3D printing polymer-coated wood filaments obtained according to any of the preparation methods provided in the second typical embodiment.

[0067] The 3D part provided in this application is prepared by continuous printing using the 3D printing polymer-coated wood filament provided in this application, realizing continuous printing processing of 3D parts. Moreover, the 3D part not only has a color closer to that of wood, but also has excellent mechanical properties, and has broad application prospects in various fields such as entertainment and education.

[0068] In some embodiments of this application, the 3D parts provided can be continuously printed using a set of printhead assemblies (including a feeding device, a thermal nozzle, and connectors) to produce 3D printed polymer-coated wood filaments. Because the surface of the 3D printed polymer-coated wood filaments is uniformly coated with thermoplastic polymer, the hardware design, weight, and cost of the entire printhead can be greatly simplified, eliminating the need for additional adhesive feeding and printing of the continuous wood. During the 3D printing process, the thermoplastic polymer coating layer acts as an adhesive. Inside the thermal nozzle, the thermoplastic polymer coating layer is heated to its melting temperature and then printed together with the wood core material into a 3D structure. Cooling and curing then effectively fixes the wood core material within the structure. Simultaneously, the 3D printer's software control system can be simplified by reducing additional adhesive feeding and printing. Furthermore, the 3D printer can also be designed to print multiple continuous filaments of polymer-coated wood. By adjusting the type of wood, different properties and colors of different wood species can be obtained in the 3D part structure.

[0069] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0070] Example 1

[0071] This embodiment provides a 3D printed polymer-coated wood filament 9, such as... Figure 1 As shown, the 3D-printed polymer-coated wood filament 9 includes a core material 1 and a coating layer 2 covering the outer surface of the core material 1. The core material 1 is a continuous linear linden wood 4 (0.55 mm in diameter), and the coating layer 2 has a thickness of 0.45 mm. The material of the coating layer 2 includes 97.5 wt% polylactic acid (melt index 15 g / min, 190℃, 2.16 kg), 2 wt% wood flour (particle size ≤ 300 mesh), and 0.5 wt% chain extender (Shangxi Chemical auxiliary PL250). The mass ratio of the continuous linear linden wood 4 to the material of the coating layer 2 is 1:1.

[0072] The 3D-printed polymer-coated wood filament was prepared according to the following steps: (1) Cut the linden wood into linden wood sheets with a length of 2500mm, a width of 3.0mm, and a thickness of 0.4mm; (2) Immerse the linden wood sheets in a 2M sodium hydroxide solution at 120°C for 600 min to remove lignin and hemicellulose from the linden wood sheets; after removing the linden wood sheets from the sodium hydroxide solution, rinse them with water for 10 min and dry them to obtain the linden wood sheets to be spliced. (3) Multiple sheets of linden wood to be spliced ​​are placed into a veneer machine for splicing end to end. The two sheets to be spliced ​​are bonded together with hot melt adhesive and then hot-pressed. The width of the splicing area is 1.0 mm, resulting in a continuous sheet of linden wood with a length of 120 m. (4) After immersing the continuous sheet linden wood in water for 5 minutes for water filling treatment, take it out and put it into a twisting machine for twisting treatment to obtain continuous twisted linden wood; (5) The continuously twisted linden wood is placed into an open mold with a diameter of 0.5 mm for wire drawing and then dried to obtain continuous linear linden wood 4; wherein, during the wire drawing process, the continuously twisted linden wood is repeatedly compressed so that the density difference between the continuous linear linden wood 4 and the continuously twisted linden wood is 1 g / cm³. 3 ; (6) The continuous linear linden wood 4 and the material of the coating layer 2 are put into the co-extrusion equipment for co-extrusion, such as... Figure 2 As shown, the co-extrusion process is carried out according to the following steps: A continuous linear linden wood roll 3 is provided. Under the action of the traction wheel 10, the continuous linear linden wood 4 passes through the guide wheel 5 and enters the die head assembly 7. Under the action of traction force, it passes through the die core. The material of the coating layer 2 is added to the screw extruder 6. After being mixed and heated to a molten state by the screw extruder 6, it enters the die head assembly 7 under the action of screw thrust and is extruded from the die sleeve, covering the outer surface of the continuous linear linden wood 4. It is then transported to the cooling zone 8. Under the action of the cooling device (not shown), the molten coating layer 2 material is cooled and solidified to obtain 3D printed polymer-coated wood filament 9. Under the traction action of the traction wheel 10, the 3D printed polymer-coated wood filament 9 passes through the diameter measuring instrument 11 and is wound into a 3D printed polymer-coated wood filament roll 12.

[0073] Example 2

[0074] The difference between this embodiment and embodiment 1 is that the material of the coating layer 2 includes 94.9% polylactic acid, 5 wt% wood flour, and 0.1 wt% chain extender.

[0075] Example 3

[0076] The difference between this embodiment and embodiment 1 is that the material of the coating layer 2 includes 98.5 wt% polylactic acid, 0.5 wt% wood flour, and 1 wt% chain extender.

[0077] Example 4

[0078] The difference between this embodiment and embodiment 1 is that the material of the coating layer 2 includes 80 wt% polylactic acid, 19.5 wt% wood flour, and 0.5 wt% chain extender.

[0079] Example 5

[0080] The difference between this embodiment and Embodiment 1 is that the inner diameter of the mold is adjusted so that the mass ratio of the continuous linear linden wood 4 to the coating layer 2 in the 3D printed polymer-coated wood filament 9 is 1:8.

[0081] Example 6

[0082] The difference between this embodiment and Embodiment 1 is that the inner diameter of the mold is adjusted so that the mass ratio of continuous linear linden wood 4 to the material of the coating layer in the 3D printed polymer-coated wood filament 9 is 1:5.

[0083] Example 7

[0084] The difference between this embodiment and embodiment 1 is that the inner diameter of the mold is adjusted so that the mass ratio of the continuous linear linden wood 4 to the coating layer 2 in the 3D printed polymer-coated wood filament 9 is 1:0.8.

[0085] Example 8

[0086] The difference between this embodiment and Embodiment 1 is that the inner diameter of the mold is adjusted so that the mass ratio of the continuous linear linden wood 4 to the coating layer 2 in the 3D printed polymer-coated wood filament 9 is 1:0.5.

[0087] Example 9

[0088] The difference between this embodiment and Embodiment 1 is that the inner diameter of the mold is adjusted so that the mass ratio of the continuous linear linden wood 4 to the coating layer 2 in the 3D printed polymer-coated wood filament 9 is 1:10.

[0089] Example 10

[0090] The difference between this embodiment and Embodiment 1 is that the inner diameter of the mold is adjusted so that the mass ratio of the continuous linear linden wood 4 to the coating layer 2 in the 3D printed polymer-coated wood filament 9 is 1:0.2.

[0091] Example 11

[0092] The difference between this embodiment and embodiment 1 is that step (5) is not performed. Instead, the twisted linden wood obtained in step (4) is dried and then placed into the equipment for co-extrusion.

[0093] Example 12

[0094] The difference between this embodiment and Embodiment 1 is that, in step (5), the density difference between the obtained continuous linear linden wood 4 and the continuously twisted linden wood is 0.1 g / cm³. 3 .

[0095] Example 13

[0096] The difference between this embodiment and Embodiment 1 is that, in step (5), the density difference between the obtained continuous linear linden wood 4 and the continuously twisted linden wood is 2 g / cm³. 3 .

[0097] Example 14

[0098] The difference between this embodiment and Embodiment 1 is that, in step (5), the density difference between the obtained continuous linear linden wood 4 and the continuously twisted linden wood is 0.05 g / cm³. 3 .

[0099] Example 15

[0100] The difference between this embodiment and Embodiment 1 is that, in step (5), the density difference between the obtained continuous linear linden wood 4 and the continuously twisted linden wood is 2.5 g / cm³. 3 .

[0101] Comparative Example 1

[0102] This comparative example provides a 3D printed polylactic acid filament with the same diameter as the 3D printed polymer-coated wood filament 9 provided in Example 1. It is prepared by extruding the material of the coating layer 2 and does not have a core material.

[0103] Comparative Example 2

[0104] This comparative example provides a continuous linear linden wood, which is the same as the continuous linear linden wood 4 used as the core material in Example 1.

[0105] Test case

[0106] The tensile strength and elongation at break of the wires provided in the above embodiments and comparative examples were measured respectively, and their color was visually inspected. The results are shown in Table 1 below.

[0107] The test methods for tensile strength and elongation at break were as follows: Wire samples with a length of 90 mm were first dried in an 80℃ drying oven for 12 hours to fully remove moisture. After conditioning in a standard environment (23℃, 50%RH) for 24 hours, the test was conducted on a CTM8010 universal electronic tensile testing machine according to the standard test method for unidirectional fiber-reinforced plastic composites as shown in ISO 527-5. The test rate was 5 mm / min, and the clamping distance was 45 mm. The tensile strength and elongation at break were obtained simultaneously after the test. The appearance of the wire was evaluated visually in a D65 standard light source color matching box.

[0108] Table 1

[0109] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: By applying the technical solution of this application, the 3D printing polymer-coated wood filament provided by this application uses continuous linear wood as the core material and wraps thermoplastic polymers on the surface of the continuous linear wood, which has excellent 3D printability. 3D parts can be prepared by continuous printing, realizing continuous printing processing of 3D parts, effectively improving the mechanical properties of 3D parts, and has broad application prospects in various fields such as entertainment and education.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A 3D-printed polymer-coated wood filament, characterized in that, The 3D printed polymer-coated wood filament includes a core material and a coating layer covering the outer surface of the core material. The core material is a continuous linear wood, and the coating layer is made of thermoplastic polymer. The mass ratio of the continuous linear wood to the coating layer material is 1:8 to 1:0.

5. The coating material further includes wood flour and chain extender; the wood flour accounts for 0.5-5% of the mass of the coating material; the chain extender accounts for 0.1-1% of the mass of the coating material. The thermoplastic polymer includes at least one of polyamide, polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyurethane, polyacrylate, polymethyl methacrylate, epoxy resin, polyetheretherketone, polyethyleneimine, and polyethylene terephthalate-1,4-cyclohexadiene-methylene terephthalate; the continuous linear wood is formed by twisting and densifying continuous sheet wood; the width W of the continuous sheet wood satisfies 1mm ≤ W ≤ 50mm; The thickness T of the continuous sheet wood satisfies 0.05mm≤T≤1mm; The method for preparing the continuous linear timber includes: Step S1: Immerse the continuous sheet wood in water for water filling treatment, and then perform twisting treatment to obtain continuous twisted wood; Step S2: The continuously twisted wood is drawn into fibers and then dried to obtain the continuous linear wood. In step S2, the diameter of the continuous linear timber is smaller than the diameter of the continuously twisted timber; and the density difference m between the continuous linear timber and the continuously twisted timber satisfies 0.1 g / cm³. 3 ≤m≤2g / cm 3 .

2. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, The mass ratio of the continuous linear timber to the material of the covering layer is 1:5 to 1:0.

8.

3. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, The wood flour accounts for 1-3% of the mass of the material in the coating layer.

4. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, The chain extender accounts for 0.3-0.8% of the mass of the coating material.

5. The 3D-printed polymer-coated wood filament according to any one of claims 1 to 4, characterized in that, The material of the continuous linear timber includes at least one of linden, beech, oak, Douglas fir, spruce, ash, maple, teak, or cherry.

6. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, The cross-section of the continuous linear timber is circular or nearly circular.

7. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, The width W of the continuous sheet wood satisfies 1mm ≤ W ≤ 5mm.

8. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, The thickness T of the continuous sheet wood satisfies 0.2mm≤T≤0.6mm.

9. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, In step S1, the continuous sheet wood is submerged in water for a time greater than 10 seconds and less than 24 hours.

10. The 3D-printed polymer-coated wood filament according to claim 9, characterized in that, In step S1, the continuous sheet wood is submerged in water for a time greater than 1 minute and less than 10 minutes.

11. The 3D-printed polymer-coated wood filament according to claim 1, characterized in that, In step S1, the continuous sheet wood undergoes a lignin and hemicellulose removal treatment before being subjected to water filling.

12. The 3D-printed polymer-coated wood filament according to claim 11, characterized in that, The removal process includes immersing the continuous sheet wood in an alkaline solution to remove lignin and hemicellulose.

13. The 3D-printed polymer-coated wood filament according to claim 12, characterized in that, The alkaline solution has a pH ≥ 10.

14. The 3D-printed polymer-coated wood filament according to claim 12, characterized in that, The alkaline solution is selected from at least one of 0.2-5M sodium hydroxide aqueous solution, 0.2-5M potassium hydroxide aqueous solution, or 0.05-1M sodium sulfite aqueous solution.

15. A method for preparing 3D-printed polymer-coated wood filament according to any one of claims 1 to 14, characterized in that, The preparation method includes: processing the continuous linear wood and the coating material through a co-extrusion process to obtain the 3D printed polymer-coated wood filament.

16. The preparation method according to claim 15, characterized in that, The equipment for performing the co-extrusion process includes a die head assembly, which includes a die core and a die sleeve. The die sleeve is fitted over the outside of the die core, through which the continuous linear wood passes, and through which the coating material is extruded.

17. The preparation method according to claim 16, characterized in that, The diameter of the mold core differs from the diameter of the continuous linear wood by 0.05~0.3mm.

18. The preparation method according to claim 16, characterized in that, The diameter of the mold sleeve differs from the diameter of the continuous linear timber by 0.1 to 1 mm.

19. The preparation method according to claim 16, characterized in that, The equipment for the co-extrusion process also includes a guide roller, a screw extruder, a cooling device, a traction roller, a diameter gauge, and a winding machine.

20. The preparation method according to claim 19, characterized in that, The co-extrusion process includes: the continuous linear wood enters the die assembly after passing through the guide wheel, and exits from the die core under the traction force of the traction wheel; the material of the coating layer is added to the screw extruder, heated to a molten state, and extruded from the die sleeve under the thrust of the screw, coating the outer surface of the continuous linear wood, and conveyed to the cooling zone; under the action of the cooling device, the molten coating layer material is cooled and solidified to obtain the 3D printed polymer-coated wood filament; the 3D printed polymer-coated wood filament is pulled by the traction wheel, passes through the diameter measuring instrument, and is wound into a 3D printed polymer-coated wood filament roll.

21. A 3D part, characterized in that, The 3D part is prepared by continuous printing of 3D printed polymer-coated wood filament as described in any one of claims 1 to 14, or by continuous printing of 3D printed polymer-coated wood filament obtained by the preparation method described in claims 15 to 20.

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