Lignin and pla 3d printing wire material with high interlayer bonding force and preparation method thereof

Abstract

The application discloses lignin and PLA 3D printing wire material with high interlayer bonding force and a preparation method thereof, the printing wire material comprises the following components in percentage by weight: 100 parts of PLA, 2.5-20 parts of lignin, 5-20 parts of polyester toughening agent, 0.05-1 part of epoxy multifunctional compatilizer and 0.5-3 parts of antioxidant; the lignin structure characteristics are utilized, the internal structure of the material and the printing mechanism are considered, the wire material formula is reasonably configured, the effective regulation of the wire material strength and toughness and interlayer adhesion is realized, and the high-performance PLA wire material is obtained; the lignin can be used as a multifunctional additive, has good interface compatibility and dispersibility with the polymer, and endows the material with antibacterial performance and ultraviolet resistance; the lignin is prepared from waste biomass resources, and the raw materials are widely distributed, recyclable and easy to obtain.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and in particular to a lignin and PLA 3D printing filament with strong interlayer bonding and its preparation method. Background Technology

[0002] 3D printing, as an innovative technology in the manufacturing field, has unique advantages in the production of special products and personalized manufacturing. It also meets the urgent social demand for environmental protection and resource conservation. Polylactic acid (PLA), as a fully biodegradable plastic that has been industrially produced, has good mechanical properties and processability. Moreover, it has low shrinkage during molding and is not prone to warping, playing a significant role in 3D printing. However, since the mechanical strength of PLA decreases after toughening, achieving a balance between strength and toughness has always been a challenge. In addition, the characteristics of 3D printing result in a decrease in the Z-axis strength of printed products, making it particularly important to solve the interlayer adhesion problem.

[0003] Lignin, as a natural, renewable, and biodegradable material, acts as a binder in wood, forming a hard wood structure together with cellulose and hemicellulose. Furthermore, lignin possesses a rigid benzene ring structure and abundant active hydroxyl groups on its surface, exhibiting UV resistance and antibacterial properties. It is often used as a reactive filler to modify polymers. For example, patent CN108948682A prepared a biodegradable film masterbatch using lignin and PLA, effectively improving the compatibility of PBAT and PLA and enhancing the mechanical properties of the film. However, this system has a maximum PLA content of 30 parts, with PBAT as the matrix. The resulting filaments are prone to buckling during printing, leading to printing failures. Moreover, lignin content exceeding 20 parts easily aggregates within the matrix, reducing the synergistic effect between lignin, the matrix, and the chain extender, causing a sharp decline in melt stability. This results in brittle fracture during filament drawing and frequent clogging during printing. Bifunctional chain extenders provide a small number of reaction sites, showing good effects in films, but are not very effective in 3D printing, especially for interlayer adhesion of printed parts.

[0004] Although there are some methods for modifying polylactic acid materials with lignin, the overall performance of these materials is basically unsuitable for the 3D printing field, and this gap cannot be bridged by simply adjusting the proportions in the formulation, especially in terms of the interlayer bonding effect required in 3D printing. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a lignin and PLA 3D printing filament for interlayer bonding, which, by weight, comprises 100 parts of PLA, 2.5-20 parts of lignin, 5-20 parts of polyester toughening agent, 0.05-1 parts of epoxy multifunctional compatibilizer, and 0.5-3 parts of antioxidant.

[0006] As a further supplement to this technical solution, the lignin is one or more of alkali lignin, lignin sulfonate, organic solvent lignin, and low eutectic solvent lignin.

[0007] As a further supplement to this technical solution, the antioxidant is one or a combination of 1010, 1076, and 164.

[0008] As a further supplement to this technical solution, the epoxy multifunctional compatibilizer is one or a combination of two of ADR and HPC-5020.

[0009] As a further supplement to this technical solution, the toughening agent is one or a combination of PBS, PBAT, and PHA.

[0010] A method for preparing lignin and PLA 3D printing filament with high interlayer bonding strength includes the following steps: 1) Preparation of PLA / lignin particles PLA, lignin, antioxidant, epoxy multifunctional compatibilizer, and polyester toughening agent are stirred in a mixer for 30 minutes, extruded in a twin-screw extruder at 160~220℃, cooled, and then pelletized. 2) Preparation of PLA wire The granules from step 1 are melt-extruded in a single-screw extruder and then cooled to prepare wire.

[0011] The beneficial effects are as follows: the filler of this invention is lignin, a biodegradable natural material. The lignin in this material is fully integrated with the matrix material, fully exposing the active hydroxyl groups on the surface. Under the action of epoxy crosslinking agents, the alcoholic and phenolic hydroxyl groups of lignin undergo in-situ chemical reactions with PLA and PBAT during the melting process, forming a three-dimensional network structure. This structure can improve the mechanical strength of the material. Simultaneously, it can increase the entanglement between the active hydroxyl groups on the lignin surface and the matrix molecules during the printing process, promoting the contact between the molten material and the previous layer, increasing the bonding force with the previous layer, and thus improving the interlayer adhesion of the printed parts. This invention comprehensively improves the performance of polylactic acid, broadens the high-value utilization of biomass resources, and, based on the structural characteristics of lignin, rationally configures the filament formulation from the perspective of the material's internal structure and printing mechanism, achieving effective control of filament strength and interlayer adhesion, obtaining high-performance PLA filaments. Lignin can also serve as a multifunctional additive, exhibiting good interfacial compatibility and dispersibility with polymers, endowing the material with antibacterial and UV-resistant properties. It uses waste biomass resources as raw materials, which are widely distributed, recyclable, and easily accessible. Detailed Implementation

[0012] To facilitate a clearer understanding of this technical solution by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to embodiments: A lignin and PLA 3D printing filament for high-layer interlayer bonding is disclosed, resulting in products printed with excellent interlayer adhesion, outstanding tensile strength, and toughness. The mechanism of action lies in the fact that the material contains a small amount of lignin and a high content of PLA matrix material, which facilitates the full integration of lignin and matrix material and fully exposes the active hydroxyl groups on the surface. Under the action of an epoxy compatibilizer, the alcoholic and phenolic hydroxyl groups of lignin undergo in-situ chemical reactions with PLA and PBAT during the melting process, forming a three-dimensional network structure. This structure enhances the mechanical strength of the material; simultaneously, it increases the entanglement between the active hydroxyl groups on the lignin surface and matrix molecules during printing, promoting contact between the molten material and the previous layer, increasing the bonding force with the previous layer, and thus improving the interlayer adhesion of the printed part.

[0013] A lignin and PLA 3D printing filament for high-layer bonding, comprising, by weight: 100 parts PLA, 2.5-20 parts lignin, 5-20 parts polyester toughening agent (PBAT, PBS, PHA, etc.), 0.05-1 part epoxy multifunctional compatibilizer, and 0.5-3 parts antioxidant.

[0014] Among them, lignin is one or more of alkali lignin, lignin sulfonate, organic solvent lignin, and low eutectic solvent lignin.

[0015] The antioxidant is one or a combination of 1010, 1076, and 164.

[0016] Among them, the epoxy multifunctional compatibilizer is one or a combination of two of ADR and HPC-5020.

[0017] The toughening agent is one or a combination of PBS, PBAT, and PHA.

[0018] A method for preparing lignin and PLA 3D printing filament with high interlayer bonding strength includes the following steps: 1) Preparation of PLA / lignin particles PLA, lignin, antioxidant, epoxy multifunctional compatibilizer, and polyester toughening agent are stirred in a mixer for 30 minutes, extruded in a twin-screw extruder at 160~220℃, cooled, and then pelletized. 2) Preparation of PLA wire The granules from step 1 are melt-extruded in a single-screw extruder and then cooled to prepare wire.

[0019] This invention first granulates lignin powder with PLA, toughening agents, epoxy multifunctional compatibilizers, and antioxidants to obtain PLA particles with uniform lignin distribution. These particles are then melt-extruded using a single-screw extruder. Under the action of the epoxy multifunctional compatibilizer, the alcohol and phenolic hydroxyl groups of lignin undergo in-situ chemical reactions with PLA and PBAT during the melting process, forming a three-dimensional network structure. This structure enhances the mechanical strength of the material. Simultaneously, it increases the entanglement between the active hydroxyl groups on the lignin surface and the matrix molecules during printing, promoting contact between the molten material and the previous layer, increasing the bonding force with the previous layer, and thus improving the interlayer adhesion of the printed part. This material exhibits excellent mechanical properties; when the lignin content is 2.5-20 parts, the tensile strength is between 40MPa and 50MPa, and the impact strength is between 20-30KJ / m. ² The Z-axis strength is between 25 MPa and 40 MPa. The PLA filament prepared by this invention is a fully biodegradable biomass material. Lignin has antibacterial and UV-resistant properties, and provides PLA with strength and interlayer adhesion, making it widely applicable as a material in the fields of food packaging and toys.

[0020] Example 1: 1) Preparation of PLA / lignin particles PLA, lignin, antioxidant, compatibilizer and toughening agent are mixed in a mixer for 30 minutes, extruded in a twin-screw extruder at 190 ℃, cooled and pelletized. Based on 100 parts by weight of PLA, the amount of antioxidant 1010 is 0.5 parts, lignin is 5 parts, compatibilizer HPC-5020 is 0.1 parts, and toughening agent PBAT is 10 parts. 2) The granules are melt-extruded in a single-screw extruder and cooled in water baths at 60, 40, and 25 ℃ to prepare wire.

[0021] Examples 2-3: The epoxy multifunctional compatibilizers in Example 1 were replaced with ADR and BDO, respectively, while the other conditions remained the same as in Example 1.

[0022] The effects of different types of compatibilizers on the mechanical properties of wires in Examples 1-3 are shown in Table 1.

[0023] Table 1. Effect of different compatibilizer types on PLA wire properties Table 1 shows that compatibilizers with different functionalities have a significant impact on the mechanical properties of PLA lignin filaments. The Z-axis strength of the printed parts produced by the multifunctional compatibilizers ADR and HPC-5020 is significantly higher than that of BDO, and there are also significant differences in tensile strength and impact strength, with ADR showing the best effect. This is mainly because BDO is a bifunctional chain extender that can only form straight chains and cannot form cross-linked structures, while ADR and HPC-5020 have multiple functional groups. They can not only promote the in-situ reaction between the matrix resin and lignin during melting to form a cross-linked network structure, thereby improving the tensile strength and toughness of the printed parts, but also increase the entanglement between the active hydroxyl groups on the lignin surface and the matrix molecules during printing, promoting the contact between the molten material and the previous layer, and improving the interlayer adhesion of the printed parts.

[0024] Examples 4-6: The lignin in Example 1 was replaced with alkali lignin, lignin sulfonate, and low co-solubility solvent lignin, while the other conditions were the same as in Example 1.

[0025] The effects of different lignin types on wire properties in Examples 1 and 4-6 are shown in Table 2.

[0026] Table 2. Effects of different lignin types on wire properties Table 2 shows that the type of lignin mainly affects the tensile strength, toughness, and Z-axis strength of the wire. Alkali lignin and lignin sulfonate have relatively little effect on the mechanical properties of the wire, while organic solvent lignin and eutectic solvent lignin have significant effects on improving the mechanical properties. Among them, organic solvent lignin has the most significant effect on Z-axis strength. This is mainly because organic solvent lignin has a lower molecular weight and a higher content of active hydroxyl groups, making it easier to undergo in-situ reactions and form cross-linked network structures under the action of reactive compatibilizers.

[0027] Examples 7-8: The toughening agent in Example 1 was replaced with PBS and PHA, and the other conditions were the same as in Example 1.

[0028] The effects of different toughening agents on the products in Examples 1 and 7-8 are shown in Table 3.

[0029] Table 3. Effects of different toughening agents on wire properties Table 3 shows that the type of toughening agent mainly affects the impact strength of the filament. Compared with PBS, PBAT and PHA have better toughening effects on PLA filament. However, the strength and interlayer adhesion of PHA decrease rapidly, while the tensile strength and Z-axis strength of PBAT are relatively high. This effect comes from the three-dimensional network structure formed between lignin, PBAT and PLA and the rapid entanglement of molecular chains between layers during printing.

[0030] Examples 9-11: The lignin content in Example 1 was changed to 10, 15, and 20 parts, while the other conditions remained the same as in Example 1.

[0031] The effects of different lignin contents on PLA wires in Examples 1 and 9-11 are shown in Table 4.

[0032] Table 4. Effects of different lignin ratios on the mechanical properties of PLA wire rods Table 4 shows that different lignin contents have a significant impact on the mechanical properties of the filament. When the lignin content is higher than 10 parts, the mechanical strength of the material decreases. When the lignin content reaches 20 parts, clogging is very likely to occur during the printing process, making normal printing impossible. This indicates that when the lignin content is within 15 parts, the active groups that can be dispersed in the matrix and fully exposed on the surface promote the formation of a three-dimensional network structure. Furthermore, the higher the lignin content, the denser the three-dimensional network structure formed. When the lignin content increases again, lignin is prone to agglomeration within the material, which affects the exposure of active groups. This not only affects the in-situ crosslinking reaction, but the agglomerated lignin also leads to internal defects in the material, further reducing its mechanical properties.

[0033] Example 12: The PBAT content in Example 1 was changed to 70 parts and PLA to 30 parts, while the other conditions remained the same as in Example 1.

[0034] The effects of different PLA contents on PLA wires in Examples 1 and 12 are shown in Table 5.

[0035] Table 5. Effect of different PBAT ratios on the mechanical properties of PLA wires Table 5 shows that when the PBAT content is 70 parts, the wire modulus of Example 12 is too low, causing buckling during the printing process and preventing the wire from feeding.

[0036] In summary, this invention utilizes low-value-added lignin as a raw material to propose a lignin-PLA 3D printing filament with enhanced interlayer bonding strength. Starting from structural design and printing mechanisms, a three-dimensional network structure is constructed within the material. This structure improves the material's mechanical strength and promotes contact between the molten material and the preceding layer, increasing the bonding force and thus enhancing the interlayer adhesion of the printed part. This invention comprehensively improves the performance of polylactic acid and broadens the high-value utilization of biomass resources.

[0037] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

Claims

1. A lignin and PLA 3D printing filament for high-layer interlayer bonding, characterized in that, By weight: including 100 parts PLA, 2.5-20 parts lignin, 5-20 parts polyester toughening agent, 0.05-1 part epoxy multifunctional compatibilizer, and 0.5-3 parts antioxidant.

2. The lignin and PLA 3D printing filament for interlayer bonding according to claim 1, characterized in that, The lignin is one or more of alkali lignin, lignin sulfonate, organic solvent lignin, and low eutectic solvent lignin.

3. The lignin and PLA 3D printing filament for interlayer bonding according to claim 2, characterized in that, The antioxidant is one or a combination of 1010, 1076, and 164.

4. The lignin and PLA 3D printing filament for interlayer bonding strength according to claim 3, characterized in that, The epoxy-based multifunctional compatibilizer is one or a combination of two of ADR and HPC-5020.

5. The lignin and PLA 3D printing filament for interlayer bonding strength according to claim 4, characterized in that, The toughening agent is one or a combination of PBS, PBAT, and PHA.

6. The method for preparing lignin and PLA 3D printing filament with high interlayer bonding strength according to any one of claims 1-5, characterized in that, Includes the following steps: 1) Preparation of PLA / lignin particles PLA, lignin, antioxidant, epoxy multifunctional compatibilizer, and polyester toughening agent are stirred in a mixer for 30 minutes, extruded in a twin-screw extruder at 160~220℃, cooled, and then pelletized. 2) Preparation of PLA wire The granules from step 1 are melt-extruded in a single-screw extruder and then cooled to prepare wire.

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