Modified PLA material for 3D printing and preparation method thereof

Abstract

The invention discloses a modified PLA (polylactic acid) material for 3D (three-dimensional) printing and a preparation method of the modified PLA material. The modified PLA material is prepared from the following raw materials: PLA resin, a three-arm cage-shaped PLA oligomer, a flow promoter and a flexibilizer. The preparation method comprises the following steps: firstly, preparing a three-arm cage-shaped PLA oligomer, and then carrying out melt extrusion on the three-arm cage-shaped PLA oligomer and PLA resin to prepare the modified PLA material. By introducing the self-made three-arm cage-shaped PLA oligomer, the molecular weight distribution width of the material is increased, and the fluidity of the material is improved, so that the PLA material can be suitable for high-speed FDM printing; interlayer molecular chain winding can be strengthened in the printing fused deposition process, interlayer bonding is greatly improved, auxiliary precipitation on the material surface in the printing process is reduced, and printing interlayer bonding is synergistically strengthened.

Description

Technical Field

[0001] The present invention belongs to the field of 3D printing materials, and in particular relates to a high-strength interlayer bonding modified PLA material suitable for high-speed 3D printing and a preparation method thereof. Background Art

[0002] 3D printing, especially the material extrusion fused deposition 3D printing technology represented by FDM, has the advantages of convenient operation and low cost, and has been widely used in industries such as crafts and cultural relics, medical protective gear, and customized parts. PLA materials have the advantages of low printing cost and good molding effect, and have been widely used in the field of 3D printing.

[0003] Conventional FDM printing generally has a printing speed of 30-60mm / s, and the printing efficiency is low, which limits the application of FDM in production. In recent years, FDM technology has made continuous breakthroughs, and more and more high-speed FDM printers have appeared on the market, with printing speeds of up to 300-600mm / s, which has largely solved the pain point of low printing efficiency. However, with the innovation of equipment technology, conventional PLA printing materials are prone to problems such as weak interlayer bonding, poor appearance, and poor extrusion during high-speed printing.

[0004] Patent CN110317442A discloses a light-shielding 3D printing PLA material with high bonding strength and its preparation method and application. By adding epoxy-containing low-viscosity compound modifiers, fluidity modifiers and melt regulators to adjust the melt fluidity, it is beneficial to improve the printing appearance effect; by increasing the viscosity of the material when it is melted, the interlayer bonding is enhanced. The viscosity of the material is greatly affected by temperature. When printing at conventional speeds, the melt temperature is relatively stable, but under high-speed printing conditions, if the viscosity of the material remains high, it will cause continuous overflow at the edge of the printed part, seriously affecting the printing appearance, and even making it impossible to print.

[0005] Patent CN116376245A discloses a FDM 3D printer consumable material and its preparation method that can achieve fast printing and shorten the cycle. The fluidity of PLA material is improved by adding a large amount of powder so that the material can be used for high-speed printing. However, the addition of a large amount of powder is easy to migrate to the surface of the material during the printing process, or even precipitate, which will cause a serious decrease in the interlayer bonding strength of the printed part.

[0006] Therefore, it is necessary to develop a modified PLA material and its preparation method that can achieve both high-speed printing and high-strength interlayer bonding. Summary of the invention

[0007] The purpose of the present invention is to provide a modified PLA material for 3D printing and a preparation method thereof. The introduction of a homemade three-arm cage-shaped PLA oligomer has the following main advantages: first, it reduces the overall molecular weight of the material, increases the molecular weight distribution width of the material, and improves the fluidity of the material, so that the PLA material can be suitable for high-speed FDM printing; second, the three-arm structure oligomer with the same structure as the matrix resin is easy to migrate to the melt surface during high-speed printing, and will strengthen the interlayer molecular chain entanglement during the printing melt deposition process, greatly improving the interlayer bonding; third, due to the cage structure, it can adsorb the powder additives in the material, reduce the precipitation of additives on the surface of the material during the printing process, and synergistically strengthen the interlayer bonding of the printing.

[0008] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0009] A modified PLA material for 3D printing, the modified PLA material comprising the following components in percentage by weight:

[0010] S1, PLA resin, 75%-95%, preferably 83%-90%;

[0011] S2, three-arm cage-like PLA oligomer, 1%-20%, preferably 8%-15%;

[0012] S3, flow aid, 1.0-5.0%, preferably 1%-2%;

[0013] S4, toughening agent, 0.1%-0.5%, preferably 0.2%-0.4%.

[0014] The PLA resin of the present invention has a melt index of 1-15 / 10min (190°C, 2.16kg) and a molecular weight of 50000-150000g / mol.

[0015] The flow aid of the present invention is one or more of oleamide, ethylene bis stearic acid amide, zinc stearate, wollastonite powder and talc, preferably one or more of zinc stearate and wollastonite powder.

[0016] The toughening agent of the present invention is preferably one or more of YF6030, YP-501, AX8900, Wacker2504, and Wacker2505.

[0017] The three-arm cage-like PLA oligomer (T-LMW) of the present invention is an oligomer generated by the reaction of trisilanol polysilsesquioxane and lactide under the action of a catalyst; preferably, the trisilanol polysilsesquioxane is preferably one or more of trisilanol phenyl polysilsesquioxane, trisilanol octyl polysilsesquioxane, and trisilanol isooctyl polysilsesquioxane, and is further preferably one or more of trisilanol octyl polysilsesquioxane and trisilanol isooctyl polysilsesquioxane;

[0018] Preferably, the lactide is one or more of L-lactide, D-lactide and DL-lactide, and DL-lactide is more preferably.

[0019] Preferably, the catalyst is an organic tin catalyst, preferably one or more of stannous octoate, stannous hexanoate, and stannous pyrophosphate, and more preferably stannous octoate.

[0020] Preferably, the molar ratio of the catalyst to trisilanol polysilsesquioxane is 1:10-1:30, preferably 1:15-1:20.

[0021] Preferably, the molar ratio of trisilanol polysilsesquioxane to lactide is 1:100-1:400, preferably 1:200-1:250.

[0022] Preferably, the reaction temperature of the trisilanol polysilsesquioxane and lactide is 80-120°C.

[0023] In one embodiment, the preparation method of the three-arm cage-like PLA oligomer comprises the following steps: adding trisilanol polysilsesquioxane and lactide to a solvent (such as toluene), fully mixing, heating at 80-120° C., preferably 90-105° C., until completely dissolved, adding a catalyst, and maintaining the temperature for 4-6 hours; after the reaction is completed, transferring to an ice bath, separating, and drying to obtain a three-arm cage-like PLA oligomer.

[0024] Preferably, the reaction solution obtained by the reaction is used to completely dissolve the product with dichloromethane, and then poured into methanol, and the precipitate is obtained by centrifugation and filtration, and then dried to obtain a three-arm cage-like PLA oligomer.

[0025] Another object of the present invention is to provide a method for preparing modified PLA material for 3D printing.

[0026] A method for preparing a modified PLA material for 3D printing comprises the following steps: mixing PLA, a three-arm cage-shaped PLA oligomer, a flow aid, and a toughening agent, adding the mixture into a twin-screw extruder for melt extrusion, cooling, pelletizing, and drying to obtain modified PLA particles;

[0027] Preferably, the modified PLA particles are added into a single screw extruder for melt extrusion and then cooled to obtain the modified PLA material.

[0028] Preferably, in the preparation method of the modified PLA material, a high-speed mixer is used for mixing, with a rotation speed of 20 to 100 rpm, a temperature of 20 to 50° C., and a mixing time of 3 to 10 min; the screw temperature of the twin-screw extruder is 160-190° C., and the rotation speed is 200-400 rpm; the screw temperature of the single-screw extruder is 180-200° C., and the rotation speed is 100-200 rpm.

[0029] Compared with the prior art, the present invention has the following technical advantages:

[0030] 1) In this application, a self-made three-arm cage-shaped PLA oligomer is introduced to reduce the overall molecular weight of the material, increase the molecular weight distribution width of the material, and improve the fluidity of the material, so that the PLA material can be suitable for high-speed FDM printing, which can solve the appearance problems such as printing voids and poor discharge during high-speed printing.

[0031] 2) This application introduces a self-made three-arm cage-shaped PLA oligomer, the overall molecular structure of which is the same as that of the matrix, and there is no compatibility problem; and due to its low molecular weight, it is easy to migrate to the melt surface during high-speed printing, and during the printing melt deposition process, it will strengthen the entanglement of the interlayer molecular chains and greatly improve the interlayer bonding, which can solve the problem of weak interlayer bonding during high-speed printing.

[0032] 3) This application introduces a homemade three-arm cage-like PLA oligomer. Due to its cage-like structure, it can adsorb powder additives in the material, ensuring printing smoothness while reducing the precipitation of additives on the surface of the material during printing, and synergistically strengthening the interlayer bonding of the printing. DETAILED DESCRIPTION

[0033] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0034] In each embodiment and comparative example, the sources of the main raw materials are as shown in Table 1 below:

[0035] Table 1 Raw materials and sources

[0036] raw materials factory PLA(LX575) Total Cobien Polylactic Acid Co., Ltd. PLA(LX175) Total Cobien Polylactic Acid Co., Ltd. Flow aid zinc stearate Shandong Siyang Biotechnology Co., Ltd. Toughening agent Wacker2504 Shanghai Kaiyin Chemical Co., Ltd. Trisilanol Octyl Polysilsesquioxane Xi'an Qiyue Biotechnology Co., Ltd. Trisilanol Isooctyl Polysilsesquioxane Xi'an Qiyue Biotechnology Co., Ltd. Trimethylolbutane Sigma-Aldrich (Shanghai) Trading Co., Ltd. DL-Lactide Total Cobien Polylactic Acid Co., Ltd. Dichloromethane Shanghai Aladdin Biochemical Technology Co., Ltd. Methanol Shanghai Aladdin Biochemical Technology Co., Ltd. Stannous Octoate Sigma-Aldrich (Shanghai) Trading Co., Ltd.

[0037] Unless otherwise specified, other raw materials and reagents were purchased from commercial sources.

[0038] In each embodiment and comparative example, the performance test parameters and test methods of the modified PLA material are shown in Table 2 below:

[0039] Table 2 Performance test parameters and methods

[0040] Test Parameters unit Test Method Melt index g / 10min ISO 1133 Tensile Strength MPa ISO 527-2 Appearance evaluation / Visual

[0041] The processing equipment used was: a twin-screw extruder, Coperion, model ZSK 26Mc 18, with an aspect ratio of 52 and a screw diameter of 26 cm; a single-screw extruder, Henri Gard, model HRJSJ-Ф45, with a screw diameter of 45 mm and a die head diameter of 1.75 mm.

[0042] The testing equipment used is: German Gottfert melt index instrument, melt index test conditions are 190°C, 2.16kg; German ZWICK universal material testing machine, tensile test conditions are 50mm / min.

[0043] Example 1

[0044] (1) Preparation of three-arm cage-like PLA oligomer (T-LMW-1)

[0045] Weigh 144g DL-lactide and 6g trisilanol octyl polysilsesquioxane (the molar ratio of trisilanol octyl polysilsesquioxane to lactide is 1:200) into a round-bottom flask, add 100mL of toluene, continue stirring, heat to 90°C until completely dissolved, add 5g of stannous octoate, and keep the temperature constant for 4h; after the reaction is completed, transfer to an ice bath, add 200mL of dichloromethane to completely dissolve the product, pour in a large amount of pre-cooled methanol, centrifuge to obtain the precipitate, and dry it at 40°C under vacuum to obtain a three-arm cage-like PLA oligomer.

[0046] (2) The three-arm cage PLA oligomer (T-LMW-1) of this embodiment was used to prepare a modified PLA material according to the following method. The mass and amount of each component are shown in Table 3. First, PLA resin and three-arm cage PLA oligomer (T-LMW-1) were dried in an electric hot air drying oven at 80°C for 4 hours; then PLA resin, three-arm cage PLA oligomer (T-LMW-1), flow aid and toughening agent were placed in a high-speed mixer, the speed was set to 50rpm, the temperature was set to 35°C, and mixed for 5 minutes. The sample was put into a twin-screw extruder for melt extrusion, and the screw temperature was set to 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, and 190°C from the feed port to the die head, and the screw speed was set to 300rpm. The extruded material was cooled and pelletized in the water tank of the extruder, and dried in an oven at 80°C for 4 hours to obtain the modified PLA particles. The modified PLA particles were added to a single screw extruder for melt extrusion and then cooled, and the screw temperature was set to 180°C, 180°C, 185°C, 185°C, 190°C, 190°C, 190°C, 200°C from the feed port to the die head, and the rod speed was set to 150rpm to obtain the modified PLA material.

[0047] Example 2

[0048] (1) Preparation of three-arm cage-like PLA oligomer (T-LMW-2)

[0049] Weigh 144g DL-lactide and 4.8g trisilanol octyl polysilsesquioxane (the molar ratio of trisilanol octyl polysilsesquioxane to lactide is 1:250) into a round-bottom flask, add 100mL of toluene, continue stirring, heat to 90°C until completely dissolved, add 5g of stannous octoate, and keep the temperature constant for 4h; after the reaction is completed, transfer to an ice bath, add 200mL of dichloromethane to completely dissolve the product, pour in a large amount of pre-cooled methanol, centrifuge to obtain the precipitate, and dry it at 40°C under vacuum to obtain a three-arm cage-like PLA oligomer.

[0050] (2) The three-arm cage PLA oligomer (T-LMW-2) of this embodiment was used to prepare a modified PLA material according to the following method. The mass and amount of each component are shown in Table 3. First, PLA resin and three-arm cage PLA oligomer (T-LMW-2) were dried in an electric hot air drying oven at 80°C for 4 hours; then PLA resin, three-arm cage PLA oligomer (T-LMW-2), flow aid and toughening agent were placed in a high-speed mixer, the speed was set to 50rpm, the temperature was set to 35°C, and mixed for 5 minutes. The sample was put into a twin-screw extruder for melt extrusion, and the screw temperature was set to 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, and 190°C from the feed port to the die head, and the screw speed was set to 300rpm. The extruded material was cooled and pelletized in the water tank of the extruder, and dried in an oven at 80°C for 4 hours to obtain the modified PLA particles. The modified PLA particles were added to a single screw extruder for melt extrusion and then cooled, and the screw temperature was set to 180°C, 180°C, 185°C, 185°C, 190°C, 190°C, 190°C, 200°C from the feed port to the die head, and the rod speed was set to 150rpm to obtain the modified PLA material.

[0051] Example 3

[0052] (1) Preparation of three-arm cage-like PLA oligomer (T-LMW-3)

[0053] Weigh 144g DL-lactide and 4.0g trisilanol phenyl polysilsesquioxane (the molar ratio of trisilanol phenyl polysilsesquioxane to lactide is 1:300) into a round-bottom flask, add 100mL of toluene, continue stirring, heat to 90°C until completely dissolved, add 5g of stannous octoate, and keep the temperature constant for 4h; after the reaction is completed, transfer to an ice bath, add 200mL of dichloromethane to completely dissolve the product, pour in a large amount of pre-cooled methanol, centrifuge to obtain the precipitate, and dry it at 40°C under vacuum to obtain a three-arm cage-like PLA oligomer.

[0054] (2) The three-arm cage PLA oligomer (T-LMW-3) of this embodiment was used to prepare a modified PLA material according to the following method. The mass and amount of each component are shown in Table 3. First, PLA resin and three-arm cage PLA oligomer (T-LMW-3) were dried in an electric hot air drying oven at 80°C for 4 hours; then PLA resin, three-arm cage PLA oligomer (T-LMW-3), flow aid and toughening agent were placed in a high-speed mixer, the speed was set to 50rpm, the temperature was set to 35°C, and mixed for 5 minutes. The sample was put into a twin-screw extruder for melt extrusion, and the screw temperature was set to 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, and 190°C from the feed port to the die head, and the screw speed was set to 300rpm. The extruded material was cooled and pelletized in the water tank of the extruder, and dried in an oven at 80°C for 4 hours to obtain the modified PLA particles. The modified PLA particles were added to a single screw extruder for melt extrusion and then cooled, and the screw temperature was set to 180°C, 180°C, 185°C, 185°C, 190°C, 190°C, 190°C, 200°C from the feed port to the die head, and the rod speed was set to 150rpm to obtain the modified PLA material.

[0055] Example 4

[0056] The three-arm cage-like PLA oligomer (T-LMW-3) and modified PLA material were prepared by the same method as in Example 3, the only difference being the amount of T-LMW-3 added to the PLA material.

[0057] Comparative Example 1

[0058] The modified PLA material was prepared according to the method in Example 1, except that the formula composition in Table 3 was different and the three-arm cage-like PLA oligomer was not added.

[0059] Comparative Example 2

[0060] The three-arm PLA oligomer (T-LMW-4) and the modified PLA material were prepared according to the same method as in Example 1, except that trisilanoloctyl polysilsesquioxane was replaced with trimethylolbutane, so the three-arm PLA oligomer (T-LMW-4) did not have a cage structure.

[0061] Comparative Example 3

[0062] The modified PLA material was prepared according to the method in Example 1, with the only difference being that the formula composition in Table 3 was different, and the homemade three-arm cage-like PLA oligomer was replaced with a commercially available linear PLA oligomer (Yusi Pharmaceutical YS-PLA201) (T-LMW-5).

[0063] The modified PLA materials obtained in Examples 1-4 and Comparative Examples 1-3 were printed in a high-speed FDM printer, the nozzle temperature was set to 210°C, the base plate temperature was 60°C, the printing speed was 300 mm / s, and standard tensile specimens in the X-axis direction, Y-axis direction, and Z-axis direction were printed. The tensile properties were tested to characterize the interlayer bonding strength of the material. The test results are shown in Table 4.

[0064] Table 3 Raw materials and amounts (mass fraction) in Examples 1-4 (A1-A4) and Comparative Examples 1-3 (B1-B3)

[0065] raw materials A1 A2 A3 A4 B1 B2 B3 PLA(LX575) 90 80 70 63 98 90 90 PLA(LX175) - 10 20 20 - - - Zinc stearate 1.8 1.7 1.6 1.6 1.8 1.8 1.8 Wacker2504 0.2 0.3 0.4 0.4 0.2 0.2 0.2 T-LMW-1 8 - - - - - - T-LMW-2 - 8 - - - - - T-LMW-3 - - 8 15 - - - T-LMW-4 - - - - - 8 - T-LMW-5 - - - - - - 8

[0066] Table 4 Performance test results of samples of Examples 1-4 (A1-A4) and Comparative Examples 1-3 (B1-B3)

[0067]

[0068] It can be seen from Comparative Examples 1-4 and Example 1 that, compared with traditional 3D printing materials (Comparative Example 1) or conventional fluidity optimized 3D printing materials (Comparative Example 3), the present invention introduces a homemade three-arm cage-like PLA oligomer. First, the overall molecular weight of the material is reduced, the molecular weight distribution width of the material is increased, and the fluidity of the material is improved, so that the PLA material can be suitable for high-speed FDM printing, and the appearance of high-speed printed products is significantly better; second, the three-arm structure oligomer with the same structure as the matrix resin is easy to migrate to the melt surface during high-speed printing, and the interlayer molecular chain entanglement will be strengthened during the printing melt deposition process, the interlayer bonding will be greatly improved, and the Z-axis tensile strength will be greatly improved; third, due to the cage structure, the powder additives in the material can be adsorbed, the additive precipitation on the surface of the material during the printing process is reduced, and the interlayer bonding of the printing is synergistically strengthened and the appearance of the printed parts is improved.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A modified PLA material for 3D printing, characterized in that: The modified PLA material comprises the following components in weight percentage: S1, PLA resin, 75%-95%, preferably 83%-90%; S2, three-arm cage-like PLA oligomer, 1%-20%, preferably 8%-15%; S3, flow aid, 1.0-5.0%, preferably 1%-2%; S4, toughening agent, 0.1%-0.5%, preferably 0.2%-0.4%.

2. The modified PLA material according to claim 1, characterized in that: The PLA resin has a melt index of 1-15 / 10min (190°C, 2.16kg) and a molecular weight of 50000-150000g / mol; Preferably, the flow aid is one or more of oleamide, ethylene bisstearamide, zinc stearate, wollastonite powder, and talc, preferably one or more of zinc stearate and wollastonite powder; Preferably, the toughening agent is one or more of YF6030, YP-501, AX8900, Wacker2504, and Wacker2505.

3. The modified PLA material according to claim 1 or 2, characterized in that: The three-arm cage-like PLA oligomer is an oligomer generated by the reaction of trisilanol polysilsesquioxane and lactide under the action of a catalyst; preferably, the trisilanol polysilsesquioxane is preferably one or more of trisilanol phenyl polysilsesquioxane, trisilanol octyl polysilsesquioxane, and trisilanol isooctyl polysilsesquioxane, and is further preferably one or more of trisilanol octyl polysilsesquioxane and trisilanol isooctyl polysilsesquioxane.

4. The modified PLA material according to any one of claims 1 to 3, characterized in that: The lactide is selected from one or more of L-lactide, D-lactide, and DL-lactide, and DL-lactide is more preferred; Preferably, the catalyst is an organic tin catalyst, preferably one or more of stannous octoate, stannous hexanoate, and stannous pyrophosphate, and more preferably stannous octoate.

5. The modified PLA material according to any one of claims 1 to 4, characterized in that: The molar ratio of the catalyst to trisilanol polysilsesquioxane is 1:10-1:30, preferably 1:15-1:20; Preferably, the molar ratio of trisilanol polysilsesquioxane to lactide is 1:100-1:400, preferably 1:200-1:250; Preferably, the reaction temperature of the trisilanol polysilsesquioxane and lactide is 80-120°C.

6. The modified PLA material according to any one of claims 1 to 5, characterized in that: The preparation method of the three-arm cage-shaped PLA oligomer comprises the following steps: adding trisilanol polysilsesquioxane and lactide into a solvent, fully mixing, heating at 80-120° C., preferably at 90-105° C., until completely dissolved, adding a catalyst, and keeping the temperature constant for 4-6 hours; after the reaction is completed, transferring to an ice bath, separating, and drying to obtain the three-arm cage-shaped PLA oligomer.

7. A method for preparing a modified PLA material for 3D printing according to any one of claims 1 to 6, comprising the following steps: mixing PLA, a three-arm cage-shaped PLA oligomer, a flow aid, and a toughening agent, adding the mixture to a twin-screw extruder for melt extrusion, cooling, pelletizing, and drying to obtain modified PLA particles; Preferably, the modified PLA particles are added into a single screw extruder for melt extrusion and then cooled to obtain the modified PLA material.

8. The preparation method according to claim 7, characterized in that: The raw materials are mixed by a high-speed mixer at a speed of 20 to 100 rpm, a temperature of 20 to 50°C, and a mixing time of 3 to 10 minutes; Preferably, the screw temperature of the twin-screw extruder is 160-190° C., and the rotation speed is 200-400 rpm; the screw temperature of the single-screw extruder is 180-200° C., and the rotation speed is 100-200 rpm.

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