A polylactic acid composition for 3D printing and preparation method thereof

Abstract

The present invention relates to the technical field of 3D printing materials, and discloses a polylactic acid composition for 3D printing and a preparation method thereof. The present invention is prepared by melt-modifying polylactic acid with modified graphene, and the graphene is modified with modified polyoxime urethane and polydimethylsiloxane. The 3D printing wire prepared from the modified polylactic acid composition has better lubricity, and the material discharge will be smoother during the 3D printing process, while shortening the printing time and improving the printing speed. For various 3D printing wires on the market, the present invention has better competitiveness and can meet the market demand for printing speed.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing materials, and in particular to a polylactic acid composition for 3D printing and a preparation method thereof. Background Art

[0002] As a widely used additive manufacturing technology, the effect of fused deposition 3D printing is highly dependent on the close cooperation between the printer and the consumables. The printer has made great progress in mechanical structure precision, motion control accuracy, and nozzle technology advancement, which has continuously improved the accuracy of the equipment and can accurately build complex and detailed three-dimensional models. The layer thickness can reach an amazingly small scale, and the dimensional accuracy is getting closer to the ideal state.

[0003] However, the current printing speed of printing consumables lags significantly behind the development of equipment precision. Taking polylactic acid as an example, this commonly used printing consumable faces many challenges in terms of printing speed. The melt strength and viscosity characteristics of polylactic acid have great limitations on printing speed. When printing at higher speeds, its melt is difficult to maintain a stable extrusion state, and it is prone to wire breakage or uneven extrusion, resulting in printing failure or serious decline in molding quality. In addition, the thermal conductivity and crystallization behavior of polylactic acid will also affect its temperature distribution and curing molding process during high-speed printing, further restricting the improvement of printing speed.

[0004] In order to fully tap the potential of fused deposition 3D printing technology, it is urgent to improve the performance of printing consumables such as polylactic acid, so as to meet diversified needs such as rapid prototyping and personalized customized production, and promote the entire 3D printing industry to a new stage of development. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies in the prior art, the present invention provides a polylactic acid composition for 3D printing and a preparation method thereof.

[0007] (II) Technical solution

[0008] A method for preparing a polylactic acid composition for 3D printing comprises the following steps:

[0009] S1. Slowly heat the lactic acid to 60-70°C under nitrogen, stir for 10-30 min, add stannous chloride, heat to 100-110°C, add toluene, stir and react for 1-3 h, then heat to 150-170°C, react for 1-3 h, dissolve in acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid;

[0010] S2. In an ice water bath, first add concentrated sulfuric acid, add graphite powder and sodium nitrate while stirring at a speed of 100-150 r / min, stir for 30-60 min, add potassium permanganate, stir for 60-90 min, heat to 30-40 ° C, stir for 1-3 h, add water, heat to 80-90 ° C, add 35 ° C warm water, and add 30% hydrogen peroxide at the same time, continue stirring for 10-30 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide;

[0011] S3, dispersing graphite oxide in water, dispersing under 40-80kHz ultrasound for 1-3h, adding thiourea dioxide and sodium hydroxide, stirring and reacting in a 90-100°C water bath for 5-10h, filtering, washing with ethanol and deionized water, and vacuum drying to obtain graphene;

[0012] S4, place polytetrahydrofuran diol in a 100-120°C oil bath to remove water in vacuum for 1-3h, cool to 50-70°C, pass nitrogen, add N,N-dimethylformamide solution containing dimethylglyoxime, stir evenly, slowly add isophorone diisocyanate, stir and react for 20-30h to obtain polyoxime urethane; then add hydroxyethyl methacrylate, stir for 10-30min, cool to 35-40°C, add triethylamine and react for 30-60min, cool to room temperature, then add perfluorohexylethyl methacrylate and hexenyl hexenoate, stir and heat to 70-80°C, add azobisisobutyronitrile, react for 5-10h to obtain modified polyoxime urethane;

[0013] S5, mixing graphene, modified polyoxime urethane and polydimethylsiloxane, stirring evenly, and vapor depositing at 220-250° C. for 1-3 h to obtain modified graphene;

[0014] S6. Mix polylactic acid and modified graphene, stir evenly, melt extrude to obtain molten lines, perform a first cooling and a first pulling, then microwave heat the lines at 400-800 W, perform a second cooling and a second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at high speed.

[0015] Preferably, in step S1, the mass ratio of lactic acid to stannous chloride is 1:0.01-0.03.

[0016] Preferably, in step S2, the mass ratio of graphite powder, sodium nitrate, potassium permanganate and concentrated sulfuric acid is 1:0.3-0.6:2-4:10-30.

[0017] Preferably, in step S3, the mass ratio of graphite oxide, thiourea dioxide and sodium hydroxide is 1:3-6:6-10.

[0018] Preferably, in step S4, the mass ratio of polytetrahydrofuran diol, dimethylglyoxime and isophorone diisocyanate is 1:0.2-0.4:0.8-1.2.

[0019] Preferably, in step S4, the mass ratio of polyoxime urethane, hydroxyethyl methacrylate, triethylamine, perfluorohexylethyl methacrylate, hexenyl hexenoate, and azobisisobutyronitrile is 1:0.03-0.06:0.1-0.2:0.1-0.3:0.1-0.3:0.01-0.05.

[0020] Preferably, in step S5, the mass ratio of graphene, modified polyoxime urethane and polydimethylsiloxane is 1:0.2-0.4:0.1-0.3.

[0021] Preferably, in step S6, the mass ratio of polylactic acid to modified graphene is 1:0.1-0.3.

[0022] Preferably, the polylactic acid composition is used in 3D rapid printing.

[0023] (III) Beneficial technical effects

[0024] The present invention is prepared by melt-modifying polylactic acid with modified graphene, wherein the graphene is modified with modified polyoxime urethane and polydimethylsiloxane. The 3D printing wire prepared from the modified polylactic acid composition has better lubricity, and the material discharge will be smoother during the 3D printing process, while shortening the printing time and increasing the printing speed. For various 3D printing wires on the market, the present invention has better competitiveness and can meet the market demand for printing speed. DETAILED DESCRIPTION

[0025] Example 1

[0026] S1. Slowly heat 10 kg of lactic acid to 60 ° C under nitrogen, stir for 10 min, add 0.1 kg of stannous chloride, raise the temperature to 100 ° C, add 3 L of toluene, stir and react for 1 h, then raise the temperature to 150 ° C, react for 1 h, dissolve in 30 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0027] S2. In an ice water bath, first add 100 kg of concentrated sulfuric acid, then add 10 kg of graphite powder and 3 kg of sodium nitrate while stirring at a speed of 100 r / min, stir for 30 min, add 20 kg of potassium permanganate, stir for 60 min, heat to 30 ° C, stir for 1 h, add 20 kg of water, heat to 80 ° C, add 30 kg of 35 ° C warm water, and at the same time add 60 kg of 30% hydrogen peroxide, continue stirring for 10 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide.

[0028] S3. Disperse 10 kg of graphite oxide in water, disperse under 40 kHz ultrasound for 1 hour, add 30 kg of thiourea dioxide and 60 kg of sodium hydroxide, stir and react in a 90°C water bath for 5 hours, filter, wash with ethanol and deionized water, and vacuum dry to obtain graphene.

[0029] S4. Place 10kg of polytetrahydrofuran diol in a 100°C oil bath and vacuum dehydrate for 1h, cool to 50°C, pass nitrogen, add 40L of N,N-dimethylformamide solution containing 2kg of dimethylglyoxime, stir evenly, slowly add 8kg of isophorone diisocyanate, stir and react for 20h to obtain polyoxime urethane; then add 0.9kg of hydroxyethyl methacrylate, stir for 10min, cool to 35°C, add 3kg of triethylamine and react for 30min, cool to room temperature, add 3kg of perfluorohexylethyl methacrylate and 3kg of hexenyl hexenoate, stir and heat to 70°C, add 0.3kg of azobisisobutyronitrile, react for 5h to obtain modified polyoxime urethane.

[0030] S5. Mix 5 kg of graphene, 2 kg of modified polyoxime urethane, and 0.8 kg of polydimethylsiloxane, stir evenly, and perform vapor deposition at 220° C. for 1 h to obtain modified graphene.

[0031] S6. Mix 6 kg of polylactic acid and 0.8 kg of modified graphene, stir evenly, melt extrude to obtain molten lines, perform the first cooling and the first pulling, then microwave heat the lines at 400 W, perform the second cooling and the second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at high speed.

[0032] Example 2

[0033] S1. Slowly heat 10 kg of lactic acid to 70 ° C under nitrogen, stir for 30 minutes, add 0.3 kg of stannous chloride, heat to 110 ° C, add 6 L of toluene, stir and react for 3 hours, then heat to 170 ° C, react for 3 hours, dissolve in 60 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0034] S2. In an ice water bath, first add 300 kg of concentrated sulfuric acid, then add 10 kg of graphite powder and 6 kg of sodium nitrate at a speed of 150 r / min, stir for 60 min, add 40 kg of potassium permanganate, stir for 90 min, heat to 40 ° C, stir for 3 h, add 40 kg of water, heat to 90 ° C, add 60 kg of 35 ° C warm water, and add 80 kg of 30% hydrogen peroxide at the same time, continue stirring for 30 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide.

[0035] S3. Disperse 10 kg of graphite oxide in water, disperse under 80 kHz ultrasound for 3 h, add 60 kg of thiourea dioxide and 100 kg of sodium hydroxide, stir and react in a 100 °C water bath for 10 h, filter, wash with ethanol and deionized water, and vacuum dry to obtain graphene.

[0036] S4, 10kg of polytetrahydrofuran diol was placed in a 120℃ oil bath for 3h of vacuum dehydration, cooled to 70℃, passed nitrogen, 40L of N,N-dimethylformamide solution containing 4kg of dimethylglyoxime was added, stirred evenly, 12kg of isophorone diisocyanate was slowly added, stirred and reacted for 30h to obtain polyoxime urethane; 1.8kg of hydroxyethyl methacrylate was added, stirred for 30min, cooled to 40℃, 6kg of triethylamine was added and reacted for 60min, cooled to room temperature, 9kg of perfluorohexylethyl methacrylate and 9kg of hexenyl hexenoate were added, stirred and heated to 80℃, 1.5kg of azobisisobutyronitrile was added, reacted for 10h to obtain modified polyoxime urethane.

[0037] S5. 8 kg of graphene, 4 kg of modified polyoxime urethane, and 1.5 kg of polydimethylsiloxane were mixed, stirred evenly, and vapor deposited at 250° C. for 3 h to obtain modified graphene.

[0038] S6. 8 kg of polylactic acid and 1.8 kg of modified graphene are mixed, stirred evenly, melt-extruded to obtain molten lines, cooled and pulled for the first time, and then microwave-heated at 800 W, and cooled and pulled for the second time at the same time. After cooling, the lines are rolled up to obtain a polylactic acid composition that can be printed at high speed.

[0039] Example 3

[0040] S1. Slowly heat 10 kg of lactic acid to 65 ° C under nitrogen, stir for 15 min, add 0.2 kg of stannous chloride, heat to 110 ° C, add 4 L of toluene, stir and react for 2 h, then heat to 160 ° C, react for 2 h, dissolve in 40 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0041] S2. In an ice water bath, first add 150 kg of concentrated sulfuric acid, then add 10 kg of graphite powder and 4 kg of sodium nitrate while stirring at a speed of 120 r / min, stir for 40 min, add 25 kg of potassium permanganate, stir for 60 min, heat to 35 ° C, stir for 1.5 h, add 22 kg of water, heat to 90 ° C, add 40 kg of 35 ° C warm water, and at the same time add 65 kg of 30% hydrogen peroxide, continue stirring for 20 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide.

[0042] S3. Disperse 10 kg of graphite oxide in water, disperse under 50 kHz ultrasound for 1.5 h, add 40 kg of thiourea dioxide and 80 kg of sodium hydroxide, stir and react in a 100 °C water bath for 6 h, filter, wash with ethanol and deionized water, and vacuum dry to obtain graphene.

[0043] S4, 10kg of polytetrahydrofuran diol was placed in a 110℃ oil bath for 2h of vacuum dehydration, cooled to 60℃, passed nitrogen, 40L of N,N-dimethylformamide solution containing 3kg of dimethylglyoxime was added, stirred evenly, 9kg of isophorone diisocyanate was slowly added, stirred and reacted for 25h to obtain polyoxime urethane; 1kg of hydroxyethyl methacrylate was added, stirred for 30min, cooled to 40℃, 4kg of triethylamine was added and reacted for 60min, cooled to room temperature, 5kg of perfluorohexylethyl methacrylate and 4kg of hexenyl hexenoate were added, stirred and heated to 70℃, 0.5kg of azobisisobutyronitrile was added, reacted for 10h, and modified polyoxime urethane was obtained.

[0044] S5. Mix 5.5 kg of graphene, 3 kg of modified polyoxime urethane, and 1 kg of polydimethylsiloxane, stir evenly, and perform vapor deposition at 240° C. for 2 h to obtain modified graphene.

[0045] S6. Mix 6.5 kg of polylactic acid and 1 kg of modified graphene, stir evenly, melt extrude to obtain molten lines, perform the first cooling and the first pulling, then microwave heat the lines at 500 W, perform the second cooling and the second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at high speed.

[0046] Example 4

[0047] S1. Slowly heat 10 kg of lactic acid to 60 ° C under nitrogen, stir for 30 minutes, add 0.15 kg of stannous chloride, raise the temperature to 100 ° C, add 4.5 L of toluene, stir and react for 2.5 hours, then raise the temperature to 150 ° C, react for 1.5 hours, dissolve in 50 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0048] S2. In an ice water bath, first add 200 kg of concentrated sulfuric acid, then add 10 kg of graphite powder and 4 kg of sodium nitrate while stirring at a speed of 120 r / min, stir for 50 min, add 30 kg of potassium permanganate, stir for 90 min, heat to 40 ° C, stir for 2 h, add 30 kg of water, heat to 90 ° C, add 45 kg of 35 ° C warm water, and at the same time add 70 kg of 30% hydrogen peroxide, continue stirring for 20 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide.

[0049] S3. Disperse 10 kg of graphite oxide in water, disperse under 60 kHz ultrasound for 2.5 h, add 35 kg of thiourea dioxide and 80 kg of sodium hydroxide, stir and react in a 90 ° C water bath for 10 h, filter, wash with ethanol and deionized water, and vacuum dry to obtain graphene.

[0050] S4, 10kg of polytetrahydrofuran diol was placed in a 120℃ oil bath for vacuum dehydration for 1h, cooled to 70℃, passed nitrogen, added 40L of N,N-dimethylformamide solution containing 2.5kg of dimethylglyoxime, stirred evenly, then slowly added 8-12kg of isophorone diisocyanate, stirred and reacted for 24h to obtain polyoxime urethane; then added 1.5kg of hydroxyethyl methacrylate, stirred for 30min, cooled to 35℃, added 5.2kg of triethylamine and reacted for 50min, cooled to room temperature, then added 6kg of perfluorohexylethyl methacrylate and 8kg of hexenyl hexenoate, stirred and heated to 70℃, added 1.2kg of azobisisobutyronitrile, reacted for 5h to obtain modified polyoxime urethane.

[0051] S5. Mix 7.2 kg of graphene, 3.5 kg of modified polyoxime urethane, and 1.3 kg of polydimethylsiloxane, stir evenly, and perform vapor deposition at 250° C. for 3 h to obtain modified graphene.

[0052] S6. Mix 7 kg of polylactic acid and 1.4 kg of modified graphene, stir evenly, melt extrude to obtain molten lines, perform the first cooling and the first pulling, then microwave heat the lines at 600 W, perform the second cooling and the second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at high speed.

[0053] Example 5

[0054] S1. Slowly heat 10 kg of lactic acid to 70 ° C under nitrogen, stir for 30 minutes, add 0.1 kg of stannous chloride, heat to 110 ° C, add 3 L of toluene, stir and react for 3 hours, then heat to 150 ° C, react for 1 hour, dissolve in 60 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0055] S2. In an ice water bath, first add 100 kg of concentrated sulfuric acid, then add 10 kg of graphite powder and 5 kg of sodium nitrate at a speed of 150 r / min, stir for 60 min, add 20 kg of potassium permanganate, stir for 90 min, heat to 30 ° C, stir for 2 h, add 30 kg of water, heat to 90 ° C, add 30 kg of 35 ° C warm water, and add 80 kg of 30% hydrogen peroxide at the same time, continue stirring for 10 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide.

[0056] S3. Disperse 10 kg of graphite oxide in water, disperse under 70 kHz ultrasound for 1.5 h, add 30 kg of thiourea dioxide and 80 kg of sodium hydroxide, stir and react in a 90 ° C water bath for 5 h, filter, wash with ethanol and deionized water, and vacuum dry to obtain graphene.

[0057] S4, 10kg of polytetrahydrofuran diol was placed in a 100°C oil bath for vacuum dehydration for 3h, cooled to 60°C, passed nitrogen, 40L of N,N-dimethylformamide solution containing 3.2kg of dimethylglyoxime was added, stirred evenly, 10kg of isophorone diisocyanate was slowly added, stirred and reacted for 24h to obtain polyoxime urethane; 1.6kg of hydroxyethyl methacrylate was added, stirred for 30min, cooled to 35°C, 3kg of triethylamine was added and reacted for 60min, cooled to room temperature, 4kg of perfluorohexylethyl methacrylate and 5kg of hexenyl hexenoate were added, stirred and heated to 80°C, 1.5kg of azobisisobutyronitrile was added, reacted for 5h, and modified polyoxime urethane was obtained.

[0058] S5. 8 kg of graphene, 3 kg of modified polyoxime urethane, and 1.5 kg of polydimethylsiloxane were mixed, stirred evenly, and vapor deposited at 220° C. for 1 h to obtain modified graphene.

[0059] S6. 8 kg of polylactic acid and 0.8 kg of modified graphene are mixed, stirred evenly, melt-extruded to obtain molten lines, cooled and pulled for the first time, and then microwave-heated at 800 W, and cooled and pulled for the second time at the same time. After cooling, the lines are rolled up to obtain a polylactic acid composition that can be printed at high speed.

[0060] Comparative Example 1

[0061] S1. Slowly heat 10 kg of lactic acid to 60 ° C under nitrogen, stir for 10 min, add 0.1 kg of stannous chloride, raise the temperature to 100 ° C, add 3 L of toluene, stir and react for 1 h, then raise the temperature to 150 ° C, react for 1 h, dissolve in 30 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0062] S2. In an ice water bath, first add 100 kg of concentrated sulfuric acid, then add 10 kg of graphite powder and 3 kg of sodium nitrate while stirring at a speed of 100 r / min, stir for 30 min, add 20 kg of potassium permanganate, stir for 60 min, heat to 30 ° C, stir for 1 h, add 20 kg of water, heat to 80 ° C, add 30 kg of 35 ° C warm water, and at the same time add 60 kg of 30% hydrogen peroxide, continue stirring for 10 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide.

[0063] S3. Disperse 10 kg of graphite oxide in water, disperse under 40 kHz ultrasound for 1 hour, add 30 kg of thiourea dioxide and 60 kg of sodium hydroxide, stir and react in a 90°C water bath for 5 hours, filter, wash with ethanol and deionized water, and vacuum dry to obtain graphene.

[0064] S4. Mix 6 kg of polylactic acid and 0.8 kg of graphene, stir evenly, melt extrude to obtain molten lines, perform the first cooling and the first pulling, then microwave heat the lines at 400 W, perform the second cooling and the second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at high speed.

[0065] Comparative Example 2

[0066] S1. Slowly heat 10 kg of lactic acid to 60 ° C under nitrogen, stir for 10 min, add 0.1 kg of stannous chloride, raise the temperature to 100 ° C, add 3 L of toluene, stir and react for 1 h, then raise the temperature to 150 ° C, react for 1 h, dissolve in 30 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0067] S2, 10kg of polytetrahydrofuran diol was placed in a 100°C oil bath for vacuum dehydration for 1h, cooled to 50°C, vented with nitrogen, 40L of N,N-dimethylformamide solution containing 2kg of dimethylglyoxime was added, stirred evenly, 8kg of isophorone diisocyanate was slowly added, stirred and reacted for 20h to obtain polyoxime urethane; 0.9kg of hydroxyethyl methacrylate was added, stirred for 10min, cooled to 35°C, 3kg of triethylamine was added and reacted for 30min, cooled to room temperature, 3kg of perfluorohexylethyl methacrylate and 3kg of hexenyl hexenoate were added, stirred and heated to 70°C, 0.3kg of azobisisobutyronitrile was added, reacted for 5h, and modified polyoxime urethane was obtained.

[0068] S3. 6 kg of polylactic acid and 0.8 kg of modified polyoxime urethane are mixed, stirred evenly, melt-extruded to obtain molten lines, cooled and pulled for the first time, and then microwave-heated at 400 W, and cooled and pulled for the second time at the same time. After cooling, the lines are rolled up to obtain a polylactic acid composition that can be printed at high speed.

[0069] Comparative Example 3

[0070] S1. Slowly heat 10 kg of lactic acid to 60 ° C under nitrogen, stir for 10 min, add 0.1 kg of stannous chloride, raise the temperature to 100 ° C, add 3 L of toluene, stir and react for 1 h, then raise the temperature to 150 ° C, react for 1 h, dissolve in 30 L of acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid.

[0071] S2. Melt-extrude 6 kg of polylactic acid to obtain molten lines, perform a first cooling and a first pulling, then microwave-heat the lines at 400 W, perform a second cooling and a second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at a high speed.

[0072] Print speed test:

[0073] 1. The polylactic acid compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to a 3D printing test. The printing model was a solid cube with a length, width and height of 50×50×50 mm, a 0.2 mm nozzle, and a 0.15 mm layer height. The printing time was recorded. The results are shown in Table 1.

[0074] Table 1

[0075] Group time Example 1 4:35:20 Example 2 4:35:52 Example 3 4:36:12 Example 4 4:35:12 Example 5 4:35:35 Comparative Example 1 4:55:32 Comparative Example 2 5:01:17 Comparative Example 3 5:12:35

[0076] It can be seen from Table 1 that the polylactic acid compositions prepared in Examples 1 to 5 have a faster printing time and smoother discharge.

[0077] 2. The polylactic acid compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to 3D printing tests. The printing model was a solid cuboid with a length, width and height of 80×10×4 mm, a 0.2 mm nozzle, and a layer height of 0.15 mm. The bending properties were measured at high and low printing speeds. The results are shown in Table 2.

[0078] Table 2

[0079]

[0080] As can be seen from Table 2, the models printed by the polylactic acid compositions of Examples 1 to 5 at a speed of 200 mm / s have higher strength, the strength of the models printed at a speed of 200 mm / s is reduced, and the comparative examples 1 to 3 cannot completely print the models at 500 mm / s.

[0081] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a polylactic acid composition for 3D printing, characterized in that: The following steps are involved: S1. Slowly heat the lactic acid to 60-70°C under nitrogen, stir for 10-30 min, add stannous chloride, heat to 100-110°C, add toluene, stir and react for 1-3 h, then heat to 150-170°C, react for 1-3 h, dissolve in acetone, filter and wash with distilled water, and vacuum dry to obtain polylactic acid; S2. In an ice water bath, first add concentrated sulfuric acid, add graphite powder and sodium nitrate while stirring at a speed of 100-150 r / min, stir for 30-60 min, add potassium permanganate, stir for 60-90 min, heat to 30-40 ° C, stir for 1-3 h, add water, heat to 80-90 ° C, add 35 ° C warm water, and add 30% hydrogen peroxide at the same time, continue stirring for 10-30 min, vacuum filter, wash with 5% hydrochloric acid and deionized water until neutral, and dry to obtain graphite oxide; S3, dispersing graphite oxide in water, dispersing under 40-80kHz ultrasound for 1-3h, adding thiourea dioxide and sodium hydroxide, stirring and reacting in a 90-100°C water bath for 5-10h, filtering, washing with ethanol and deionized water, and vacuum drying to obtain graphene; S4, place polytetrahydrofuran diol in a 100-120°C oil bath to remove water in vacuum for 1-3h, cool to 50-70°C, pass nitrogen, add N,N-dimethylformamide solution containing dimethylglyoxime, stir evenly, slowly add isophorone diisocyanate, stir and react for 20-30h to obtain polyoxime urethane; then add hydroxyethyl methacrylate, stir for 10-30min, cool to 35-40°C, add triethylamine and react for 30-60min, cool to room temperature, then add perfluorohexylethyl methacrylate and hexenyl hexenoate, stir and heat to 70-80°C, add azobisisobutyronitrile, react for 5-10h to obtain modified polyoxime urethane; S5, mixing graphene, modified polyoxime urethane and polydimethylsiloxane, stirring evenly, and vapor depositing at 220-250° C. for 1-3 h to obtain modified graphene; S6. Mix polylactic acid and modified graphene, stir evenly, melt extrude to obtain molten lines, perform a first cooling and a first pulling, then microwave heat the lines at 400-800 W, perform a second cooling and a second pulling at the same time, and roll up after cooling to obtain a polylactic acid composition that can be printed at high speed.

2. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In the step S1, the mass ratio of lactic acid to stannous chloride is 1:0.01-0.

03.

3. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In step S2, the mass ratio of graphite powder, sodium nitrate, potassium permanganate and concentrated sulfuric acid is 1:0.3-0.6:2-4:10-30.

4. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In step S3, the mass ratio of graphite oxide, thiourea dioxide and sodium hydroxide is 1:3-6:6-10.

5. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In the step S4, the mass ratio of polytetrahydrofuran diol, dimethylglyoxime and isophorone diisocyanate is 1:0.2-0.4:0.8-1.

2.

6. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In the step S4, the mass ratio of polyoxime urethane, hydroxyethyl methacrylate, triethylamine, perfluorohexylethyl methacrylate, hexenyl hexenoate, and azobisisobutyronitrile is 1:0.03-0.06:0.1-0.2:0.1-0.3:0.1-0.3:0.01-0.

05.

7. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In the step S5, the mass ratio of graphene, modified polyoxime urethane and polydimethylsiloxane is 1:0.2-0.4:0.1-0.

3.

8. The method for preparing a polylactic acid composition for 3D printing according to claim 1, characterized in that: In the step S6, the mass ratio of polylactic acid to modified graphene is 1:0.1-0.

3.

9. An application of a polylactic acid composition prepared by the method for preparing a polylactic acid composition for 3D printing as claimed in claim 1, characterized in that: Application of the polylactic acid composition in 3D rapid printing.

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