A lignin-rubber material prepared using 3D printing

Abstract

The application discloses a lignin-rubber material prepared by 3D printing and application thereof, and the lignin-rubber material is prepared by 3D printing of ink prepared by reaction of rubber and esterified lignin. The application provides a new method for 3D printing of rubber at normal temperature, and the high rigidity of the benzene ring structure of lignin creates a self-supporting framework for the rubber ink, and a crosslinking network between the lignin and the rubber matrix is constructed, so that the structural stability can be maintained during the printing process, the printing precision and resolution are improved, and three-dimensional printing of the rubber matrix is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of 3D printing, and particularly relates to a lignin-rubber material prepared by 3D printing. BACKGROUND

[0002] The part provided in this part is only background information related to the present disclosure, which is not necessarily prior art.

[0003] Due to the long heat curing molding time, large thermal shrinkage and low controllability of the rubber material, the main processing methods at present are melt accumulation and material extrusion, which seriously limit the complexity of the molded structure. The 3D printing technology is concerned due to its ability to quickly manufacture complex microstructures and macrostructures, and can create shapes that cannot be achieved by traditional mechanical processing. The combination of rubber materials and 3D printing technology can effectively solve the limitations of traditional processes in rapid prototyping, personalized customization and high-precision printing, etc. with higher degree of design freedom, and further expand the application range of rubber-based elastomers.

[0004] Direct ink writing (DIW) is one of the most common 3D printing technologies due to its wide range of precision and strong material expansion, which can print almost any material with correct rheological behavior. The swollen rubber material has shear thinning properties suitable for DIW printing ink. However, rubber single-component pure polymer products used for DIW printing lack strength and function as load-bearing components, resulting in diffusion or shape collapse. Lignin is the main component of plant cell walls, has high branching and amorphous, plays a "glue" role in the cell wall, and forms lignin-carbohydrate complexes through ether bonds to bind cellulose and hemicellulose together. These combined structures provide the plant cell wall with high stiffness, excellent water stability and thermal stability. By combining lignin as a reinforcing material with a rubber ink matrix, more complex shapes and superior functional products can be created at room temperature without the need for post-processing of light / thermal curing.

[0005] However, due to the complexity of the structure and morphology of lignin itself, phase separation occurs between lignin and the rubber matrix during DIW printing, resulting in insufficient adhesion between the printed layers, defects in the internal structure of the product, affecting the mechanical properties, and thus limiting the application range of the product. Therefore, the present application provides a method for preparing a lignin-rubber material by 3D printing and its application. SUMMARY

[0006] The technical problem to be solved by the present application is to provide an ink and a preparation method thereof to overcome the shortcomings of the prior art.

[0007] The present application also aims to solve the technical problem of providing the lignin-rubber material prepared by the aforementioned ink and a preparation method thereof.

[0008] To solve the above technical problems, the present application discloses the following technical solutions:

[0009] In a first aspect, the present application discloses an ink for 3D printing and a preparation method thereof.

[0010] The ink is prepared by the following method:

[0011] (1) Preparation of esterified modified lignin: dissolve lignin in tetrahydrofuran solution, slowly inject esterification modification reagent and alkaline catalyst under ice water bath and argon atmosphere with a syringe, and increase the temperature to keep stirring under condensation reflux for a period of time; after the reaction is completed, wash the solution with water and ethanol to obtain esterified modified lignin;

[0012] (2) Dissolve the rubber in tetrahydrofuran solution, then add the esterified lignin to the rubber solution for blending, and after stirring at elevated temperature for a period of time, obtain esterified lignin-rubber printing ink with a certain viscosity.

[0013] In step (1), the lignin includes but is not limited to industrial lignin such as organic solvent type lignin, enzymatic hydrolysis lignin, and alkali lignin, and is preferably organic solvent type lignin.

[0014] In step (1), the esterification modification reagent is an acid anhydride compound and / or an acyl chloride compound; specifically including acryloyl chloride, undecylenoyl chloride, lauroyl chloride, acetic anhydride, succinic anhydride, maleic anhydride, itaconic anhydride, methacrylic anhydride, and combinations of any of the foregoing, and is preferably acryloyl chloride, succinic anhydride, undecylenoyl chloride, maleic anhydride, itaconic anhydride, and combinations of any of the foregoing.

[0015] The mass ratio of the lignin to the esterification modifier is 1:0.1-1.0, preferably 1:0.4-0.8, and more preferably 1:0.5.

[0016] In step (1), the alkaline catalyst includes pyridine compounds, imidazole compounds, and amine compounds, and is preferably 1-methylimidazole, pyridine, triethylamine, N-methylaminopyridine, and combinations of any of the foregoing.

[0017] The mass-volume ratio of the lignin to the alkaline catalyst is 1g:0.05-0.3ml, preferably 1g:0.15-0.3ml, and more preferably 1g:0.15ml.

[0018] In step (1), the mass-volume ratio of the lignin to tetrahydrofuran is 1g:4-6ml.

[0019] In step (1), the reaction is carried out at 60-80℃ for 1-8h, preferably, the first reaction is carried out in an ice bath, and then the second reaction is carried out at 60-80℃; the first reaction is carried out for 0.2-0.8h, and the second reaction is carried out for 1-8h.

[0020] In step (2), the rubber includes nitrile rubber, natural rubber, epoxy natural rubber, styrene butadiene rubber, cis-butadiene rubber, and combinations of any of the foregoing.

[0021] In step (2), the mass ratio of the rubber and the esterified lignin is 1:0.1-1, preferably 1:0.3-0.7, and preferably 1:0.5.

[0022] In step (2), the mass-volume ratio of the rubber and tetrahydrofuran is 1g:5-50ml, preferably 1g:10-30ml.

[0023] In step (2), after mixing the rubber, the esterified lignin and the solvent, the mixture is reacted at 50-80℃ for 0.5-8h to obtain the ink; the temperature is preferably 65-80℃, and preferably 75℃; the reaction time is preferably 0.5-4h, and preferably 2h.

[0024] The viscosity of the ink provided by the present application is 6*10 3 Pa·s, preferably 1*10 6 Pa·s, preferably 1*10 4 Pa·s, preferably 1*10 6 Pa·s, preferably 1*10 5 Pa·s, preferably 1*10 6 Pa·s.

[0025] In a second aspect, the present application discloses a lignin-rubber material and a preparation method thereof.

[0026] The lignin-rubber material is prepared by 3D printing of the ink according to the first aspect, and specifically comprises:

[0027] S1: using esterified lignin-rubber ink to perform 3D printing at room temperature to obtain a preform;

[0028] S2: obtaining a 3D printed structure model after curing at room temperature.

[0029] In step S1, the 3D printing method is upright ink writing 3D printing.

[0030] In step S1, the printing dispensing pressure of the 3D printing needle is 20-100 psi, preferably 50 psi; the printing speed is 800-1800 mm / min, preferably 1000-1300 mm / min; and the printing needle diameter is 0.05-0.8 mm, preferably 0.15-0.45 mm.

[0031] In step S2, the curing time is 2-8 h, preferably 6 h.

[0032] In some embodiments, the lignin-rubber material is a material for photo-thermal water evaporation, such as a photo-thermal water collection material, such as a photo-thermal evaporator.

[0033] The solar steam conversion efficiency of the material for photo-thermal water evaporation is 80%-90%, and the water mass change is 2.0-2.5 kg m -2 h -1 ; the evaporation rate of the photo-thermal water collection material is 2.0-2.4 kg m -2 h -1 after 10 cycles.

[0034] Advantages: Compared with the prior art, the present application has the following advantages:

[0035] 1. The present application esterifies lignin, which helps to improve the dispersibility and compatibility of lignin in the rubber matrix. The esterified lignin can be grafted with PAB to construct a crosslinked network, thereby increasing the crosslinking density of the rubber and improving the mechanical properties of the rubber.

[0036] 2. The present application provides a new method for 3D printing of rubber at room temperature, which utilizes the high rigidity of the benzene ring structure of lignin to create a self-supporting framework for rubber ink, and constructs a crosslinked network between lignin and the rubber matrix, thereby maintaining structural stability during printing, improving printing accuracy and resolution, and realizing three-dimensional printing of the rubber matrix.

[0037] 3. The lignin used in the present application has strong π-π interaction, which can induce photo-thermal conversion, and can be used as a cheap and sustainable photo-thermal reagent. The addition of lignin to the rubber ink can endow the three-dimensional printed parts with excellent thermal stability and photo-thermal conversion ability, and can be used to manufacture polymer elastomers with various deformation capabilities, extreme temperature resistance, and good photo-thermal effects. BRIEF DESCRIPTION OF DRAWINGS

[0038] The above and / or other aspects of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0039] Figure 1SEM spectra of 3D printed model parts prepared for Example 1.

[0040] Figure 2 Ink prepared for Example 2, Example 3, Example 5, Example 8, Example 9, physical map of model parts of different patterns prepared by 3D printing.

[0041] Figure 3 Ink prepared for Comparative Example 2, Example 1 and Example 4, photothermal conversion temperature map of 2cm*2cm*0.5cm film prepared by 3D printing.

[0042] Figure 4 Schematic diagram of photothermal evaporation experiment of photothermal water collection material prepared for Example 12. DETAILED DESCRIPTION

[0043] The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0044] The present application provides an esterified modified lignin-rubber-based DIW 3D printing ink. The esterified modified lignin can improve its compatibility with rubber materials, and the intermolecular interaction between the esterified modified lignin-rubber can promote the crosslinking of the composite ink. Thus, an esterified lignin-rubber viscoelastic ink with optimal rheological properties and high solid content (esterified lignin addition amount up to 50-70wt%) is developed. A variety of 3D structure models with ideal elastic properties are prepared by printing with the ink, further expanding the application field of lignin-rubber composite materials.

[0045] The 3D printing ink provided by the present application has obvious shear thinning characteristics, good rheological properties and printing precision, and can be smoothly extruded from the printing needle at room temperature and under a certain pressure. The high rigidity of the benzene ring structure of lignin can create a self-supporting framework for rubber ink, and the intermolecular interaction between esterified lignin-rubber is constructed to promote the crosslinking of the composite ink. After 3D printing at room temperature, the esterified lignin-rubber ink can obtain a new type of 3D printed polymer network model with shape independence and adjustable performance without post-processing.

[0046] Example 1

[0047] 10.0g of organic solvent lignin was dissolved in 50mL of tetrahydrofuran solution. Under an ice water bath and argon atmosphere, 5g of acryloyl chloride and 1.5ml of pyridine were slowly injected with a syringe, and the stirring reaction was continued for 0.5h. Then the temperature was gradually increased to 70℃, and the stirring reaction was continued for 2h. After the reaction was completed, the solution was washed with water and ethanol to obtain esterified modified lignin.

[0048] The 5 g of nitrile rubber was dissolved in 50 ml of tetrahydrofuran solution, and then 2.5 g of esterified modified lignin was added for blending. After being stirred at 70 °C for 2 h, 2.3 * 10 5 Pa·s. of esterified lignin-rubber printing ink. The prepared ink was transferred to a printing needle cylinder, the printing needle head dispensing pressure was 50 psi, the printing speed was 1300 mm / min, the printing needle head diameter was 0.25 mm, and a preform was printed. The preform was placed at room temperature for 4 h for curing and molding to obtain a model piece.

[0049] Figure 1 SEM spectrum of the 3D printed model piece prepared in Example 1. As can be seen from the SEM image, the modified lignin has good dispersibility in the rubber material.

[0050] Example 2

[0051] 10.0 g of organic solvent lignin was dissolved in 50 mL of tetrahydrofuran solution. Under an ice water bath and argon atmosphere, 3 g of acetic anhydride and 2.5 ml of 1-methylimidazole were slowly injected with a syringe, and the stirring reaction was continued for 0.5 h. Then the temperature was gradually increased to 50 °C, and the stirring reaction was maintained for 4 h. After the reaction was completed, the solution was washed with water and ethanol to obtain esterified modified lignin.

[0052] 5 g of natural rubber was dissolved in 100 ml of tetrahydrofuran solution, and then 1 g of esterified modified lignin was added for blending. After being stirred at 60 °C for 4 h, 6.3 * 10 4 Pa·s. of esterified lignin-rubber printing ink. The prepared ink was transferred to a printing needle cylinder, the printing needle head dispensing pressure was 30 psi, the printing speed was 1500 mm / min, the printing needle head diameter was 0.15 mm, and a preform was printed. The preform was placed at room temperature for 6 h for curing and molding to obtain a model piece.

[0053] Example 3

[0054] 10.0 g of alkali lignin was dissolved in 50 mL of tetrahydrofuran solution. Under an ice water bath and argon atmosphere, 8 g of succinic anhydride and 3 ml of N-methyl amino pyridine were slowly injected with a syringe, and the stirring reaction was continued for 0.5 h. Then the temperature was gradually increased to 65 °C, and the stirring reaction was maintained for 6 h. After the reaction was completed, the solution was washed with water and ethanol to obtain esterified modified lignin.

[0055] 5 g of epoxy natural rubber was dissolved in 80 ml of tetrahydrofuran solution, and then 2 g of esterified modified lignin was added for blending. After being stirred at 55 °C for 5 h, 8.1 * 10 4Esterified lignin-rubber printing ink with 0.5 Pa-s. The prepared ink was transferred to the printing needle cylinder, the printing needle head dispensing pressure was 45 psi, the printing speed was 1200 mm / min, the printing needle head diameter was 0.35 mm, and a preform was printed. The preform was placed at room temperature for 5 h to cure and form a model piece.

[0056] Example 4

[0057] 10.0 g of organosolv lignin was dissolved in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, 8 g of succinic anhydride and 3 ml of N-methyl amino pyridine were slowly injected with a syringe, and the reaction was continued to stir for 0.5 h. Then the temperature was gradually increased to 65 °C, and the reaction was stirred for 6 h. After the reaction was completed, the solution was washed with water and ethanol to obtain the esterified modified lignin.

[0058] 5 g of epoxidized natural rubber was dissolved in 100 ml of tetrahydrofuran solution, and 2 g of esterified modified lignin was added for blending. After being heated to 55 °C and stirred for 5 h, 8.1*10 4 Esterified lignin-rubber printing ink with 0.5 Pa-s. The prepared ink was transferred to the printing needle cylinder, the printing needle head dispensing pressure was 45 psi, the printing speed was 1200 mm / min, the printing needle head diameter was 0.35 mm, and a preform was printed. The preform was placed at room temperature for 5 h to cure and form a model piece.

[0059] Example 5

[0060] 10.0 g of organosolv lignin was dissolved in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, 8 g of succinic anhydride and 3 ml of N-methyl amino pyridine were slowly injected with a syringe, and the reaction was continued to stir for 0.5 h. Then the temperature was gradually increased to 65 °C, and the reaction was stirred for 6 h. After the reaction was completed, the solution was washed with water and ethanol to obtain the esterified modified lignin.

[0061] 5 g of epoxidized natural rubber was dissolved in 100 ml of tetrahydrofuran solution, and 2 g of esterified modified lignin was added for blending. After being heated to 55 °C and stirred for 5 h, 8.1*10 6 Esterified lignin-rubber printing ink with 0.5 Pa-s. The prepared ink was transferred to the printing needle cylinder, the printing needle head dispensing pressure was 45 psi, the printing speed was 1200 mm / min, the printing needle head diameter was 0.35 mm, and a preform was printed. The preform was placed at room temperature for 5 h to cure and form a model piece.

[0062] Example 6

[0063] Dissolve 10.0 g of alkali lignin in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, slowly inject 7.5 g of dodecanoyl chloride and 3 ml of pyridine with a syringe, continue to stir the reaction for 0.5 h. Then gradually increase the temperature to 68 °C, keep stirring the reaction for 7 h. After the reaction is completed, wash the solution with water and ethanol to obtain esterified modified lignin.

[0064] Dissolve 5 g of epoxidized natural rubber in 120 ml of tetrahydrofuran solution, then add 3.5 g of esterified modified lignin for blending, after heating to 75 °C and stirring for 7 h, 4.1*10 5 Pa·s. of esterified lignin-rubber printing ink. Transfer the prepared ink to a printing needle cylinder, the printing needle head distribution pressure is 45 psi, the printing speed is 1350 mm / min, the printing needle head diameter is 0.25 mm, and a preform is printed; the preform is placed at room temperature for 6 h to solidify and form a model piece.

[0065] Example 7

[0066] Dissolve 10.0 g of organic solvent lignin in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, slowly inject 5 g of maleic anhydride and 3 ml of 1-methylimidazole with a syringe, continue to stir the reaction for 0.5 h. Then gradually increase the temperature to 75 °C, keep stirring the reaction for 6 h. After the reaction is completed, wash the solution with water and ethanol to obtain esterified modified lignin.

[0067] Dissolve 5 g of cis-butadiene rubber in 100 ml of tetrahydrofuran solution, then add 1.5 g of esterified modified lignin for blending, after heating to 65 °C and stirring for 4.5 h, 9.3*10 5 Pa·s. of esterified lignin-rubber printing ink. Transfer the prepared ink to a printing needle cylinder, the printing needle head distribution pressure is 45 psi, the printing speed is 1350 mm / min, the printing needle head diameter is 0.25 mm, and a preform is printed; the preform is placed at room temperature for 6 h to solidify and form a model piece.

[0068] Example 8

[0069] Dissolve 10.0 g of alkali lignin in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, slowly inject 5 g of maleic anhydride and 3 ml of triethylamine with a syringe, continue to stir the reaction for 0.5 h. Then gradually increase the temperature to 70 °C, keep stirring the reaction for 4 h. After the reaction is completed, wash the solution with water and ethanol to obtain esterified modified lignin.

[0070] Dissolve 5 g of butadiene-styrene rubber in 60 ml of tetrahydrofuran solution, then add 4.5 g of esterified modified lignin for blending, after heating to 70 °C and stirring for 4 h, 6.4*10 5Esterified lignin-rubber printing ink with 0.5 Pa-s. The prepared ink was transferred to the printing needle cylinder, the printing needle head dispensing pressure was 85 psi, the printing speed was 800 mm / min, the printing needle head diameter was 0.65 mm, and a preform was printed. The preform was placed at room temperature for 5 h to cure and form a model piece.

[0071] Example 9

[0072] 10.0 g of organosolv lignin was dissolved in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, 8 g of itaconic anhydride and 3 ml of pyridine were slowly injected with a syringe, and the stirring reaction was continued for 0.5 h. Then the temperature was gradually increased to 70 °C, and the stirring reaction was maintained for 4 h. After the reaction was completed, the solution was washed with water and ethanol to obtain esterified modified lignin.

[0073] 5 g of butyl nitrile rubber was dissolved in 50 ml of tetrahydrofuran solution, and 3.5 g of esterified modified lignin was added for blending. After the temperature was increased to 72 °C and stirred for 5.5 h, 2.7*10 4 Esterified lignin-rubber printing ink with 0.5 Pa-s. The prepared ink was transferred to the printing needle cylinder, the printing needle head dispensing pressure was 85 psi, the printing speed was 800 mm / min, the printing needle head diameter was 0.65 mm, and a preform was printed. The preform was placed at room temperature for 5 h to cure and form a model piece.

[0074] Example 10

[0075] 10.0 g of organosolv lignin was dissolved in 50 mL of tetrahydrofuran solution. Under ice water bath and argon atmosphere, 8 g of itaconic anhydride and 3 ml of pyridine were slowly injected with a syringe, and the stirring reaction was continued for 0.5 h. Then the temperature was gradually increased to 70 °C, and the stirring reaction was maintained for 4 h. After the reaction was completed, the solution was washed with water and ethanol to obtain esterified modified lignin.

[0076] 5 g of butyl nitrile rubber was dissolved in 50 ml of tetrahydrofuran solution, and 3.5 g of esterified modified lignin was added for blending. After the temperature was increased to 72 °C and stirred for 5.5 h, 2.7*10 5 Esterified lignin-rubber printing ink with 0.5 Pa-s. The prepared ink was transferred to the printing needle cylinder, the printing needle head dispensing pressure was 85 psi, the printing speed was 800 mm / min, the printing needle head diameter was 0.65 mm, and a preform was printed. The preform was placed at room temperature for 5 h to cure and form a model piece.

[0077] Figure 2The inks prepared in Example 2, Example 3, Example 5, Example 8, and Example 9 are used to print the physical model of the 3D printing model. The modified lignin-rubber ink prepared by the present application can realize the two-dimensional and three-dimensional model printing of various rubber materials, and build various shaped and more complex functional molded parts.

[0078] Comparative Example 1

[0079] The single-component nitrile rubber solution, natural rubber solution, cis-butadiene rubber solution, styrene-butadiene rubber solution, and epoxy natural rubber solution dissolved in THF (100 ml of THF and 5 g of rubber) are transferred into the printing needle cylinder as printing ink (the viscosity of the nitrile rubber ink is 2.8*10 2 Pa·s, the viscosity of the natural rubber ink is 1.2*10 3 Pa·s, the viscosity of the cis-butadiene rubber ink is 7.4*10 2 Pa·s, the viscosity of the styrene-butadiene rubber ink is 3.3*10 3 Pa·s, and the viscosity of the epoxy natural rubber ink is 2.1*10 3 Pa·s), and the printing conditions are the same as those in Example 3: the printing needle dispensing pressure is 45 psi, the printing speed is 1200 mm / min, the printing needle diameter is 0.35 mm, and the preformed part is obtained by printing. The preformed part is cured into a molded part at room temperature for 5 h. It is found that the resolution of the molded part obtained by all single-component rubber inks is poor, the structure of the molded part collapses obviously, the molded part shrinks obviously after curing, and the molded part cannot be used for subsequent application.

[0080] Comparative Example 2

[0081] In this comparative example, the esterified lignin is replaced by unmodified lignin, and the other experimental steps are the same as those in Example 1. It is found that the printing ink is not smooth, and the printing needle is often blocked. The surface structure of the printed molded part is rough, and the resolution is low. This is because the dispersibility and compatibility of lignin in the rubber matrix are poor, and the agglomerated lignin particles in the rubber matrix block the printing needle, and the printability is poor. The mechanical properties of the molded part are tested by a universal testing machine, and the tensile strength is 12 MPa, and the elongation at break is 68%. The mechanical properties are poor.

[0082] Figure 3For the ink prepared in Comparative Example 2, Example 1 and Example 4, a photothermal conversion temperature diagram of a 2cm*2cm*0.5cm film prepared by using a 3D printing model piece is prepared. The test results show that, due to the introduction of the modified lignin, the photothermal conversion performance of the rubber material is improved, and compared with the pure rubber material, the rubber composite material after adding the modified lignin can play a good photothermal conversion effect, the surface temperature rises obviously under the simulation sunlight irradiation, and has excellent photothermal conversion characteristics.

[0083] Example 11: Mechanical property and photothermal effect test of 3D printing model piece

[0084] Mechanical property test: the inks prepared in Examples 1-10 and Comparative Example are printed into 115mm*6mm*2mm dumbbell-shaped samples by using 3D printing, and the mechanical properties of the samples are tested by using a universal testing machine, and the tensile strength and elongation at break are recorded respectively.

[0085] Photothermal effect test: the inks prepared in Examples 1-10 and Comparative Example are printed into 2cm*2cm*0.5cm films by using 3D printing, and the films are placed under the irradiation of a 1KW xenon lamp, and the surface temperature after irradiation for 0min, 2min, 5min, 10min and 30min is recorded by using an infrared thermal imager.

[0086] Table 1: Comparison of mechanical properties of 3D printing formed pieces

[0087]

[0088]

[0089] Table 2: Comparison of photothermal conversion performance of 3D printing formed pieces

[0090] Group 0 min 2 min 5 min 10 min 30 min Comparative Example 1 24.2℃ 25.1℃ 25.6℃ 25.9℃ 27.8℃ Comparative Example 2 25.6℃ 38.6℃ 49.1℃ 53.6℃ 55.4℃ Example 1 25.4℃ 48.3℃ 56.3℃ 61.1℃ 63.4℃ Example 2 25.0℃ 45.2℃ 53.8℃ 63.4℃ 68.1℃ Example 3 24.6℃ 46.8℃ 57.1℃ 59.8℃ 62.3℃ Example 4 25.6℃ 44.3℃ 54.8℃ 65.3℃ 66.6℃ Example 5 24.0℃ 43.3℃ 51.9℃ 60.4℃ 67.1℃ Example 6 24.7℃ 44.7℃ 53.7℃ 64.1℃ 68.8℃ Example 7 25.3℃ 40.5℃ 49.7℃ 58.8℃ 62.0℃ Example 8 25.1℃ 47.2℃ 55.9℃ 66.5℃ 69.4℃ Example 9 25.5℃ 47.6℃ 54.1℃ 63.3℃ 66.5℃ Example 10 24.9℃ 48.5℃ 56.2℃ 62.1℃ 65.8℃

[0091] From the above table, it can be seen that the modified lignin-based-rubber printing ink developed in the application has good mechanical properties, the formed piece has a good three-dimensional appearance, and the surface is smooth and has high resolution; the 3D printing of rubber can be realized at room temperature, and various types of lignin-based-rubber three-dimensional models can be constructed; meanwhile, the introduced lignin can play a good photothermal conversion effect, the surface temperature rises obviously under the simulation sunlight irradiation, and further widens the application field of the lignin-based-rubber material.

[0092] Example 12: Application of 3D printing lignin-rubber-based photothermal elastomer in photothermal water collecting material

[0093] The ink prepared in Example 8 was used to print a 2cm*2cm*0.5mm photothermal water collection material (photothermal evaporator). This material was placed under a solar simulator (300W xenon lamp) for sunlight irradiation, and the amount of steam generated by the irradiation was collected over a period of time. The room temperature for the sunlight irradiation experiment was 25°C, and the relative humidity was ~50%. The printed photothermal evaporator was floated on the surface of a glass container filled with water, with white foam covering the water surface not covered by the evaporator. Then, the solar simulator was used at a solar irradiance of 1 kW m³ / h. -2 The evaporation performance of the sample was tested over 1 hour to calculate its solar steam generation rate (see schematic diagram). Figure 4 Experimental results show that, using the photo-thermal evaporator printed in Example 8, the mass change of water reaches 2.25 kg m³. -2 h -1 The solar vapor conversion efficiency was 84.6%. Ten cycles of interfacial evaporation experiments were also conducted, with the evaporation rate consistently maintained at 2.19 kg / m³. -2 h -1 The left and right sides demonstrate the excellent recyclability and sustainability of the printed structure.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing an ink, characterized in that, It was prepared according to the following method: (1) Preparation of esterified lignin: Dissolve lignin in tetrahydrofuran solution, and slowly inject esterification agent and alkaline catalyst with a syringe under ice-water bath and argon atmosphere, and raise the temperature and keep stirring for a period of time under reflux. After the reaction was completed, the solution was washed with water and ethanol to obtain esterified lignin; (2) Dissolve rubber in tetrahydrofuran solution, then add esterified lignin and mix with the rubber solution, and heat and stir for a period of time to obtain esterified lignin-rubber printing ink with a certain viscosity. In step (1), the esterification modifying agent is an acid anhydride compound and / or an acyl chloride compound.

2. The preparation method according to claim 1, characterized in that, In step (1), the esterification modifier is acryloyl chloride, undecenoyl chloride, dodecyl chloride, acetic anhydride, succinic anhydride, maleic anhydride, itaconic anhydride, methacrylic anhydride, or any combination thereof.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of lignin to esterification modifier is 1:0.1~1.

0.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of lignin to esterification modifier is 1:0.4~0.

8.

5. The preparation method according to claim 1, characterized in that, In step (1), the alkaline catalyst includes pyridine compounds, imidazole compounds, and amine compounds.

6. The preparation method according to claim 1, characterized in that, In step (1), the alkaline catalyst is pyridine, 1-methylimidazole, N-methylaminopyridine, triethylamine, or any combination thereof.

7. The preparation method according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of lignin to alkaline catalyst is 1 g: 0.05~0.3 ml.

8. The preparation method according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of lignin to alkaline catalyst is 1 g: 0.15~0.3 ml.

9. The preparation method according to claim 1, characterized in that, In step (1), the solvent for the reaction is tetrahydrofuran; the mass-volume ratio of lignin to solvent is 1 g: 4~6 mL.

10. The preparation method according to claim 1, characterized in that, In step (1), the reaction is carried out at 60~80℃ for 1~8 h.

11. The preparation method according to claim 1, characterized in that, In step (1), the reaction is first carried out in an ice bath for 0.2 to 0.8 h, and then heated to 60 to 80 °C for 1 to 8 h.

12. The preparation method according to claim 1, characterized in that, In step (2), the rubber is nitrile rubber, natural rubber, epoxy natural rubber, styrene-butadiene rubber, cis-butadiene rubber, or any combination thereof.

13. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the rubber to the esterified lignin is 1:0.1~1.

14. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the rubber to the esterified lignin is 1:0.3~0.

7.

15. The preparation method according to claim 1, characterized in that, In step (2), the solvent for the reaction includes tetrahydrofuran; the mass-volume ratio of the rubber to the solvent is 1g : 15~50 ml.

16. The preparation method according to claim 1, characterized in that, In step (2), the rubber, esterified lignin and solvent are mixed and reacted at 50~80℃ for 0.5~8 h to obtain ink.

17. The ink prepared by the method according to any one of claims 1 to 16, characterized in that, The viscosity of the ink is 6*10. 3 ~1*10 6 Pa·s.

18. The ink according to claim 17, characterized in that, The viscosity of the ink is 1*10. 4 ~1*10 6 Pa·s.

19. A lignin-rubber material, characterized in that, Made by 3D printing from the ink described in claim 17 or 18.

20. The application of the lignin-rubber material according to claim 19, characterized in that, The lignin-rubber material is used for photothermal evaporation.

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