A method for preparing Pickering emulsion using ribbon-like nanocellulose and its application

Abstract

The invention discloses a method and application of a Pickering emulsion prepared using ribbon-like nanocellulose, relates to the technical field of new materials, and comprises the following steps: step one, preparing a ribbon-like nanocellulose dispersion, wherein the concentration of the ribbon-like nanocellulose dispersion is 0.01-0.5wt%; step two, measuring an oily solvent to be added to the ribbon-like nanocellulose dispersion, wherein the volume ratio of the oily solvent to the ribbon-like nanocellulose dispersion is 1: (1-9); step three, forming a stable water-in-oil Pickering emulsion after ultrasonic / homogeneous emulsification 2-10min with the mixed solution of the oily solvent prepared in step two and the ribbon-like nanocellulose dispersion. The present invention uses ribbon-like nanocellulose to prepare a Pickering emulsion, and an emulsification effect can be achieved at a lower dosage, and the emulsion stability is also significantly improved.

Description

Technical Field

[0001] The invention relates to the technical field of new materials, and in particular to a method for preparing a Pickering emulsion by utilizing ribbon-shaped nanocellulose and application thereof. Background Art

[0002] Pickering emulsion refers to an emulsion stabilized by solid particles, which replaces traditional surfactants. Pickering emulsion has many special properties: 1) significantly reducing the amount of emulsifier used, saving costs; 2) the emulsion is highly stable and not easily affected by external environmental factors. Therefore, it has important application prospects in many fields such as cosmetics, food processing, biomedicine and environmental protection. The mechanism of Pickering emulsion is to use fine solid particles to wrap one phase and disperse it in the other phase. Therefore, the shape, charge and interaction between the emulsifier particles of the Pickering emulsifier will significantly affect its emulsification performance.

[0003] 3D printing technologies can generally be divided into four categories: (1) extrusion-based methods, such as fused deposition modeling (FDM) and direct ink writing (DIW); 2) particle fusion-based methods, such as selective laser sintering (SLS); (3) stereolithography (SLA); and (4) inkjet printing. The same material can be printed using different technologies, but the "ink formula" (i.e., the composition of the printed material) varies greatly.

[0004] Nanocellulose includes cellulose nanofibers (CNF) and cellulose nanocrystals (CNC), which have many excellent properties such as high strength, high specific surface area and excellent chemical properties. Nanocellulose can be used as a substrate for 3D printing or as a component of 3D printing bio-ink. However, when cellulose nanofibers (CNF) are used for 3D printing, CNF is easier to form hydrogels due to the presence of a large number of hydroxyl groups and the flexibility brought by chain entanglement. A large number of studies have shown that the concentration of CNF needs to be at least 0.8%, and the structure formed by it is easy to collapse, so it is often necessary to assist with metal chelation and cross-linking agents to improve strength. Hakansson et al. used a microvalve 3D printer to print 2% (wt) carboxymethylated CNF hydrogels. Highly charged CNF can form grid cubes with self-supporting characteristics. However, too high a concentration will bring difficulties to the printing process. When cellulose nanocrystals (CNC) are used in 3D printing, CNC with high crystallinity and stress conduction ability can enhance the performance of the substrate at low dosage. CNC-based 3D printing ink has shear thinning properties at an appropriate CNC addition amount [>1% (wt)], which is suitable for 3D printing.

[0005] At present, the materials used for direct writing 3D printing (DIW) are mainly based on photocurable polymers. There are also related studies reporting on 3D printing materials that add an appropriate amount of degradable biomass colloid materials. However, relying solely on the rheological properties of natural polymers cannot meet the printing suitability, which is a huge challenge as a 3D printing material.

[0006] The ribbon-like nanocellulose (CR) in the present invention is prepared by the invention patent method we applied for previously, and the patent name is "A method for preparing ultra-fine ribbon-like nanocellulose", and the application number is 202110607104.9. Ribbon-like nanocellulose (CR) is a new type of nanocellulose and a new member of the cellulose family. It is peeled along a specific hydrophilic surface. In addition to the biodegradability, sustainable regeneration, large surface area, high Young's modulus, high crystallinity and high transparency of existing nanocellulose, it also presents certain polymer physical properties, such as softer, more hydrophilic, easier to form physical entanglement with each other, and can also stabilize Pickering emulsions through bridging mechanisms like flexible molecular chains. And the surface charge of CR reaches 3.0mmol / g. The nanofibrils (TEMPO-CNF) prepared by the classic TEMPO method generally have a carboxyl content of 0.4 to 1.5mmol / g, and the surface charge of CR is more than twice the highest amount of nanofibrils (TEMPO-CNF). Summary of the invention

[0007] Purpose of the invention: The present invention provides a method for preparing a Pickering emulsion using ribbon-like nanocellulose and its application.

[0008] Technical solution: A method for preparing Pickering emulsion using filamentous ribbon nanocellulose, comprising the following steps:

[0009] Step 1, preparing a ribbon-shaped nanocellulose dispersion, wherein the concentration of the ribbon-shaped nanocellulose dispersion is 0.01-0.5 wt %;

[0010] Step 2, measuring an oily solvent and adding it to the ribbon-like nanocellulose dispersion, wherein the volume ratio of the oily solvent to the ribbon-like nanocellulose dispersion is 1:(1-9);

[0011] Step 3: subjecting the mixture of the oily solvent prepared in step 2 and the ribbon-like nanocellulose dispersion to ultrasonic / homogeneous emulsification for 2 to 10 minutes to form a stable water-in-oil Pickering emulsion.

[0012] Furthermore, the ribbon-like nanocellulose dispersion is a mixture of ribbon-like nanocellulose and deionized water, and the specifications of the ribbon-like nanocellulose are: a width of 10 to 30 nanometers, a length of 1 to 10 micrometers, and a thickness of 0.4 to 2 nanometers.

[0013] Furthermore, in the step one, xylan and a multivalent metal ion compound are added to the ribbon-like nanocellulose dispersion, stirred evenly and left for 30 minutes, and then the operation of the step two is performed; in the ribbon-like nanocellulose dispersion after adding xylan and the multivalent metal ion compound: the concentration of xylan is 0.01wt%, and the concentration of the multivalent metal ion compound is 10mmol / L.

[0014] Furthermore, the raw material for preparing the ribbon-like nanocellulose is eucalyptus, wheat straw, bamboo, metasequoia or poplar; the multivalent metal ion compound is one of CaCl2, ZnCl2 and CaSO4; and the oily solvent is specifically one of liquid paraffin, toluene, edible oil, cyclohexane and chloroform.

[0015] The present invention also provides a method for preparing 3D printing materials, characterized in that it comprises the following steps:

[0016] Step 1, preparing a ribbon-shaped nanocellulose dispersion, wherein the concentration of the ribbon-shaped nanocellulose dispersion is 0.2-0.5 wt %;

[0017] Step 2, measuring an oily solvent and adding it to the ribbon-like nanocellulose dispersion, wherein the volume ratio of the oily solvent to the ribbon-like nanocellulose dispersion is 1:(1-4);

[0018] Step 3, subjecting the mixture of the oily solvent prepared in step 2 and the ribbon-like nanocellulose dispersion to ultrasonic / homogeneous emulsification for 2 to 10 minutes to form a stable water-in-oil Pickering emulsion;

[0019] Step 4: Centrifuge the oil-in-water Pickering emulsion prepared in step 3 to remove the water at the bottom, thereby obtaining a 3D printing material.

[0020] Furthermore, in step 4, the rotation speed of the centrifuge is 2000-4000 r / min.

[0021] Furthermore, in step 4, the oily solvent is one of toluene, cyclohexane and chloroform.

[0022] Beneficial effects:

[0023] 1) The present invention uses ribbon-shaped nanocellulose when preparing Pickering emulsion, which can achieve emulsification effect at a lower dosage than existing nanocellulose (cellulose nanocrystals and cellulose nanofibrils), and the emulsion stability is also significantly improved. At the same time, it also avoids the adverse effects of inorganic nanoparticles on the human body and the environment.

[0024] 2) The present invention utilizes the high charge of CR and the coupling effect of multivalent metals to form a more stable flexible film, thereby improving the stability of the Pickering emulsion; the hemicellulose component-xylan introduced by the present invention forms a complex with CR, which can further improve the stability of the Pickering emulsion. The Pickering emulsion prepared by the present invention using ribbon-shaped nanocellulose has broad application prospects in the fields of aerogel, coating stabilization, food emulsification, etc.

[0025] 3) When the present invention uses ribbon-like nanocellulose to prepare 3D printing materials, a sample with stable geometric shape can be obtained with very little ribbon-like nanocellulose as a stabilizer. The use of ribbon-like nanocellulose to prepare 3D printing materials avoids the use of non-degradable polymers, and does not require the addition of any cross-linking components, thereby reducing environmental pollution. The prepared 3D printing materials have broad application prospects in hydrogels, textile engineering, medical tissue engineering, and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The emulsions prepared in Example 1 and Example 2 are photographs, graphs showing the change of the emulsion phase volume fraction with the placement time, and photographs of the centrifugal stability under different conditions;

[0027] Figure 2 The emulsions prepared in Example 3 and Example 4 are photographs, graphs showing the change of the emulsion phase volume fraction with the placement time, and photographs of the centrifugal stability under different conditions;

[0028] Figure 3 The emulsions prepared in Example 5 and Example 6 are photographs, graphs showing the change of the emulsion phase volume fraction with the placement time, and photographs of the centrifugal stability under different conditions;

[0029] Figure 4 The rheological results of Pickering emulsions of soybean oil stabilized by CR and CNF are shown;

[0030] Figure 5 The emulsions prepared in Example 7 and Example 8 are photographs, graphs showing the change of the emulsion phase volume fraction with the placement time, and photographs of the centrifugal stability under different conditions;

[0031] Figure 6 The rheological results of Pickering emulsions of cyclohexane stabilized by CR and CNF are shown;

[0032] Figure 7 This is a photo of the sample prepared in Example 10;

[0033] Figure 8 The photos of samples prepared in Example 12 and Example 13;

[0034] Fig. 9The appearance pictures of the printed model of Example 11 after being placed for different time periods and the printed model after being pressed and dried;

[0035] Fig.10 The digital images and corresponding compressive stress-strain curves of the printed model after freeze drying in Example 11;

[0036] Fig.11 Rheological curves and corresponding photos of CR, CNR and CNC.

[0037] in, Figure 1 (a) shows the Pickering emulsions prepared with 0.5% CNC / CNF / CR and soybean oil after 1, 3, 5, 7, and 60 days. Figure 1 (b) is the corresponding graph showing the change of emulsion phase volume fraction with placement time. Figure 1 (c) is a photograph of the centrifugal stability of the corresponding emulsion under the conditions of 2000, 4000, 6000, and 8000 rpm;

[0038] Figure 2 (a) shows the Pickering emulsions prepared with 0.1% CNC / CNF / CR and soybean oil after 1, 3, 5, 7, and 60 days. Figure 2 (b) is the corresponding graph showing the change of emulsion phase volume fraction with placement time. Figure 2 (c) is a photograph of the centrifugal stability of the corresponding emulsion under the conditions of 2000, 4000, 6000, and 8000 rpm;

[0039] Figure 3 (a) shows the photos of Pickering emulsions prepared with 0.01% CNC / CNF / CR and soybean oil after 1, 3, 5, 7, and 60 days. Figure 3 (b) is the corresponding graph showing the change of emulsion phase volume fraction with placement time. Figure 3 (c) is a photograph of the centrifugal stability of the corresponding emulsion under the conditions of 2000, 4000, 6000, and 8000 rpm;

[0040] Figure 4 Apparent viscosity, G' and G" of (a-a')CR-5:5-Pe; Figure 4 (b-b') is the apparent viscosity, G' and G" of CR-2:8-Pe; Figure 4 (c-c') are the apparent viscosities, G' and G" of CNF-5:5-Pe; Figure 4 (d-d') Apparent viscosity, G' and G" of CNF-2:8-Pe;

[0041] Figure 5(a) shows the Pickering emulsions prepared with cyclohexane and CNC / CNF / CR at a mass concentration of 0.01% after being placed for 1, 3, 5, 7, and 60 days. Figure 5 (b) is the corresponding graph showing the change of emulsion phase volume fraction with placement time. Figure 5 (c) is a photograph of the centrifugal stability of the corresponding emulsion under the conditions of 2000, 4000, 6000, and 8000 rpm;

[0042] Figure 6 where (a-a') is the apparent viscosity, G' and G" of CR-5:5-Pe; Figure 6 (b-b') is the apparent viscosity, G' and G" of CR-2:8-Pe; Figure 6 (c-c') are the apparent viscosities, G' and G" of CNF-5:5-Pe; Figure 6 (d-d') are the apparent viscosities, G' and G" of CNF-2:8-Pe;

[0043] Figure 7 (a) is a digital photo of the sample prepared in Example 10, Figure 7 (b) is a digital photo of the sample prepared as the control sample of Example 10;

[0044] In Figure 8 (a) is a digital photo of the sample prepared in Example 12, Figure 8 (b) is a digital photo of the sample prepared in Example 13;

[0045] Fig. 9 (a) Appearance diagram of the printed model of Example 11 after being placed for different time periods, Fig. 9 (b) is a picture of the printed model of Example 11 after being pressed and dried with a 1000 g weight;

[0046] Fig.10 (a) is a digital image of a cube (10×5×3 mm) printed in Example 11 after freeze drying. Fig.10 The corresponding compressive stress-strain curve is shown in the figure.

[0047] Fig.11 (a, b, c) are the rheological curves and corresponding photos of CR, CNR and CNC at a concentration of 0.5%; (d, e, f) are the rheological curves and corresponding photos of CR, CNR and CNC at a concentration of 0.3%. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0049] The preparation method of CR in the embodiment of the present invention is as follows:

[0050] 500 mg of strip-shaped metasequoia raw material, 15 mL of glacial acetic acid (17.5 mol / L), and 15 mL of hydrogen peroxide (30 wt%) were added to a 50 mL stoppered test tube, and soaked at 60°C for 48 hours. The heating was stopped to terminate the reaction, and the metasequoia fibers were allowed to settle to the bottom. After the upper layer solution was recovered, the lower layer precipitate was filtered and washed with deionized water until the pH of the filtrate was weakly acidic. The nanocellulose in the supernatant was collected by centrifugation, and then the obtained nanocellulose was processed by a low-power ultrasonic cell crusher with a power of 300 W for 5 minutes to obtain uniform ultra-thin ribbon-shaped nanocellulose (CR), with the specifications of 10 to 30 nanometers in width, 1 to 10 micrometers in length, and 0.4 to 2 nanometers in thickness. The CR dispersion in the embodiment of the present invention is a mixture of the above-mentioned ribbon-shaped nanocellulose (CR) and deionized water.

[0051] The characterization and detection methods of the prepared emulsion are as follows:

[0052] (1) Storage stability and phase volume fraction measurement: 1 mL of freshly prepared Pickering emulsion was taken out and placed in a transparent vial, stored at room temperature, monitored by visual observation, and digital photos were taken at 0, 1, 3, 5, 7, and 60 days to ensure that the vial did not tilt during the whole process. The height of the emulsion layer was measured with an electronic micrometer, and the volume fraction of the emulsion phase was calculated.

[0053] (2) Centrifugal stability: 1 mL of freshly prepared Pickering emulsion was centrifuged at 2000, 4000, 6000, and 8000 rpm for 2 min, and the samples were photographed and recorded after centrifugation. The volume of the aqueous phase separated after centrifugation was measured using a pipette, and the volume fraction of the internal phase after centrifugation was calculated. The calculation formula is shown below:

[0054]

[0055] Where V0 is the initial volume of the oil phase, Vt is the initial volume of the emulsion 1 mL, and V1 is the volume of water removed after centrifugation.

[0056] (3) Rheological properties: The samples were tested using a rheometer (MAR S60, Thermo Fisher Scientific, Germany) with a 60 mm parallel plate and a gap of 0.45 mm. The shear viscosity was tested when the shear rate increased from 0.01 to 100 s-1, and the storage modulus G' and loss modulus G" were recorded within the dynamic scanning frequency range of 0.1 to 10 Hz.

[0057] Example 1

[0058] 80mL of 0.5wt% CR dispersion was measured and xylan and CaCl2 were added thereto. After adding xylan and CaCl2, the concentration of xylan in the CR dispersion was 0.01wt% and the concentration of CaCl2 was 10mmol / L. After mixing evenly and standing for 30 minutes, 20mL of soybean oil was added and emulsified by a homogenizer at a speed of 15000 rpm for 2 minutes. The prepared soybean oil pickering emulsion is extremely stable and remains stable after being placed for 60 days. The photos of the emulsion, the graph of the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion at 2000, 4000, 6000, and 8000rmp are attached. Figure 1 In the figure, O:W=2:8 data.

[0059] The control sample nanocellulose crystals (CNC), even at such a high concentration, still cannot stabilize the pickering emulsion well. It can only be stable for a while when it is just prepared, and phase separation occurs after one day.

[0060] The pickering emulsion prepared by the control sample cellulose nanofibrils (CNF) has good emulsification performance and is very stable after 60 days, and the performance is not much different from that of CR.

[0061] Example 2

[0062] 50mL of 0.5wt% CR dispersion was measured and xylan and CaCl2 were added thereto. After adding xylan and CaCl2, the concentration of xylan in the CR dispersion was 0.01wt% and the concentration of CaCl2 was 10mmol / L. After mixing evenly and standing for 30 minutes, 50mL of soybean oil was measured and added thereto. Finally, a homogenizer was used for emulsification at a speed of 15,000 rpm and an emulsification time of 5 minutes. The prepared soybean oil pickering emulsion is extremely stable and remains stable after being placed for 60 days. The photos of the emulsion, the graph of the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion at 2000, 4000, 6000, and 8000 rpm are attached. Figure 1 In the figure, O:W=5:5 data.

[0063] The control sample, nanocellulose crystals (CNC), could not form an emulsion at all at this oil-water ratio.

[0064] The pickering emulsion prepared by the control sample cellulose nanofibrils (CNF) has good emulsification performance and is very stable after 60 days. The performance is not much different from that of CR, but its centrifugal stability is not as good as that of CR.

[0065] Example 3

[0066] 80mL of 0.1wt% CR dispersion was measured and xylan and ZnCl2 were added thereto. In the CR dispersion with xylan and ZnCl2, the concentration of xylan was 0.01wt% and the concentration of ZnCl2 was 10mmol / L. After mixing evenly and standing for 30 minutes, 20mL of soybean oil was measured and added thereto. Finally, ultrasonic emulsification was performed with a power of 300W and an emulsification time of 30 minutes. The prepared soybean oil pickering emulsion is extremely stable and remains stable after being placed for 60 days. The photos of the emulsion, the graph of the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion at 2000, 4000, 6000, and 8000rmp are attached. Figure 2 In the figure, O:W=2:8 data.

[0067] The control nanocellulose crystals (CNC) were unable to form an emulsion.

[0068] The pickering emulsification performance of the control sample cellulose nanofibrils (CNF) is acceptable, with slight phase separation within 60 days, but the centrifugal stability is poor, with severe phase separation occurring at 2000 rpm.

[0069] The pickering emulsion prepared by CR performed excellently, and the stability was still very good even at 8000rmp.

[0070] Example 4

[0071] 50mL of 0.1wt% CR dispersion was measured and xylan and ZnCl2 were added thereto. In the CR dispersion with xylan and ZnCl2, the concentration of xylan was 0.01wt% and the concentration of ZnCl2 was 10mmol / L. After mixing evenly and standing for 30 minutes, 50mL of soybean oil was measured and added thereto. Finally, ultrasonic emulsification was performed with a power of 300W and an emulsification time of 30 minutes. The prepared soybean oil pickering emulsion is extremely stable and remains stable after being placed for 60 days. The photos of the emulsion, the graph of the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion at 2000, 4000, 6000, and 8000rmp are attached. Figure 2 In the data, O:W=5:5.

[0072] The control nanocellulose crystals (CNC) were unable to form an emulsion.

[0073] The pickering emulsion prepared by cellulose nanofibrils (CNF) has poor emulsification performance, and turbidity appears at the bottom after one day, and the centrifugal stability is poor. CR performs well and has good stability even at 8000rmp.

[0074] Example 5

[0075] 80mL of 0.1wt% CR dispersion was measured and xylan and CaSO4 were added thereto. In the CR dispersion with xylan and CaSO4, the concentration of xylan was 0.01wt% and the concentration of CaSO4 was 10mmol / L. After mixing evenly and standing for 30 minutes, 20mL of soybean oil was measured and added thereto. Finally, a homogenizer was used for emulsification at a speed of 15,000 rpm and an emulsification time of 5 minutes. The prepared soybean oil pickering emulsion has a certain stability. The photos of the emulsion, the graph of the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion at 2000, 4000, 6000, and 8000 rpm are attached. Figure 3 In the figure, O:W=2:8 data.

[0076] The pickering emulsions prepared from the control samples of cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) had poor emulsification properties, especially the centrifugal stability was not as good as that of CR.

[0077] Example 6

[0078] Measure 50mL of 0.01wt% CR dispersion, add xylan and CaSO4, add xylan concentration to 0.01wt% CR dispersion, CaSO4 concentration to 10mmol / L; mix evenly and let stand for 30 minutes, then measure 50mL soybean oil and add it, finally use homogenizer to emulsify, homogenizer speed is 15000 rpm, emulsification time is 5 minutes. The prepared soybean oil pickering emulsion has a certain stability. The photos of the emulsion, the change of emulsion phase volume fraction with the placement time and the centrifugal stability of the emulsion under 2000, 4000, 6000, 8000rmp conditions are attached. Figure 3 In the figure, O:W=5:5 data.

[0079] The pickering emulsions prepared from the control samples of cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) have poor emulsification properties, especially the centrifugal stability is not as good as that of CR.

[0080] The rheological properties of the pickering emulsion prepared by CR are shown in the attached Figure 4 From a and b (the data of the control sample CNF are c and d), it can be seen that the viscosity of the soybean oil emulsion stabilized by CR is significantly higher than that of CNF, which is determined by the unique structure of CR.

[0081] Example 7

[0082] 80mL of 0.01wt% CR dispersion was measured and xylan and CaSO4 were added thereto. The concentration of xylan was 0.01wt% and the concentration of CaSO4 was 10mmol / L in the CR dispersion of xylan and CaSO4. After mixing evenly and standing for 30 minutes, 20mL of cyclohexane was measured and added thereto. Finally, a homogenizer was used for emulsification at a speed of 15,000 rpm and an emulsification time of 5 minutes. The prepared cyclohexane pickering emulsion has a certain stability. The photos of the emulsion, the graph of the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion at 2000, 4000, 6000, and 8000 rpm are attached. Figure 5 In the figure, O:W=2:8 data.

[0083] The control sample nanocellulose crystals (CNC) had poor emulsification performance for cyclohexane;

[0084] The pickering emulsion prepared by cellulose nanofibrils (CNF) has slightly better emulsification performance than CR. This may also be determined by the unique structure of CR. Because CR is too hydrophilic, its emulsification performance for cyclohexane with very low polarity is not as good as that for soybean oil. Figure 6 , the viscosity of CR emulsion is still higher than that of CNF, which may be due to the flexibility, high carboxyl content, and conjugation with calcium ions of CR.

[0085] Example 8

[0086] Measure 50mL of 0.01wt% CR dispersion, add xylan and CaSO4, add xylan and CaSO4 to the CR dispersion: the concentration of xylan is 0.01wt%, the concentration of CaSO4 is 10mmol / L; mix evenly and let stand for 30 minutes, then measure 50mL of cyclohexane and add it into it, and finally use ultrasonic emulsification with a power of 300W and an emulsification time of 30 minutes. The prepared cyclohexane pickering emulsion has a certain stability. The photos of the emulsion, the change of the emulsion phase volume fraction with the placement time, and the centrifugal stability of the emulsion under the conditions of 2000, 4000, 6000, and 8000rmp are attached. Figure 5 In the figure, O:W=5:5 data.

[0087] The whole phenomenon is similar to that in Example 7. The emulsification performance of the control sample nanocellulose crystals (CNC) to cyclohexane is not good, while the emulsification performance of the pickering emulsion prepared by cellulose nanofibrils (CNF) is slightly better than that of CR. This may also be determined by the unique structure of CR. Because CR is too hydrophilic, its emulsification performance to cyclohexane with very low polarity is not as good as that to soybean oil. Figure 6, the viscosity of CR emulsion is still higher than that of CNF, which may be due to the flexibility, high carboxyl content, and conjugation with calcium ions of CR.

[0088] Example 9

[0089] Three 90 mL portions of 0.01 wt % CR dispersion were measured and xylan and CaSO4 were added to the CR dispersion of xylan and CaSO4: the concentration of xylan was 0.01 wt % and the concentration of CaSO4 was 10 mmol / L;

[0090] Then 10 mL of paraffin, toluene ring and chloroform were respectively added to three portions of CR dispersions mixed with xylan and CaSO4, and finally ultrasonic emulsification was used with a power of 300 W and an emulsification time of 5 minutes. The prepared pickering emulsions can be stably stored for more than 1 month.

[0091] Example 10

[0092] Weigh 2 mL of toluene and add it to 8 mL of 0.2 wt% CR nanocellulose dispersion to form a phase-separated mixture; emulsify the resulting mixture using a homogenizer at a speed of 15,000 rpm for 5 minutes. Then centrifuge the emulsion for 2 minutes at a centrifugal speed of 4,000 rpm to obtain a 3D printing material. Add the prepared 3D printing material to the extruder of the BioX biological 3D printer for printing. The printing pressure is 30 KPa and the nozzle size is 25 G. After printing, use a digital camera to record the shape, such as Figure 7 As shown in (a), it can form a self-supporting structure with good shape fidelity.

[0093] For the control sample of Example 10: weigh 2 mL of toluene and add it to 8 mL of 0.2 wt% ordinary cellulose nanofibril (CNF) dispersion to form a phase-separated mixture; the obtained mixture is emulsified by a homogenizer at a speed of 15,000 rpm for 5 minutes. The emulsion is then centrifuged for 2 minutes at a centrifugal speed of 2,000 rpm to obtain a 3D printing material. The prepared 3D printing material is added to the extruder of the BioX biological 3D printer for printing. The printing pressure is 30 KPa and the nozzle size is 25 G. After printing, the shape is recorded with a digital camera, such as Figure 7 As shown in (b), it is not self-supporting and collapses obviously, so the shape cannot be maintained. This is consistent with the literature that CNF printing requires a higher CNF concentration (0.8-2%).

[0094] Embodiment 11

[0095] Weigh 2 mL of toluene and add it to 8 mL of 0.5 wt% CR nanocellulose dispersion to form a phase-separated mixture; emulsify the resulting mixture using a homogenizer at a speed of 15,000 rpm for 5 minutes. Then centrifuge the emulsion for 2 minutes at a centrifugal speed of 4,000 rpm to obtain a 3D printing material. Add the prepared 3D printing material to the extruder of the BioX biological 3D printer for printing. The printing pressure is 30 KPa and the nozzle size is 25 G. After printing, use a digital camera to record the shape, such as Figure 8 As shown in (a), it can form a self-supporting structure with good shape fidelity. The change of its natural drying in air over time and the strength after drying are shown in Fig. 9 Its density after drying is only 0.18g / mL, and it can be placed on grass leaves ( Fig.10 (a)), its strength test data is as follows Fig.10 (b), significantly higher than the control CNF-printed one.

[0096] Control sample of Example 11: Weigh 2 mL of toluene and add it to 8 mL of 0.5 wt% CNF dispersion to form a phase-separated mixture; emulsify the resulting mixture using a homogenizer at a speed of 15,000 rpm for 5 minutes. The emulsion was then centrifuged for 2 minutes at a speed of 4,000 rpm to obtain a 3D printing material. The prepared 3D printing material was added to the extruder of the BioX biological 3D printer for printing. The printing pressure was 30 KPa and the nozzle size was 25 G. After printing, the shape was recorded with a digital camera. This concentration can basically form a self-supporting structure, but the shape fidelity is not good. Its strength test data is as follows Fig.10 The control curve CNF in (b) is significantly lower than that printed by CR.

[0097] Example 12

[0098] Weigh 5 mL of toluene and add it to 5 mL of 0.5 wt% CR nanocellulose dispersion to form a phase-separated mixture; the obtained mixture is ultrasonically emulsified with a power of 300 W and an emulsification time of 10 minutes. Then the emulsion is centrifuged for 2 minutes at a centrifugal speed of 4000 rpm to obtain a 3D printing material. The prepared 3D printing material is added to the extruder of the BioX biological 3D printer for printing. The pressure during printing is 30 KPa and the nozzle size is 25 G. After printing, a self-supporting structure can be formed with good shape fidelity.

[0099] Example 13

[0100] Weigh 2 mL of cyclohexane and add it to 8 mL of 0.5% CR nanocellulose dispersion to form a phase-separated mixture; emulsify the obtained mixture using a homogenizer at a speed of 15,000 rpm for 5 minutes. Then centrifuge the emulsion for 2 minutes at a centrifugal speed of 4,000 rpm to obtain a 3D printing material. Add the prepared 3D printing material to the extruder of the BioX biological 3D printer for printing. The printing pressure is 30 KPa and the nozzle size is 25 G. After printing, use a digital camera to record the shape, such as Figure 8 As shown in (b), it can form a self-supporting structure with good shape fidelity.

[0101] Embodiment 14

[0102] Weigh 2 mL of chloroform and add it to 8 mL of 0.5% CR nanocellulose dispersion to form a phase-separated mixture; emulsify the obtained mixture with a homogenizer at a speed of 15,000 rpm for 5 minutes. Then centrifuge the emulsion for 2 minutes at a centrifugal speed of 2,000 rpm to obtain a 3D printing material. Add the prepared 3D printing material to the extruder of the BioX biological 3D printer for printing. The printing pressure is 30 KPa and the nozzle size is 25 G. After printing, a self-supporting structure can be formed with good shape fidelity.

[0103] Based on the experiments and result analysis of the above-mentioned Examples 1-9, the present invention uses ribbon-like nanocellulose in the method for preparing Pickering emulsions, which can achieve an emulsification effect at a lower dosage than existing nanocellulose (cellulose nanocrystals and cellulose nanofibrils), and the stability of the emulsion is also significantly improved. At the same time, it also avoids the adverse effects of inorganic nanoparticles on the human body and the environment. The present invention utilizes the high charge carried by CR, combined with the coupling effect of multivalent metals, to form a more stable flexible film, thereby improving the stability of the Pickering emulsion; the hemicellulose component-xylan introduced by the present invention forms a complex with CR, which can further improve the stability of the Pickering emulsion. The Pickering emulsion prepared by the present invention using ribbon-like nanocellulose has broad application prospects in the fields of aerogels, coating stabilization, and food emulsification.

[0104] Because, during the preparation process, the ribbon-like nanocellulose (CR) is treated with glacial acetic acid and hydrogen peroxide. Under the synergistic treatment of oxidation, the polar solvent penetrates through the hydrophilic surface of the cellulose crystal, thereby weakening the strong hydrogen bonding between the hydrophilic surfaces of the cellulose crystal. Therefore, the ribbon-like nanocellulose (CR) is more hydrophilic, such as Fig.11As shown in the figure, under the same concentration conditions, its zero shear viscosity is 1 to 2 orders of magnitude higher than that of CNF with the same concentration, indicating that CR is an ideal DIW printing material.

[0105] The new type of ribbon-like nanocellulose CR not only has biodegradability, sustainable regeneration, large surface area, high Young's modulus, high crystallinity and high transparency, but also presents certain polymer physical properties, such as being softer, easier to form physical entanglements with each other, and able to enhance the internal interaction of the material through a bridging mechanism like a flexible molecular chain. Therefore, when the present invention uses ribbon-like nanocellulose to prepare 3D printing materials, a very small amount of ribbon-like nanocellulose can be used as a stabilizer to obtain a sample with a stable geometric shape.

[0106] Based on the experiments and result analysis of the above embodiments 10-14, the application in 3D printing. This patent can realize DIW printing of self-supporting materials with 0.2% CR without any cross-linking agent, and has good fidelity. This patent can achieve lighter (concentration as low as 0.2% CR), stronger (with the flexibility and hydrogen bonding of CR, it has higher compressive strength), high biocompatibility (100% cellulose, no cross-linking agent, no other organic polymers), and high fidelity. This is far beyond the reach of traditional nanocellulose and has significant advancement.

[0107] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for preparing a Pickering emulsion using filamentous ribbon nanocellulose, characterized in that: The steps include: Step 1: preparing a ribbon-shaped nanocellulose dispersion, wherein the concentration of the ribbon-shaped nanocellulose dispersion is 0.01-0.5 wt %; Step 2, measuring an oily solvent and adding it to the ribbon-like nanocellulose dispersion, wherein the volume ratio of the oily solvent to the ribbon-like nanocellulose dispersion is 1:(1-9); Step 3: subjecting the mixture of the oily solvent prepared in step 2 and the ribbon-like nanocellulose dispersion to ultrasonic / homogeneous emulsification for 2 to 10 minutes to form a stable water-in-oil Pickering emulsion; The ribbon-like nanocellulose dispersion is a mixture of ribbon-like nanocellulose and deionized water. The specifications of the ribbon-like nanocellulose are: a width of 10 to 30 nanometers, a length of 1 to 10 micrometers, and a thickness of 0.4 to 2 nanometers.

2. A method for preparing a Pickering emulsion using filamentous ribbon nanocellulose according to claim 1, characterized in that: In the step 1, xylan and a multivalent metal ion compound are added to the ribbon-like nanocellulose dispersion, stirred evenly and allowed to stand for 30 minutes, and then the step 2 is performed; In the ribbon-like nanocellulose dispersion after adding xylan and the multivalent metal ion compound: the concentration of xylan is 0.01wt%, and the concentration of the multivalent metal ion compound is 10 mmol / L.

3. A method for preparing a Pickering emulsion using filamentous ribbon nanocellulose according to claim 2, characterized in that: The raw materials for preparing the ribbon-shaped nanocellulose are eucalyptus, wheat straw, bamboo, metasequoia or poplar; The multivalent metal ion compound is one of CaCl2, ZnCl2 and CaSO4; The oily solvent is specifically one of liquid paraffin, toluene, edible oil, cyclohexane and chloroform.

4. A method for preparing 3D printing materials based on the method for preparing Pickering emulsion using filamentous ribbon nanocellulose according to claim 1, characterized in that: The steps include: Step 1, preparing a ribbon-shaped nanocellulose dispersion, wherein the concentration of the ribbon-shaped nanocellulose dispersion is 0.2-0.5wt%; Step 2, measuring an oily solvent and adding it to the ribbon-like nanocellulose dispersion, wherein the volume ratio of the oily solvent to the ribbon-like nanocellulose dispersion is 1:(1-4); Step 3, subjecting the mixture of the oily solvent prepared in step 2 and the ribbon-like nanocellulose dispersion to ultrasonic / homogeneous emulsification for 2 to 10 minutes to form a stable water-in-oil Pickering emulsion; Step 4: Centrifuge the oil-in-water Pickering emulsion prepared in step 3 to remove the water at the bottom, thereby obtaining a 3D printing material.

5. A method for preparing 3D printing materials according to claim 4, characterized in that: In step 4, the rotation speed of the centrifuge is 2000-4000 r / min.

6. A method for preparing 3D printing materials according to claim 4, characterized in that: In step 4, the oily solvent is one of toluene, cyclohexane and chloroform.

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