Preparation method and application of a mechanical cellulose nanofibril-based high internal phase pickering emulsion

Abstract

The application provides a preparation method of a mechanical cellulose nanofibril-based high internal phase Pickering emulsion, comprising the following steps: step S1, performing nanomechanical grinding treatment and homogenization treatment on lignocellulose to obtain cellulose nanofibril CNF; step S2, performing complexing on the cellulose nanofibril CNF obtained in step S1 and lauroyl arginine ethyl ester hydrochloride LAE to obtain a CNF / LAE complex; and step S3, mixing the obtained CNF / LAE complex with a Pickering emulsion, and stirring for a period of time to obtain a high internal phase Pickering emulsion. The preparation method uses CNF and LAE prepared by a pure mechanical method to stabilize the Pickering emulsion and the high internal phase Pickering emulsion, forms a complex through the CNF and the LAE, and uses a simple homogenization technology to stabilize the oil-in-water Pickering emulsion.

Description

TECHNICAL FIELD

[0001] The present application relates to emulsion preparation technology, in particular to a preparation method and application of a mechanical cellulose nanofibril-based high internal phase Pickering emulsion. BACKGROUND

[0002] Pickering emulsion has attracted much attention due to its stability, environmental friendliness and low particle load at the oil-water interface. Its biggest feature is that solid particles are irreversibly adsorbed on the surface of emulsion droplets, with high stability and almost no influence from any factors in the system. With the improvement of people's living standards and the development of science and technology, in order to meet the needs of Pickering emulsion in various situations, such as templates for porous materials, oil extraction, biological catalyst matrix, functional food and tissue engineering scaffolds, it is often necessary to increase the proportion of the dispersed phase. When the volume fraction of the dispersed phase is as high as 0.74, this system is called high internal phase Pickering emulsion (HIPPEs). Compared with the use of a large amount of surfactants dissolved in the continuous phase, the use of colloidal particles can effectively improve the stability of the emulsion and help to inhibit the inversion of the emulsion. Although some progress has been made in the production of polysaccharide and protein-based micro / nanoparticles capable of stabilizing HIPPEs, there are few reports on CNFs, especially unmodified CNFs. Therefore, a sustainable method for producing stable HIPPEs with CNF is very important and in great demand.

[0003] Lauroyl ethyl arginate hydrochloride (LAE) is a cationic surfactant that has attracted widespread attention in recent years as a new type of food preservative. LAE has a significant inhibitory effect on gram-positive bacteria, gram-negative bacteria, yeast and mold, and is a broad-spectrum antibacterial agent. It can be degraded by the human body and has high biological safety. It has been approved by the US Food and Drug Administration (FDA), the US Department of Agriculture (USDA), the European Food Safety Authority (EFSA) and the International Food Codex Commission for food preservation, and has a wide application prospect and huge market demand. LAE can strongly interact with negatively charged parts. The present application first uses CNF prepared by a pure mechanical method and LAE to stabilize Pickering emulsion and high internal phase Pickering emulsion. By forming a complex of CNF and LAE, an oil-in-water Pickering emulsion is stabilized using a simple homogenization technique. The rheological properties, particle size and 3D printing performance of the emulsion are characterized. The present application will help to further apply CNF prepared by a pure mechanical method as an effective emulsifier to prepare Q / W emulsion with high internal phase stability, which can be used as a core component of a green system. SUMMARY

[0004] The main purpose of the present application is to provide a preparation method and application of a mechanical cellulose nanofibril-based high internal phase Pickering emulsion, CNF and LAE prepared by a pure mechanical method are used to stabilize Pickering emulsion and high internal phase Pickering emulsion, a complex is formed by CNF and LAE, and a simple homogenization technology is used to stabilize the oil-in-water Pickering emulsion.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a preparation method of a mechanical cellulose nanofibril-based high internal phase Pickering emulsion, characterized by comprising the following steps:

[0006] Step S1, wood cellulose is subjected to nanomechanical grinding treatment and homogenization treatment to obtain cellulose nanofibril CNF;

[0007] Step S2, the cellulose nanofibril CNF obtained in step S1 is complexed with lauroyl arginine ethyl ester hydrochloride LAE to obtain a CNF / LAE complex;

[0008] Step S3, the obtained CNF / LAE complex is mixed with an oil phase, and after stirring for a period of time, a high internal phase Pickering emulsion is obtained.

[0009] Preferably, in step S1, when the nanomechanical grinding treatment is performed, the pressure is 0-60MPa, and the grinding is performed 20-50 times.

[0010] Preferably, in step S1, when the homogenization treatment is performed, the internal pressure is 70-250MPa, and the number of times is 5-30 times.

[0011] Preferably, in step S3, the proportion of the oil phase is 50-80wt%.

[0012] Preferably, in step S3, first, stirring is performed at a first speed for a period of time, and then stirring is performed at a second speed for a period of time, the second speed being greater than the first speed.

[0013] The present application also provides an application of a high internal phase Pickering emulsion as ink in 3D printing, the high internal phase Pickering emulsion being prepared by the above preparation method.

[0014] Compared with the prior art, the present application has the following beneficial effects:

[0015] (1) The raw materials used are low in cost and abundant in resources, the preparation process is pollution-free to the environment, the process is simple and easy to operate, the repeatability is good, and the high internal phase Pickering emulsion prepared can be stably present for more than 1 month;

[0016] (2) The CNF prepared by mechanical method is easy to form a solid three-dimensional network structure in the water system with the presence of LAE due to its large aspect ratio and dispersed dendritic shape, which can prevent or delay the movement of droplets. On the other hand, the CNF / LAE complex preferentially adsorbs at the oil-water interface, while the electrostatic repulsion and steric hindrance between the CNF in the water phase and the complex delay / prevent the aggregation and coalescence of droplets. Therefore, the CNF / LAE complex of the present application effectively stabilizes the high internal phase Pickering emulsion;

[0017] (3) The particle size of the oil droplets of the emulsion changes with the mass of the oil phase, realizing the particle size adjustability, providing a scheme for the emulsion templating technology, and providing technical guidance for porous materials;

[0018] (4) The high internal phase Pickering emulsion prepared by the present application has good printing suitability and can realize multifunctional application, and is easy to realize industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure is the visual appearance diagram of Pickering emulsion with different oil-water ratios stabilized by CNF / LAE complex, (a) is 0 days, (b) is placed for 30 days;

[0020] Figure 2 Figure is the particle size distribution diagram of Pickering emulsion with different oil-water ratios stabilized by CNF / LAE complex, (a) is 0 days, (b) is placed for 30 days;

[0021] Figure 3 Figure is the average particle size diagram of Pickering emulsion with different oil-water ratios stabilized by CNF / LAE complex, (a) is 0 days, (b) is placed for 30 days;

[0022] Figure 4 Figure is the rheological curve diagram of Pickering emulsion with different oil-water ratios stabilized by CNF / LAE complex, (a) is 0 days, (b) is placed for 30 days;

[0023] Figure 5 Figure is the three-dimensional object diagram of Pickering emulsion with different oil-water ratios stabilized by CNF / LAE complex ink printing. DETAILED DESCRIPTION

[0024] The following description is used to disclose the present application so that those skilled in the art can implement the present application. The preferred embodiments in the following description are only as examples, and other obvious modifications can be conceived by those skilled in the art.

[0025] Example one

[0026] A method for preparing a mechanical cellulose nanofilament-based high internal phase Pickering emulsion, comprising the following steps:

[0027] Step S1, the lignocellulose is subjected to nanomechanical grinding treatment, the pressure is 0-60MPa, the grinding is 20-40 times, and the homogenization treatment is carried out, the internal pressure is 70-250MPa, and the homogenization is 5-30 times, to obtain cellulose nanofilament CNF;

[0028] Step S2, the cellulose nanofilament CNF obtained in step S1 is complexed with 0.005-0.07wt% lauroyl arginine ethyl ester hydrochloride LAE, to obtain a CNF / LAE complex; the CNF is negatively charged in water, and the LAE is positively charged, and the two are complexed together by electrostatic adsorption;

[0029] Step S3, the obtained CNF / LAE complex is mixed with a Pickering emulsion, the oil phase in the Pickering emulsion accounts for 50-80wt%, stirring is carried out at a speed of 11000rpm for 5-20min, and stirring is carried out at a speed of 15000rpm for 5-20min, to obtain a high internal phase Pickering emulsion.

[0030] In step S3, the oil phase can be olive oil, or other oil phases can be used.

[0031] The above Pickering emulsion is used as ink for 3D printing, to obtain a 3D printing product.

[0032] Experimental Example One

[0033] Under the same conditions, five Pickering emulsions are prepared by using the method in Example One and the oil phase ratios are 50 / 50, 60 / 40, 70 / 30, 77 / 23 and 80 / 20 respectively.

[0034] The above five high internal phase Pickering emulsions are respectively taken into corresponding bottles and inverted, no layering phenomenon appears after inversion, and no layering phenomenon appears after standing for 30 days, which shows that the high internal phase Pickering emulsion has good stability and uniform density, see Figure 1 .

[0035] The particle sizes of the above five Pickering emulsions are analyzed, and the particle sizes of the Pickering emulsions placed for 0 days and 30 days are obtained, from Figure 2As can be seen, the oil droplet size consistently maintains a unimodal distribution, and the droplet size gradually increases with the increase of the oil-water ratio. In practical applications, users can adjust the oil phase ratio to obtain the desired Pickering emulsion particle size. After standing for 30 days, although the particle size of all five Pickering emulsions increased, the increase was small, indicating good emulsion stability. (See [link to relevant documentation]). Figure 3 .

[0036] from Figure 4 It can be seen that as the oil phase ratio increases, the modulus of the high internal phase Pickering emulsion gradually increases, indicating that as the oil phase ratio increases, the CNF network becomes more robust, improving printability.

[0037] Figure 5 The products printed from high internal phase Pickering emulsions with oil phase ratios of 50 / 50, 70 / 30, and 80 / 20 are from... Figure 5 The results show that the product printed using a high internal phase Pickering emulsion with an oil-to-water ratio of 80 / 20 is more complete, which verifies the... Figure 4 As the amount of ink increases, printability will improve.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. The application of a high internal phase Pickering emulsion as an ink in 3D printing, wherein the high internal phase Pickering emulsion is prepared by the following method: Step S1: The lignocellulose is subjected to nano-mechanical grinding and homogenization to obtain cellulose nanofibers (CNF). Step S2: Complex the cellulose nanofibers CNF obtained in step S1 with lauroyl arginine ethyl ester hydrochloride (LAE) to obtain a CNF / LAE complex. Step S3: Mix the obtained CNF / LAE complex with the oil phase and stir for a period of time to obtain a high internal phase Pickering emulsion; In step S1, during the nanomechanical grinding process, the pressure is 0-60 MPa and the grinding is performed 20-50 times. In step S3, the proportion of the oil phase is 70-80 wt%; In step S3, the mixture is first stirred at a first speed for a period of time, and then stirred at a second speed for a period of time, wherein the second speed is greater than the first speed.

2. The application according to claim 1, characterized in that, In step S1, during the homogenization process, the internal pressure is 70-250 MPa, and the number of cycles is 5-30.

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