Method for preparing controllable cellulose nanocrystal water-in-oil emulsion by microfluidic instantaneous double emulsion method and cellulose nanocrystal water-in-oil emulsion

Abstract

The invention belongs to the technical field of interface chemistry, and provides a method for preparing a controllable cellulose nanocrystal water-in-oil emulsion by a microfluidic instantaneous double-emulsion method and the cellulose nanocrystal water-in-oil emulsion. According to the preparation method, a glycerol aqueous solution is used as an inner phase, a cellulose nanocrystal aqueous dispersion is used as an intermediate phase, an oil phase is used as an outer phase, and the cellulose nanocrystal is only deposited on the surface of a liquid drop by utilizing the dissolution characteristics of microfluidics and cellulose nanocrystals, so that a cellulose nanocrystal water-in-oil emulsion is prepared; the cellulose nanocrystals are only deposited on an interface formed by the water phase and the oil phase, and the viscosity and wetting characteristics of the water phase and the oil phase and the appearance of the finally obtained liquid drops are not influenced. Besides, by controlling the flow velocity of the external phase, the intermediate phase and the external phase, the size and the interface coverage rate of the liquid drops in the emulsion can be adjusted, and the obtained liquid drops are regular in morphology.

Description

Technical Field

[0001] The invention relates to the technical field of interface chemistry, and in particular to a method for preparing a controllable cellulose nanocrystal oil-in-water emulsion by using a microfluidic instantaneous double emulsion method and the cellulose nanocrystal oil-in-water emulsion. Background Art

[0002] Cellulose nanocrystals are a new type of nanoscale cellulose material with advantages such as high biocompatibility, non-toxicity, excellent mechanical strength and easy surface modification. They perform well in emulsion stabilizers, packaging materials, functional ingredients, and the preparation of hydrogels and porous materials. However, due to their strong hydrophilicity, cellulose nanocrystals are difficult to form stable water-in-oil (W / O) emulsions alone. Chemical modification or the addition of additional surfactants is usually required to prepare stable water-in-oil emulsions. Chemical modification or the use of additional surfactants may destroy the biocompatibility advantages of cellulose nanocrystals in food, cosmetics and other green materials. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a method for preparing a controllable cellulose nanocrystal oil-in-water emulsion by a microfluidic transient double emulsion method and a cellulose nanocrystal oil-in-water emulsion. The method provided by the present invention does not use an emulsifier or chemical modification, and obtains a cellulose nanocrystal oil-in-water emulsion with good stability.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a controllable cellulose nanocrystal oil-in-water emulsion by a microfluidic instantaneous double emulsion method, comprising the following steps:

[0006] A cellulose nanocrystal oil-in-water emulsion was obtained by microfluidics using a glycerol aqueous solution as the inner phase, a cellulose nanocrystal aqueous dispersion as the middle phase, and an oil phase as the outer phase.

[0007] Preferably, the mass fraction of the glycerol aqueous solution is 30-70%.

[0008] Preferably, the injection flow rate of the glycerol aqueous solution is 500-1500 μL / h.

[0009] Preferably, the cellulose nanocrystals in the cellulose nanocrystal aqueous dispersion present a typical rod-like structure with a width of 6.2±1.5 nm and a length of 127.5±28.7 nm.

[0010] Preferably, the mass fraction of the cellulose nanocrystal aqueous dispersion is 0.01-1.00%.

[0011] Preferably, the injection flow rate of the cellulose nanocrystal aqueous dispersion is 500-1500 μL / h.

[0012] Preferably, the oil phase comprises one or more of n-decanol, medium chain triglycerides, corn oil, rapeseed oil, peanut oil and soybean oil.

[0013] Preferably, the injection flow rate of the oil phase is 4000-10000 μL / h.

[0014] Preferably, the injection flow rate of the oil phase is 5000-8000 μL / h.

[0015] The present invention also provides a cellulose nanocrystal oil-in-water emulsion obtained by the method described in the above technical solution.

[0016] The invention provides a method for preparing an adjustable cellulose nanocrystal oil-in-water emulsion by using a microfluidic instantaneous double emulsion method.

[0017] The method provided by the present invention uses a glycerol aqueous solution as the inner phase, a cellulose nanocrystal aqueous dispersion as the middle phase, and an oil phase as the outer phase. By using microfluidics, the dissolution characteristics of the cellulose nanocrystals cause them to be deposited only on the surface of the droplets, thereby preparing a cellulose nanocrystal oil-in-water emulsion; in the emulsion, the cellulose nanocrystals are only deposited on the interface formed by the aqueous phase and the oil phase, and will not affect the viscosity, wetting characteristics of the aqueous phase and the oil phase, and the appearance of the droplets finally obtained. At the same time, the method of the present invention does not use an emulsifier or chemical modification, and still obtains an oil-in-water emulsion system with good stability, which is more environmentally friendly. In addition, the present invention can adjust the size and interface coverage of the droplets in the emulsion by controlling the injection flow rate of the external phase, the middle phase, and the external phase, and the morphology of the droplets obtained is regular. In addition, by adjusting the mass fraction of the middle phase cellulose nanocrystal aqueous dispersion, the interface coverage of the droplets in the emulsion can also be adjusted.

[0018] Furthermore, the mass fraction of the cellulose nanocrystal aqueous dispersion in the intermediate phase is controlled to be 0.01-1.00%, which further ensures that the cellulose nanocrystals exist only at the interface formed by the water phase and the oil phase, and will not affect the viscosity, wetting properties and appearance of the final droplets. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure of the microfluidic device used in the present invention;

[0020] Figure 2 It is a microscopic picture of the droplets in the water-in-oil emulsion obtained in Examples 1 to 3;

[0021] Figure 3 This is a comparison diagram of droplet diameters in the water-in-oil emulsions obtained in Examples 1 to 3;

[0022] Figure 4 is the interface coverage of the droplets in the water-in-oil emulsions obtained in Examples 1 to 3;

[0023] Figure 5 It is a microscopic picture of the droplets in the water-in-oil emulsion obtained in Examples 4 to 6;

[0024] Figure 6 This is a comparison diagram of droplet diameters in the water-in-oil emulsions obtained in Examples 4 to 6;

[0025] Figure 7 It is the interface coverage of droplets in the water-in-oil emulsions obtained in Examples 4 to 6. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a controllable cellulose nanocrystal oil-in-water emulsion by a microfluidic instantaneous double emulsion method, comprising the following steps:

[0027] A cellulose nanocrystal oil-in-water emulsion was obtained by microfluidics using a glycerol aqueous solution as the inner phase, a cellulose nanocrystal aqueous dispersion as the middle phase, and an oil phase as the outer phase.

[0028] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0029] In the present invention, the mass fraction of the glycerol aqueous solution is preferably 30-70%, specifically 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or 70%. In the present invention, the injection flow rate of the glycerol aqueous solution is preferably 500-1500 μL / h, more preferably 800-1200 μL / h, specifically 500 μL / h, 600 μL / h, 700 μL / h, 800 μL / h, 900 μL / h, 1000 μL / h, 1100 μL / h, 1200 μL / h, 1300 μL / h, 1400 μL / h or 1500 μL / h. In the present invention, when other parameters (including the injection flow rate of the intermediate phase, the injection flow rate of the external phase, the mass fraction of the glycerol aqueous solution and the mass fraction of the cellulose nanocrystal aqueous dispersion) are fixed, the greater the injection flow rate of the internal phase, the larger the diameter of the droplets in the resulting oil-in-water emulsion.

[0030] In the present invention, the cellulose nanocrystals in the cellulose nanocrystal aqueous dispersion preferably present a typical rod-like structure, with a width of preferably 6.2±1.5 nm and a length of preferably 127.5±28.7 nm. In the present invention, the mass fraction of the cellulose nanocrystal aqueous dispersion is preferably 0.01-1.00%, specifically 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1.0%. In the present invention, the injection flow rate of the cellulose nanocrystal aqueous dispersion is preferably 500-1500 μL / h, more preferably 800-1200 μL / h, and specifically preferably 500 μL / h, 600 μL / h, 700 μL / h, 800 μL / h, 900 μL / h, 1000 μL / h, 1100 μL / h, 1200 μL / h, 1300 μL / h, 1400 μL / h or 1500 μL / h. In the present invention, when other parameters (including the injection flow rate of the inner phase, the injection flow rate of the outer phase, the mass fraction of the glycerol aqueous solution and the mass fraction of the cellulose nanocrystal aqueous dispersion) are fixed, the greater the injection flow rate of the intermediate phase, the thicker the intermediate phase shell layer is formed, and the larger the diameter of the droplets in the resulting oil-in-water emulsion.

[0031] According to the preparation method provided by the present invention, due to solubility limitation, cellulose nanocrystals only exist on the surface of droplets and are not dissolved in the outer oil phase, thereby avoiding the problems of excessive colloidal particles in the bulk phase of the prior art that lead to increased viscosity, changed wetting properties and deteriorated appearance.

[0032] In the present invention, the oil phase preferably includes one or more of n-decanol, medium-chain triglycerides, corn oil, rapeseed oil, peanut oil and soybean oil, and can be specifically n-decanol. In the present invention, the injection flow rate of the oil phase is preferably 4000-10000 μL / h, more preferably 5000-8000 μL / h, and can be specifically 4000 μL / h, 5000 μL / h, 6000 μL / h, 7000 μL / h, 8000 μL / h, 9000 μL / h or 10000 μL / h. In the present invention, when other parameters (including the injection flow rate of the inner phase, the injection flow rate of the intermediate phase, the mass fraction of the glycerol aqueous solution and the mass fraction of the cellulose nanocrystal aqueous dispersion) are fixed, the greater the injection flow rate of the outer phase, the smaller the diameter of the droplets in the resulting oil-in-water emulsion, and the smaller the cross-sectional coverage.

[0033] In the present invention, the preparation of the cellulose nanocrystal oil-in-water emulsion is preferably carried out in a microfluidic device, and the structural schematic diagram of the microfluidic device is as shown in Figure 1 shown. Figure 1 In the figure, the red box is the droplet generation area, and the green box is the droplet collection area.

[0034] The present invention also provides a cellulose nanocrystal oil-in-water emulsion obtained by the preparation method described in the above technical solution.

[0035] The cellulose nanocrystal oil-in-water emulsion provided by the invention has excellent biocompatibility and stability, and the droplet size and interface coverage are adjustable.

[0036] The method for preparing a controllable cellulose nanocrystal oil-in-water emulsion by a microfluidic transient double emulsion method and the cellulose nanocrystal oil-in-water emulsion provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1

[0038] A glycerol aqueous solution with a mass fraction of 50% was configured as the internal phase, and the injection flow rate was 1000 μL / h.

[0039] A cellulose nanocrystal aqueous dispersion with a mass fraction of 1.00% was prepared as the intermediate phase, and the injection flow rate was 1000 μL / h.

[0040] n-Decanol was used as the external phase, and the injection flow rate was 5000 μL / h.

[0041] The above system is continuously injected by a syringe pump Figure 1 The microfluidic device shown.

[0042] Example 2

[0043] The difference from Example 1 is that the injection flow rate of the external phase is 6000 μL / h.

[0044] Example 3

[0045] The difference from Example 1 is that the injection flow rate of the external phase is 8000 μL / h.

[0046] Figure 2 This is a microscopic picture of the droplets in the water-in-oil emulsion obtained in Examples 1 to 3. Figure 2 The scale bars in each figure are 500 μm. Figure 3 This is a comparison chart of droplet diameters in the water-in-oil emulsions obtained in Examples 1 to 3. Figure 4 is the interface coverage of the droplets in the water-in-oil emulsions obtained in Examples 1 to 3. Figure 2 to Figure 4 It can be seen that: when other parameters are fixed, the greater the injection flow rate of the external phase, the smaller the diameter of the droplets in the resulting oil-in-water emulsion and the smaller the interface coverage.

[0047] Example 4

[0048] A glycerol aqueous solution with a mass fraction of 50% was configured as the internal phase, and the injection flow rate was 600 μL / h.

[0049] A cellulose nanocrystal aqueous dispersion with a mass fraction of 1.00% was prepared as the intermediate phase, and the injection flow rate was 700 μL / h.

[0050] n-Decanol was used as the external phase, and the injection flow rate was 6500 μL / h.

[0051] The above system is continuously injected by a syringe pump Figure 1 The microfluidic device shown.

[0052] Example 5

[0053] The difference from Example 4 is that the mass fraction of the cellulose nanocrystal aqueous dispersion is 0.10%.

[0054] Example 6

[0055] The difference from Example 4 is that the mass fraction of the cellulose nanocrystal aqueous dispersion is 0.01%.

[0056] Figure 5 This is a microscopic picture of the droplets in the water-in-oil emulsion obtained in Examples 4 to 6. Figure 5 The scale bars in each figure are 500 μm; Figure 6 This is a comparison chart of droplet diameters in the water-in-oil emulsions obtained in Examples 4 to 6. Figure 7 is the interface coverage of the droplets in the water-in-oil emulsions obtained in Examples 4 to 6. Figure 5-6 It can be seen that when other parameters are fixed, there is no obvious linear relationship between the concentration of cellulose nanocrystal dispersion and the droplet diameter in the obtained oil-in-water emulsion. Figure 7 It can be seen that the greater the mass fraction of the mesophase nanocrystalline cellulose aqueous dispersion, the higher the interface coverage of the resulting droplets.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a controllable cellulose nanocrystal oil-in-water emulsion by a microfluidic transient double emulsion method, comprising the following steps: A cellulose nanocrystal oil-in-water emulsion was obtained by microfluidics using a glycerol aqueous solution as the inner phase, a cellulose nanocrystal aqueous dispersion as the middle phase, and an oil phase as the outer phase.

2. The method according to claim 1, characterized in that The mass fraction of the glycerol aqueous solution is 30-70%.

3. The method according to claim 1 or 2, characterized in that: The injection flow rate of the glycerol aqueous solution is 500-1500 μL / h.

4. The method according to claim 1, characterized in that: The cellulose nanocrystals in the cellulose nanocrystal water dispersion present a typical rod-like structure with a width of 6.2±1.5 nm and a length of 127.5±28.7 nm.

5. The method according to claim 1, characterized in that The mass fraction of the cellulose nanocrystal aqueous dispersion is 0.01-1.00%.

6. The method according to claim 1 or 5, characterized in that: The injection flow rate of the cellulose nanocrystal aqueous dispersion is 500-1500 μL / h.

7. The method according to claim 1, characterized in that The oil phase comprises one or more of n-decyl alcohol, medium chain triglycerides, corn oil, rapeseed oil, peanut oil and soybean oil.

8. The method according to claim 1 or 7, characterized in that: The injection flow rate of the oil phase is 4000-10000 μL / h.

9. The method according to claim 8, characterized in that The injection flow rate of the oil phase is 5000-8000 μL / h.

10. The cellulose nanocrystal oil-in-water emulsion obtained by the method according to any one of claims 1 to 9.

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