Method for preparing oil-in-water or water-in-oil emulsion by using Janus vertical through hole membrane

Abstract

The invention discloses a method for preparing an oil-in-water or water-in-oil emulsion by using a Janus vertical through-hole membrane, which comprises the following steps: preparing a polylactic acid membrane, spraying a hydrophobic material onto the surface of the polylactic acid membrane to prepare the Janus vertical through-hole membrane, mixing a water-phase material or an oil-phase material with a surfactant to prepare a continuous phase, and preparing the oil-in-water or water-in-oil emulsion by using the Janus vertical through-hole membrane. And taking the corresponding oil phase or water phase as a dispersing agent to enter the continuous phase through the Janus vertical through hole membrane, and stopping stirring after reaction to obtain the oil-in-water or water-in-oil emulsion. Starting from preparation of a Janus polylactic acid thin film with a vertical through hole structure, the vertical through hole emulsion film with an asymmetric wettability structure is prepared through a reverse copying method and a spraying method, and a film pore channel is of a straight-through hole structure and is narrow in pore size distribution; the emulsion with highly uniform particle size can be prepared while a dispersed phase rapidly passes through membrane pores, efficient and rapid emulsification is achieved, and the emulsion is expected to be widely applied to multiple industries such as medicine and food.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane emulsification, and particularly to a method for preparing oil-in-water or water-in-oil emulsions by using a Janus vertical through-hole membrane. Background Art

[0002] Emulsification technology refers to the process of mixing two immiscible liquid phases (usually an aqueous phase and an oil phase) together through physical or chemical methods to form a stable and homogeneous emulsion system. Common emulsion emulsification methods include membrane emulsification, spraying, stirring emulsification, and microfluidic methods, etc. Among them, membrane emulsification technology has been widely used in the fields of cosmetics, food, drug carrier preparation, etc. due to its advantages such as low energy consumption, high production throughput, mild preparation conditions, and easy scale-up operation. Membrane emulsification technology is based on a porous membrane as a medium. Through the restriction and shear force of the membrane pores, the dispersed phase (usually the oil phase) liquid is dispersed into fine droplets and mixed with the continuous phase (usually the aqueous phase) to form a stable emulsion. During this process, the size of the dispersed phase is affected by various forces such as the surface tension of the membrane, the transmembrane pressure, and the drag force of the continuous phase. However, the currently used porous membranes have a relatively wide pore size distribution, resulting in non-uniform particle sizes of the prepared emulsions and unable to meet the production requirements for high-precision applications of emulsions. At the same time, the high tortuosity of the membrane pores often requires a large external pressure to initiate the transmembrane of the dispersed phase.

[0003] Among them, the design of a vertical through-hole membrane with a simple pore structure and uniform pore size can effectively solve the above problems. The so-called vertical through-hole refers to a structure where the pore channels go straight through the upper and lower layers of the membrane. Among them, the narrow pore size distribution provides a prerequisite for the preparation of emulsions with uniform sizes; the straight pore channels only require extremely low pressure to achieve the rapid transmembrane of the dispersed phase. However, during the membrane emulsification process, the hydrophilicity and hydrophobicity of the membrane material surface must be consistent with the continuous phase. This means that hydrophilic membranes are suitable for preparing oil-in-water emulsions, while hydrophobic membranes are suitable for preparing water-in-oil emulsions. If hydrophilic and hydrophobic membranes are respectively used to prepare water-in-oil and oil-in-water emulsions, it will cause the coalescence of the dispersed phase during membrane passage, resulting in a wider droplet size distribution.

[0004] Janus membrane is a new concept in the field of membrane research in recent years, referring to a membrane material with morphological structure or chemical composition asymmetry on both sides of the membrane, commonly the difference in wettability on both sides of the membrane. This asymmetric anisotropy endows Janus membranes with some excellent physical, chemical, biological, etc. properties superior to traditional homogeneous membranes. Among them, Janus membranes with asymmetric wettability can utilize hydrophilic and hydrophobic surfaces to respectively achieve the preparation of oil-in-water and water-in-oil emulsions.

[0005] Patent ZL202210685902.8, "A Poly(lactic acid) Vertical Through-hole Membrane for Cell Separation and Its Preparation Method", discloses a vertical through-hole membrane prepared by the reverse replication template method. However, the membrane material is a single hydrophilic material, poly(lactic acid), which can only be used for the separation of blood cells and does not involve the structure of Janus asymmetric wettability. Therefore, it does not have the conditions or potential to be simultaneously applied to the preparation of water-in-oil and oil-in-water emulsions. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing water-in-oil or oil-in-water emulsions using a Janus vertical through-hole membrane in view of the deficiencies of the prior art, which includes the following steps: Step (1): Melt the dried poly(lactic acid) at high temperature or blend it with a solution to form a poly(lactic acid) fluid, and then pour it evenly on a silicon template substrate. After cooling at room temperature, a poly(lactic acid) film loaded on the silicon template is obtained. Among them, the silicon template substrate is provided with an array composed of periodically distributed columnar protrusions, the height of the columnar protrusions is 100 nm to 50 μm, there is a certain distance between adjacent columnar protrusions, and the diameter of the cross-section of the columnar protrusions is 100 nm to 100 μm; Step (2): Blend the dried hydrophobic material with a dispersant to obtain a hydrophobic dispersion, spray it onto the surface of the poly(lactic acid) film through a spray gun, then place the silicon template in a water bath at 60 - 100 °C, and after standing, peel off the poly(lactic acid) film; Step (3): Place the peeled poly(lactic acid) film in a water bath at 60 - 100 °C, take it out and cool it to room temperature, and dry it with an inert gas to obtain a Janus vertical through-hole membrane; Step (4): Mix the aqueous phase material or the oil phase material with a surfactant to prepare a continuous phase; Step (5): Under the condition of continuously stirring the continuous phase, drop the dispersed phase above the Janus vertical through-hole membrane, and apply a positive pressure to make the dispersed phase pass through the Janus vertical through-hole membrane and enter the continuous phase. After the constant temperature reaction, stop stirring to obtain a water-in-oil or oil-in-water emulsion.

[0007] Preferably, in step (1), the poly(lactic acid) is L-poly(lactic acid) or D-poly(lactic acid).

[0008] Preferably, in step (1), the dried poly(lactic acid) is blended with a good solvent in solution; the good solvent for the poly(lactic acid) is chloroform, dichloromethane or acetone; more preferably chloroform, and 2.5 g of poly(lactic acid) is added to each liter of chloroform; Preferably, the high-temperature melting temperature of the poly(lactic acid) in step (1) is 170 - 200 °C.

[0009] Preferably, the cross-section of the columnar protrusions in step (1) is circular.

[0010] Preferably, the time for cooling at room temperature in step (1) is 1 to 50 min.

[0011] Preferably, in step (2), the mass-volume ratio of the hydrophobic material to the dispersant is 2.5 to 3 g: 1 L, more preferably 2.5 g: 1 L; the hydrophobic material may be carbon black or hydrophobic nano-silica particles; more preferably carbon black. The dispersant is a solution such as dichloromethane or chloroform; more preferably dichloromethane.

[0012] Preferably, the spraying amount of the hydrophobic dispersion liquid in step (2) is 1 to 50 mL, more preferably 2.5 mL.

[0013] Preferably, the standing time in step (2) is 10 to 100 s.

[0014] Preferably, the time for water bath in step (3) is 1 to 5 min, and the inert gas is nitrogen.

[0015] Preferably, the volume ratio of the aqueous phase material or the oil phase material in step (4) to the sum of the dispersed phases in step (5) is 50: 0.1 to 5.

[0016] Advantages of the present invention: The present invention discloses the application of a Janus vertical through-hole membrane in the preparation of water-in-oil and / or oil-in-water emulsions. When preparing a water-in-oil emulsion, the hydrophilic side of the Janus vertical through-hole membrane faces the continuous phase (aqueous phase), and the hydrophobic side faces the dispersed phase side (oil phase); when preparing an oil-in-water emulsion, the hydrophobic side of the Janus vertical through-hole membrane faces the continuous phase (oil phase), and the hydrophilic side faces the dispersed phase (aqueous phase). In the preparation of water-in-oil and oil-in-water emulsions, the state of the continuous phase being hydrophilic and the dispersed phase being hydrophobic is always maintained, thereby inhibiting the diffusion of the dispersed phase on the membrane surface and ensuring the uniformity and stability of the emulsion.

[0017] The present invention starts from the preparation of a Janus polylactic acid film with a vertical through-hole structure, and prepares a vertical through-hole emulsification membrane with an asymmetric wettability structure by a reverse replication method and a spraying method. Its membrane pore channels are straight through-hole structures and the pore size distribution is narrow, which can enable the dispersed phase to quickly pass through the membrane pores while preparing an emulsion with highly uniform particle size, realizing efficient and rapid emulsification, and is expected to be widely used in multiple industries such as medicine and food.

[0018] The membrane material of the present invention can prepare porous membranes with different membrane pore sizes according to silicon template arrays of different sizes, thereby enabling the preparation of emulsions with different particle sizes.

[0019] The preparation method of the present invention. The Janus vertical through-hole membrane is prepared by a process combining the spraying method and the reverse replication method using a silicon template. The preparation process is simple, highly operable, and has high repeatability, enabling industrial production. Description of the Drawings

[0020] Figure 1 It is the polarization diagram of the emulsion droplets obtained in Comparative Example 1.

[0021] Figure 2 Statistical chart of the particle size distribution of the emulsion droplets obtained in Comparative Example 1.

[0022] Figure 3 It is the working schematic diagram of the membrane emulsification device in the example.

[0023] Figure 4 It is the polarization diagram of the emulsion droplets obtained in Comparative Example 2.

[0024] Figure 5 Statistical chart of the particle size distribution of the emulsion droplets obtained in Comparative Example 2.

[0025] Figure 6 It is the scanning electron microscope image of the Janus vertical through-hole membrane with a pore size of 3 μm prepared in Example 1.

[0026] Figure 7 It is the polarization diagram of the emulsion obtained by emulsifying the Janus vertical through-hole membrane with a pore size of 3 μm prepared in Example 1.

[0027] Figure 8 It is the percentage of the particle size distribution of the emulsion droplets obtained by emulsifying the Janus vertical through-hole membrane with a pore size of 3 μm prepared in Example 1.

[0028] Figure 9 It is the percentage of the particle size distribution of the emulsion droplets obtained by emulsifying the Janus vertical through-hole membrane with a pore size of 5 μm prepared in Example 2.

[0029] Figure 10 It is the percentage of the particle size distribution of the emulsion droplets obtained by emulsifying the Janus vertical through-hole membrane with a pore size of 3 μm prepared in Example 3.

[0030] Figure 11 It is the percentage of the particle size distribution of the emulsion droplets obtained by emulsifying the Janus vertical through-hole membrane with a pore size of 5 μm prepared in Example 4. Detailed Embodiments

[0031] The present invention will be described in detail below in conjunction with the drawings and specific embodiments, but the present invention is not limited to the scope of the specific embodiments described. In addition, the technical features involved in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] The present invention provides an application of a Janus vertical through-hole membrane for emulsification in the preparation of water-in-oil or oil-in-water emulsions. The specific implementation scheme of the Janus vertical through-hole membrane is as follows: Step (1): Place polylactic acid in a vacuum drying oven and dry it at 60-100 °C until the weight remains unchanged; Preferably, the polylactic acid is L-polylactic acid or D-polylactic acid.

[0033] Step (2): Make the dried polylactic acid into a fluid state by high-temperature melting or solution blending with a good solvent.

[0034] Preferably, the good solvent for polylactic acid is chloroform, dichloromethane or acetone; more preferably chloroform, and 2.5 g of polylactic acid is added to each liter of chloroform; Preferably, the melting temperature of polylactic acid is 170-200 °C.

[0035] Step (3): Pour the polylactic acid fluid evenly onto a silicon template substrate. The silicon template substrate is provided with an array composed of a periodic distribution of several columnar protrusions. The height of the columnar protrusions is 100 nm-50 μm, there is a certain distance between adjacent columnar protrusions, and the diameter of the cross-section of the columnar protrusions is 100 nm-100 μm; Preferably, the cross-section of the columnar protrusions is circular.

[0036] Step (4): Place the silicon template cast with polylactic acid fluid in step (3) at room temperature for cooling for 1-50 min, and place the cooled silicon template in a dry environment to volatilize the good solvent for 10 s-50 min to obtain a polylactic acid film loaded on the silicon template; Step (5): Make a suspension by solution blending a dry hydrophobic material and a dispersant; Preferably, 2.5 g of the hydrophobic material is added to each liter of the dispersant. The hydrophobic material can be carbon black or hydrophobic nano-silica particles; more preferably carbon black. The dispersant is a solution such as dichloromethane or trichloromethane; more preferably dichloromethane; Step (6): Spray 1-50 mL of the carbon black dispersion prepared in step (5) onto the polylactic acid film in step (4) by a spray gun; Preferably, the volume of the sprayed carbon black dispersion is 2.5 mL.

[0037] Step (7): Place the silicon template loaded with the Janus vertical through-hole membrane in step (6) in a water bath at 60-100 °C, let it stand for 10-100 s, and then peel off the Janus vertical through-hole membrane to obtain a Janus vertical through-hole polylactic acid film with simple pores.

[0038] Step (8): Leave the torn Janus porous membrane in a hot water bath at 60 - 100 °C for 1 - 5 min, take it out and cool it to room temperature, and dry it with N 2 Blow it dry.

[0039] Preferably, the drying temperature is 60 °C.

[0040] The Janus vertical through-hole membrane obtained by the present invention is a double-layer composite structure of a carbon black layer and a polylactic acid layer. The two are closely arranged, forming a structure with pore channels directly leading to the upper and lower layers. Among them, the carbon black layer has superhydrophobic and hydrophilic wettability, and the polylactic acid layer has hydrophilic wettability. The difference in wettability between the two constitutes the Janus performance of the membrane. The thickness of the carbon black layer is 20 nm - 10 μm, and the thickness of the polylactic acid layer is 50 nm - 50 μm. The membrane pore size is 100 nm - 100 μm, the membrane pores are uniformly arranged, the pore sizes are uniform, and the proportion of the pore area in the total membrane area is 5% - 80%.

[0041] The specific process in the present invention is as follows: Comparative Example 1 Step (1): Take 50 mL of kerosene and 0.4 g of Span 80, mix them, and stir magnetically for 30 min at a rotor speed of 1000 rpm / min to obtain a mixed solution as the continuous phase.

[0042] Step (2): Directly drop 3 mL of deionized water into the continuous phase in step (1), stop stirring after stirring at a constant temperature for 3 min to form emulsion droplets of different sizes, and its polarized light diagram is as Figure 1 shown.

[0043] Use Image J to measure the particle size distribution of the emulsion droplets and count the percentage. The results are as Figure 2 shown.

[0044] Comparative Example 2 Step (1): Place the commercial polytetrafluoroethylene (PTFE) membrane in a vacuum drying oven and dry it at 60 - 100 °C until the weight remains unchanged.

[0045] Step (2): Disperse the carbon black powder in dichloromethane to prepare a suspension with a concentration of 2.5 g / L. Measure 3 mL of the above suspension, spray it evenly onto the PTFE film with a spray gun, and then dry it to obtain a Janus membrane with tortuous pores.

[0046] Step (3): Take 50 mL of kerosene and 0.4 g of Span 80, mix them, and stir magnetically for 30 min at a rotor speed of 1000 rpm / min to obtain a mixed solution as the continuous phase.

[0047] Step (4): Cut the Janus tortuous pore membrane obtained in step (3) into 1×1 cm² squares and place them in the membrane cell of the emulsification device as shown in Figure 3 shown.

[0048] Step (5): Immerse the above device in the mixed solution obtained in step (5). At the same time, keep the continuous phase below at a rotation speed of 1000 rpm / min. Drop 3 mL of deionized water above the membrane, apply a positive pressure of 0.1 MPa to make the water disperse into the continuous phase through the membrane pores, stop stirring after constant temperature stirring for 3 min, and form emulsion droplets of different sizes. The polarized light diagram is as shown in Figure 4 shown.

[0049] Use Image J to measure the particle size distribution of the emulsion droplets and count the percentage. The results are as shown in Figure 5 shown.

[0050] Example 1 Step (1): Place polylactic acid in a vacuum drying oven and dry it at 60 - 100 °C until the weight remains unchanged.

[0051] Step (2): Dissolve the dried polylactic acid in chloroform to prepare a solution with a concentration of 2.5 g / L. Take 3 mL of the prepared solution and evenly pour it on a silicon template substrate with a columnar array of a diameter of 3 μm and a height of 5 μm, and cool it in an environment at 25 °C for 5 min. Then place it in a drying environment at 60 °C to volatilize chloroform for 1 min.

[0052] Step (3): Disperse carbon black powder in dichloromethane to prepare a suspension with a concentration of 2.5 g / L. Measure 3 mL of the above suspension and evenly spray it onto the silicon template loaded with the polylactic acid film to obtain a silicon template loaded with a Janus vertical through-hole membrane.

[0053] Step (4): Place the above silicon template loaded with the Janus vertical through-hole membrane in an oven at 60 °C, dry it, and let it stand for 10 - 100 s. Then peel off the Janus vertical through-hole membrane to obtain a Janus vertical through-hole membrane. Then fish it out with tin foil paper, cool it to room temperature, and dry it to obtain a Janus vertical through-hole membrane with an average pore diameter of 3 μm and a thickness of 2 μm. The scanning electron microscope image is as shown in Figure 6 shown.

[0054] Step (5): Take 50 mL of kerosene and 0.4 g of Span 80, mix them, and stir magnetically for 30 min with a rotor speed of 1000 rpm / min to obtain a mixed solution as the continuous phase.

[0055] Step (6): Cut the Janus vertical through-hole membrane obtained in step (4) into 1×1 cm² squares and place them in the membrane cell as shown in Figure 3in the membrane pool of the emulsifying device shown.

[0056] Step (7): Immerse the above device in the mixed solution obtained in step (5), while keeping the continuous phase below at a rotation speed of 1000 rpm / min. Drop 3 mL of deionized water above the membrane, and apply a positive pressure of 0.02 MPa to allow the water to disperse into the continuous phase through the membrane pores. After stirring at a constant temperature for 3 min, stop stirring to form emulsion droplets of different sizes. The polarized light diagram is as Figure 7 shown.

[0057] Use Image J to measure the particle size distribution of the emulsion droplets and count the percentage. The results are as Figure 8 shown.

[0058] Example 2 Step (1): Place polylactic acid in a vacuum drying oven and dry it at 60 - 100 °C until the weight remains unchanged.

[0059] Step (2): Dissolve the dried polylactic acid in chloroform to prepare a solution with a concentration of 2.5 g / L. Take 3 mL of the prepared solution and evenly pour it onto a silicon template substrate with a columnar array of a diameter of 5 μm and a height of 5 μm. Place it in an environment at 25 °C and cool for 1 min, then place it in a drying environment to volatilize chloroform for 1 min.

[0060] Step (3): Disperse carbon black powder in dichloromethane to prepare a suspension with a concentration of 2.5 g / L. Measure 3 mL of the above suspension and evenly spray the suspension onto the silicon template loaded with the polylactic acid film using a spray gun to obtain a silicon template loaded with a Janus vertical through-hole membrane.

[0061] Step (4): Place the silicon template of the above Janus vertical through-hole membrane in an oven at 60 °C and dry it. Let it stand for 10 - 100 s, then peel off the Janus vertical through-hole membrane to obtain the Janus vertical through-hole membrane. Then fish it out with tin foil paper, cool it to room temperature, and dry it to obtain a Janus vertical through-hole membrane with an average pore diameter of 5 μm and a thickness of 2 μm.

[0062] Step (5): Take 50 mL of kerosene and 0.4 g of Span 80, mix them, and stir magnetically for 30 min with a rotor speed of 1000 rpm / min to obtain a mixed solution as the continuous phase.

[0063] Step (6): Cut the Janus vertical through-hole membrane obtained in step (4) into 1×1 cm² squares and place them in the membrane pool of the emulsifying device as shown in Figure 3 shown.

[0064] Step (7): Immerse the above device in the mixed solution obtained in step (5). At the same time, keep the continuous phase below at a rotation speed of 1000 rpm / min. Drop 3 mL of deionized water above the membrane, and apply a positive pressure of 0.02 MPa to make the water disperse into the continuous phase through the membrane pores. Stop stirring after stirring at a constant temperature for 3 min to form emulsion droplets of different sizes.

[0065] Measure the particle size distribution of the emulsion droplets using Image J and count the percentage. The results are as Figure 9 shown.

[0066] Example 3 Step (1): Place polylactic acid in a vacuum drying oven and dry it at 60 - 100 °C until the weight remains unchanged.

[0067] Step (2): Dissolve the dried polylactic acid in chloroform to prepare a solution with a concentration of 2.5 g / L. Take 3 mL of the prepared solution and evenly pour it on a silicon template substrate with a columnar array having a diameter of 3 μm and a height of 5 μm. Cool it in an environment at a temperature of 25 °C for 1 min, and then place it in a dry environment to volatilize chloroform for 1 min.

[0068] Step (3): Disperse carbon black powder in dichloromethane to prepare a suspension with a concentration of 2.5 g / L. Measure 3 mL of the above suspension and evenly spray the suspension onto the silicon template loaded with the polylactic acid film using a spray gun to obtain a silicon template loaded with a Janus vertical through-hole membrane.

[0069] Step (4): Place the silicon template of the above Janus vertical through-hole membrane in an oven at 60 °C and dry it. Let it stand for 10 - 100 s, and then peel off the Janus vertical through-hole membrane to obtain a Janus vertical through-hole membrane. Then fish it out with tin foil paper, cool it to room temperature, and dry it to obtain a Janus vertical through-hole membrane with an average pore diameter of 3 μm and a thickness of 2 μm.

[0070] Step (5): Take 50 mL of deionized water and 0.4 g of sodium dodecyl sulfate, and stir magnetically for 30 min with a rotor speed of 1000 rpm / min to obtain a mixed solution as the continuous phase.

[0071] Step (6): Cut the Janus vertical through-hole membrane obtained in step (4) into 1×1 cm² square pieces and place them in the membrane cell of the emulsification device as shown Figure 4 in the figure.

[0072] Step (7): Immerse the above device in the mixed solution obtained in step (5), while maintaining the continuous phase below at a rotation speed of 1000 rpm / min. Drop 3 mL of kerosene above the membrane, apply a positive pressure of 0.02 MPa to allow water to disperse into the continuous phase through the membrane pores, stop stirring after 3 min of constant-temperature stirring, and form emulsion droplets of different sizes.

[0073] Measure the particle size distribution of the emulsion droplets using Image J, and count the percentage. The results are as Figure 10 shown.

[0074] Example 4 Step (1): Place polylactic acid in a vacuum drying oven and dry it at 60 - 100 °C until the weight remains unchanged.

[0075] Step (2): Dissolve the dried polylactic acid in chloroform to prepare a solution with a concentration of 2.5 g / L. Take 3 mL of the prepared solution and evenly pour it onto a silicon template substrate with a columnar array having a diameter of 5 μm and a height of 5 μm. Place it in an environment at 25 °C and cool for 1 min, then place it in a drying environment to volatilize chloroform for 1 min.

[0076] Step (3): Disperse carbon black powder in dichloromethane to prepare a suspension with a concentration of 2.5 g / L. Measure 3 mL of the above suspension, and evenly spray the suspension onto the silicon template loaded with the polylactic acid film using a spray gun to obtain a silicon template loaded with a Janus vertical through-hole membrane.

[0077] Step (4): Place the above silicon template of the Janus vertical through-hole membrane in an oven at 60 °C and dry it, let it stand for 10 - 100 s, then peel off the Janus vertical through-hole membrane to obtain the Janus vertical through-hole membrane. Then fish it out with tin foil, cool it to room temperature, and dry it to obtain a Janus vertical through-hole membrane with an average pore diameter of 5 μm and a thickness of 2 μm.

[0078] Step (5): Take 50 mL of deionized water and 0.4 g of sodium dodecyl sulfate, stir magnetically for 30 min, and the rotor speed is 1000 rpm / min.

[0079] Step (6): Cut the Janus vertical through-hole membrane obtained in step (4) into 1×1 cm² squares and place them in the membrane cell of the emulsifying device as shown Figure 4 in the figure.

[0080] Step (7): Immerse the above device in the mixed solution obtained in step (5), while keeping the continuous phase below at a rotation speed of 1000 rpm / min. Drop 3 mL of kerosene above the membrane, apply a positive pressure of 0.02 MPa to allow water to disperse into the continuous phase through the membrane pores, stop stirring after constant-temperature stirring for 3 min to form emulsion droplets of different sizes.

[0081] Measure the particle size distribution of the emulsion droplets using Image J and count the percentage. The results are as Figure 11 shown.

[0082] The above embodiments are not limitations on the present invention. The present invention is not limited to the above embodiments. As long as it meets the requirements of the present invention, it falls within the protection scope of the present invention.

Claims

1. A method for preparing an oil-in-water or water-in-oil emulsion using a Janus vertical through-hole membrane, characterized in that: The method comprises the following steps: Step (1), preparing a polylactic acid fluid by high-temperature melting or solution blending of the dried polylactic acid, and then uniformly pouring the polylactic acid on a silicon template substrate, and obtaining a polylactic acid film supported on the silicon template after cooling at room temperature; wherein the silicon template substrate is provided with an array of a plurality of periodically distributed columnar protrusions, the height of the columnar protrusions is 100 nm to 50 μm, there is a certain distance between adjacent columnar protrusions, and the diameter of the cross section of the columnar protrusions is 100 nm to 100 μm; Step (2), mixing a dry hydrophobic material with a dispersant to obtain a hydrophobic dispersion, spraying the dispersion onto the surface of the polylactic acid film by a spray gun, and then placing the silicon template in a water bath at 60 to 100° C., and peeling off the polylactic acid film after standing. Step (3), placing the peeled polylactic acid film in a water bath at 60-100° C., taking it out and cooling it to room temperature, and drying it with an inert gas to obtain a Janus vertical through-hole film; Step (4), mixing the aqueous phase material or the oil phase material with a surfactant to prepare a continuous phase; Step (5), under the condition of continuous stirring of the continuous phase, dripping the dispersed phase on the Janus vertical through-pore membrane, and applying positive pressure to make the dispersed phase pass through the Janus vertical through-pore membrane into the continuous phase, and stopping stirring after the constant temperature reaction to obtain an oil-in-water or water-in-oil emulsion.

2. The method according to claim 1, characterized in that The polylactic acid in step (1) is left-handed polylactic acid or right-handed polylactic acid.

3. The method according to claim 1, characterized in that In step (1), the dried polylactic acid is mixed with a good solvent to form a solution; the good solvent for the polylactic acid is chloroform, dichloromethane or acetone.

4. The method according to claim 1, characterized in that: The temperature of the high-temperature melting of polylactic acid in step (1) is 170-200°C.

5. The method according to claim 1, characterized in that The cross section of the columnar protrusion in step (1) is circular.

6. The method according to claim 1, characterized in that The mass volume ratio of the hydrophobic material to the dispersant in step (2) is 2.5-3 g:1 L.

7. The method according to claim 1 or 6, characterized in that: The hydrophobic material is carbon black or hydrophobic nano silicon dioxide particles, and the dispersant is dichloromethane or chloroform.

8. The method according to claim 1, characterized in that The spraying amount of the hydrophobic dispersion in step (2) is 1 to 50 mL.

9. The method according to claim 1, characterized in that: The water bath time in step (3) is 1 to 5 minutes, and the inert gas is nitrogen.

10. The method according to claim 1, characterized in that The volume ratio of the aqueous phase material or the oil phase material in step (4) to the dispersed phase in step (5) is 50:0.1-5.

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