A double-layer membrane filament gas-liquid mixing device and a method for preparing double-layer membrane filaments

Abstract

The present invention provides a double-layer membrane filament gas-liquid mixing device and a method for preparing a double-layer membrane filament. Among them, the double-layer membrane filament gas-liquid mixing device includes a housing. Liquid inlet holes and liquid outlet holes are provided at both ends of the housing in the length direction. An air inlet hole is provided on the side wall of the housing. The housing is connected to a first permeable membrane and a second permeable membrane with different permeation efficiencies. The second permeable membrane is arranged in a tubular shape and is respectively communicated with the liquid inlet hole and the liquid outlet hole at both ends. Pure water enters the housing through the liquid inlet hole and then flows into the second permeable membrane. Carbon dioxide enters the housing through the air inlet hole and then sequentially permeates through the first permeable membrane and the second permeable membrane and dissolves into the pure water in the second permeable membrane. The carbonated water after gas-liquid mixing is discharged from the housing through the second permeable membrane and the liquid outlet hole. The present invention is used to solve the problems that in the prior art, the dissolution rate of carbon dioxide into pure water is too fast and exceeds the expected dissolution rate, and the conductivity distribution of carbonated water is uneven, making it difficult to meet the requirements of the conductivity of carbonated water for cleaning wafers by subsequent semiconductor equipment.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor cleaning equipment, and particularly to a double-layer membrane wire gas-liquid mixing device and a method for preparing a double-layer membrane wire. Background Art

[0002] In semiconductor manufacturing processes, gases need to be applied. Taking a pure water anti-static device as an example, its principle is to add high-purity carbon dioxide to high-resistivity pure water to generate an appropriate amount of ions in the water to enhance the conductivity of the pure water, thereby reducing the resistivity of the pure water to prevent static charge accumulation during the wafer dicing process, effectively eliminating the static adsorption of silicon chips and ceramic chips, and facilitating ultrasonic cleaning. After drying, the carbon dioxide volatilizes, and no impurities remain on the surface of the object being cleaned, having the advantage of no secondary pollution. It is widely used in steps such as chip cutting, wafer dicing and cleaning, and photomask cleaning in semiconductor manufacturing processes.

[0003] In the pure water anti-static device, there is a gas-liquid mixing device for mixing carbon dioxide and pure water. A membrane wire is provided in the gas-liquid mixing device, and carbon dioxide and pure water are respectively introduced into both sides of the membrane wire in the gas-liquid mixing device, and the carbon dioxide penetrates into the pure water to achieve the purpose of gas-liquid mixing. In the prior art, since the carbon dioxide directly contacts the membrane wire after being introduced into the gas-liquid mixing device and penetrates and mixes into the pure water, there is no buffer structure between the carbon dioxide and the membrane wire, resulting in the problem that the dissolution rate of carbon dioxide into the pure water is too fast and exceeds the expected dissolution rate. Moreover, since there is no buffer region between the carbon dioxide and the membrane wire, the carbon dioxide directly dissolves into the pure water from the place where it is introduced into the gas-liquid mixing device, resulting in uneven distribution of the conductivity of the dissolved carbonated water, making it difficult to meet the requirements of the conductivity of carbonated water for cleaning wafers by backend semiconductor equipment.

[0004] In view of this, it is necessary to improve the gas-liquid mixing device in the prior art to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to disclose a double-layer membrane wire gas-liquid mixing device and a method for preparing a double-layer membrane wire, so as to solve the problems in the prior art that the dissolution rate of carbon dioxide into pure water is too fast and exceeds the expected dissolution rate, and the conductivity distribution of the dissolved carbonated water is uneven, making it difficult to meet the requirements of the conductivity of carbonated water for cleaning wafers by backend semiconductor equipment.

[0006] To achieve the above object, the present invention provides a double-layer membrane filament gas-liquid mixing device, which includes a housing. Liquid inlet holes and liquid outlet holes are provided at both ends of the housing in the length direction. An air inlet hole is provided on the side wall of the housing. The housing is connected to a first permeable membrane and a second permeable membrane with different permeation efficiencies. The second permeable membrane is tubularly arranged and is respectively communicated with the liquid inlet hole and the liquid outlet hole at both ends. Pure water enters the housing through the liquid inlet hole and then flows into the second permeable membrane. Carbon dioxide enters the housing through the air inlet hole and then successively passes through the first permeable membrane and the second permeable membrane and dissolves into the pure water in the second permeable membrane. The carbonated water after gas-liquid mixing is discharged from the housing through the second permeable membrane and the liquid outlet hole.

[0007] As a further improvement of the present invention, the first permeable membrane is arranged around the inner wall of the housing. A plurality of the second permeable membranes arranged in a tubular shape are evenly distributed on the side of the first permeable membrane away from the housing. The linear distances between the axes of the plurality of second permeable membranes and the axis of the first permeable membrane are all equal.

[0008] As a further improvement of the present invention, the air inlet hole is connected to a membrane frame assembly. The membrane frame assembly includes a first frame body and a second frame body. The first frame body is fixedly connected to the air inlet hole. The second frame body is detachably connected to the first frame body. The first permeable membrane is clamped between the first frame body and the second frame body;

[0009] A plurality of the second permeable membranes arranged in a tubular shape are evenly distributed around the inner diameter of the housing. The linear distances between the axes of the plurality of second permeable membranes and the axis of the housing are all equal.

[0010] As a further improvement of the present invention, the housing includes a first cover body, a second cover body and a mixing pipe. The first cover body and the second cover body are buckled at both ends of the mixing pipe in the length direction. The first cover body is provided with a liquid inlet hole. The second cover body is provided with a liquid outlet hole. The air inlet hole is provided on the side wall of the mixing pipe.

[0011] As a further improvement of the present invention, the first cover body is connected to a first liquid distribution block. The first liquid distribution block is evenly provided with a plurality of first liquid distribution holes communicated with the liquid inlet hole. Each first liquid distribution hole corresponds to and communicates with one of the second permeable membranes;

[0012] The second cover body is connected to a second liquid distribution block. The second liquid distribution block is evenly provided with a plurality of second liquid distribution holes communicated with the liquid outlet hole. Each second liquid distribution hole corresponds to and communicates with one of the second permeable membranes;

[0013] The pore size and porosity of the first permeable membrane are both smaller than those of the second permeable membrane.

[0014] As a further improvement of the present invention, a sealing gasket is respectively arranged between the first cover body and the end face of the mixing pipeline and between the second cover body and the end face of the mixing pipeline.

[0015] Based on the same inventive concept, the present invention discloses a method for preparing a double-layer membrane filament, comprising the following steps:

[0016] S1. Mixing polytetrafluoroethylene resin, extrusion aid, superhydrophobic fluorine-containing material and solvent to form a paste;

[0017] S2. Screening, pre-pressing and extrusion molding the paste in sequence to form a tubular primary membrane including an outer tube and a plurality of inner tubes nested in the outer tube;

[0018] S3. Heat-treating the tubular primary membrane, respectively stretching the inner tube and the outer tube at different stretching multiples and then sintering them to form a double-layer membrane filament composed of a first permeable membrane and a second permeable membrane.

[0019] As a further improvement of the present invention, the volume fractions of the components in the paste are respectively 30% - 40% of polytetrafluoroethylene resin, 20 - 30% of extrusion aid, 20% - 35% of superhydrophobic fluorine-containing material, and 20% - 30% of solvent. Among them, the crystallinity of the polytetrafluoroethylene resin is greater than or equal to 98%, and the number-average molecular weight is 3 million - 9 million.

[0020] As a further improvement of the present invention, the heat-treatment temperature of the tubular primary membrane is 120°C, the stretching temperature is 90°C, the stretching multiple of the outer tube is 1 - 2 times, the stretching multiple of the inner tube is 15 - 20 times, and the outer tube membrane and the inner tube membrane formed by stretching are sintered at 320°C for 120 min to form a first permeable membrane and a second permeable membrane.

[0021] As a further improvement of the present invention, the inner diameter of the first permeable membrane is 2.5 mm - 4 mm, the inner diameter of the second permeable membrane is 0.4 - 1 mm, and the membrane thicknesses of the first permeable membrane and the second permeable membrane are both 0.1 mm - 0.4 mm.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: first, by sequentially arranging the first permeable membrane and the second permeable membrane in the housing, pure water enters into the second permeable membranes arranged in a plurality of tubular shapes through the liquid inlet hole, and carbon dioxide passes through the air inlet hole and sequentially passes through the first permeable membrane and the second permeable membrane to dissolve into the pure water in the second permeable membrane. Since the permeation efficiency of the first permeable membrane and the second permeable membrane is different, when carbon dioxide passes through the air inlet hole and permeates into the first permeable membrane, a pressure difference is formed between the first permeable membrane and the second permeable membrane. Compared with the prior art, the first permeable membrane and the second permeable membrane cooperate in a manner that effectively buffers carbon dioxide and pure water, thereby effectively slowing down the permeation efficiency of carbon dioxide permeating into the pure water in the second permeable membrane, so as to solve the problem that carbon dioxide dissolves too quickly in pure water and exceeds the expected dissolution rate in the prior art. At the same time, by passing pure water through the tubular second permeable membrane, carbon dioxide can permeate into the second permeable membrane from all parts of the tubular second permeable membrane after passing through the first permeable membrane to dissolve into pure water, thereby effectively improving the dissolution uniformity of carbon dioxide in pure water to meet the subsequent wafer cleaning requirements.

[0023] Secondly, through the shell composed of the first cover body, the second cover body and the mixing pipe, the first cover body connects each second permeable membrane with the liquid inlet hole through the first liquid separator block, and the second cover body connects each second permeable membrane with the liquid outlet hole through the second liquid separator block, so as to fix each second permeable membrane and connect each second permeable membrane with the liquid inlet hole and the liquid outlet hole.

[0024] Finally, since the pore size and porosity of the first permeable membrane are smaller than those of the second permeable membrane, the first permeable membrane is mainly used to adjust the intake efficiency of carbon dioxide, thereby achieving the purpose of slow permeation of carbon dioxide; and the carbon dioxide passing through the first permeable membrane dissolves into pure water through the second permeable membrane with a large pore size and a large porosity. When the applied carbon dioxide concentration fluctuates, the double-layer membrane filaments composed of the first permeable membrane and the second permeable membrane can play a buffering role, so that the concentration of carbonated water formed by carbon dioxide dissolving in pure water changes more slowly and less, thereby improving the stability of the carbonated water concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the double-layer membrane wire gas-liquid mixing device in the present invention;

[0026] Figure 2 It is an exploded view used to reflect the assembly relationship of various parts in the present invention;

[0027] Figure 3 for Figure 1 Schematic diagram of the cross section formed by cutting along the FF direction;

[0028] Figure 4 for Figure 2 Enlarged view of part A in the middle;

[0029] Figure 5 is Figure 2 The enlarged view of part B in

[0030] Figure 6 The structural schematic diagram for embodying the second liquid separation block in this embodiment;

[0031] Figure 7 The exploded view for embodying the assembly relationship of each part in another embodiment of the present utility model;

[0032] Figure 8 is Figure 7 The enlarged view of part C in

[0033] Figure 9 The flow chart of the preparation method of the double-layer membrane filaments;

[0034] Figure 10 The electron microscope image of the first permeable membrane magnified by 2000 times;

[0035] Figure 11 The electron microscope image of the second permeable membrane magnified by 2000 times. Specific embodiments

[0036] The present invention will be described in detail below in conjunction with the embodiments shown in the accompanying drawings. It should be noted, however, that these embodiments are not intended to limit the present invention, and any equivalent transformation or substitution in terms of function, method, or structure made by those of ordinary skill in the art based on these embodiments shall fall within the protection scope of the present invention.

[0037] Refer to Figures 1 to 6As shown in the figure, a double-layer membrane fiber gas-liquid mixing device provided by the present invention, compared with the gas-liquid mixing devices in the prior art, has an air inlet hole 131 opened on the housing. After the carbon dioxide gas passes through the air inlet hole 131, it sequentially penetrates through the membrane pores of the first permeable membrane 2 and the membrane pores of the second permeable membrane 3, and dissolves into the pure water that enters the housing through the liquid inlet 111 and flows through the inside of the second permeable membrane 3 to form carbonated water required for wafer cleaning. Through the arrangement of the first permeable membrane 2 and the second permeable membrane 3 with different permeation efficiencies, when carbon dioxide penetrates through the first permeable membrane 2, a pressure difference is formed between the first permeable membrane 2 and the second permeable membrane 3. The cooperation mode of the first permeable membrane 2 and the second permeable membrane 3 has an effective buffering effect between carbon dioxide and pure water, thereby effectively slowing down the permeation efficiency of carbon dioxide dissolving into the pure water in the second permeable membrane 3 to solve the problem that carbon dioxide dissolves too fast in pure water beyond the expected dissolution rate in the prior art. At the same time, through the pure water passing through the tubular second permeable membrane 3, after carbon dioxide passes through the first permeable membrane 2, it can penetrate into the second permeable membrane 3 through the membrane pores at various parts of the tubular second permeable membrane 3 to dissolve into the pure water, thereby effectively improving the dissolution uniformity of carbon dioxide in pure water to meet the subsequent wafer cleaning requirements.

[0038] As shown in the figure Figures 1 to 6 As shown in the figure, a double-layer membrane fiber gas-liquid mixing device (hereinafter referred to as the gas-liquid mixing device) disclosed by the present invention includes a housing 1. Liquid inlet holes 111 and liquid outlet holes 121 are opened at both ends of the housing 1 in the length direction. An air inlet hole 131 and an air outlet hole 132 are opened on the side wall of the housing 1. The housing 1 is connected to a first permeable membrane 2 and a second permeable membrane 3 with different permeation efficiencies. Specifically, the pore diameter and porosity of the first permeable membrane 2 are both smaller than those of the second permeable membrane 3. The second permeable membrane 3 is arranged in a tubular shape and is respectively communicated with the liquid inlet hole 111 and the liquid outlet hole 121 at both ends. Pure water enters the housing 1 through the liquid inlet hole 111 and then flows into the second permeable membrane 3. Carbon dioxide enters the housing 1 through the air inlet hole 131 and sequentially penetrates through the first permeable membrane 2 and the second permeable membrane 3 and dissolves into the pure water in the second permeable membrane 3. The carbonated water after gas-liquid mixing is discharged from the housing 1 through the second permeable membrane 3 and the liquid outlet hole 121.

[0039] As shown in the figure Figures 2 to 6 As shown in the figure, the first permeable membrane 3 is arranged around the inner diameter of the housing 1. A plurality of second permeable membranes 3 arranged in a tubular shape are evenly distributed on the side of the first permeable membrane 3 away from the housing 1. The linear distances between the axes of the multiple second permeable membranes 3 and the axis of the first permeable membrane 2 are all equal. The housing 1 includes a first cover body 11, a second cover body 12 and a mixing pipe 13. The first cover body 11 and the second cover body 12 are buckled at both ends of the mixing pipe 13 in the length direction. The first cover body 11 is provided with a liquid inlet hole 111, the second cover body 12 is provided with a liquid outlet hole 121, and the air inlet hole 131 is opened on the side wall of the mixing pipe 13.

[0040] By setting the first permeable membrane 2 and the second permeable membrane 3, the pore size and porosity of the first permeable membrane 2 are smaller than those of the second permeable membrane 3, so that the permeation efficiency of the first permeable membrane 2 is lower than that of the second permeable membrane 3. Figures 3 to 6 As shown, after carbon dioxide enters the mixing pipe 13 through the air inlet 131, it passes through the first permeable membrane 2 with a lower permeability efficiency. Since the first permeable membrane 2 is annularly distributed in the mixing pipe 13, the carbon dioxide entering the mixing pipe 13 evenly and slowly permeates from various places on the outside of the first permeable membrane 2 to the inside of the first permeable membrane 2, that is, between the first permeable membrane 2 and the second permeable membrane 3, thereby limiting the rate at which carbon dioxide dissolves into pure water for the first time. Since pure water flows in the second permeable membrane 3, after carbon dioxide permeates between the first permeable membrane 2 and the second permeable membrane 3, carbon dioxide permeates into the second permeable membrane 3 again to dissolve in the pure water flowing in the second permeable membrane to form carbonated water required for wafer cleaning. It should be noted that since the first permeable membrane 2 has already limited the permeability efficiency of carbon dioxide for the first time, the permeation rate of the second permeable membrane 3 is larger than that of the first permeable membrane 2. In the present application, as shown in FIG. Figure 2 The evenly distributed second permeable membranes 3 shown in the figure can make the pure water entering the shell 1 through the liquid inlet hole 111 be evenly distributed into each second permeable membrane 3 connected to the liquid inlet hole 111, and the carbon dioxide between the first permeable membrane 2 and the second permeable membrane 3 can then evenly penetrate into the second permeable membrane 3 through the membrane pores of each second permeable membrane 3 and dissolve into the pure water. By limiting the inner pore diameter of each second permeable membrane 3, the carbon dioxide can be dissolved in the pure water in each second permeable membrane 3 in a uniform state. Compared with the permeable membrane with a larger inner diameter and a smaller number of permeable membranes, it can effectively avoid the problem that the pure water near the axis of the permeable membrane is difficult to contact with carbon dioxide, thereby causing uneven concentration of carbonated water and difficulty in meeting the needs of wafer cleaning. The dissolved carbonated water is discharged from the mixing pipe through the liquid outlet hole 121. It should be noted that the flow direction of carbon dioxide in this embodiment is as follows: Figures 3 to 5 As shown by the dashed arrow, the flow direction of pure water in this embodiment is as follows Figures 2 to 5 As shown by the solid arrow, the mixing pipe 13 also has an air outlet 132 for carbon dioxide to be discharged from the mixing pipe 13. A sealing gasket 16 is disposed between the first cover 11 and the end surface of the mixing pipe 13 and between the second cover 12 and the end surface of the mixing pipe 13 respectively.

[0041] Ginseng Figures 2 to 6 As shown, the first cover 11 is connected to the first liquid separation block 14, and the first liquid separation block 14 is evenly distributed with a plurality of first liquid separation holes 141 connected to the liquid inlet hole 111, and each first liquid separation hole 141 is connected to a corresponding second permeable membrane 3; the second cover 12 is connected to the second liquid separation block 15, and the second liquid separation block 15 is evenly distributed with a plurality of second liquid separation holes connected to the liquid outlet hole, and each second liquid separation hole is connected to a corresponding second permeable membrane.Figures 3 to 5 , the first liquid separation block 14 and the second liquid separation block 15 are respectively embedded in the first cover body 11 and the second cover body 12, and the annular side walls of the first liquid separation block 14 are fixed to the first cover body 11 everywhere, and there is a gap between the bottom surface of the first liquid separation block 14 and the first cover body 11. The annular side walls of the second liquid separation block 15 are fixed to the second cover body 12, and there is a gap between the top surface of the second liquid separation block 15 and the second cover body 12. Refer Figure 2 and Figure 6 As shown, a plurality of first liquid separation holes 141 are evenly distributed around the axis of the first liquid separation block 14, and a plurality of second liquid separation holes 151 are evenly distributed around the axis of the second liquid separation block 15. The top and bottom ends of each second permeable membrane 3 are respectively inserted between a second liquid separation hole 151 and a first liquid separation hole 141. When pure water is introduced at the liquid inlet hole 111, the pure water flows through the space between the first liquid separation block 141 and the first cover body 11, and then flows into each second permeable membrane 3 communicated with the first liquid separation hole 141. The carbonated water with dissolved carbon dioxide flows into the second liquid separation hole 151 from the other end of the second permeable membrane 3, and then passes through the space between the second liquid separation block 15 and the second cover body 12 and finally flows out from the liquid outlet hole 121. The arrangements of the first liquid separation block 14 and the second liquid separation block 15 not only achieve the effect of connecting the liquid inlet hole 111, the second permeable membrane 3 and the liquid outlet hole 121, but also play a role in fixing the second permeable membrane 3. It should be noted that the two ends of the first permeable membrane 2 can be inserted into the first liquid separation block 14 and the second liquid separation block 15 respectively as shown Figures 3 to 6 , or can be only clamped between the first liquid separation block 14 and the second liquid separation block 15.

[0042] In this embodiment, since the first permeable membrane 2 with a small pore diameter and a small porosity is used as the outer layer tube, and the second permeable membrane 3 with a large pore diameter and a large porosity is used as the outer layer tube, it is possible to adjust the intake efficiency of carbon dioxide, achieve the purpose of slow penetration of carbon dioxide, and then dissolve carbon dioxide in pure water. When the rate of applying carbon dioxide at the gas inlet hole 131 fluctuates, the double-layer membrane formed by the first permeable membrane 2 and the second permeable membrane 3 can play a buffering role, and part of the carbon dioxide remains between the first permeable membrane 2 and the mixing pipe 13, and the carbon dioxide slowly passes through at the penetration efficiency of the first permeable membrane 2, making the concentration change of the carbonated water slower and smaller, so as to improve the concentration stability of the carbonated water.

[0043] It should be noted that according to Henry's law, P = Hx, where P is the partial pressure of the gas, H is the Henry constant, and x is the solubility of the gas in mole fraction. In the case of a single-layer membrane, P = Hx. When using the double-layer membrane structure with different permeation efficiencies in this embodiment, a buffer region is formed between the first permeation membrane 2 and the second permeation membrane 3. Carbon dioxide permeates and dissolves into pure water through the second permeation membrane 3 with a higher permeation efficiency, but carbon dioxide is replenished into the buffer region through the first permeation membrane 2 with a lower permeation efficiency. Eventually, the pressure in the buffer region between the first permeation membrane 2 and the second permeation membrane 3 in the equilibrium state is P1, and P1 is less than P. At this time, x1 < x. In the single-layer membrane state, when the P value changes, since the Henry constant remains unchanged, the solubility x of the carbon dioxide gas in mole fraction changes positively with the P value. However, the double-layer membrane in this embodiment can maintain the pressure in the buffer region between the first permeation membrane 2 and the second permeation membrane 3 as P1. When P changes, the pressure in the buffer region can still be maintained as P1, thereby keeping the solubility x1 of the carbon dioxide gas in mole fraction unchanged and further maintaining the stability of the concentration of carbonated water.

[0044] As Figure 7 and Figure 8 shown, a modified embodiment of a double-layer membrane wire gas-liquid mixing device disclosed by the present invention is different from the foregoing embodiment in that: the air inlet hole 111 is connected to the membrane frame assembly 41. The membrane frame assembly 41 includes a first frame body 411 and a second frame body 412. The first frame body 411 is fixedly connected to the air inlet hole 131, the second frame body 412 is detachably connected to the first frame body 411, and the first permeation membrane 4 is clamped between the first frame body 411 and the second frame body 412; a plurality of second permeation membranes 5 arranged in a tubular shape are evenly distributed around the inner wall of the housing 1, and the linear distances between the axes of the plurality of second permeation membranes 4 and the axis of the housing 1 are all equal.

[0045] It should be noted that in this embodiment, the permeation efficiency of the first permeation membrane 4 is still lower than that of the second permeation membrane 5. Since the first permeation membrane 4 is clamped at the air inlet hole 131 by the first frame body 411 and the second frame body 412, when carbon dioxide is introduced into the housing through the air inlet hole 131, the first permeation membrane 4 covering the air inlet hole 131 can still serve the purpose of allowing the carbon dioxide gas to slowly enter the housing and then permeate into the second permeation membrane 5 and dissolve in pure water. In this embodiment, the housing still consists of a first cover body 11, a second cover body 12, and a mixing pipe 13. The mixing pipe 13 is provided with an air outlet hole 132. To prevent a large amount of carbon dioxide from escaping from the air outlet hole 132, a first permeation membrane 4 is also clamped by the first frame body 411 and the second frame body 412 at the air outlet hole 132.

[0046] Based on the same inventive concept, the present invention discloses a method for preparing a double-layer membrane wire. As Figure 9 shown, it includes the following steps:

[0047] S1. Mix polytetrafluoroethylene resin, an extrusion aid, a superhydrophobic fluorine-containing material, and an optional solvent to form a paste.

[0048] S2. Screen, pre-press, and extrude the paste in sequence to form a tubular primary film including an outer tube and a plurality of inner tubes nested inside the outer tube.

[0049] S3. Heat-treat the tubular primary film, stretch the inner tube and the outer tube at different stretching multiples respectively, and then sinter them to form a double-layer film filament composed of a first permeable membrane and a second permeable membrane.

[0050] It should be noted that the volume fractions of the components in the paste formed in step S1 are 30% - 40% for polytetrafluoroethylene resin, 20 - 30% for the extrusion aid, 20% - 35% for the superhydrophobic fluorine-containing material, and 20% - 30% for the solvent. Among them, the crystallinity of the polytetrafluoroethylene resin is greater than or equal to 98%, and the number-average molecular weight is 3 million - 9 million. The superhydrophobic fluorine-containing material is set as one or more of a fluoroalkyl acrylate polymer with a fluorine content of 5% - 50%, a fluoroalkyl methacrylate polymer with a fluorine content of 5% - 50%, a perfluoroalkyl acrylate polymer with a fluorine content of 5% - 50%, and a perfluoroalkyl acrylate polymer with a fluorine content of 5% - 50%. Among them, in this embodiment, the volume fractions of the components in the paste are 32% for polytetrafluoroethylene resin, 26% for the extrusion aid, 27% for the superhydrophobic fluorine-containing material, and 22% for the solvent.

[0051] In step S2, the paste formed in step S1 is screened, pre-pressed, and finally fed into a paste extrusion device for extrusion molding to form a tubular primary film including an outer tube and a plurality of inner tubes nested inside the outer tube. Among them, one end of the outer tube and the inner tube is adhered perpendicular to the length direction, and the outer tube and the inner tube do not contact each other at all points in the length direction. In this embodiment, the inner diameter of the outer tube is 2.5 mm - 4 mm, the inner diameter of the inner tube is 0.4 - 1 mm, and the film thickness of both the outer tube and the inner tube is 0.1 mm - 0.4 mm. Specifically, the inner diameter of the outer tube is set to 2.8 mm, the inner diameter of the inner tube is 0.7 mm, and the film thickness of both the outer tube and the inner tube is 0.25 mm.

[0052] In step S3, the tubular primary membrane formed in step S2 is heat-treated. The heat treatment temperature is 120°C, the stretching temperature is 90°C, the stretching ratio of the outer tube is 1 - 2 times, and the stretching ratio of the inner tube is 15 - 20 times. The outer tube membrane and the inner tube membrane formed by stretching are sintered at 320°C for 120 min to form a first permeable membrane and a second permeable membrane. It should be noted that the porosity and pore size of the first permeable membrane and the second permeable membrane are both positively correlated with the stretching ratio. When the stretching ratio of the outer tube is 1 - 2 times, the porosity of the first permeable membrane formed is 20% - 35%, and the pore size is 1 - 2 μm. Specifically, in this embodiment, the stretching ratio of the outer tube is 2 times, the porosity of the first permeable membrane formed is 35%, and the pore size is 2 μm. When the stretching ratio of the inner tube is 15 - 20 times, the porosity of the second permeable membrane formed is 40% - 55%, and the pore size is 4 - 6 μm. Specifically, in this embodiment, the stretching ratio of the inner tube is 20 times, the porosity of the second permeable membrane formed is 55%, and the pore size is 6 μm.

[0053] As shown in Figure 10 and Figure 11 , the electron micrographs of the first permeable membrane and the second permeable membrane magnified 2000 times are shown respectively. From Figure 10 and Figure 11 comparison, it can be seen that the number of permeation pores and the permeation pore size of the membrane filaments formed by the treated first permeable membrane are both smaller than those of the membrane filaments formed by the second permeable membrane. Therefore, when permeating carbon dioxide, it is easier to form a pressure difference between the first permeable membrane and the second permeable membrane to achieve the effect of uniformly and slowly dissolving carbon dioxide into pure water to form carbonated water with a certain conductivity in the foregoing embodiment.

[0054] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

[0055] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0056] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A double-layer membrane fiber gas-liquid mixing device, characterized in that, it includes: A housing, with a liquid inlet hole and a liquid outlet hole opened at both ends in the length direction of the housing, an air inlet hole opened on the side wall of the housing, the housing is connected to a first permeable membrane and a second permeable membrane with different permeation efficiencies, the second permeable membrane is arranged in a tubular shape and is respectively communicated with the liquid inlet hole and the liquid outlet hole at both ends, pure water enters the housing from the liquid inlet hole and then flows into the second permeable membrane, carbon dioxide enters the housing from the air inlet hole and then successively passes through the first permeable membrane and the second permeable membrane and dissolves into the pure water in the second permeable membrane, and the carbonated water with gas-liquid mixing completed is discharged from the housing through the second permeable membrane and the liquid outlet hole.

2. The double-layer membrane fiber gas-liquid mixing device according to claim 1, characterized in that, The first permeable membrane is arranged around the inner wall of the housing, and a plurality of the second permeable membranes arranged in a tubular shape are evenly distributed on the side of the first permeable membrane away from the housing, and the linear distances between the axes of the plurality of second permeable membranes and the axis of the first permeable membrane are all equal.

3. The double-layer membrane fiber gas-liquid mixing device according to claim 1, characterized in that, The air inlet hole is connected to a membrane frame assembly, the membrane frame assembly includes a first frame body and a second frame body, the first frame body is fixedly connected to the air inlet hole, the second frame body is detachably connected to the first frame body, and the first permeable membrane is clamped between the first frame body and the second frame body; A plurality of the second permeable membranes arranged in a tubular shape are evenly distributed around the inner diameter of the housing, and the linear distances between the axes of the plurality of second permeable membranes and the axis of the housing are all equal.

4. The double-layer membrane fiber gas-liquid mixing device according to claim 2 or 3, characterized in that, The housing includes a first cover body, a second cover body and a mixing pipeline, the first cover body and the second cover body are buckled at both ends in the length direction of the mixing pipeline, the first cover body is provided with a liquid inlet hole, the second cover body is provided with a liquid outlet hole, and the air inlet hole is opened on the side wall of the mixing pipeline.

5. The double-layer membrane fiber gas-liquid mixing device according to claim 4, characterized in that, The first cover body is connected to a first liquid distribution block, the first liquid distribution block is evenly provided with a plurality of first liquid distribution holes communicated with the liquid inlet hole, and each first liquid distribution hole corresponds to and communicates with one of the second permeable membranes; The second cover body is connected to a second liquid distribution block, the second liquid distribution block is evenly provided with a plurality of second liquid distribution holes communicated with the liquid outlet hole, and each second liquid distribution hole corresponds to and communicates with one of the second permeable membranes; The pore diameter and porosity of the first permeable membrane are both smaller than those of the second permeable membrane.

6. The double-layer membrane fiber gas-liquid mixing device according to claim 5, characterized in that, A sealing gasket is respectively arranged between the end face of the first cover body and the mixing pipeline and between the end face of the second cover body and the mixing pipeline.

7. A method for preparing a double-layer membrane fiber, characterized in that, this method includes the following steps: S1. Mix polytetrafluoroethylene resin, an extrusion aid, a superhydrophobic fluorine-containing material and a solvent to form a paste; S2. Screen, pre-press and extrude the paste in sequence to form a tubular primary membrane including an outer tube and a plurality of inner tubes nested in the outer tube. S3. Heat-treat the tubular primary membrane, and after separately stretching the inner tube and the outer tube at different stretching multiples, sinter them to form a double-layer membrane filament composed of a first permeable membrane and a second permeable membrane.

8. The method for preparing the double-layer membrane filament according to claim 7, characterized in that the heat treatment temperature of the tubular primary membrane is 120 °C, the stretching temperature is 90 °C, the stretching multiple of the outer tube is 1 - 2 times, the stretching multiple of the inner tube is 15 - 20 times, and the outer tube membrane and the inner tube membrane formed by stretching are sintered at 320 °C for 120 min to form the first permeable membrane and the second permeable membrane.

9. The method for preparing the double-layer membrane filament according to claim 8, characterized in that the inner diameter of the first permeable membrane is 2.5 mm - 4 mm, the inner diameter of the second permeable membrane is 0.4 - 1 mm, and the membrane thickness of both the first permeable membrane and the second permeable membrane is 0.1 mm - 0.4 mm.

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