Nitrocellulose membrane, and preparation method therefor and use thereof

Abstract

A filter material, specifically, a nitrocellulose membrane, and a preparation method therefor and a use thereof. The nitrocellulose membrane is formed by means of nitrocellulose fibers; the fibers are intersected, interwoven, and interconnected to form a mesh structure; a flow channel for liquid to pass through is formed in the mesh structure; the thickness of the nitrocellulose membrane is 100 μm to 130 μm; nodes are provided on the fibers; the ratio of the average diameter of the nodes to the average diameter of the fibers is 1.5 to 2.5; and the distribution density of the nodes on the outer surface of the nitrocellulose membrane is 35-70 / (50 μm)2.

Description

Nitrocellulose membrane and its preparation method and application Technical Field

[0001] The present application relates to filtration materials, and in particular to nitrocellulose membranes and their preparation methods and applications. Background Art

[0002] Immunochromatography is an important method for protein detection. It involves labeling a color developer with a bound antigen and a labeled antigen, fixing them on a chromatographic membrane, and fixing a detection antibody on the detection line. When the binding structure of protein-bound antigen-color developer-labeled antibody moves on the chromatographic membrane, the detection antibody on the detection line can bind to the target protein, causing the color developer bound to the target protein to produce a color reaction on the detection line, while the labeled antibody-color developer-bound antigen structure that is not bound to the target protein will continue to move to the quality control line, where an antigen for binding to the labeled antibody is fixed, allowing the above system to remain on the quality control line and produce a color reaction on the quality control line. Based on the above process, samples that only develop color on the quality control line are negative, while samples that develop color on both the quality control line and the detection line are positive. Commonly used color developers include latex microspheres, polystyrene microspheres, colloidal gold, and the like.

[0003] The properties of the chromatographic membrane have an important influence on the process of the colorimetric immunoassay. Among them, nitrocellulose membrane is a commonly used chromatographic membrane. It has the characteristics of low background, high signal-to-noise ratio, simple use, and easy blocking. It is widely used in the field of protein chromatography detection.

[0004] For nitrocellulose membranes, the rate at which proteins migrate through the system is closely related to the porosity and pore size within the membrane. Generally speaking, nitrocellulose membranes with larger porosity and pore diameter have faster migration rates and can also allow larger-sized developers to pass through. However, when the protein molecular weight is large and the developer particle size is large, membrane clogging can easily occur in the pores, leading to inaccurate chromatography results, resulting in higher noise, darker background colors, and jagged lines in the marked areas.

[0005] Summary of the Invention

[0006] In order to reduce the nonspecific adsorption of the membrane and improve the protein separation effect of the nitrocellulose membrane, the present application provides a nitrocellulose membrane and its preparation method and application. When used for protein detection at a higher climbing speed, the detection sensitivity is improved, the background color is reduced, and the occurrence of membrane clogging is reduced.

[0007] First, the nitrocellulose membrane provided in the present application is formed by fibers of nitrocellulose material, the fibers are interwoven to form a network structure, and flow channels for liquid to pass through are generated inside. The fibers have nodes, and the ratio of the average diameter of the nodes to the average diameter of the fibers is 1.5 to 2.5. On the outer surface of the nitrocellulose membrane, the node distribution density is 35 to 70 / (50 μm). 2 .

[0008] Cellulose membranes are typically prepared using methods such as phase separation. Small nodes form on the fibers on their surface. These nodes are typically formed by the aggregation of nitrocellulose in a solution environment. These nodes contain a complex entangled molecular chain structure, but overall can be considered as small spheres attached to the fibers. This significantly affects the flow properties of liquids and the retention of materials. Because the phase separation surface of nitrocellulose membranes generally has faster nucleation and precipitation rates, more fiber nodes form on the surface.

[0009] In this application, for the surface of nitrocellulose membrane, the number and number of fiber nodes must be controlled within a certain range. First, the nodes should not be dense and small, and the diameter of the nodes should not be too large. Thin and small nodes will fill the pores of the nitrocellulose membrane, further encroaching on the original pore space, thereby causing the strips to turn white. At the same time, excessively large nodes will cause uneven resistance to the material during movement within the membrane, in which proteins will be subject to greater resistance from the nodes. In some cases, the node surface will even be enriched with charge, affecting the electrostatic balance of the entire membrane, thereby causing the protein to be adsorbed on the nitrocellulose membrane.

[0010] Preferably, the distribution density of the nodes, the average diameter of the nodes and the average thickness of the nitrocellulose membrane have the following relationship N·D1 2 =L·K1; where N is the node distribution density, D1 is the average node diameter, L is the thickness of the nitrocellulose membrane, and K1 is a constant whose value range is 12000 to 25000 nodes / μm.

[0011] In the above scheme, the greater the membrane thickness, the greater the node distribution density. According to the above formula, the node distribution density corresponding to membranes of different thicknesses can be approximately deduced, or the thickness of the prepared membrane can be limited to a specific node distribution density. Specifically, the greater the thickness of the membrane, the larger the average node diameter and node distribution density it can accommodate. When the membrane thickness is large, a larger internal space can be generated inside the membrane, and the effect of the epidermis on the interior is small. Therefore, the area with obvious fibrosis inside is larger, so it can have a larger load capacity as a whole. Protein can have a better passage rate inside the cellulose membrane, so more protein will flow through the internal space of the nitrocellulose membrane. Therefore, even with a larger fiber node diameter and fiber distribution density, a good climbing speed and separation effect can still be achieved.

[0012] Preferably, the average diameter of the fibers D2 and the average SEM pore size R1 of the nitrocellulose membrane have the following relationship:

[0013] Among them, K2 is a constant, and its value range is 0.295~0.445μm 0.5 .

[0014] In the above scheme, the fiber diameter is proportional to the square root of the average pore size on the outer surface and inversely proportional to the square root of the average pore size on the outer surface. This parameter is controlled within a certain range, which means that in the surface area or the area near the surface of the nitrocellulose membrane, the smaller the overall pores, the finer the fiber structure should be, and the corresponding porosity should be larger. Therefore, in the case of a specific fiber diameter, the fragmentation of the surface pores requires an increase in the overall porosity to maintain a good creep rate and better separation effect.

[0015] Preferably, the average node diameter ranges from 3.5 to 5.2 μm, and the average fiber diameter ranges from 1.3 to 2.3 μm.

[0016] In the above scheme, the average diameter of the fiber nodes is limited to a certain range, and the average diameter of the fiber is also limited. Within this range, the efficiency of protein passage can be met and the obstruction of the fiber and fiber nodes to the protein can be reduced. At the same time, it can also play a good role in supporting the flow channel, so that the cellulose membrane is not easy to collapse during use, and the membrane pores maintain good performance, thereby maintaining a good climbing speed level and load level.

[0017] Preferably, the average SEM pore size of the nitrocellulose membrane is 20 to 35 μm, and the specific surface area ratio of the nitrocellulose membrane is 40 to 80%.

[0018] In the above scheme, the specific surface area of ​​the nitrocellulose membrane is further limited. When used for protein chromatography, the larger the specific surface area of ​​the nitrocellulose membrane, the stronger its ability to adsorb proteins, and the more likely it is to cause the flow rate in the membrane to slow down. Therefore, in this application, the specific surface area of ​​the membrane should be controlled within a certain range. An excessively large specific surface area of ​​the membrane will cause the adsorption performance of proteins in the region to be too strong, thereby causing the noise to increase and the sensitivity to decrease. An excessively small specific surface area of ​​the membrane will also lead to insufficient loading capacity of the membrane, and the amount of color developer and detection antibody that can be fixed is small, resulting in higher detection limits for the test line and the quality control line.

[0019] Preferably, the ratio of the node coverage area ratio on the surface of the nitrocellulose membrane to the cross-sectional pore area ratio of the nitrocellulose membrane is not greater than 0.48.

[0020] For high-speed nitrocellulose membrane systems, when liquids rapidly pass through the cellulose membrane, polymer systems such as proteins will be affected by the nodes within the membrane, thereby generating resistance. In the cross-sectional SEM of the membrane, there are transversely extending flow channels for liquids and proteins to pass through. The nodes protruding from the fibers cover the pores in the cross section, thereby generating flow resistance. This causes the protein to have different flow rates in different areas during the flow process, which in turn causes the strips to widen and whiten. Through the above solution, the area of ​​the membrane pores covered by the nodes is limited, resulting in a membrane with a similar porosity area ratio, with lower flow resistance, greater capacity, and more regular strips.

[0021] Preferably, the ratio between the average length of the pores in the horizontal direction and the average diameter of the nodes on the surface of the nitrocellulose membrane is 1.5 to 3.5.

[0022] The horizontal pore length of a membrane's cross-section represents the degree to which liquid can flow smoothly. Liquid flowing through a nitrocellulose membrane follows the horizontal fibers and is guided by the nodes. Therefore, a ratio between the average horizontal pore length and the average node diameter within the above range achieves good flow. Excessively large pore length may result in lower surface flow resistance, but internal support may be compromised, making membrane pore collapse more likely during use and leading to clogging.

[0023] Preferably, the outer surface node coverage area ratio P1 and the outer surface pore area ratio P2, and the node average diameter D1 and the fiber average diameter D2 have the following relationship: (P2 / P1): (D1 / D2) = 0.1 to 0.2.

[0024] A nitrocellulose membrane with a higher flow rate has a larger pore area ratio on its outer surface. The ratio between the node coverage area and the pore area indirectly reflects the channels available for liquid flow. The larger this ratio, the greater the available flow rate. For a specific ratio between node coverage area and pore area, the square of the node diameter is inversely proportional to the available flow rate. This is primarily due to the positive correlation between the cross-sectional area of ​​the node in the flow channel and the resistance it creates to the liquid. Therefore, larger node diameters result in lower applicable flow rates.

[0025] Preferably, the ratio of the outer surface node coverage ratio P1 to the outer surface porosity P2 ranges from P2 / P1 to 0.25 to 0.35.

[0026] In the above scheme, the nodes should not cover too large a surface area in the system, otherwise it will lead to excessive resistance to liquid flow and uneven spatial distribution in the system, which will lead to whitening and breakage of the strips.

[0027] On the basis of the above, this application also provides the following technical solutions for preparing the corresponding nitrocellulose membrane:

[0028] The preparation method of nitrocellulose membrane comprises the following steps:

[0029] S1. Dissolving nitrocellulose in solvent A to prepare a casting solution, wherein solvent A comprises a combination of an ester or ketone organic solvent and an alcohol solvent, and the mass fraction of nitrocellulose in the casting solution is 20-50%;

[0030] S2, applying the casting solution on the substrate. In this step, the substrate is pre-wetted with solvent A.

[0031] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0032] S4, immersing the first intermediate product in a water-based coagulation bath and performing phase separation treatment to obtain a second intermediate product;

[0033] S5. Washing and drying the second intermediate product to complete the preparation;

[0034] The thickness of the nitrocellulose membrane is 100-130 μm.

[0035] In the above scheme, the substrate is first moistened with solvent A before preparation, followed by a two-step vapor-liquid separation process. The vapor separation process can regulate the nucleation step of the nitrocellulose. In this process, the solvent system uses a combination of low-polarity solvents such as ketones or esters and high-polarity solvents such as alcohols. The difference in polarity improves the stability of the system during the vapor separation process. During the vapor separation process, after nucleation within the system, the nitrocellulose tends to continue growing on the surface of the nuclei rather than forming new nuclei. Consequently, the system does not produce overly small and fragmented nuclei, resulting in a relatively uniform overall structure and easier control of node formation in the surface area.

[0036] Preferably, in step S1, the mass ratio of the casting solution is as follows: 20-30 parts of nitrocellulose, 0.5-3 parts of surfactant, 0.1-3 parts of pore former, and 60 parts of solvent A.

[0037] In the above scheme, a casting liquid with a relatively high concentration of nitrocellulose is used. The node structure and fiber diameter formed on the surface of the casting liquid within this concentration range can just meet the corresponding parameters in this application. However, too high a concentration will cause the nitrocellulose membrane to easily form a denser cortex on the surface, which will have an adverse effect on color development. Too low a density will cause the fiberization step in the system to be too slow, forming a finer fiber structure and producing finely distributed porous fibers, which will increase the resistance to liquid flow.

[0038] Preferably, the solvent A is a combination of a branched alkyl ketone or a cycloalkyl ketone and a monohydric fatty alcohol.

[0039] The above-mentioned solvent A system has good polarity, can fully accommodate the dispersion system of nitrocellulose, and has a good precipitation rate during the phase separation process, especially when steam phase separation is performed in step S3, it can form a system with a moderate node particle size and node distribution density, thereby improving the quality of the prepared nitrocellulose membrane.

[0040] Further preferably, the solvent A is cyclopentanone or a combination of cyclohexanone and fatty alcohol, wherein the mass fraction of the fatty alcohol is 25-50%.

[0041] Within this range, the prepared nitrocellulose membrane has better properties and is easier to control the number and size of nodes.

[0042] Preferably, in step S3, the steam used is an air system mixed with water and isopropyl alcohol, wherein the water partial pressure in the steam is 30-60% and the isopropyl alcohol partial pressure is 0.2-5%. Further preferably, in step S3, the temperature is 30-50°C, the air flow rate is 0.5-5 m / s, and the contact time is 45-120 s.

[0043] In the above scheme, by adding a certain amount of isopropyl alcohol to the steam, the phase separation in this step will not be too fast, which will lead to too fast surface precipitation. At the same time, isopropyl alcohol can make the relationship between the generated node diameter and the fiber diameter more stable.

[0044] Preferably, in step S4, the temperature is controlled to be 20-50° C., and the processing time is 30-300 s.

[0045] The nitrocellulose membrane prepared within the above range has appropriate porosity and specific surface area, is stable in structure, can produce a good creep speed, and has good sensitivity and signal-to-noise ratio.

[0046] The present application also relates to a protein chromatography test paper prepared using the above-mentioned nitrocellulose membrane or the nitrocellulose membrane prepared by the above-mentioned method as a raw material.

[0047] In summary, the present application provides a nitrocellulose membrane and a series of preparation methods that can be used to prepare the above-mentioned nitrocellulose membrane. When used in the field of color developer protein immunoassay, a high climbing speed can still be achieved when the protein molecular weight is large or the color developer particle size is large, and the membrane clogging phenomenon is not easy to occur, thereby reducing background noise and improving the signal-to-noise ratio, so that the nitrocellulose membrane has higher sensitivity when used for protein detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG1 is a SEM schematic diagram of the surface of the nitrocellulose membrane in Example 1;

[0049] FIG2 is a cross-sectional SEM diagram of the nitrocellulose membrane in Example 1;

[0050] FIG3 is a SEM schematic diagram of the surface of the nitrocellulose membrane in Example 8;

[0051] FIG4 is a schematic diagram comparing the chromatographic uniformity of nitrocellulose membranes in Example 1 and Example 8; the area indicated by the arrow in the figure is the underlined area;

[0052] FIG5 is a schematic diagram of the scribing of the nitrocellulose membrane in Example 9 and Example 10. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] In the description of the present invention, it should be noted that terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are intended solely to facilitate and simplify the description of the present invention and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0055] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0056] Nitrocellulose membranes are commonly used for protein chromatography using colorimetric reagents. Modifying and expanding their properties has long been a research focus in related fields. However, there is currently no clear research plan for the diverse applications of nitrocellulose chromatography membranes in different fields.

[0057] Nitrocellulose membrane is usually prepared by the phase separation method, which can form a relatively uniform system. Since its outer area in the thickness direction plays a major color development effect, and the phase separation method can more conveniently adjust the structure of the surface area of ​​the nitrocellulose membrane, this application mainly uses the phase separation method to prepare the target nitrocellulose membrane. However, it should be noted that other preparation methods can also prepare nitrocellulose membranes with similar physical and chemical properties as in the following examples.

[0058] In the following examples, various parameters of nitrocellulose membrane properties were measured by the following methods:

[0059] The SEM average pore size of the nitrocellulose membrane surface, or the SEM average pore size of the cross section, or the node, can be measured by using a scanning electron microscope to characterize the membrane structure, and then using computer software (such as Matlab, NIS-Elements, etc.) or manually to measure and perform corresponding calculations. When actually measuring, the membrane surface can be characterized by an electron microscope first to obtain the corresponding SEM image. Since the pores on the membrane surface are roughly uniform, a certain area can be selected, such as 1μm 2 (1 μm times 1 μm) or 25 μm 2(5μm multiplied by 5μm), the specific area size depends on the actual situation, and then the pore diameters of all holes in the area are measured using corresponding computer software or manually, and then calculated to obtain the average pore diameter of the holes on the surface.

[0060] The areas of nodes and holes can be calculated in the same way. This can be done by manually demarcating the hole and node areas and then analyzing and calculating them using a computer, or by using a grid method. Fiber length can also be calculated by manually marking the fiber's trajectory and then calculating it using a computer.

[0061] It should be noted that those skilled in the art may also obtain the above parameters through other measurement methods, and the above measurement methods are for reference only.

[0062] Examples 1 to 25 respectively relate to different nitrocellulose membranes and corresponding prepared protein chromatography test strips. The surface SEM electron micrograph of the nitrocellulose membrane in Example 1 is shown in FIG1 , and the cross-sectional SEM electron micrograph is shown in FIG2 .

[0063] The nitrocellulose membrane is formed by fibers of nitrocellulose material. The nitrocellulose fibers are precipitated by a phase separation method and form an interwoven network structure with channels for liquid to pass through inside. As can be seen from Figure 1, the nitrocellulose membrane in this embodiment has nodes on the surface.

[0064] For Examples 1 to 25, the microscopic parameters of the prepared nitrocellulose membranes are shown in Table 1.

[0065] Where K1 = node distribution density N·average node diameter D1 2 / Film thickness L, unit is pieces / μm.

[0066] Unit is μm 0.5 .

[0067] K3 is the outer surface node coverage area ratio P1 and the outer surface hole area ratio P2, and the node average diameter D1 and the fiber average diameter D2 have the following relationship (P2 / P1): (D1 / D2).

[0068] In the above table, the statistical method of node distribution density is to count the number of nodes with clear outlines after dividing the area. If the node does not have a clear outline, for example, in the area marked by circle 1 in Figure 1, the number of nodes in this area is recorded as 1, and it is not included in the statistics of the average diameter of the nodes. Area A illustrates a node structure with a clustered shape. In this area, the clustered nodes are only divided according to the outermost node structure in the manner of circle 2, and when counting the average node diameter, only the nodes in circle 2 are counted. However, when counting the outer surface node coverage area rate, all clustered nodes in area A are included in the statistics.

[0069] It is worth noting that in the figure, the agglomerated node structure in area A is actually caused by the stacking of some nodes in the thickness direction, so it will show agglomeration phenomenon in the microscopic image, so only the node structure on the outermost side is counted.

[0070] When calculating the average SEM pore size and pore area ratio of the membrane, only the pore size of the outermost pores under the SEM electron microscope is counted, that is, the circle formed by the outermost fiber structure in the figure. For example, in Figure 1, the circle shown by circle 3 can be included in the statistics, while the circle formed by circle 4 is not included in the statistics.

[0071] The statistical methods for the cross-sectional area ratio covered by nodes and the cross-sectional area ratio of pores are the same as those for the external surface.

[0072] The specific surface area ratio (SAR) is calculated by dividing the specific surface area of ​​the system by the membrane area. The specific surface area of ​​nitrocellulose membranes is determined using the BET surface area method.

[0073] The nitrocellulose membrane preparation method in Example 1 is as follows:

[0074] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0075] Solvent A: 60 parts;

[0076] Nitrocellulose: 20 parts;

[0077] Surfactant: 1 part;

[0078] Pore ​​former: 2 parts;

[0079] Specifically, solvent A is a mixed solution of 70% by mass of cyclopentanone and 30% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0080] The surfactant is polyethylene glycol octylphenyl ether;

[0081] The porogen is PEG800.

[0082] S2. Immerse the substrate in solvent A to moisten the surface of the substrate, and then apply the casting solution on the substrate to a thickness of 500 μm;

[0083] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0084] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 50% and an isopropyl alcohol partial pressure of 3.2% in the steam; the temperature is 45° C., the air flow rate is 2.8 m / s, and the contact time is 60 s.

[0085] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 180 seconds.

[0086] It should be noted that an electrolyte such as sodium chloride or a pH adjuster such as sodium hydroxide may also be added to the water-based coagulation bath.

[0087] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0088] The preparation method of nitrocellulose membrane in Example 2 is as follows:

[0089] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0090] Solvent A: 45 parts;

[0091] Nitrocellulose: 45 parts;

[0092] Surfactant: 1 part;

[0093] Pore ​​former: 1.8 parts;

[0094] Specifically, solvent A is a mixed solution of 70% by mass of cyclopentanone and 30% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0095] The surfactant is polyethylene glycol octylphenyl ether;

[0096] The porogen is PEG800.

[0097] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0098] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0099] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 48% and an isopropyl alcohol partial pressure of 3.2% in the steam; the temperature is 50° C., the air flow rate is 1.0 m / s, and the contact time is 120 s.

[0100] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 35° C., and the immersion time is 150 s.

[0101] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0102] The preparation method of nitrocellulose membrane in Example 3 is as follows:

[0103] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0104] Solvent A: 60 parts;

[0105] Nitrocellulose: 20 parts;

[0106] Surfactant: 1 part;

[0107] Pore ​​former: 2.3 parts;

[0108] Specifically, solvent A is a mixed solution of 70% by mass of cyclopentanone and 30% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0109] The surfactant is polyethylene glycol octylphenyl ether;

[0110] The porogen is PEG800.

[0111] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0112] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0113] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 5% in the steam; the temperature is 50° C., the air flow rate is 5.0 m / s, and the contact time is 55 s.

[0114] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 240 s.

[0115] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0116] The nitrocellulose membrane preparation method in Example 4 is as follows:

[0117] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0118] Solvent A: 80 parts;

[0119] Nitrocellulose: 20 parts;

[0120] Surfactant: 1.5 parts;

[0121] Pore ​​former: 2.5 parts;

[0122] Specifically, solvent A is a mixed solution of 70% by mass of cyclopentanone and 30% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0123] The surfactant is polyethylene glycol octylphenyl ether;

[0124] The porogen is PEG800.

[0125] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0126] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0127] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 50% and an isopropyl alcohol partial pressure of 0.5% in the steam; the temperature is 30° C., the air flow rate is 4.6 m / s, and the contact time is 120 s.

[0128] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 180 seconds.

[0129] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0130] The nitrocellulose membrane preparation method in Example 5 is as follows:

[0131] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0132] Solvent A: 60 parts;

[0133] Nitrocellulose: 20 parts;

[0134] Surfactant: 1 part;

[0135] Pore ​​former: 1.3 parts;

[0136] Specifically, solvent A is a mixed solution of 60% by mass of cyclopentanone and 40% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0137] The surfactant is polyethylene glycol octylphenyl ether;

[0138] The porogen is PEG800.

[0139] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0140] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0141] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 50% and an isopropyl alcohol partial pressure of 3.2% in the steam; the temperature is 50° C., the air flow rate is 1.1 m / s, and the contact time is 95 s.

[0142] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 180 seconds.

[0143] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0144] The nitrocellulose membrane preparation method in Example 6 is as follows:

[0145] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0146] Solvent A: 50 parts;

[0147] Nitrocellulose: 30 parts;

[0148] Surfactant: 1 part;

[0149] Pore ​​former: 2 parts;

[0150] Specifically, solvent A is a mixed solution of 50% by mass of cyclopentanone and 50% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0151] The surfactant is polyethylene glycol octylphenyl ether;

[0152] The porogen is PEG800.

[0153] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0154] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0155] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 35% and an isopropyl alcohol partial pressure of 5% in the steam; the temperature is 30° C., the air flow rate is 0.5 / s, and the contact time is 60 s.

[0156] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 40° C., and the immersion time is 300 s.

[0157] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0158] The nitrocellulose membrane preparation method in Example 7 is as follows:

[0159] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0160] Solvent A: 60 parts;

[0161] Nitrocellulose: 34 parts;

[0162] Surfactant: 1 part;

[0163] Pore-forming agent: 0.5 parts;

[0164] Specifically, solvent A is a mixed solution of 65% by mass of cyclopentanone and 35% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0165] The surfactant is polyethylene glycol octylphenyl ether;

[0166] The porogen is PEG800.

[0167] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0168] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0169] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 55% and an isopropyl alcohol partial pressure of 2.4% in the steam; the temperature is 50° C., the air flow rate is 2.8 m / s, and the contact time is 90 s.

[0170] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 180 seconds.

[0171] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0172] The nitrocellulose membrane preparation method in Example 8 is as follows:

[0173] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0174] Solvent A: 60 parts;

[0175] Nitrocellulose: 20 parts;

[0176] Surfactant: 1 part;

[0177] Pore ​​former: 3 parts;

[0178] Specifically, solvent A is cyclopentanone, and nitrocellulose is selected with a number average molecular weight of 10 5 ~107 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0179] The surfactant is polyethylene glycol octylphenyl ether;

[0180] The porogen is PEG800.

[0181] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0182] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0183] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 50% and an isopropyl alcohol partial pressure of 3.2% in the steam; the temperature is 45° C., the air flow rate is 2.8 m / s, and the contact time is 60 s.

[0184] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 180 seconds.

[0185] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0186] The nitrocellulose membrane preparation method in Example 9 is as follows:

[0187] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0188] Solvent A: 60 parts;

[0189] Nitrocellulose: 30 parts;

[0190] Surfactant: 1 part;

[0191] Pore ​​former: 1 part;

[0192] Specifically, solvent A is a mixed solution of 80% by mass of cyclopentanone and 20% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0193] The surfactant is polyethylene glycol octylphenyl ether;

[0194] The porogen is PEG800.

[0195] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0196] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0197] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 1.5% in the steam; the temperature is 40° C., the air flow rate is 4 m / s, and the contact time is 90 s.

[0198] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 300 s.

[0199] It should be noted that an electrolyte such as sodium chloride or a pH adjuster such as sodium hydroxide may also be added to the water-based coagulation bath.

[0200] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0201] The nitrocellulose membrane preparation method in Example 10 is as follows:

[0202] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0203] Solvent A: 85 parts;

[0204] Nitrocellulose: 12 parts;

[0205] Surfactant: 1 part;

[0206] Pore ​​former: 2 parts;

[0207] Specifically, solvent A is a mixed solution of 80% by mass of cyclopentanone and 20% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0208] The surfactant is polyethylene glycol octylphenyl ether;

[0209] The porogen is PEG800.

[0210] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0211] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0212] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 45% and an isopropyl alcohol partial pressure of 8% in the steam; the temperature is 40° C., the air flow rate is 4 m / s, and the contact time is 90 s.

[0213] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 35° C., and the immersion time is 300 s.

[0214] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0215] The method for preparing the nitrocellulose membrane in Example 11 is as follows:

[0216] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0217] Solvent A: 60 parts;

[0218] Nitrocellulose: 30 parts;

[0219] Surfactant: 1 part;

[0220] Pore ​​former: 2 parts;

[0221] Specifically, solvent A is a mixed solution of 80% by mass of cyclopentanone and 20% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0222] The surfactant is polyethylene glycol octylphenyl ether;

[0223] The porogen is PEG800.

[0224] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0225] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0226] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 40% and an isopropyl alcohol partial pressure of 5% in the steam; the temperature is 30° C., the air flow rate is 4 m / s, and the contact time is 90 s.

[0227] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 40° C., and the immersion time is 100 s.

[0228] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0229] The method for preparing the nitrocellulose membrane in Example 12 is as follows:

[0230] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0231] Solvent A: 60 parts;

[0232] Nitrocellulose: 25 parts;

[0233] Surfactant: 1 part;

[0234] Pore ​​former: 1.8 parts;

[0235] Specifically, solvent A is cyclopentanone with a mass fraction of 10, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0236] The surfactant is polyethylene glycol octylphenyl ether;

[0237] The porogen is PEG800.

[0238] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0239] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0240] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, the water partial pressure in the steam is 60%, no isopropyl alcohol is contained, the temperature is 60° C., the air flow rate is 8 m / s, and the contact time is 120 s.

[0241] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 50° C., and the immersion time is 120 seconds.

[0242] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0243] The method for preparing the nitrocellulose membrane in Example 13 is as follows:

[0244] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0245] Solvent A: 60 parts;

[0246] Nitrocellulose: 25 parts;

[0247] Surfactant: 1 part;

[0248] Pore ​​former: 2.2 parts;

[0249] Specifically, solvent A is a mixed solution of 75% by mass of cyclopentanone and 25% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0250] The surfactant is polyethylene glycol octylphenyl ether;

[0251] The porogen is PEG800.

[0252] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0253] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0254] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 3.5% in the steam; the temperature is 45° C., the air flow rate is 5 m / s, and the contact time is 45 s.

[0255] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 120 seconds.

[0256] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0257] The nitrocellulose membrane preparation method in Example 14 is as follows:

[0258] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0259] Solvent A: 60 parts;

[0260] Nitrocellulose: 30 parts;

[0261] Surfactant: 1 part;

[0262] Pore ​​former: 1.6 parts;

[0263] Specifically, solvent A is a mixed solution of 60% by mass of cyclopentanone and 40% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0264] The surfactant is polyethylene glycol octylphenyl ether;

[0265] The porogen is PEG800.

[0266] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0267] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0268] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 55% and an isopropyl alcohol partial pressure of 0.9% in the steam; the temperature is 40° C., the air flow rate is 3.0 m / s, and the contact time is 80 s.

[0269] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 120 seconds.

[0270] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0271] The method for preparing the nitrocellulose membrane in Example 15 is as follows:

[0272] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0273] Solvent A: 60 parts;

[0274] Nitrocellulose: 20 parts;

[0275] Surfactant: 1 part;

[0276] Pore ​​former: 1.5 parts;

[0277] Specifically, solvent A is a mixed solution of 50% by mass of cyclopentanone and 50% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0278] The surfactant is polyethylene glycol octylphenyl ether;

[0279] The porogen is PEG800.

[0280] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0281] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0282] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 55% and an isopropyl alcohol partial pressure of 2.5% in the steam; the temperature is 50° C., the air flow rate is 1.20 m / s, and the contact time is 60 s.

[0283] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 120 seconds.

[0284] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0285] The nitrocellulose membrane preparation method in Example 16 is as follows:

[0286] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0287] Solvent A: 60 parts;

[0288] Nitrocellulose: 30 parts;

[0289] Surfactant: 1 part;

[0290] Pore ​​former: 1.6 parts;

[0291] Specifically, solvent A is a mixed solution of 75% by mass of cyclopentanone and 50% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0292] The surfactant is polyethylene glycol octylphenyl ether;

[0293] The porogen is PEG800.

[0294] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0295] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0296] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 55% and an isopropyl alcohol partial pressure of 0.9% in the steam; the temperature is 45° C., the air flow rate is 3.0 m / s, and the contact time is 80 s.

[0297] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 120 seconds.

[0298] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0299] The method for preparing the nitrocellulose membrane in Example 17 is as follows:

[0300] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0301] Solvent A: 60 parts;

[0302] Nitrocellulose: 20 parts;

[0303] Surfactant: 1 part;

[0304] Pore ​​former: 3 parts;

[0305] Specifically, solvent A is a mixed solution of 75% by mass of cyclopentanone and 25% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0306] The surfactant is polyethylene glycol octylphenyl ether;

[0307] The porogen is PEG800.

[0308] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0309] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0310] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 0.2% in the steam; the temperature is 40° C., the air flow rate is 1.8 m / s, and the contact time is 120 s.

[0311] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 50° C., and the immersion time is 120 seconds.

[0312] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0313] The nitrocellulose membrane preparation method in Example 18 is as follows:

[0314] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0315] Solvent A: 60 parts;

[0316] Nitrocellulose: 23 parts;

[0317] Surfactant: 1 part;

[0318] Pore ​​former: 1.5 parts;

[0319] Specifically, solvent A is a mixed solution of 75% by mass of cyclopentanone and 50% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0320] The surfactant is polyethylene glycol octylphenyl ether;

[0321] The porogen is PEG800.

[0322] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0323] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0324] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 58% and an isopropyl alcohol partial pressure of 0.9% in the steam; the temperature is 30° C., the air flow rate is 3.0 m / s, and the contact time is 80 s.

[0325] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 120 seconds.

[0326] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0327] The nitrocellulose membrane preparation method in Example 19 is as follows:

[0328] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0329] Solvent A: 60 parts;

[0330] Nitrocellulose: 21 parts;

[0331] Surfactant: 1 part;

[0332] Pore ​​former: 1 part;

[0333] Specifically, solvent A is a mixed solution of 50% by mass of cyclopentanone and 50% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0334] The surfactant is polyethylene glycol octylphenyl ether;

[0335] The porogen is PEG800.

[0336] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0337] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0338] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 35% and an isopropyl alcohol partial pressure of 2.5% in the steam; the temperature is 48° C., the air flow rate is 4.2 m / s, and the contact time is 100 s.

[0339] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 120 seconds.

[0340] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0341] The nitrocellulose membrane preparation method in Example 20 is as follows:

[0342] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0343] Solvent A: 60 parts;

[0344] Nitrocellulose: 30 parts;

[0345] Surfactant: 0.8 parts;

[0346] Pore ​​former: 1.9 parts;

[0347] Specifically, solvent A is a mixed solution of 90% by mass of cyclopentanone and 10% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0348] The surfactant is polyethylene glycol octylphenyl ether;

[0349] The porogen is PEG800.

[0350] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0351] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0352] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 70% and an isopropyl alcohol partial pressure of 1.2% in the steam; the temperature is 40° C., the air flow rate is 2.0 m / s, and the contact time is 100 s.

[0353] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 20° C., and the immersion time is 300 s.

[0354] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0355] The method for preparing the nitrocellulose membrane in Example 21 is as follows:

[0356] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0357] Solvent A: 60 parts;

[0358] Nitrocellulose: 27 parts;

[0359] Surfactant: 0.8 parts;

[0360] Pore ​​former: 1.5 parts;

[0361] Specifically, solvent A is a mixed solution of 70% by mass of cyclopentanone and 30% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0362] The surfactant is polyethylene glycol octylphenyl ether;

[0363] The porogen is PEG800.

[0364] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0365] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0366] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 3.5% in the steam; the temperature is 50° C., the air flow rate is 4.0 m / s, and the contact time is 90 s.

[0367] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 40° C., and the immersion time is 150 seconds.

[0368] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0369] The method for preparing the nitrocellulose membrane in Example 22 is as follows:

[0370] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0371] Solvent A: 60 parts;

[0372] Nitrocellulose: 20 parts;

[0373] Surfactant: 1.5 parts;

[0374] Pore ​​former: 3 parts;

[0375] Specifically, solvent A is a mixed solution of 60% by mass of cyclopentanone and 40% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0376] The surfactant is polyethylene glycol octylphenyl ether;

[0377] The porogen is PEG800.

[0378] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0379] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0380] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 0.5% in the steam; the temperature is 40° C., the air flow rate is 2.5 m / s, and the contact time is 120 s.

[0381] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 20° C., and the immersion time is 300 s.

[0382] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0383] The method for preparing the nitrocellulose membrane in Example 23 is as follows:

[0384] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0385] Solvent A: 60 parts;

[0386] Nitrocellulose: 30 parts;

[0387] Surfactant: 1 part;

[0388] Pore ​​former: 2 parts;

[0389] Specifically, solvent A is a mixed solution of 75% by mass of cyclopentanone and 25% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0390] The surfactant is polyethylene glycol octylphenyl ether;

[0391] The porogen is PEG800.

[0392] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0393] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0394] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 55% and an isopropyl alcohol partial pressure of 3.6% in the steam; the temperature is 35° C., the air flow rate is 2.5 m / s, and the contact time is 80 s.

[0395] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 260 s.

[0396] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0397] The nitrocellulose membrane preparation method in Example 24 is as follows:

[0398] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0399] Solvent A: 60 parts;

[0400] Nitrocellulose: 22 parts;

[0401] Surfactant: 1 part;

[0402] Pore ​​former: 2 parts;

[0403] Specifically, solvent A is a mixed solution of 55% by mass of cyclopentanone and 45% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0404] The surfactant is polyethylene glycol octylphenyl ether;

[0405] The porogen is PEG800.

[0406] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0407] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0408] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 55% and an isopropyl alcohol partial pressure of 4.0% in the steam; the temperature is 35° C., the air flow rate is 4 m / s, and the contact time is 80 s.

[0409] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 30° C., and the immersion time is 260 s.

[0410] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0411] The nitrocellulose membrane preparation method in Example 25 is as follows:

[0412] S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. The specific materials in the casting solution are proportioned by mass as follows:

[0413] Solvent A: 60 parts;

[0414] Nitrocellulose: 30 parts;

[0415] Surfactant: 1 part;

[0416] Pore ​​former: 1 part;

[0417] Specifically, solvent A is a mixed solution of 60% by mass of cyclopentanone and 40% by mass of ethanol, and nitrocellulose is selected with a number average molecular weight of 10 5 ~10 7 The resin system (in this embodiment, the number average molecular weight is 6×10 5 );

[0418] The surfactant is polyethylene glycol octylphenyl ether;

[0419] The porogen is PEG800.

[0420] S2, immersing the substrate in solvent A to wet the surface of the substrate, and then applying the casting solution on the substrate;

[0421] S3, performing a phase separation treatment on the product obtained in step S2 by steam phase separation to obtain a first intermediate product;

[0422] Specifically, in this step, the steam used is an air system mixed with water and isopropyl alcohol, with a water partial pressure of 60% and an isopropyl alcohol partial pressure of 2.0% in the steam; the temperature is 45° C., the air flow rate is 1.0 m / s, and the contact time is 120 s.

[0423] S4. Immerse the first intermediate product in a water-based coagulation bath and perform phase separation to obtain a second intermediate product; wherein the water-based coagulation bath is pure water, the temperature is 20° C., and the immersion time is 240 s.

[0424] S5. Wash the second intermediate product with water and ethanol, and dry it to complete the preparation.

[0425] Example 26: The nitrocellulose membrane prepared in Examples 1 to 25 is prepared into a chromatography test paper. The specific preparation method includes the following steps:

[0426] 1. The prepared nitrocellulose membrane was streaked to draw the test line and the quality control line. The quality control line used goat anti-mouse IgG polyclonal and the test line used hepatitis B virus monoclonal antibody 1.

[0427] 2. Cut the scribed nitrocellulose membrane and spread it on a base material to obtain a reaction area. In this application, the base material is a polyester board.

[0428] 3. Place a developer pad at one end of the reaction zone. In this embodiment, the developer pad is a microporous membrane structure. In this application, a polypropylene fiber membrane is selected. The developer pad is prepared as follows:

[0429] The developer solution was adjusted to pH 10 with potassium carbonate, and the labeled antibody was added to the solution. The reaction was shaken at room temperature, and the developer surface was then blocked with BSA. The solution was then centrifuged and washed to obtain a gold-labeled complex, which was then sprayed onto the developer pad. In this example, the developer particles used were latex microspheres with a diameter distribution of 300-400 nm, and the labeled antibody was hepatitis B virus monoclonal antibody 2.

[0430] 4. Lay the sample pad on the outside of the developer pad. The sample pad is a glass fiber membrane.

[0431] 5. Lay an absorbent pad at the other end of the reaction area.

[0432] It should be noted that in this application, hepatitis B surface antigen is selected for illustration only. In fact, different antigens can also be detected by replacing different antibodies.

[0433] In this embodiment, different protein chromatography test strips obtained in different embodiments were used to test the test strips. The specific detection method is as follows:

[0434] Prepare a hepatitis B surface antigen buffer solution, the buffer solution is a 10M PBS system, add 0.05% mass fraction of triton and an appropriate amount of surfactant, and prepare a hepatitis B surface antigen sample with a concentration of 100 ng / mL. Drop the prepared hepatitis B surface antigen buffer solution on the sample pad for detection.

[0435] In addition, norovirus and adenovirus were added as negative control groups. The concentration of the control groups was 1000 ng / ml.

[0436] Various tests were performed on Examples 1 to 25, and the specific test results are shown in Table 2.

[0437] Table 2

[0438] Through the above experimental results, it is not difficult to see that in the present application, the prepared nitrocellulose membrane can obtain negative test results for both norovirus and adenovirus, and can also obtain positive results for the detection of hepatitis B surface antigen. The main differences between the embodiments are reflected in whether the chromatography is uniform, whether the lines are sharp, whether there is no whitishness, and whether the background color is too dark. Specifically in the above table, the line morphology is obtained by observing the morphology after the quality control line and the test line are crossed in step 1. The chromatography uniformity is obtained by immersing the prepared developer at one end in the buffer chromatography solution with an immersion depth of 3mm, and then observing the situation of the solution climbing. The climbing speed of the nitrocellulose membrane can also be determined in this way. The background depth of field is determined by observing the color change of the reaction zone after antigen detection.

[0439] In the above examples, Examples 1, 3, 5, 6, 7, 14, 15, 19, 21, and 25 all performed well, with uniform overall markings and no obvious defects. The chromatography process was also relatively uniform, belonging to the category of preferred embodiments. In Examples 4 and 12, the ratio between the node diameter and the fiber diameter was significantly too large, and therefore, compared to the excessively large nodes with fiber diameters, an uneven surface was produced, which blocked the flow of the liquid, and the surface was more susceptible to clogging, resulting in a darker color on the surface. In Examples 2 and 13, compared to Example 4, although the ratio between the node and fiber diameter was lower, an excessively large node diameter was produced during the preparation process, which had a significant impact on the chromatography uniformity of the membrane. Since the region where the nodes were present would produce a larger flow resistance, the membrane would have a problem of poor overall uniformity in the climbing speed in some regions, but the depth of field effect on the overall line shape and background was relatively small.

[0440] In contrast, in Example 18, the ratio of node diameter to fiber diameter is small, which easily leads to the enrichment of node structures on the fibers, forming a locally uneven structure. Furthermore, despite the small number of nodes, their internal distribution is highly uneven, resulting in the formation of darker color blocks in local areas on the basis of the overall background color, and poor chromatographic uniformity. In Example 24, although the ratio of node diameter to fiber diameter is within the range, the node particle size itself is relatively small, making it easier for the surface to accumulate charge, thereby causing some color developer structures to agglomerate or adsorb on the node surfaces, which in turn leads to a deepening of the background color. This can also easily lead to lighter bands, reduced sensitivity, and false negatives.

[0441] Although Example 20 has a smaller node diameter than Example 2 and Example 13, the average length of its cross-sectional aperture is also lower, and then relatively the liquid flow resistance in the local area is too large, and similar phenomena are produced as in Example 2 and Example 13. However, both of the above situations will not have darker background noise as a whole. It should be noted that, in the case of uneven chromatography, the developer after binding to the protein to be detected will have different migration rates in different regions, so the reaction time of each part is different, which may produce a false negative phenomenon. In addition, in Example 13, the value of K1 is larger, which represents that the number distribution density of surface nodes is larger. In the case of a smaller film thickness, an excessively large node density will cause a reduction in membrane capacity and dispersion of materials in the ruled area, resulting in a certain whitish phenomenon on the ruled line, and the flatness is also poor.

[0442] In Example 8, although the node size meets the requirements, the excessive number of nodes in the system not only affects the chromatographic uniformity, but also causes the background color to darken. This may be because the excessive number of nodes hinders the protein in the chromatography process, resulting in membrane clogging, resulting in high nonspecific adsorption within the membrane, and thus causing greater background noise. On this basis, in addition to having a larger number of nodes, Example 12 also has a larger node diameter than the fiber diameter, and the outer surface node coverage area ratio is also larger than the outer surface pore area ratio. While causing a significant reduction in the overall climbing speed, it also produces a larger adsorption phenomenon internally, resulting in more obvious membrane clogging than in Example 8 and a darker background color.

[0443] In Example 9, although the number of nodes is small and nonspecific adsorption and membrane clogging are not likely to occur, the fiber diameter is also small, so the adhesion and retention properties of the material on the surface are poor, and there is a certain whitening of the strips.

[0444] In Example 10, the value of K2 is low, which means that it has a low fiber diameter and a large surface average SEM pore size. Therefore, the liquid will have an excessively fast flow rate in the surface area of ​​the membrane, and the line will be uneven in the lined area. In Example 16 and Example 23, the K2 value is high and the fiber diameter is large. The effect is that the excessive fiber diameter causes the flow in the surface area to be unbalanced, and the material distribution is uneven in the lined area, resulting in the phenomenon of white stripes. In addition, the excessively large fiber diameter on the surface will produce a certain amount of non-specific adsorption, and this part of the adsorption is difficult to be washed away when the pores are small, thus forming a certain background color. In Example 16, the node area of ​​the surface area occupies a large area and has a large K3 value. The K3 value is the ratio of the node coverage area rate of the outer surface to the surface pore area rate, the ratio of the node average diameter to the fiber average diameter. If this value is too large, it will result in a larger overall resistance, which will reduce the climbing speed and make it more likely to cause membrane blocking. Overall, Example 16 has a larger background color than Example 23.

[0445] In Example 11, the larger K3 value, similar to Example 16, will lead to a deepening of the background color. At the same time, in Example 11, the coverage area of ​​the node is too large compared to the surface gap surface, which will cause the aggregation performance of the material on the surface of the membrane to deteriorate, the overall color of the strip will tend to be lighter, and the sensitivity will deteriorate.

[0446] In embodiment 17, contrary to embodiment 13, there is too small K1 value, although the reduction of K1 value means the decreasing of node number, but its surface does not have the nitrocellulose membrane of node, in fact there is the characteristic of poor material binding performance on the lined area, in addition, although its node number is small, but it still has fragmented nodes, its regulation performance variation to climbing speed (being specifically embodied as climbing speed is too fast) and surface nonspecific adsorption is enhanced, easily pollutes, and then causes background color to be darker relative to embodiment 1. Similar situation is also embodied in embodiment 22, although its node size is larger than embodiment 17 and embodiment 24, but owing to having larger cross-sectional fiber length on its cross section, therefore can more easily form uneven flow area in the horizontal direction during liquid flow, that is, liquid cannot make full use of the space in the membrane, therefore also be easy to retain part antibody, developer component in the region where some small nodes agglomerate, cause it to have certain background color. Meanwhile, the present embodiment also causes the phenomenon of climbing speed too fast to occur.

[0447] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A nitrocellulose membrane formed by fibers of nitrocellulose material, the fibers being intertwined with each other to form a network structure and having channels for liquid passage formed therein, characterized in that, The fibers have nodes, and the ratio of the average diameter of the nodes to the average diameter of the fibers is 1.5 to 2.

5. On the outer surface of the nitrocellulose membrane, the distribution density of the nodes is 35 to 70 per (50 μm). 2 .

2. The cellulose nitrate film according to claim 1, characterized in that, There is the following relationship N·D1 among the distribution density of the nodes, the average diameter of the nodes, and the average thickness of the nitrocellulose membrane 2 = L·K1; where N is the node distribution density, D1 is the average diameter of the nodes, L is the thickness of the nitrocellulose membrane, and K1 is a constant, and its value range is 12,000 - 25,000 pieces / μm.

3. The cellulose nitrate membrane according to claim 1, wherein The average diameter between the average fiber diameter D2 and the average SEM pore diameter R1 of the nitrocellulose membrane has the following relationship: Among them, K2 is a constant, and its value range is 0.295 to 0.445 μm 0.5 .

4. The cellulose nitrate film according to claim 1, wherein The value range of the average diameter of the nodes is 3.5 - 5.2 μm, and the average diameter of the fibers is 1.3 - 2.3 μm.

5. The cellulose nitrate membrane according to claim 1, characterized in that, The average SEM pore diameter of the nitrocellulose membrane is 20 - 35 μm, and the specific surface area ratio of the nitrocellulose membrane is 40 - 80%.

6. The cellulose nitrate membrane according to claim 1, wherein The ratio of the surface node coverage area rate of the nitrocellulose membrane to the cross-sectional pore area rate of the nitrocellulose membrane is not greater than 0.

48.

7. The cellulose nitrate membrane according to claim 6, wherein, On the cross-section of the nitrocellulose membrane, the ratio between the average length of the pores in the horizontal direction and the average diameter of the nodes on the surface of the nitrocellulose membrane is 1.5 - 3.

5.

8. The cellulose nitrate membrane according to claim 1, wherein The outer surface node coverage area rate P1, the outer surface pore area rate P2, and the average diameter of the nodes D1 and the average diameter of the fibers D2 have the following relationship: (P2 / P1)∶(D1 / D2) = 0.1 - 0.

2.

9. The nitrocellulose membrane according to claim 8, wherein The value range of the ratio of the outer surface node coverage area rate P1 to the outer surface porosity P2, P2 / P1, is 0.25 - 0.

35.

10. The method for preparing the nitrocellulose membrane according to any one of claims 1 to 9, characterized in that, It includes the following steps: S1. Dissolve nitrocellulose in solvent A to prepare a casting solution. Among them, solvent A contains a combination of an ester or ketone organic solvent and an alcohol solvent. In the casting solution, the mass fraction of nitrocellulose is 20 - 50%; S2. Coat the casting solution on a substrate. In this step, the substrate is first pre-wetted with solvent A; S3. Perform a primary phase separation treatment on the product obtained in step S2 through vapor phase separation to obtain a first intermediate product; S4. Immerse the first intermediate product in an aqueous coagulation bath for phase separation treatment to obtain a second intermediate product; S5. Clean and dry the second intermediate product to complete the preparation; The thickness of the nitrocellulose membrane is 100 - 130 μm.

11. The method for preparing a cellulose nitrate membrane according to claim 10, characterized in that: In step S1, the mass ratio of the casting solution is as follows: nitrocellulose: 20 - 30 parts, surfactant 0.5 - 3 parts, pore former 0.1 - 3 parts, solvent A: 60 parts.

12. The method for preparing a nitrocellulose membrane according to claim 11, wherein, Solvent A is a combination of a branched-chain alkyl ketone or cycloalkyl ketone and a monohydric fatty alcohol.

13. The preparation method of the nitrocellulose membrane according to claim 12, characterized in that, Solvent A is a combination of cyclopentanone or cyclohexanone and a fatty alcohol, where the mass fraction of the fatty alcohol is 25 - 50%.

14. The method for preparing a nitrocellulose membrane according to claim 10, characterized in that, In step S3, the used vapor is an air system mixed with water and isopropanol. The water partial pressure in the vapor is 30 - 60%, and the isopropanol partial pressure is 0.2 - 5%.

15. The method for preparing a nitrocellulose membrane according to claim 14, wherein, In step S3, the temperature is 30 - 50 °C, the air flow rate is 0.5 - 5 m / s, and the contact time is 45 - 120 s.

16. The method for preparing a nitrocellulose membrane according to claim 10, characterized in that, In step S4, the temperature is controlled at 20 - 50 °C, and the treatment time is 30 - 300 s.

17. A protein chromatography test strip obtained by the nitrocellulose membrane described in any one of claims 1 - 9, or by the preparation method of the nitrocellulose membrane described in any one of claims 10 - 16.

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