Pmp hollow fiber membrane for degassing and preparation method and application thereof

Abstract

The present application relates to a kind of PMP hollow fiber membranes for degassing, including main body, non-oriented tortuous passage is formed in main body, main body includes skin layer and support layer, one side of skin layer is outer surface, the side of support layer away from skin layer is inner surface, the other side of skin layer and the other side of support layer transition with continuous fiber;The thickness of skin layer is greater than 0.1 μm;The thickness of hollow fiber membrane is 80-120 μm;Several degassing holes are provided on inner surface, the hole area rate of degassing hole on inner surface is 3%-25%, the SEM average pore size of degassing hole is 10-90nm;The O2 permeation rate of hollow fiber membrane is not higher than 1000ml / (min·bar·m 2 );Under the action of 0.2MPa inlet pressure, the breakthrough time of hollow fiber membrane is greater than 10min.The hollow fiber membrane of the present application has excellent long-term resistance, and also has good degassing efficiency, and the membrane filament has good toughness, and the tensile strength and elongation at break are higher, especially suitable for application in the degassing of active solution such as ink and / or electroplating solution.

Description

Technical Field

[0001] This invention relates to the technical field of membrane materials, and in particular to a PMP hollow fiber membrane for degassing, its preparation method, and its application. Background Technology

[0002] In the semiconductor, food, ink, biotechnology, and pharmaceutical industries, there are specific requirements regarding the oxygen content in liquids. For example, in electroplating solutions used in the semiconductor field, if the oxygen content is too high, it may participate in the electrode reaction during electroplating, interfering with the process. Oxygen can further affect the deposition of metal ions on the surface of the workpiece, leading to defects such as pinholes and pitting in the metal layer. Similarly, in the ink industry, high oxygen content can cause air bubbles during inkjet printing, resulting in printing defects. Furthermore, at high temperatures, some ink components may oxidize with oxygen, potentially causing color differences in the ink printing. Therefore, in these applications, it is crucial to minimize the oxygen content in the liquid. Membrane degassing is widely used in degassing. Compared to flat sheet membranes, hollow fiber membranes have a larger gas-liquid two-phase contact area, enabling them to better reduce the oxygen content in liquids, making them more suitable for degassing various liquids.

[0003] Currently, various hollow fiber degassing membranes exist on the market. For example, US Patent No. 4055696A, concerning porous polypropylene hollow filaments and their preparation method (applied by Mitsubishi Rayon Corporation), discloses a hollow fiber membrane made of PP membrane material. This membrane has a thickness of less than 60 μm and interconnected pores in the thickness direction, exhibiting good degassing efficiency and rate, making it suitable for degassing mild liquids such as ultrapure water. However, PP material is relatively reactive with high surface energy. When encountering reactive solutions (complex liquids containing organic components) containing halogenated compounds, aromatics, and small molecule alcohols, it is prone to swelling, which prevents proper degassing. For instance, during degassing of reactive solutions such as inks and electroplating solutions, the presence of reactive substances like organic matter, strong alkaline or acidic substances in the ink / electroplating solution makes the porous hollow fiber membrane (even if the outer surface of the PP degassing membrane is dense) easily penetrated and broken through by the ink / electroplating solution, thus reducing the service life of the porous hollow fiber membrane.

[0004] Furthermore, Japanese Patent Publication No. JP1995155568A, entitled "Manufacturing Method of Hollow Fiber Heterogeneous Membrane with Non-porous Inner Surface Layer" (applied by DIC Corporation), discloses a hollow fiber membrane prepared from poly(4-methyl-1-pentene) (PMP). The membrane filament has an outer surface pore diameter of approximately 0.05 μm, and the obliquely cut hollow fiber cross-section has a large number of pores with a diameter of approximately 0.03 μm, thus exhibiting good degassing efficiency and degassing rate. Simultaneously, since the membrane filament is made of PMP material, which is more stable than PP material, it can be used relatively stably, even when in contact with water or organic solvents (and their aqueous solutions) containing surfactants, making it suitable for degassing these liquids. However, due to the 0.05 μm pores on the outer surface of the hollow fiber membrane, active solutions such as inks / electroplating solutions can still easily penetrate into the hollow fiber membrane, causing a breach. This results in the PMP degassing membrane failing to function properly, and its service life still cannot meet the needs of practical applications.

[0005] Building upon this, the outer surface of hollow fiber membranes prepared from poly(4-methyl-1-pentene) (PMP) was also made dense. While this improved the long-term durability of the hollow fiber membranes in active solutions (complex liquids containing organic components) such as inks / electroplating solutions, the dense structure of the hollow fiber membranes on both the inner and outer surfaces significantly impacted degassing efficiency, often leading to a substantial reduction in degassing efficiency and hindering effective degassing. Therefore, obtaining hollow fiber membranes with both long-term durability and high degassing efficiency remains a pressing problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a PMP hollow fiber membrane for degassing, its preparation method and application, aiming to obtain a hollow fiber membrane with long-lasting durability and high degassing efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A PMP hollow fiber membrane for degassing includes a body, one side of which is an inner surface facing the inner cavity, and the other side of which is an outer surface. Non-directional tortuous pathways are formed within the body. The body is characterized in that it includes a skin layer and a support layer, one side of which is an outer surface, and the side of which is opposite to the skin layer is an inner surface. The other side of the skin layer and the other side of the support layer are connected by continuous fibers.

[0009] The thickness of the skin layer is greater than 0.1 μm; the thickness of the hollow fiber membrane is 80-120 μm;

[0010] The inner surface has a plurality of degassing pores, the pore area ratio of the degassing pores on the inner surface is 3%-25%, and the SEM average pore diameter of the degassing pores is 10-90nm.

[0011] The O2 permeation rate of the hollow fiber membrane is no higher than 1000 ml / (min·bar·m). 2 );

[0012] Under an inlet pressure of 0.2 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 10 min.

[0013] First, those skilled in the art know that, under normal circumstances, when hollow fiber membranes are used to degas active solutions such as inks / electroplating solutions, the active solutions contain complex components such as halogenated compounds, aromatic hydrocarbons, and small molecule alcohols, making the active solutions such as inks / electroplating solutions highly corrosive to the hollow fiber membranes. Therefore, in the application of degassing active solutions such as inks / electroplating solutions, the long-term durability of hollow fiber membranes is a performance parameter that those skilled in the art highly value during the membrane fiber selection process.

[0014] Because PMP (poly-4-methyl-1-pentene) has relatively stable chemical properties and relatively low surface energy, it has better long-term durability compared to materials such as polyethylene and polypropylene. This makes hollow fiber membranes made from PMP more suitable for degassing applications in active solutions such as inks and electroplating solutions.

[0015] The hollow fiber membrane of this invention comprises a skin layer and a support layer. Specifically, through SEM electron microscopy observation of the cross-sectional structure of the hollow fiber membrane, it was found that the main structure of the hollow fiber membrane mainly includes two regions. The skin layer refers to a certain region (near the outer surface) where the membrane pore size is very small, the porosity is very low, and it is relatively dense. Generally, the porosity in this region is no more than 5%, and gas usually permeates through this region by dissolution-diffusion. The support layer refers to a certain region (near the inner surface) where the membrane pore size is relatively large, the porosity is relatively large, and there are more gas flow paths, which facilitates gas permeation.

[0016] The skin layer of this invention is used to prevent the permeation of active solutions such as inks / electroplating solutions. The thickness of the skin layer is limited to at least 0.1 μm. If the skin layer thickness is less than 0.1 μm, the risk of permeation during degassing of active solutions such as inks / electroplating solutions may increase due to the thin skin layer, meaning the membrane fiber's resilience is still insufficient and cannot meet practical application requirements. Meanwhile, the thickness of the hollow fiber membrane of this invention is limited to 80-120 μm, which is greater than the thickness of ordinary degassing membrane fibers. This allows for increased permeation paths of active solutions such as inks / electroplating solutions through the combined effect of the greater thickness and the non-directional tortuous pathways within the main body, thus appropriately enhancing the resilience of the hollow fiber membrane.

[0017] This invention tests the durability of hollow fiber membranes using a standard isobutanol solution containing methyl orange. Isobutanol, being a small-molecule alcohol with low surface tension, readily permeates the membrane fibers and can be considered a "reactive solution." Therefore, the isobutanol standard solution is chosen to simulate systems with reactive solutions such as ink / electroplating solutions. For example, under an inlet pressure of 0.2 MPa (under certain pressure conditions), the isobutanol solution containing methyl orange is used as the standard solution to fill the outer surface of the hollow fiber membrane. A breakthrough time test is then performed on the hollow fiber membrane. If the time for breakthrough and permeation is greater than or equal to 10 minutes, the hollow fiber membrane is considered to have excellent durability. The hollow fiber membrane of this invention is made of P... Made of MP material, the membrane fibers exhibit excellent long-term durability due to the combined effects of a large skin layer thickness, overall thickness, and non-directional tortuous pathways. Simultaneously, such durability tests and results also reflect the membrane structure to a certain extent; that is, a membrane structure that meets these test results is required for degassing active solutions such as inks / electroplating solutions. Furthermore, methyl orange (a color developer) is added to the solution. The purpose of adding methyl orange is to stain the membrane and facilitate observation of whether the hollow fiber membrane has been permeated. Since the surface tension of methyl orange is not significantly different from that of isobutanol, its addition amount is relatively arbitrary. The conventional addition amount is 5% of the isobutanol volume, and the specific addition amount can be adjusted adaptively to facilitate observation of staining breakthrough.

[0018] In applications involving active solutions such as ink / electroplating solution degassing, a high oxygen content is typically required. For example, in electroplating solutions, oxygen can further affect the deposition process of metal ions on the surface of the workpiece, leading to defects such as pinholes and pitting in the metal layer. Additionally, under high-temperature conditions, some components in the ink may undergo oxidation reactions with oxygen in the ink, potentially causing color differences in the ink printing. Furthermore, since oxygen content is easier to detect than gases like nitrogen, dissolved oxygen meters are generally used to measure the degassing liquid. In this invention, the oxygen permeation rate is used to characterize the degassing rate of the hollow fiber membrane.

[0019] Under normal circumstances, when the degassing rate of a hollow fiber membrane is low (the amount of gas removed within a certain time is relatively small), its final degassing efficiency will also be affected, resulting in the inability to remove gases (mainly oxygen) from the corresponding solution, thus reducing its practical application value. In this invention, the O2 permeation rate of the hollow fiber membrane is no higher than 1000 ml / (min·bar·m). 2 While the degassing rate of the membrane fibers is relatively low, research has shown that when the inner surface of the membrane fibers has several degassing pores with an average SEM pore size of 10-90 nm and a pore area ratio of 3%-25%, the overall deoxygenation efficiency of the membrane fibers remains high, reaching over 80%. The degassing liquid (active solution) is virtually bubble-free, ensuring the normal use of the active solution. Researchers hypothesize that the low degassing rate is due to the thicker skin layer and overall membrane thickness of the membrane fibers. However, the degassing efficiency is also related to the material's inherent properties and the overall membrane thickness. Under the influence of PMP material, with a suitable membrane thickness, and with the synergistic effect of appropriate pore size and number of degassing pores on the inner surface, various gases (mainly oxygen) in the active solution can be removed as much as possible, achieving a "slow but steady" degassing effect. In other words, although the degassing rate of this PMP degassing membrane is low, its degassing efficiency is high. This clearly breaks the bias of existing technologies and is innovative.

[0020] Due to the high rigidity of PMP material, PMP membrane fibers may be prone to breakage during transportation and fabrication of degassing components. We were pleasantly surprised to find that when the inner surface of the membrane fiber has a suitable pore size and number of degassing pores, combined with the membrane fiber thickness and a relatively low deoxygenation rate (the deoxygenation rate reflects the overall membrane structure, primarily in terms of porosity), the membrane fiber exhibits excellent toughness, i.e., a high elongation at break. This allows for various processing methods, making the fabrication process convenient and greatly simplifying various processing techniques.

[0021] In summary, the hollow fiber membrane of the present invention not only has excellent long-term durability but also good degassing efficiency. At the same time, the membrane fibers have good toughness, high tensile strength and elongation at break, making it particularly suitable for degassing of active solutions such as inks and / or electroplating solutions.

[0022] The degassing pores in this invention may have two morphologies when observed by SEM: one is a relatively regular circular pore, and the other is a pore that is similar to an ellipse. The SEM average pore diameter of the degassing pores claimed in this invention specifically refers to the diameter of the relatively regular circular pores and the length of the minor axis of the elliptical pores.

[0023] A dissolved oxygen reading of less than 2 ppm and a change in the reading of the dissolved oxygen meter of less than 1% within 5 minutes can be considered as indicating that there are essentially no bubbles in the degassed liquid. This is a generally accepted and conventional testing indicator in the industry. The oxygen permeation rate of this invention is determined by subjecting one side of the membrane sample to the test gas (oxygen) at a temperature of 25°C, a pressure of 0.1 bar, and a membrane sample area of ​​0.1 square meters. The test gas (oxygen) is supplied into the inner cavity of the hollow fiber membrane. The volumetric flow rate of the gas permeating through the membrane wall is measured using a flow meter (KOFLOC / 4800, Japan). The test is performed three times from inside the membrane to outside and three times from outside the membrane to inside, and the average value is taken. This average value is the oxygen permeation rate of the membrane, and the unit of oxygen permeation rate is ml / (min·bar·m). 2 ).

[0024] In this invention, both the skin layer and the support layer are composed of the same material, and the two layers are combined into a whole structure, which is formed directly during the membrane preparation process. In the transition from the skin layer to the support layer, there is only a change in the membrane structure. Therefore, the membrane prepared by this invention is an asymmetric membrane. In contrast, for example, there is a composite membrane, which has a multi-layer structure. It is made by applying a dense layer, which serves as the support layer, onto a porous, often microporous support layer or support membrane in a separate process step. The materials constituting the support layer and the skin layer in a composite membrane are often different.

[0025] In this invention, the non-directional tortuous pathways refer to randomly oriented groove structures and / or discretely distributed pore structures, and each non-directional tortuous pathway is interconnected; and the fibers forming the porous membrane structure are continuous. It can be understood that "continuous" means that essentially all the fibers are interconnected as a whole and are formed integrally without the need for additional adhesives or the like to connect them. Unless torn by external force, the network of fibers cannot be separated from each other. That is, the hollow fiber membrane of this invention is a single-layer membrane structure, rather than a composite membrane structure.

[0026] In this invention, the SEM average pore size and pore area ratio of the degassing pores on the inner surface of the hollow fiber membrane can be characterized by scanning electron microscopy (SEM), followed by measurement and calculation using computer software (such as Matlab, NIS-Elements, etc.) or manually. During membrane fabrication, the pore size and distribution are generally uniform and consistent in the direction perpendicular to the membrane thickness (planar if the membrane is flat; perpendicular to the radius if it is hollow fiber). Therefore, the overall pore size and pore area ratio on a given plane can be reflected by the pore size and pore area ratio in a specific region. In actual measurement, the inner surface of the membrane fibers can be characterized using an electron microscope to obtain the corresponding SEM image. Since the pore size and pore distribution on the inner surface are generally uniform, a specific area, such as 1 μm, can be selected. 2 (1μm x 1μm) or 100μm 2 (10μm x 10μm) or, the specific area size depends on the actual situation. Then, use appropriate computer software or manual measurement to determine the membrane pore size and pore area ratio on that area. Perform several tests and take the average value to obtain the SEM average pore diameter and pore area ratio of the degassing pores on the inner surface of the membrane. The skin thickness on the cross section can also be obtained by a similar method. Of course, those skilled in the art can also obtain the above parameters by other measurement methods. The above measurement methods are for reference only.

[0027] Furthermore, the outer surface is a dense surface, and the surface energy of the outer surface is 15-27 mN / m;

[0028] The O2 permeation rate of the hollow fiber membrane is 50-600 ml / (min·bar·m). 2 );

[0029] Under an inlet pressure of 0.4 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 30 min.

[0030] The outer surface of this invention is a dense surface. The synergistic effect of the dense surface and the skin layer of a certain thickness further increases the difficulty for the liquid to be degassed to penetrate the hollow fiber membrane. The dense surface acts as a "barrier" for the liquid to be degassed to penetrate into the hollow fiber membrane. At the same time, the surface energy of the outer surface is limited to 15-27 mN / m, keeping the surface energy at a relatively low level, which increases the difficulty for active solutions such as ink / electroplating solutions to penetrate the dense surface. After the liquid to be degassed penetrates the dense surface and enters the hollow fiber membrane, the skin layer further blocks the liquid, hindering and increasing the resistance of the liquid to be degassed within the hollow fiber membrane. The difficulty of internal permeation within the hollow fiber membrane gives it excellent long-term durability. Even under higher inlet pressures, the hollow fiber membrane of this invention maintains a relatively long breakthrough time, demonstrating superior long-term durability. This allows the hollow fiber membrane to be used in higher-pressure working environments for degassing reactive solutions that easily permeate the membrane fibers, thus broadening its application range. Furthermore, due to its dense outer surface structure, the overall oxygen permeation rate of the membrane is not high. Studies have shown that under this membrane structure, the O2 permeation rate is 50-600 ml / (min·bar·m). 2 Surprisingly, it was discovered that the membrane still had good deoxygenation efficiency, that is, it completely removed the gas from the active solution, ensuring that the active solution could be used efficiently for a long time.

[0031] In this invention, "dense" refers to a surface area ratio (i.e., pore area: outer surface area) of the outer surface that is no greater than 1% when photographed under a scanning electron microscope at 50,000x magnification. This means that there are two situations: either the pore structure cannot be observed or a very small number of pore structures can be observed. The surface energy test method of the hollow fiber membrane outer surface of this invention is to test the hollow fiber membrane with a dyne pen. A 5cm long ink strip is brushed onto the hollow fiber membrane with the dyne pen, and it is observed whether more than 90% of the ink strip shrinks and forms ink droplets within 2 seconds until it stops shrinking and ink droplets appear. The surface energy of the ink tested in this way is the surface energy of the outer surface of the membrane.

[0032] Furthermore, the outer surface has several silver-like cracks, the SEM width of the cracks is no greater than 20 nm, and the SEM average length of the cracks is 10-100 nm.

[0033] The O2 permeation rate of the hollow fiber membrane is 200-800 ml / (min·bar·m). 2 );

[0034] Under an inlet pressure of 0.2 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 30 min.

[0035] In some hollow fiber membranes prepared by this invention, the outer surface has several crazing-like cracks. Compared with a dense outer surface structure, the oxygen permeation rate of hollow fiber membranes with crazing-like cracks on the outer surface is relatively increased. When the outer surface of the membrane fibers has crazing-like cracks, by controlling the SEM width of the cracks to be no greater than 20 nm and the average SEM length to be 10-100 nm, and the O2 permeation rate of the membrane to be 200-800 ml / (min·bar·m), 2 Under the combined effect of these factors, the membrane exhibits good overall durability and high degassing efficiency, allowing for relatively rapid gas removal, making it particularly suitable for applications requiring fast degassing. Furthermore, the applicant unexpectedly discovered that when the outer surface of the hollow fiber membrane has silver crazing cracks of this length, compared to hollow fiber membranes with a dense outer surface, the former exhibits better toughness in the membrane fibers, resisting fiber breakage during transport or fabrication of degassing components.

[0036] Furthermore, the support layer contains porous fibers for forming a porous structure, and the average SEM diameter of the porous fibers is 10-100 nm; a flow path for gas circulation is formed between adjacent porous fibers, and the SEM width of the flow path is no greater than 150 nm.

[0037] This invention, by defining the SEM average diameter of porous fibers and the flow path between adjacent porous fibers, allows the SEM average diameter of porous fibers to reflect, to some extent, the size of each solid part within the support layer, while the flow path between adjacent porous fibers to some extent reflects, to some extent, the size of each virtual part within the support layer. This indirectly reflects that the porous fibers are relatively densely distributed within the support layer, and the relatively dense distribution of the porous fibers also results in relatively good mechanical strength of the support layer. On the other hand, during long-term and continuous degassing of the hollow fiber membrane with active solutions such as inks / electroplating solutions, the impact of corrosion on the porous fibers on the mechanical strength, tensile strength, and elongation at break of the hollow fiber membrane is also reduced to some extent.

[0038] The SEM width of the flow path in this invention is no greater than 150 nm. While providing a flow channel for gas removal, the relatively small SEM width of the flow path also reduces the flow path of active solutions such as ink / electroplating solutions within the support layer after penetrating into the hollow fiber membrane. This increases the difficulty of penetration of active solutions such as ink / electroplating solutions into the support layer, thus enhancing the long-term durability of the hollow fiber membrane to some extent. The cross-sectional characteristics of the hollow fiber membrane are obtained by argon ion cutting, liquid nitrogen quenching, and then observation of the cross-section of the hollow fiber membrane using an electron microscope.

[0039] Furthermore, the ratio of the average SEM diameter of the porous fiber to the average SEM width of the flow path is 1:(0.7-3); the density of the porous fiber is 100-400 fibers / μm. 2 .

[0040] This invention, by limiting the density of porous fibers, reflects the number of porous fibers distributed on the cross-section to a certain extent, indicating that the porous fibers are densely distributed on the cross-section. Combining the ratio of the average diameter of the porous fibers in SEM images to the average width of the flow paths in SEM images directly reflects the dense distribution of porous fibers, thus endowing the hollow fiber membrane with good resistance to corrosive gas erosion. Simultaneously, it also indirectly reflects that the distribution of flow paths within the hollow fiber membrane is also numerous and dense, resulting in more and denser paths for gas removal and flow within the hollow fiber membrane. Consequently, although the degassing rate of the hollow fiber membrane of this invention is not high, the final degassing efficiency is high, overcoming the technical prejudice that "a low degassing rate in hollow fiber membranes will also affect their degassing efficiency."

[0041] Meanwhile, the limitation of the ratio of the average diameter of the porous fiber in the SEM to the average width of the flow path in the SEM allows the hollow fiber membrane to have high degassing efficiency and good resistance. This enables the hollow fiber membrane to be used for a long time and continuously in the degassing process of active solutions such as ink / electroplating solution. Even after some corrosive gases introduced during the degassing process erode the hollow fiber membrane, the hollow fiber membrane still has good mechanical strength and long-term resistance.

[0042] If the ratio of the average diameter of the porous fiber SEM to the average width of the flow path SEM is too small, it indicates that the average width of the flow path is too large or the average diameter of the porous fiber SEM is too small. If the average width of the flow path SEM is too large, active solutions such as ink / electroplating solution may easily penetrate the support layer after breaking through the skin layer, thus affecting the durability of the hollow fiber membrane. If the average diameter of the porous fiber SEM is too small, some corrosive gases introduced during the degassing process may erode the hollow fiber membrane, which will greatly affect the mechanical strength of the hollow fiber membrane and reduce it significantly.

[0043] If the ratio of the average diameter of the porous fiber in the SEM to the average width of the flow path in the SEM is too large, it indicates that the average width of the flow path is too small or the average diameter of the porous fiber in the SEM is too large. If the average width of the flow path is too small, it may lead to a low degassing rate of the hollow fiber membrane, which may affect the normal degassing operation. If the average diameter of the porous fiber in the SEM is too large, it may lead to a high proportion of porous fiber in the cross-section, which will reduce the number of flow paths that provide degassing channels, and may affect the degassing efficiency of the hollow fiber membrane and cause it to decrease.

[0044] The oxygen permeation rate of the hollow fiber membrane in this invention is not high, but the final deoxygenation efficiency is relatively high, reaching over 80%. The applicant analyzed the cross-sectional structure of the hollow fiber membrane using SEM and concluded that the reason may be that the pore area ratio of the support layer in the thickness direction of the hollow fiber membrane is different from that of the inner surface, and the former is greater than the latter. This results in the gas movement rate within the support layer of the hollow fiber membrane being greater than the gas exiting from the pores on the inner surface during the degassing process of active solutions such as ink / electroplating solutions. Ultimately, this manifests macroscopically as a low degassing rate of the hollow fiber membrane. At the same time, the relatively large pore area ratio of the support layer in the thickness direction of the hollow fiber membrane ensures the gas movement rate within the support layer.

[0045] Based on this, as the degassing process continues, because the gas velocity within the hollow fiber membrane support layer is relatively greater than the gas velocity exiting from the inner surface pores, gas "accumulation" may occur along the thickness direction of the hollow fiber membrane. This may create a temporary pressure difference between the inside of the hollow fiber membrane support layer and the inner surface pores. This pressure difference further propels the gas to exit from the inner surface pores. Due to this pressure difference effect, when testing the degassing efficiency of the hollow fiber membrane within a specified time, the degassing efficiency of the hollow fiber membrane of this invention exhibits a high value, reaching over 80%.

[0046] Furthermore, the average SEM diameter of the porous fibers near the cortex is smaller than that of the porous fibers far from the cortex, and the average SEM diameter of the porous fibers varies in gradient from 0.1 to 1.5 nm / μm.

[0047] The gradient of the average SEM diameter of porous fibers is calculated as follows: (average SEM diameter of porous fibers far from the cortex - average SEM diameter of porous fibers close to the cortex) / thickness of the support layer.

[0048] Research has revealed that the thickness of porous fibers within the support layer is not constant. In some membrane fibers, those further away from the skin layer (i.e., near the inner surface) are relatively thicker, while those closer to the skin layer are relatively thinner. In this invention, the variation in the average SEM diameter of the porous fibers is used to represent the change in the thickness of the porous fibers within the membrane support layer. Therefore, this value is obtained by first subtracting the average SEM diameter of the porous fibers further away from the skin layer from the average SEM diameter of the porous fibers closer to the skin layer, and then dividing this difference by the thickness of the support layer. In this invention, the region closer to the skin layer refers to the area within the cross-section of the support layer 3 μm from the interface between the skin layer and the support layer as the starting line. The region further away from the skin layer refers to the area within the cross-section of the support layer 3 μm from the inner surface as the starting line.

[0049] In this invention, the gradient of the average diameter variation of porous fibers directly reflects the trend of a gradual increase in the average diameter of the porous fibers along the thickness direction of the hollow fiber membrane (from the outer surface to the inner surface of the hollow fiber membrane). Further, combined with the density of the porous fibers, it can be seen that in the cross-section, the porous fibers in the hollow fiber membrane of this invention initially exhibit smaller pore sizes and a relatively dense distribution, followed by larger pore sizes and a relatively dispersed distribution. Firstly, through SEM observation of the hollow fiber membrane cross-section, the region with smaller and denser pore sizes of the porous fibers is located near the skin layer. This region supplements the skin layer's ability to prevent the penetration of active solutions such as ink / electroplating solutions, minimizing the likelihood of these solutions penetrating the support layer and further penetrating the inner surface. This slows down the penetration rate of active solutions such as ink / electroplating solutions within the support layer to a certain extent, appropriately increasing the durability of the hollow fiber membrane. Secondly, the larger and more dispersed pores of the porous fibers are located far from the cortex, which increases the movement rate of the degassed gas within the support layer during degassing, thus giving the hollow fiber membrane a good degassing rate and efficiency. At the same time, the coarser porous fibers far from the cortex (closer to the inner surface) also enhance the mechanical strength of the inner surface, allowing the degassing pores on the inner surface to withstand a greater pressure difference, thus minimizing the risk of pore collapse due to excessive pressure difference during degassing.

[0050] Furthermore, the average SEM width of the flow path near the skin layer is smaller than that of the flow path far from the skin layer, and the gradient of the average SEM width of the flow path is 0.05-1.2 nm / μm;

[0051] The gradient of the average SEM width of the flow path is calculated as follows: (average SEM width of the flow path farther from the skin layer - average SEM width of the flow path closer to the skin layer) / thickness of the support layer.

[0052] Research has revealed that the flow path size within the support layer is not constant. In some membrane fibers, the flow paths further away from the skin layer (i.e., near the inner surface) are relatively larger, while those closer to the skin layer are relatively smaller. In this invention, the variation in flow path size within the membrane support layer is represented by the gradient of the average SEM diameter of the flow paths. Therefore, this value is obtained by first subtracting the average SEM width of the flow paths further away from the skin layer from the average SEM width of the flow paths closer to the skin layer, and then dividing this difference by the thickness of the support layer. In this invention, the region closer to the skin layer refers to the area within the cross-section of the support layer with a distance of 3 μm from the interface between the skin layer and the support layer as the starting line. The region further away from the skin layer refers to the area within the cross-section of the support layer with a distance of 3 μm from the starting line (inner surface) as the starting line.

[0053] The flow path variation gradient in this invention reflects a gradual increase in the SEM average width diameter of the flow path from the outer surface to the inner surface of the hollow fiber membrane. The flow path width of the support layer near the skin layer is relatively small, which supplements the anti-permeation capability of active solutions such as ink / electroplating solutions at the skin layer. This minimizes the likelihood of these solutions penetrating the support layer and further penetrating the inner surface, thus slowing down the permeation rate and appropriately increasing the hollow fiber membrane's resilience. Conversely, the flow path of the support layer farther from the skin layer is relatively large, amplifying the gas removal velocity in the latter half of the degassing process within the support layer, resulting in good degassing rate and efficiency for the hollow fiber membrane.

[0054] Furthermore, the thickness of the skin layer is 0.15-3 μm, and the thickness ratio of the skin layer to the support layer is 1:40-1:500;

[0055] The O2 permeation rate of the hollow fiber membrane is 100-500 ml / (min·bar·m). 2 );

[0056] Under an inlet pressure of 0.4 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 60 min.

[0057] Preferably, the hollow fiber membrane of the present invention has a thicker skin layer, and the thickness ratio of the skin layer to the support layer is limited within the above-mentioned range, which can give the hollow fiber membrane better resistance, making it difficult for active solutions such as ink / electroplating solution to penetrate and break through the hollow fiber membrane during degassing applications. At the same time, it can make the hollow fiber membrane have both good degassing rate and high degassing efficiency. In addition, the hollow fiber membrane also has good mechanical strength.

[0058] If the thickness ratio of the cortex to the support layer is too large, it indicates that the cortex is too thick or the support layer is too thin. If the cortex is too thick, the degassing rate of the hollow fiber membrane may be extremely low, thus affecting the normal operation of the degassing process. If the support layer is too thin, reactive gases such as ink / electroplating solution may easily penetrate the support layer after passing through the cortex (the porosity of the support layer is much higher than that of the cortex), which will affect the durability of the hollow fiber membrane to some extent. On the other hand, if the support layer is too thin, it will also result in poor mechanical strength (mainly toughness) of the hollow fiber membrane.

[0059] If the ratio of the thickness of the skin layer to the thickness of the support layer is too small, it indicates that the thickness of the skin layer is too small or the thickness of the support layer is too large. If the thickness of the skin layer is too small, the hollow fiber membrane may have a poor ability to prevent the penetration of active solutions such as ink / electroplating solution, thus affecting the long-term durability of the hollow fiber membrane.

[0060] Furthermore, the skin layer has a plurality of dense fibers, the dense fibers being elongated structures, and the dense fibers being stacked and fused together in a first direction; the average SEM length of the dense fibers in the first direction is 80-2800 nm; and the average SEM length in the second direction is 20-500 nm.

[0061] The first direction is parallel to the thickness direction of the hollow fiber membrane, and the second direction is perpendicular to the thickness direction of the hollow fiber membrane.

[0062] This invention utilizes the stacking and fusing of dense fibers in the first direction. Compared to having only a single dense fiber in the first direction, the stacking and fusing of multiple dense fibers increases the sealing path at the skin layer. When active solutions such as ink / electroplating solutions penetrate, they not only need to travel the length of the dense fibers in the first direction, but may also need to travel the length between the stacked and fused dense fibers in the first direction (i.e., the length of the dense fibers in the second direction). To a certain extent, this increases the path that the liquid flows through when penetration occurs, thereby improving the anti-penetration performance of the skin layer.

[0063] Since the direction of liquid penetration is along the first direction, the longer the average SEM length of the dense fiber in the first direction, the more difficult it is to penetrate. The selection of the average SEM length in the second direction ensures the mechanical strength of the dense fiber and avoids the situation where the dense fiber is too long and too thin. If the dense fiber is too long and too thin, it will reduce the mechanical strength of the dense fiber and the formed skin. The appropriate length of the dense fiber in the second direction makes the dense fiber have good mechanical strength, and it is also reflected in the dense distribution of the dense fiber in the skin, which makes the overall skin have good mechanical strength. When the hollow fiber membrane is used for a long time and continuously in the field of degassing of active solutions such as ink / electroplating solution, even after being eroded by corrosive gases introduced during the degassing process, the skin can still have good mechanical strength and anti-penetration ability.

[0064] The lengths of the dense fibers in the first and second directions can be measured in the following way: after the hollow fiber membrane is subjected to argon ion cutting and quenched with liquid nitrogen, the cross-section of the hollow fiber membrane skin is observed using SEM electron microscopy, and the measurement is performed using computer software (such as Matlab, NIS-Elements, etc.) or manually, and the corresponding calculations are performed.

[0065] Furthermore, the ratio of the average SEM length of the dense fiber in the first direction to the average SEM length in the second direction is 2.5-20.

[0066] The ratio of the average SEM length of dense fiber in the second direction to the average SEM diameter of porous fiber is (1.1-5):1.

[0067] This invention endows dense fibers with better mechanical strength and impermeability by limiting the ratio of the average SEM length of the dense fibers in the first and second directions. The longer the dense fibers are in the first direction, the more difficult it is for active solutions such as ink / electroplating solutions to penetrate. The length of the dense fibers in the second direction reflects the density of the dense fibers on the dense skin layer, which increases the path required for active solutions such as ink / electroplating solutions to penetrate, making it more difficult for ink to leak between adjacent dense fibers.

[0068] This invention, through research, discovered that controlling the ratio of the average SEM length of dense fibers in the first and second directions to a suitable range reflects the characteristics of long and densely distributed dense fibers. This makes it difficult for liquid to leak along the length of the dense fibers or between the gaps between adjacent dense fibers, ensuring the mechanical strength and impermeability of the skin layer. At the same time, combined with the stacking and fusing of dense fibers along the first direction, it minimizes the impact of excessively long and thin dense fibers on the mechanical strength of the skin layer, and to a certain extent increases the path for liquid to penetrate within the skin layer, thereby improving the impermeability of the skin layer while ensuring its mechanical strength.

[0069] This invention, through research, discovered that controlling the ratio of dense fibers to porous fibers within a suitable range further reflects the size of the dense fibers in the cortex and the porous fibers in the support layer. This indicates that the dense fibers in the cortex are wider, providing better support and mechanical strength to the cortex, while the porous fibers, while supporting the support layer, also provide channels for gas removal, ensuring the mechanical strength of the support layer and enabling the hollow fiber membrane to have high degassing efficiency.

[0070] Furthermore, the inner surface includes several sparsely distributed degassing pores in a dispersed region, the pore area ratio of which is no greater than 5%; the SEM average area of ​​the dispersed region is 0.1-0.5 μm. 2 The sum of the areas of the dispersed regions accounts for 0.01-0.4 of the area of ​​the inner surface.

[0071] Furthermore, on the inner surface of the hollow fiber membrane, a plurality of degassing holes are regularly arranged to form a degassing zone for degassing; the length of the degassing zone is consistent with the circumferential direction of the hollow fiber membrane; the width of the degassing zone is consistent with the length direction of the hollow fiber membrane.

[0072] The average length of the degassing zone in SEM is 100-400 nm, and the average length of the degassing zone is greater than the average width of the degassing zone.

[0073] In this invention, the pore area ratio of the dispersed zone is no greater than 5%. The dispersed zone serves as a connector to adjacent degassing zones and, to a certain extent, hinders liquid penetration. This invention reflects the dispersion of the dispersed zones across the entire inner surface by limiting the ratio of the sum of the dispersed zones to the inner surface area. If the proportion of the dispersed zone area is large, it indicates low porosity on the inner surface, which is detrimental to gas removal in that area. Conversely, if the proportion of the dispersed zone area is too small, it indicates a large distribution of degassing zones on the inner surface, which are essentially hollow, potentially resulting in poor mechanical strength, toughness, and support performance. By controlling the area of ​​the dispersed zone within a suitable range, this invention ensures that the dispersed zone provides good support during degassing while maintaining good tensile strength and elongation at break of the hollow fiber membrane under long-term resistance to corrosive gases in active solutions such as inks / electroplating solutions.

[0074] Meanwhile, the area of ​​the dispersion zone can reflect the distance between adjacent degassing zones to some extent. If the area of ​​a single dispersion zone is too large, it reflects that the distance between adjacent degassing zones is too large, which is reflected in the poor uniformity of the distribution of degassing pores on the inner surface. This makes it difficult for the degassing gas to be removed from the inner surface, thus leading to a decrease in the degassing rate.

[0075] Because the overall pore area of ​​the inner surface is relatively small, a uniform pore distribution on the inner surface could lead to a low gas removal rate. However, by utilizing the distribution of degassing and dispersion zones, the degassing zone primarily increases the degassing rate; the dispersion zone acts as a "vent" for gas removal, further increasing the removal rate. Therefore, although the inner surface pore area and overall porosity of this invention are small, the degassing and dispersion zones result in a higher degassing rate for the hollow fiber membrane compared to other membranes under similar conditions. In this invention, the average length of the degassing zone is 100-400 nm, and the average length is greater than the average width, resulting in both a good gas removal rate and good mechanical strength.

[0076] The areas of the dispersion zone and the degassing zone can be characterized by scanning electron microscopy of the inner surface of the membrane, and then measured and calculated using computer software (such as Matlab, NIS-Elements, etc.) or manually.

[0077] Furthermore, on the inner surface, some adjacent degassing pores are separated by supporting fibers; the average SEM length of the supporting fibers is 30-90 nm; the average SEM width of the supporting fibers is 10-50 nm.

[0078] Furthermore, the aspect ratio of the supporting fiber is 1.5-6;

[0079] The ratio of the average SEM width of the supporting fiber to the average SEM pore diameter of the degassing pores is 0.25-0.8.

[0080] The ratio of the average SEM length of the degassing zone to the average SEM width of the degassing zone is (1.5-6):1.

[0081] This invention, by controlling the supporting fibers between adjacent degassing pores and the SEM average length-to-width ratio of the supporting fibers within a suitable range, can further enhance the mechanical strength of the degassing zone and improve the stability of the degassing pores. If the supporting fibers are too long, it indicates a large long-axis diameter of the degassing pores. A large long-axis diameter of the degassing pores can lead to a significant decrease in the mechanical strength of the pores during the degassing process of active solutions such as inks / electroplating solutions, and it can also make the supporting fibers more prone to breakage, thus failing to support and enhance the mechanical strength and stability of the degassing zone. Conversely, if the supporting fibers are too short, it indicates a small long-axis diameter of the degassing pores. In this case, the presence of the supporting fibers may prevent gas from passing through the degassing pores effectively, thereby reducing the degassing rate of the hollow fiber membrane.

[0082] If the width of the support fiber is too large, it will provide better support for the pores. However, if the average pore diameter of the degassing pores on the inner surface is not high, the excessively thick support fiber will occupy the degassing space, which will not be conducive to the degassing process and will reduce the degassing rate. On the other hand, if the width of the support fiber is too small, the support fiber may be prone to breakage after being eroded for a long time, and thus it will not be able to provide good support for the degassing zone.

[0083] This invention controls the average length and average width of the supporting fibers within a suitable range, which can provide better support for the degassing pores on the inner surface, improve the tensile strength and elongation at break of the hollow fiber membrane, and maintain the stability of the pores on the inner surface under long-term resistance to corrosive gases, thereby increasing the service life of the hollow fiber membrane.

[0084] In this invention, the aspect ratio of the supporting fiber determines the stability of the supporting fiber. If the aspect ratio of the supporting fiber is too small, the supporting fiber will have poor support for the degassing pores. If the aspect ratio of the supporting fiber is too large, the supporting fiber may be long and thin, resulting in low strength and easy breakage under long-term erosion.

[0085] This invention controls the ratio of the average width of the support fiber to the average diameter of the degassing pores within a suitable range. When the ratio is too low, the corrosive gas introduced during the continuous degassing process may erode the support fiber, causing adjacent degassing pores to merge due to the erosion of the support fiber, thereby reducing the mechanical strength of the degassing zone. When the ratio is too high, the thickness of the support fiber may occupy too large a proportion of the degassing zone, which may interfere with the degassing efficiency of the degassing zone.

[0086] Furthermore, the density of degassing pores on the inner surface is 10-80 pores / μm. 2 And / or, the crack density on the outer surface is 10-50 cracks / μm. 2 .

[0087] If the degassing pore density on the inner surface is too high, it means that the pore area ratio on the inner surface will further increase. On the one hand, the pore area ratio on the inner surface represents the proportion of the virtual part. If the proportion of the virtual part is too large, it means that the proportion of the solid part on the inner surface is too small, which leads to poor mechanical strength on the inner surface of the hollow fiber membrane. On the other hand, a further increase in the pore area ratio on the inner surface may increase the possibility of active solutions such as ink / electroplating solution penetrating and breaking through the inner surface, which may affect the durability of the hollow fiber membrane. If the degassing pore density on the inner surface is too low, it means that the channels for the degassed gas to leave the inner surface are too small, which leads to a low degassing rate of the hollow fiber membrane, and may even affect the degassing efficiency of the hollow fiber membrane (even though the hollow fiber membrane cross-sectional structure of the present invention can improve the degassing efficiency of the hollow fiber membrane).

[0088] If the crack density on the outer surface is too high, it means that there are too many pathways for the degassing gas to flow through. When the hollow fiber membrane is subjected to long-term and continuous degassing of active liquids such as ink / electroplating solution, it may erode the structure at the cracks, which may damage the anti-permeability function of the cracks and the skin layer, and affect the long-term durability of the hollow fiber membrane. If the crack density on the outer surface is too low, it means that there are too few pathways for the degassing gas to flow through, which will not be able to effectively increase the degassing rate of the hollow fiber membrane.

[0089] This invention controls the pore density of the inner surface of the hollow fiber membrane within a relatively suitable range, enabling the hollow fiber membrane to have both a good degassing rate and high degassing efficiency. Furthermore, it was surprisingly discovered that a suitable pore density on the inner surface can endow the hollow fiber membrane with good mechanical strength and good toughness. This invention also controls the density of cracks on the outer surface within a relatively suitable range, enabling the hollow fiber membrane to have both a good degassing rate and high degassing efficiency, as well as long-term resistance to active solutions such as inks and electroplating solutions.

[0090] Furthermore, the hollow fiber membrane has a tensile strength of not less than 200 CN and an elongation at break of 30-150%.

[0091] The hollow fiber membrane has a deoxygenation efficiency greater than 80%.

[0092] When the pure water flow rate is 150 ml / min, the pressure loss of the hollow fiber membrane is no greater than 0.9 kPa.

[0093] The hollow fiber membrane in this invention has good tensile strength and elongation at break, and its deoxygenation efficiency is also good, reaching over 80%, indicating that there are basically no bubbles in the degassing liquid (active solution). At the same time, the pressure loss of the hollow fiber membrane is also small, making it suitable for long-term and continuous degassing of active solutions such as ink / electroplating solutions.

[0094] The tensile strength and elongation at break of hollow fiber membranes can be tested using the following method: At room temperature, the hollow fiber membrane sample is stretched uniformly using a stretching machine (stretching speed of 50 mm / min, distance between upper and lower clamps of 30 mm) until the hollow fiber membrane breaks, thereby measuring the tensile strength and elongation at break. This is repeated 3 times, and the average value is taken; this average value is the final tensile strength and elongation at break value of the membrane.

[0095] The deoxygenation efficiency of the hollow fiber membrane can be tested using the following method: Using the hollow fiber membrane of this invention as raw material, assemble a membrane with an area of ​​0.65 m². 2 The components are assembled, and a dissolved oxygen meter, water circuit, and assembly are connected for testing. The water circuit is used to transport the degassing liquid (such as active solutions like ink / electroplating solution), the assembly is used to degas the degassing liquid, and the dissolved oxygen meter is used to detect the oxygen content of the degassing liquid after degassing. The degassing liquid, which is deionized water, flows outside the membrane at a temperature of 25°C. Vacuum purging is performed inside the membrane.

[0096] Step 1: Detect the initial oxygen content of the degassed liquid. Pump the degassed liquid into the water circuit. At this time, turn off the vacuum equipment to maintain atmospheric pressure inside the membrane. After passing through the module (without degasing), the degassed liquid passes through the dissolved oxygen meter, maintaining a flow rate of approximately 1.8 GLH. Observe the changes in the dissolved oxygen reading on the dissolved oxygen meter in real time. Once the dissolved oxygen meter reading stabilizes (the change in the dissolved oxygen meter reading is less than 1% within 5 minutes), read the dissolved oxygen reading. 始 .

[0097] Step 2: Detect the final oxygen content of the degassed liquid. Based on Step 1, turn on the vacuum equipment to perform vacuum purging on the inner layer of the membrane to degauge the liquid. Maintain a vacuum reading of -0.094 MPa (50 torr) during vacuum purging. Observe the changes in dissolved oxygen readings on the dissolved oxygen meter in real time. Once the dissolved oxygen meter reading stabilizes (the change in the dissolved oxygen meter reading is less than 1% within 5 minutes), degassed liquid is considered to have reached equilibrium, and the dissolved oxygen reading on the dissolved oxygen meter is read as O. 终 The deoxygenation efficiency is calculated using the following formula:

[0098] The pressure loss test of the hollow fiber membrane can be performed using the following method: using the hollow fiber membrane of the present invention as raw material, it is assembled in a 1-inch × 5.5-inch membrane contactor, and pure water is used to test the pressure loss of the hollow fiber membrane. When the pure water flow rate is 150 ml / min, the pressure loss generated after the pure water passes through the 1-inch × 5.5-inch membrane contactor is tested, and the pressure loss of the hollow fiber membrane is obtained.

[0099] Furthermore, a method for preparing a PMP hollow fiber membrane for degassing includes the following steps:

[0100] S1, spinning, where PMP material is melt-extruded in a die to form a molded product with an inner and outer surface, the die extrusion temperature is 245-290℃; the melt index of the PMP material is 8-15 g / min@(260℃, 5kg), and its crystallinity is 40%-75%;

[0101] S2, Air section pre-crystallization: The molded product is placed in an air section for pre-crystallization. The temperature of the air section is 40-100℃, and the pre-crystallization time is 0.1-0.6s.

[0102] S3, air-cooled crystallization: the molded product obtained in step S2 is cooled by blowing air to obtain nascent fibers, wherein the blowing temperature is 10-40℃ and the blowing speed is 20-50m / min;

[0103] S4, First heat setting, the nascent fibers are subjected to the first heat setting treatment. The first heat setting temperature is not higher than 90℃, and a heat-set semi-finished product is obtained.

[0104] S5, cold drawing to form holes, the heat-set semi-finished product is cold drawn to obtain the cold-drawn semi-finished product, wherein the cold drawing temperature is 20-40℃ and the cold drawing elongation rate is 10%-60%;

[0105] S6, Second heat setting: The cold-drawn semi-finished product undergoes a second heat setting process. The second heat setting temperature is not higher than 150℃, resulting in a hollow fiber membrane.

[0106] As is well known, poly(4-methyl-1-pentene) (PMP) is more stable than PP, making PMP degassing membranes more resistant to the erosion of active solutions. However, due to its stable properties, PMP has poorer crystallinity than PP (PMP is characterized by low crystallinity), which can easily lead to dense inner and outer surfaces of the resulting degassing membrane. Consequently, the overall deoxygenation efficiency of the membrane is too low, failing to meet the requirements of practical applications. In the preparation of the PMP membrane in this invention, the first step is to melt and extrude the PMP material in a die to form a molded product with an inner and outer surface. During the extrusion process, a cavity-forming fluid is simultaneously introduced. Common cavity-forming fluids are inert gases, such as nitrogen and argon. The introduction of the cavity-forming fluid can effectively prevent the molded product from concave deformation, ensuring that the film has a relatively uniform wall thickness.

[0107] As is well known, the properties of raw materials are fundamental to the surface properties and pore morphology of membrane fibers. Studies have shown that parameters such as the crystallinity and melt index of raw materials have a significant impact on the performance of film formation. In this invention, the crystallinity of PMP material is 40-75% (measured by DSC). However, due to the low crystallinity of PMP, if the crystallinity of the raw material PMP is too low, it will lead to excessively low porosity of the film (such as a dense inner surface), which in turn reduces the gas permeation rate and degassing efficiency. Therefore, selecting PMP raw materials with appropriate crystallinity is beneficial to ensuring that the film has high degassing efficiency and excellent mechanical properties.

[0108] Melt flow index (MFI) is a numerical value indicating the fluidity of a material during processing. A higher MFI value indicates better processing fluidity, and vice versa. However, when the MFI is low, the resistance to molecular chain arrangement increases, the activation energy required for molecular chain diffusion to the crystal nucleus increases, resulting in a decrease in the ability of molecular chains to arrange themselves regularly, thus reducing crystallinity and making it impossible to obtain a film with high deoxidation efficiency. When the MFI is high, the plasticity of the material deteriorates, making it difficult to form and easily leading to low uniformity of characteristics such as pore size in the formed film. This invention limits the MFI of PMP material to 8-15 g / min@(260℃, 5kg), giving PMP material better processing fluidity and more uniform film thickness. At the same time, under the action of stretching attraction, PMP material is given a certain orientation. With appropriate crystallinity and die extrusion temperature controlled at 245-290℃, the inner and outer surface thickness of the film filaments during the spinning process of PMP material is also more uniform, which is more conducive to the formation of a film with relatively uniform pore size and excellent degassing efficiency.

[0109] Meanwhile, by controlling the die extrusion temperature to 245-290℃ (the melting point of PMP is around 240℃, so the die extrusion temperature must be at least 5℃ higher than the melting point), the flow viscosity of the polymer melt is significantly affected by temperature; generally, viscosity decreases as temperature increases. When the die extrusion temperature is too low, the viscosity of the PMP melt increases, increasing the resistance of the extrusion die, thereby increasing the energy consumption of the extrusion process. It also increases the thickness of the prepared film (easily leading to excessive film thickness), hindering expansion and stretching, and thus affecting the tensile strength of the film. When the die extrusion temperature is too high, it not only easily leads to PMP... Thermal degradation of PMP causes the main chain of PMP to break at the weakest bond in the middle, thereby reducing its molecular weight and significantly decreasing its mechanical properties, which in turn reduces the mechanical properties of the membrane. It also tends to increase the chain segment mobility of polymer molecules, expand the "free volume" of the melt, increase the fluidity of the melt, and greatly reduce its viscosity, resulting in an excessively thin membrane, which in turn affects the degassing rate and degassing efficiency. In this invention, the crystallinity, melt index, and die extrusion temperature of the material are all closely related to the PMP raw materials and the corresponding preparation process, rather than being independent. Only under the combined effect of these parameters can the ideal membrane structure be obtained.

[0110] Based on this, step S2 of this invention performs air-segment pre-crystallization on the molded product. The main purpose of the air segment is to control the slow cooling of the molded product and increase the crystallization time, thereby increasing the formation of more crystal nuclei in the internal region of the molded product (the region that will form the support layer in the future). This is because PMP material itself has low crystallinity. If the temperature of the air segment is too high (the controlled temperature is closely related to the melting point and glass transition temperature of PMP) and / or the time the molded product stays in the air segment is too short, then the number of crystal nuclei in the internal region of the molded product will be too small after the air segment pre-crystallization and partial cooling crystallization. This invention prepares the corresponding film structure through melt stretching, where the number and size of crystal nuclei are key to the formation of the size and number of pores (which in turn affects the overall film structure). If the crystal volume in the internal region of the molded product is too small and the number is too small, then after the stretching and pore-forming stage, the final film pores will be too small and the number will be too small (one obvious characteristic is that the inner surface is also very dense). Almost non-porous films have low deoxidation efficiency and poor fiber toughness. When the air section temperature is too low or the air section residence time is too long, it leads to the formation of more crystal nuclei inside the molded product, and even a significant drop in the overall temperature of the molded product. This results in a thin skin layer (or even no skin layer) and excessively large pores in the support layer, greatly reducing the film's resilience. Active solutions can quickly penetrate the fiber, making the fiber unsuitable for degassing active solutions like inks / electroplating solutions. In this invention, by controlling the air section temperature to 40-100℃ and the pre-crystallization time to 0.1s-0.6s, the combined effect of this air section temperature and pre-crystallization time allows the molded product sufficient time for pre-crystallization in the air section. This results in a relatively large number of crystal nuclei forming in the internal region of the molded product, leading to an ideal pore structure on the inner surface of the final formed fiber and even in the support layer. This ensures high deoxidation efficiency and good fiber toughness.

[0111] Next, the molded product is subjected to air-cooling crystallization, resulting in a relatively fast cooling rate on the outer surface. This leads to fewer crystal nuclei forming near the outer surface, resulting in a skin layer with low porosity near the outer surface during the stretching and pore-forming stage. Simultaneously, steps S2 and S3 of this invention generate sufficient crystal nuclei in the internal region of the molded product, resulting in a larger porous structure after stretching. However, due to the low crystallinity of PMP, the pore size formed by the membrane fibers is not very large. At the same time, the relatively rapid cooling of the outer surface of the membrane fibers results in fewer crystal nuclei near the outer surface, which in turn leads to a relatively thick skin layer on the outer surface of the membrane fibers. Due to the presence of the dense skin layer, the overall oxygen permeation rate of the membrane fibers is not high. Also, due to the presence of the dense skin layer, the overall resistance of the membrane fibers is good, and active solutions such as inks / electroplating solutions have difficulty penetrating and breaking through the membrane fibers.

[0112] Studies have found that when the initial heat-setting temperature is controlled below the melting point of PMP but more than 150°C above it, the crystal nuclei within the heat-set semi-finished product will not be too large. Even if a large number of pore structures are formed after stretching and pore formation, the diameter of the pore structures is relatively small, ensuring the hollow fiber membrane's durability while improving its degassing efficiency. Furthermore, the initial low-temperature, long-duration heat-setting process can effectively eliminate structural defects in the nascent fibers, improve their structural integrity, and reduce the possibility of excessive tensile stress concentration during subsequent stretching and pore formation.

[0113] Preferably, the temperature of the first heat setting in step S4 is 30-70℃, and the time of the first heat setting is 60-180h;

[0114] Since the hollow fiber membrane of this invention is used in active solutions such as inks / electroplating solutions, excessively high crystallinity can lead to large porosity within the membrane, thus affecting its long-term durability. Therefore, it is necessary to further control the temperature of the first heat setting. In this invention, the temperature of the first heat setting should not be too high, preferably 30-70°C. If the temperature of the first heat setting is too high, it may cause the formation of more and larger crystal nuclei within the heat-set semi-finished product. After the stretching and pore-forming process, the aforementioned structure may form more and larger membrane pore structures, resulting in poor durability of the hollow fiber membrane and failing to meet the requirements of practical applications.

[0115] This invention involves cold drawing the membrane fibers after the first heat setting, which pulls open the crystal nuclei inside the heat-set semi-finished product and forms a porous structure. By controlling the cold drawing temperature and cold drawing elongation within a suitable range, and combining this with the effect of not performing hot drawing to expand the pores, the hollow fiber membrane has a relatively large thickness and a small pore structure on the inner surface and cross-section. This gives the hollow fiber membrane excellent resistance in applications with active solutions such as inks / electroplating solutions, while also having high degassing efficiency. In addition, it also endows the hollow fiber membrane with good mechanical strength and toughness.

[0116] Preferably, the temperature for the second heat setting in step S6 is 100-140℃, and the time for the second heat setting is 4-15 minutes.

[0117] In this invention, the temperature of the second heat setting should not exceed 150°C, and is preferably controlled at 100-140°C. Studies have found that controlling the temperature of the second heat setting at 100-140°C greatly avoids the melting of the boundary between adjacent pore structures due to excessively high heat setting temperature after the membrane fibers are cold-drawn into pores, which may eventually lead to the fusion of adjacent pore structures and affect the mechanical strength and degassing rate of the hollow fiber membrane. In addition, the second heat setting can effectively eliminate the stress residue in the stretching and pore-forming stage without damaging the membrane pore structure.

[0118] Furthermore, in S1, the PMP material and the elastomer are first mixed evenly, and then melt-extruded; the elastomer consists only of olefinic substances containing only carbon and hydrogen elements, and the surface energy of the elastomer is not greater than 30mN / m, and the mass ratio between the elastomer and the PMP material is 5-30%.

[0119] Due to the high rigidity of PMP materials, direct melt spinning of PMP materials may easily lead to filament breakage. Adding an elastomer can further mitigate the excessive rigidity of PMP materials, making them easier to spin. On the other hand, since the surface tension of active solutions such as inks / electroplating solutions is relatively low, this invention further limits the surface energy of the elastomer to no more than 30 mN / m. This ensures that the surface energy of the resulting filaments after the elastomer and PMP materials are mixed and melted is also at a relatively low level, thus guaranteeing the durability of the filaments when applied to active solutions such as inks / electroplating solutions. The elastomer is an olefinic substance, similar in structure to PMP, resulting in good compatibility between the elastomer and PMP materials. The elastomer can be POE-based substances, pentene-based elastomers, etc., and the amount of elastomer added should not be excessive. Excessive elastomer addition may affect the crystallization behavior of the PMP material itself, potentially preventing the formation of a good porous structure in the final filaments, thereby affecting the degassing efficiency and durability of the filaments.

[0120] Furthermore, the stretch ratio of the die head is 10-50, the length of the air section is 200-1000mm, preferably 300-500mm, and the atmosphere of the air section is air or nitrogen.

[0121] In this invention, the die stretching ratio has a significant impact on the tensile stress on the fiber. The larger the die stretching ratio, the greater the tensile stress on the fiber. This invention controls the die stretching ratio to be 10-50, thereby enabling the nascent fiber to have a better crystallization distribution. Since the crystallinity of PMP material is relatively low, this invention further limits and maintains the length of the air section, allowing the molded product to undergo sufficient pre-crystallization in the air section. This results in the molded product having a good number of crystal nuclei, providing more membrane pore structures for the stretching and pore-forming stage.

[0122] Furthermore, in step S4, the temperature for the first heat setting is 30-70℃, and the time for the first heat setting is 60-180h.

[0123] In step S6, the temperature for the second heat setting is 100-140℃, and the time for the second heat setting is 4-15 minutes.

[0124] Furthermore, the present invention also provides an application of a PMP hollow fiber membrane for degassing, wherein the hollow fiber membrane is used in various ink degassing and / or electroplating solution degassing.

[0125] In summary, the present invention has at least one of the following beneficial technical effects:

[0126] 1. The PMP hollow fiber membrane of the present invention, through the combination of PMP material, appropriate skin thickness and relatively thick hollow fiber membrane, endows the hollow fiber membrane with good long-term resistance to corrosion by active solutions such as ink / electroplating solution; at the same time, through the synergistic effect of PMP material, appropriate membrane thickness and degassing pores with appropriate pore size and number on the inner surface, the hollow fiber membrane of the present invention, although the degassing rate is not high, has a high degassing efficiency, which can reach more than 80%, breaking the prejudice of the prior art.

[0127] 2. The hollow fiber membrane of the present invention has a suitable porous fiber diameter and density and a suitable average flow path width in its cross-section, which makes the hollow fiber membrane of the present invention have a high degassing efficiency despite a low degassing rate. At the same time, the hollow fiber membrane has high degassing efficiency and good resistance, which allows it to be used for a long time and continuously in the degassing process of active solutions such as ink / electroplating solution. Even after some corrosive gases introduced during the degassing process erode the hollow fiber membrane, the hollow fiber membrane still has good mechanical strength and long-term resistance. Attached Figure Description

[0128] The present invention will be further described below with reference to the accompanying drawings:

[0129] Figure 1 The image shown is a scanning electron microscope (SEM) image of the cross-section of the hollow fiber membrane prepared in Example 1, with a magnification of 15K×.

[0130] Figure 2 The image shown is a scanning electron microscope (SEM) image of the cross-section of the hollow fiber membrane prepared in Example 1, near the outer surface, with a magnification of 67K×.

[0131] Figure 3 The image shown is a scanning electron microscope (SEM) image of the outer surface of the hollow fiber membrane prepared in Example 5, with a magnification of 50K×.

[0132] Figure 4 The image shown is a scanning electron microscope (SEM) image of the outer surface of the hollow fiber membrane prepared in Example 7, with a magnification of 50K×.

[0133] Figure 5 The image shown is a scanning electron microscope (SEM) image of the inner surface of the hollow fiber membrane prepared in Example 5, with a magnification of 20K×. Detailed Implementation

[0134] The present invention will be further described in detail below with reference to the embodiments. Unless otherwise specified, the raw materials and equipment used to prepare the filter membrane in the following embodiments can be purchased commercially.

[0135] Example 1

[0136] A method for preparing a PMP hollow fiber membrane for degassing includes the following steps:

[0137] S1, spinning, PMP material is melted and extruded through a die to form a molded product with an inner surface and an outer surface, wherein the die stretch ratio is 20, the die extrusion temperature is 250℃, the melt index of the PMP material is 10g / min@(260℃, 5kg), and the crystallinity is 50%.

[0138] S2, Air Section Pre-crystallization: The molded product is placed in an air section (under nitrogen atmosphere) for pre-crystallization. The length of the air section is 300 mm, the temperature of the air section is 50 °C, and the pre-crystallization time is 0.2 s.

[0139] S3, air-cooled crystallization, the molded product is air-cooled and crystallized by blowing air, the temperature of the cooling airflow is 20℃, and the blowing speed is 45m / min;

[0140] S4, First heat setting: The nascent fibers are subjected to the first heat setting treatment to obtain a heat-set semi-finished product. The first heat setting temperature is 40℃ and the first heat setting time is 150h.

[0141] S5, cold drawing to form holes, the heat-set semi-finished product is cold drawn to obtain the cold-drawn semi-finished product, wherein the cold drawing temperature is 20℃ and the cold drawing elongation is 20%.

[0142] S6, Second heat setting: The cold-drawn semi-finished product undergoes a second heat setting process to obtain a hollow fiber membrane; the second heat setting temperature is 100℃ and the second heat setting time is 15min.

[0143] Examples 2-4

[0144] The difference between Examples 2-4 and Example 1 lies in the different process parameters, as shown in Table 1-1.

[0145] Table 1-1

[0146] Die extrusion temperature / ℃ 250 260 275 265 Die head stretch ratio 20 35 25 40 Melt flow index (g / min @ (260℃, 5kg)) 10 8 12 15 Crystallinity / % 50 55 60 65 Air section temperature / ℃ 50 65 65 80 Air section length / mm 300 500 600 900 Pre-crystallization time / s 0.2 0.3 0.35 0.55 Blower temperature / ℃ 20 30 25 35 Airflow speed (m / min) 45 35 40 25 First heat setting temperature / ℃ 40 60 50 70 First heat setting time / h 150 95 125 65 Cold drawing temperature / ℃ 20 25 28 35 Cold drawing elongation rate / % 20 30 35 45 Second heat setting temperature / ℃ 100 105 115 125 Second heat setting time / min 15 13 11 8

[0147] Example 5

[0148] A method for preparing a PMP hollow fiber membrane for degassing includes the following steps:

[0149] S1, spinning: PMP material and elastomer are mixed evenly and then melt-extruded through a die to form a molded product with an inner and outer surface. The die stretch ratio is 30, the die extrusion temperature is 250℃, the melt index of the PMP material is 10 g / min@(260℃, 5kg), and the crystallinity is 55%. The elastomer is polyisoprene elastomer (cis-1,4-polyisoprene), and the mass ratio of polyisoprene elastomer to PMP is 5%.

[0150] S2, Air Section Pre-crystallization: The molded product is placed in an air section (under nitrogen atmosphere) for pre-crystallization. The length of the air section is 600 mm, the temperature of the air section is 60 °C, and the pre-crystallization time is 0.4 s.

[0151] S3, air-cooled crystallization, the molded product is air-cooled and crystallized by blowing air, the temperature of the cooling airflow is 30℃, and the blowing speed is 30m / min;

[0152] S4, First heat setting: The nascent fibers are subjected to the first heat setting treatment to obtain a heat-set semi-finished product. The first heat setting temperature is 55℃ and the first heat setting time is 110h.

[0153] S5, cold drawing to form holes, the heat-set semi-finished product is cold drawn to obtain the cold-drawn semi-finished product, wherein the cold drawing temperature is 25℃ and the cold drawing elongation is 35%;

[0154] S6, Second heat setting: The cold-drawn semi-finished product undergoes a second heat setting process to obtain a hollow fiber membrane; the second heat setting temperature is 105℃ and the second heat setting time is 13min.

[0155] Examples 6-8

[0156] The difference between Examples 6-8 and Example 5 lies in the different process parameters, as shown in Tables 1-2. The amount of elastomer added in Examples 6-8 is 10%, 20%, and 30%, respectively. The polyisoprene elastomers used in Examples 5 and 6 are cis-1,4-polyisoprene and trans-1,4-polyisoprene, respectively. The elastomer in Example 7 is ExxonMobil's POE elastomer, and the elastomer in Example 8 is ExxonMobil's POP elastomer.

[0157] Table 1-2

[0158] Die extrusion temperature / ℃ 255 265 270 260 Die head stretch ratio 30 40 35 45 Melt flow index (g / min @ (260℃, 5kg)) 10 12 14 11 Crystallinity / % 55 60 60 65 Air section temperature / ℃ 60 80 75 95 Air section length / mm 600 850 800 1000 Pre-crystallization time / s 0.4 0.5 0.45 0.5 Blower temperature / ℃ 30 35 30 40 Airflow speed (m / min) 30 20 30 20 First heat setting temperature / ℃ 55 65 60 70 First heat setting time / h 110 75 90 70 Cold drawing temperature / ℃ 25 30 35 40 Cold drawing elongation rate / % 35 40 50 60 Second heat setting temperature / ℃ 105 120 130 140 Second heat setting time / min 13 10 6 4

[0159] Comparative Example 1

[0160] The difference between Comparative Example 1 and Example 1 lies in the different process parameters, as shown in Tables 1-3.

[0161] Comparative Example 2

[0162] The difference between Comparative Example 2 and Example 1 is that the process parameters are different and a hot drawing process was performed between cold drawing and the second heat setting. The specific parameters are shown in Tables 1-3.

[0163] Table 1-3

[0164] Die extrusion temperature / ℃ 255 250 Die head stretch ratio 25 15 Melt flow index (g / min @ (260℃, 5kg)) 12 9 Crystallinity / % 50 55 Air section temperature / ℃ 30 50 Air section length / mm 100 300 Pre-crystallization time / s 0.03 0.2 Blower temperature / ℃ 20 25 Airflow speed (m / min) 40 45 First heat setting temperature / ℃ 40 45 First heat setting time / h 145 140 Cold drawing temperature / ℃ 25 20 Cold drawing elongation rate / % 20 20 Hot drawing temperature / ℃ / 180 Thermal stretching ratio / % / 120 Second heat setting temperature / ℃ 105 100 Second heat setting time / min 14 15

[0165] Membrane structure parameter detection

[0166] The PMP hollow fiber membranes prepared in Examples 1-8 and Comparative Examples 1-2 were characterized by scanning electron microscopy (Hitachi S-5500). The outer surface, inner surface and cross-section of the PMP hollow fiber membrane were selected as the observation objects. The specific detection and measurement results are shown in Tables 2-1 and 2-2.

[0167] Table 2-1

[0168]

[0169]

[0170] Table 2-2

[0171]

[0172]

[0173] Membrane performance parameter testing

[0174] 1.1 Tensile strength and elongation at break tests

[0175] After testing, the hollow fiber membranes prepared in Examples 1-8 showed a tensile strength of not less than 200 CN and an elongation at break of 30-150%, which means they all have high tensile strength and elongation at break, and can meet the needs of industrialization.

[0176] 1.2 Pressure Loss Test

[0177] After testing, the hollow fiber membranes prepared in Examples 1-8 all had a pressure loss of no more than 0.9 kPa when the pure water flow rate was 150 ml / min, which means they all had a small pressure loss and could meet the industrial requirements.

[0178] 1.3 Oxygen permeation rate test

[0179] The test results are shown in Table 3.

[0180] 1.4 Deoxygenation efficiency test

[0181] The test results are shown in Table 3.

[0182] 1.5 Tolerance Test

[0183] The test results are shown in Table 3.

[0184] 1.6 Surface Energy Test of External Surface

[0185] The test results are shown in Table 3.

[0186] Table 3

[0187]

[0188] As can be seen from the above, the hollow fiber membranes prepared in Examples 1-8 of the present invention all have high degassing efficiency, all reaching over 80%. At the same time, the hollow fiber membranes all have high tolerance, making them suitable for use in active solutions such as inks / electroplating solutions and have a long service life. In contrast, the hollow fiber membrane of Comparative Example 1 has low degassing efficiency and degassing rate. Although the oxygen permeation rate of the hollow fiber membrane of Comparative Example 2 is high, the deoxygenation efficiency may also be related to factors such as membrane structure. The hollow fiber membrane does not have high deoxygenation efficiency. In addition, the hollow fiber membrane of Comparative Example 2 has poor tolerance and cannot meet the actual application requirements, making it unsuitable for use in active solutions such as inks / electroplating solutions.

[0189] The preferred embodiments of the present invention have been described in detail above. However, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A PMP hollow fiber membrane for degassing, comprising a main body, one side of which is an inner surface facing the inner cavity, and the other side of which is an outer surface, wherein non-directional tortuous pathways are formed within the main body, characterized in that, The main body includes a skin layer and a support layer. One side of the skin layer is the outer surface, and the side of the support layer opposite to the skin layer is the inner surface. The other side of the skin layer and the other side of the support layer are connected by continuous fibers. The thickness of the skin layer is greater than 0.1 μm; the thickness of the hollow fiber membrane is 80-120 μm; The inner surface has a plurality of degassing pores, the pore area ratio of the degassing pores on the inner surface is 3%-25%, and the SEM average pore diameter of the degassing pores is 10-90nm. The O2 permeation rate of the hollow fiber membrane is no higher than 1000 ml / (min·bar·m). 2 ); Under an inlet pressure of 0.2 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test the breakthrough time of the hollow fiber membrane. The breakthrough time of the hollow fiber membrane was greater than 10 min. The support layer contains porous fibers for forming a porous structure, and a flow path for gas circulation is formed between adjacent porous fibers. The average SEM width of the flow path near the skin layer is smaller than that of the flow path far from the skin layer, and the gradient of the average SEM width of the flow path is 0.05-1.2 nm / μm; The gradient of the average SEM width of the flow path = (average SEM width of the flow path far from the skin layer - average SEM width of the flow path close to the skin layer) / support layer thickness; The outer surface satisfies any one of the following: (1) The outer surface is a dense surface, and the pore area ratio of the outer surface is not greater than 1%; (2) The outer surface has several silver-like cracks, and the SEM width of the cracks is no more than 20 nm.

2. The PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The outer surface is a dense surface, and the surface energy of the outer surface is 15-27 mN / m; The O2 permeation rate of the hollow fiber membrane is 50-600 ml / (min·bar·m). 2 ); Under an inlet pressure of 0.4 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 30 min.

3. The PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The outer surface has several silver-like cracks, the SEM width of the cracks is no greater than 20 nm, and the SEM average length of the cracks is 10-100 nm. The O2 permeation rate of the hollow fiber membrane is 200-800 ml / (min·bar·m). 2 ); Under an inlet pressure of 0.2 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 30 min.

4. The PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The average diameter of the porous fiber in SEM is 10-100 nm; the width of the flow path in SEM is no greater than 150 nm.

5. A PMP hollow fiber membrane for degassing according to claim 4, characterized in that, The ratio of the average SEM diameter of the porous fiber to the average SEM width of the flow path is 1:(0.7-3); the density of the porous fiber is 100-400 fibers / μm. 2 .

6. The PMP hollow fiber membrane for degassing according to claim 4, characterized in that, The average SEM diameter of the porous fibers near the cortex is smaller than that of the porous fibers far from the cortex, and the average SEM diameter of the porous fibers varies in gradient from 0.1 to 1.5 nm / μm. The gradient of the average SEM diameter of porous fibers is calculated as follows: (average SEM diameter of porous fibers far from the cortex - average SEM diameter of porous fibers close to the cortex) / thickness of the support layer.

7. The PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The thickness of the skin layer is 0.15-3 μm, and the thickness ratio of the skin layer to the support layer is 1:40-1:500; The O2 permeation rate of the hollow fiber membrane is 100-500 ml / (min·bar·m). 2 ); Under an inlet pressure of 0.4 MPa, the hollow fiber membrane was filled with an isobutanol solution containing methyl orange as a standard solution to test its breakthrough time. The breakthrough time of the hollow fiber membrane was greater than 60 min.

8. The PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The skin layer has a plurality of dense fibers, which are elongated structures and are stacked and fused together in a first direction; the average SEM length of the dense fibers in the first direction is 80-2800 nm; and the average SEM length in the second direction is 20-500 nm. The first direction is parallel to the thickness direction of the hollow fiber membrane, and the second direction is perpendicular to the thickness direction of the hollow fiber membrane.

9. A PMP hollow fiber membrane for degassing according to claim 8, characterized in that, The ratio of the average SEM length of the dense fiber in the first direction to the average SEM length in the second direction is 2.5-20. The ratio of the average SEM length of dense fiber in the second direction to the average SEM diameter of porous fiber is (1.1-5):

1.

10. A PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The inner surface includes several sparsely distributed degassing pores, with the porosity of the dispersed pores not exceeding 5%; the SEM average area of ​​the dispersed pores is 0.1-0.5 μm. 2 The sum of the areas of the dispersed regions accounts for 0.01-0.4 of the area of ​​the inner surface.

11. A PMP hollow fiber membrane for degassing according to claim 1, characterized in that, In the circumferential direction of the inner surface of the hollow fiber membrane, a plurality of degassing holes are regularly arranged to form a degassing zone for degassing; the length direction of the degassing zone is consistent with the circumferential direction of the hollow fiber membrane; the width direction of the degassing zone is consistent with the length direction of the hollow fiber membrane. The average length of the degassing zone in SEM is 100-400 nm, and the average length of the degassing zone is greater than the average width of the degassing zone.

12. A PMP hollow fiber membrane for degassing according to claim 11, characterized in that, On the inner surface, some adjacent degassing pores are separated by supporting fibers; the average SEM length of the supporting fibers is 30-90 nm; the average SEM width of the supporting fibers is 10-50 nm.

13. A PMP hollow fiber membrane for degassing according to claim 12, characterized in that, The aspect ratio of the supporting fiber is 1.5-6; The ratio of the average SEM width of the supporting fiber to the average SEM pore diameter of the degassing pores is 0.25-0.

8. The ratio of the average SEM length of the degassing zone to the average SEM width of the degassing zone is (1.5-6):

1.

14. A PMP hollow fiber membrane for degassing according to claim 3, characterized in that, The density of degassing pores on the inner surface is 10-80 pores / μm. 2 And / or, the crack density on the outer surface is 10-50 cracks / μm. 2 .

15. A PMP hollow fiber membrane for degassing according to claim 1, characterized in that, The hollow fiber membrane has a tensile strength of not less than 200 CN and an elongation at break of 30-150%. The hollow fiber membrane has a deoxygenation efficiency greater than 80%. When the pure water flow rate is 150 ml / min, the pressure loss of the hollow fiber membrane is no greater than 0.9 kPa.

16. A method for preparing a PMP hollow fiber membrane for degassing according to any one of claims 1-15, characterized in that, The process includes the following steps: S1, spinning, where PMP material is melt-extruded through a die to form a molded product with an inner and outer surface; the die extrusion temperature is 245-290℃; the melt index of the PMP material is 8-15 g / min@260℃ / 5kg, and its crystallinity is 40%-75%. S2, Air section pre-crystallization: The molded product is placed in an air section for pre-crystallization. The temperature of the air section is 40-100℃, and the pre-crystallization time is 0.1s-0.6s. S3, air-cooled crystallization: the molded product obtained in step S2 is cooled by blowing air to obtain nascent fibers, wherein the blowing temperature is 10-40℃ and the blowing speed is 20-50m / min; S4, First heat setting, the nascent fibers are subjected to the first heat setting treatment. The first heat setting temperature is not higher than 90℃, and a heat-set semi-finished product is obtained. S5, cold drawing and hole forming: The heat-set semi-finished product is cold-drawn to obtain a cold-drawn semi-finished product. The cold drawing temperature is 20-40℃ and the elongation rate is 10%-60%. S6, Second heat setting: The cold-drawn semi-finished product undergoes a second heat setting process. The second heat setting temperature is not higher than 150℃, resulting in a hollow fiber membrane.

17. The method for preparing a PMP hollow fiber membrane for degassing according to claim 16, characterized in that, In S1, the PMP material and the elastomer are first mixed evenly, and then melt-extruded; the elastomer consists only of olefinic substances containing only carbon and hydrogen elements, and the surface energy of the elastomer is not greater than 30mN / m; the mass ratio between the elastomer and the PMP material is 5%-30%.

18. The method for preparing a PMP hollow fiber membrane for degassing according to claim 16, characterized in that, The drawing ratio of the die head is 10-50; the length of the air section is 200-1000 mm; the atmosphere of the air section is air or nitrogen.

19. The method for preparing a PMP hollow fiber membrane for degassing according to claim 18, characterized in that, The length of the air section is 300-500mm.

20. The method for preparing a PMP hollow fiber membrane for degassing according to claim 16, characterized in that, In step S4, the temperature for the first heat setting is 30-70℃, and the time for the first heat setting is 60-180h. In step S6, the temperature for the second heat setting is 100-140℃, and the time for the second heat setting is 4-15 minutes.

21. The application of a PMP hollow fiber membrane for degassing according to any one of claims 1-15, characterized in that, The PMP hollow fiber membrane is used for degassing various inks, and / or for degassing electroplating solutions.

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