Interlocking structure of a separation membrane support and a method for manufacturing the same

Abstract

The application belongs to the field of non-woven material and membrane separation technology, and particularly relates to a separation membrane support with an interlocking structure and a preparation method thereof. The method first introduces low-crystallinity and sulfonated modified ultrafine polyester fibers into the compact layer slurry, and introduces skeleton polyester fibers and polyester thermal bonding fibers into the skeleton layer slurry; then a double-layer wet web is formed by using a double-channel wet laying device, a gradient increasing negative pressure is applied to one side of the skeleton layer, controlled migration of the ultrafine fibers from the compact layer to the skeleton layer pores is realized by the viscous drag effect of the directional high-speed water flow on the ultrafine fibers, and a gradient transition interlocking interface layer is formed; finally, the interlayer structure is locked by sectionally hot pressing through the coarse pressing section and the fine pressing section by using the plastic deformation of the low-crystallinity fibers and the melting welding of the bonding fibers, and then is cooled and shaped. The prepared separation membrane support has excellent interlayer peeling strength, ultra-low surface roughness, high air permeability, wide adaptability and high safety of the preparation process.

Description

Technical Field

[0001] This invention specifically relates to an interlocking separation membrane support and its preparation method, belonging to the field of nonwoven materials and membrane separation technology. Background Technology

[0002] In the preparation of reverse osmosis (RO) and nanofiltration (NF) membranes, the support not only plays a physical role but also directly affects the coating quality and service life of the membrane. Patent application CN1819866A discloses a method for preparing a wet-process and spunbond composite separation membrane support. Spunbond filaments can indeed improve the physical and mechanical properties and structural stability of the membrane support material to a certain extent. Although a double-layer support can be prepared by hot rolling at temperatures above 220°C and under high pressure, problems remain, such as fewer bonding points between the spunbond material and the wet process, and low bonding strength, leading to easy delamination between layers.

[0003] To achieve both high throughput and surface smoothness, the industry commonly employs a double-layer composite nonwoven material as the support system. In this structure, the upper layer typically uses ultrafine fibers to enhance surface smoothness, while the lower layer uses relatively coarse-denier fibers to provide the necessary mechanical strength and maintain high throughput. However, existing double-layer supports still face the following technical challenges in practical applications:

[0004] (1) Insufficient interfacial bonding: Due to the significant difference in fiber diameter between the upper ultrafine fibers and the lower coarse denier fibers, traditional composite processes cannot achieve sufficient physical entanglement and structural interlocking at the interface. This weak interfacial bonding state easily leads to interlayer delamination, especially under dynamic impacts such as high-pressure backwashing, which affects the integrity and service life of the support structure.

[0005] (2) Mismatch in rheological behavior: When using single-channel mixed flow, the ultrafine fibers are prone to flocculation due to their large specific surface area, while the coarse fibers tend to settle. The mismatch in rheological behavior between the two can easily lead to stratification and uneven distribution, resulting in poor uniformity of the membrane and affecting the overall performance of the membrane.

[0006] In summary, the existing technology has obvious shortcomings. Therefore, developing a method that can effectively enhance the interfacial bonding between heterogeneous fibers, optimize the uniformity of the network, and ensure the high flux performance of the membrane has become a key problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an interlocking separation membrane support and its preparation method. This separation membrane support has excellent interlayer peel strength, ultra-low surface roughness, high air permeability, wide adaptability, and high safety in its preparation process.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for preparing an interlocking separation membrane support, the preparation method comprising the following steps:

[0009] S1. Preparation of heterogeneous slurry: Prepare a first fiber suspension for constructing the dense layer and a second fiber suspension for constructing the skeleton layer, respectively;

[0010] S2. Dual-channel layered web formation: A dual-channel wet web formation device is used to supply the first fiber suspension and the second fiber suspension from two independent headboxes to the web formation curtain, and lay them sequentially on the web formation curtain to form a double-layer wet web structure.

[0011] S3, Vacuum negative pressure composite: The double-layer wet web structure is transferred to a vacuum dehydration device. Negative pressure is applied to one side of the skeleton layer, driving water to carry some of the ultrafine fibers in the dense layer to migrate to the skeleton layer and embed into its pores, forming a gradient transition interlocking interface layer, while completing dehydration.

[0012] S4. Pre-drying and stepped hot pressing for shaping: The dehydrated wet web is pre-dried, followed by segmented hot pressing and cooling shaping.

[0013] Furthermore, in step S1, the first fiber suspension is composed of 60-90 wt% ultrafine polyester fiber and 10-40 wt% sulfonated modified ultrafine polyester fiber, based on the solid phase mass content.

[0014] Furthermore, in step S1, the crystallinity of the ultrafine polyester fiber is ≤40%, the average diameter is 0.5μm~3μm, and the length is 3mm~8mm.

[0015] Furthermore, in step S1, the sulfonated modified ultrafine polyester fiber has a sulfonation degree of 3~8%, an average diameter of 0.5μm~3μm, and a length of 3mm~8mm.

[0016] Furthermore, in step S1, the second fiber suspension is composed of 70-85 wt% skeleton polyester fiber and 15-30 wt% polyester thermal bonding fiber, based on the solid phase mass content.

[0017] Furthermore, in step S1, the linear density of the skeleton polyester fiber is 1.5~4.0 dtex, the diameter is 12μm~20μm, and the length is 5mm~12mm.

[0018] Furthermore, in step S1, the linear density of the polyester thermal bonding fiber is 1.5~5.0 dtex.

[0019] Furthermore, in step S1, the polyester thermal bonding fiber is an unstretched polyester fiber or a core-sheath composite low-melting-point fiber.

[0020] Furthermore, the softening point of unstretched polyester fiber is 110~135℃.

[0021] Furthermore, the sheath-core type composite low-melting-point fiber has a sheath melting point of 110~130℃ and a core melting point of 240~260℃.

[0022] Furthermore, in step S1, the fiber solids content of the first fiber suspension is controlled at 0.05~0.15wt%, and the fiber solids content of the second fiber suspension is controlled at 0.08~0.25wt%.

[0023] Furthermore, in step S2, the dual-channel wet web forming device includes a first headbox and a second headbox. The first headbox (upper channel) supplies the first fiber suspension, and the second headbox (lower channel) supplies the second fiber suspension. The amount of sizing in the two headboxes is adjusted to control the quantitative amount of the dense layer to be 10~40g / m² and the quantitative amount of the skeleton layer to be 40~80g / m².

[0024] Furthermore, in step S3, the negative pressure is achieved through 2-5 consecutively set vacuum dehydration zones, with the negative pressure intensity gradually increasing from an initial 5 kPa to 60 kPa along the direction of wet web operation.

[0025] Furthermore, in step S3, the gradient increases as follows: initial stage 5 kPa~12 kPa, middle stage 12 kPa~35 kPa, and later stage 35 kPa~60 kPa.

[0026] Furthermore, in step S4, the moisture content of the pre-dried double-layer wet net is reduced from 40-60% to 5-15%.

[0027] Furthermore, in step S4, the segmented hot pressing is as follows: coarse pressing section: hot roller temperature 140~170℃, linear pressure 50kN / m~120kN / m; fine pressing section: hot roller temperature 180~225℃, linear pressure 150kN / m~300kN / m.

[0028] Furthermore, in step S4, the cooling and shaping process involves a cooling roller temperature of 40~80℃ and a tension of 0.5kN / m~5.0kN / m.

[0029] The present invention also provides an interlocking separation membrane support, which is prepared by a method for preparing an interlocking separation membrane support according to the present invention.

[0030] Furthermore, the support includes a dense layer, a skeletal layer, and a gradient transition interlocking interface layer located between the two.

[0031] Furthermore, the dense layer is composed of ultrafine polyester fibers and sulfonated modified ultrafine polyester fibers.

[0032] Furthermore, the skeleton layer is composed of skeleton polyester fibers and polyester thermal bonding fibers.

[0033] Furthermore, the gradient transition interlocking interface layer is formed by embedding some of the ultrafine fibers in the dense layer into the pores of the skeleton layer.

[0034] Furthermore, the thickness of the gradient transition interlock interface layer is 5μm~50μm, preferably 10μm~30μm.

[0035] Furthermore, the thickness of the dense layer is 20μm~60μm.

[0036] Furthermore, the thickness of the skeleton layer is 40μm~90μm.

[0037] Furthermore, the average pore size of the dense layer is 0.1 μm to 5 μm.

[0038] Furthermore, the average pore size of the framework layer is 10 μm to 50 μm.

[0039] Furthermore, the surface roughness of the dense layer is Ra≤5μm, the interlayer peel strength is 30N / 50mm~55.6N / 50mm, and the air permeability is 65L / (m²·s)~280L / (m²·s); preferably, the surface roughness is Ra≤3μm and the interlayer peel strength is 40N / 50mm~55.6N / 50mm.

[0040] Furthermore, the total thickness of the support is 60μm~150μm, and the total amount is 50g / m²~120g / m²; preferably, the total thickness of the support is 80μm~120μm, and the total amount is 60g / m²~100g / m².

[0041] The beneficial effects of this invention are:

[0042] (1) The interlocking structure of the separation membrane support provided by the present invention forms a gradient transition interlocking interface layer with a thickness of 5~50μm through the synergistic effect of sulfonation modification, gradient negative pressure and step-by-step hot pressing. The interlayer peel strength reaches 30N / 50mm~55.6N / 50mm, which effectively solves the problem of weak interlayer bonding and easy delamination of heterogeneous slurry in the prior art.

[0043] (2) The interlocking structure of the separation membrane support provided by the present invention utilizes the thermoplastic rheological behavior of low crystallinity (≤40%) ultrafine fibers at 180-225℃. Through the high temperature and high pressure of the fine pressing section, the fibers undergo plastic deformation and fuse together, resulting in ultra-low surface roughness. At the same time, it maintains the three-dimensional pore structure of the skeleton layer, and the air permeability reaches 65L / (m²·s)~280L / (m²·s). It achieves the unity of high peel strength, low surface roughness and high air permeability, providing an ideal flat substrate for the interface polymerization or coating of subsequent functional layers.

[0044] (3) The interlocking structure of the separation membrane support provided by the present invention has a simple process, is easy to scale up and apply, has high process safety, and the gradient increasing negative pressure design effectively prevents the perforation defect of the dense layer, ensuring the success rate of the preparation of the thin support.

[0045] (4) The interlocking structure of the separation membrane support provided by the present invention can be used to prepare supports suitable for different application scenarios (thin and light high-flux type, comprehensive balance type, high-strength pressure-resistant type) by adjusting the degree of sulfonation, quantitative amount, negative pressure gradient and hot pressing temperature, so as to meet the needs of various separation processes such as low-pressure nanofiltration, conventional reverse osmosis and seawater desalination. Detailed Implementation

[0046] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0048] This invention provides a method for preparing an interlocking separation membrane support, the method comprising the following steps:

[0049] S1. Preparation of heterogeneous slurry: Prepare a first fiber suspension for constructing the dense layer and a second fiber suspension for constructing the skeleton layer, respectively;

[0050] S2. Dual-channel layered web formation: A dual-channel wet web formation device is used to supply the first fiber suspension and the second fiber suspension from two independent headboxes to the web formation curtain, and lay them sequentially on the web formation curtain to form a double-layer wet web structure.

[0051] S3, Vacuum negative pressure composite: The double-layer wet web structure is transferred to a vacuum dehydration device. Negative pressure is applied to one side of the skeleton layer, driving water to carry some of the ultrafine fibers in the dense layer to migrate to the skeleton layer and embed into its pores, forming a gradient transition interlocking interface layer, while completing dehydration.

[0052] S4. Pre-drying and stepped hot pressing for shaping: The dehydrated wet web is pre-dried, followed by segmented hot pressing and cooling shaping.

[0053] To better understand the technology of this invention, the specific processes involved in the preparation of the interlocking structure separation membrane support provided by this invention are as follows:

[0054] S1. Preparation of heterogeneous slurry: Prepare a first fiber suspension for constructing the dense layer and a second fiber suspension for constructing the skeleton layer.

[0055] In step S1, the fiber solids content of the first fiber suspension is controlled at 0.05~0.15wt%, and the fiber solids content of the second fiber suspension is controlled at 0.08~0.25wt%.

[0056] Specifically, in step S1, the first fiber suspension is composed of 60-90 wt% ultrafine polyester fiber and 10-40 wt% sulfonated modified ultrafine polyester fiber, based on the solid phase mass content.

[0057] More specifically, in step S1, the crystallinity of the ultrafine polyester fiber is ≤40%, the average diameter is 0.5μm~3μm, and the length is 3mm~8mm. The sulfonated modified ultrafine polyester fiber has an average diameter of 0.5μm~3μm and a length of 3mm~8mm; the degree of sulfonation is 3~8%, so that the water contact angle of the dense layer is ≤60°.

[0058] Specifically, the ultrafine polyester fiber provided by this invention is obtained through continuous phase dissolution and separation of indeterminate island-type sea-island fibers. The specific method is as follows: indeterminate island-type sea-island fibers (island phase is PET, number of islands is 64-128) are used, and after melt spinning, a low-orientation drawing process (drawing ratio ≤ 2.5) is employed to maintain the low crystallinity of the fiber. Subsequently, the sea-island phase is dissolved and removed in an alkaline solution, followed by washing, neutralization, and drying to obtain ultrafine PET fibers.

[0059] The ultrafine polyester fiber provided by this invention is obtained through continuous phase dissolution and separation of indeterminate island-type fibers. Unlike conventional island-type ultrafine fibers (which are typically fully stretched and have a crystallinity >45%), the low-crystallinity ultrafine fiber (≤40%) used in this invention belongs to an insufficiently stretched intermediate or low-oriented yarn (UDY). Its molecular chain segments are loosely arranged, and it can exhibit excellent thermoplastic rheological behavior during subsequent high-temperature hot pressing (180-225℃), making it easy to undergo plastic deformation, thereby achieving a mirror-level smoothness (Ra≤3μm) on the surface of the dense layer. This is the key material basis for achieving ultra-low surface roughness in this invention.

[0060] The sulfonated modified ultrafine polyester fiber provided by this invention is obtained by post-sulfonation treatment of the above-mentioned ultrafine PET fiber. The specific method is as follows: the ultrafine PET fiber is placed in a 98% concentrated sulfuric acid solution and reacted at 80°C. The degree of sulfonation is controlled by potentiometric titration. After the reaction, the fiber is thoroughly washed with deionized water until neutral and then dried for later use.

[0061] Specifically, in step S1, the second fiber suspension is composed of 70-85 wt% skeleton polyester fiber and 15-30 wt% polyester thermal bonding fiber, based on the solid phase mass content.

[0062] More specifically, in step S1, the linear density of the skeleton polyester fiber is 1.5~4.0 dtex, the diameter is 12μm~20μm, and the length is 5mm~12mm. The linear density of the polyester thermal bonding fiber is 1.5~5.0 dtex.

[0063] Specifically, the polyester thermal bonding fiber is either unstretched polyester fiber or core-sheath composite low-melting-point fiber. The softening point of unstretched polyester fiber is 110~135℃. The core-sheath composite low-melting-point fiber is a bicomponent composite fiber, with the sheath melting point of 110~130℃ and the core melting point of 240~260℃. The sheath begins to melt in the coarse pressing section (140-170℃), providing initial adhesion; the core maintains the fiber skeleton throughout the hot pressing process, preventing structural collapse.

[0064] S2. Dual-channel layered web formation: A dual-channel wet web formation device is used to supply the first fiber suspension and the second fiber suspension from two independent headboxes to the web forming curtain, and lay them sequentially on the web forming curtain to form a double-layer wet web structure.

[0065] Specifically, in step S2, the dense layer is formed by the deposition of ultrafine fibers in the first fiber suspension and is used for the subsequent composite of functional layers; the skeleton layer is formed by the co-deposition of skeleton polyester fibers and polyester thermal bonding fibers in the second fiber suspension, providing mechanical strength and high-throughput support; the double-layer wet web maintains a high moisture content during web formation, providing fluid driving conditions for subsequent vacuum negative pressure composite.

[0066] Specifically, in step S2, the dual-channel wet web forming apparatus includes a first headbox and a second headbox. The first headbox (upper channel) supplies the first fiber suspension, and the second headbox (lower channel) supplies the second fiber suspension. The first and second fiber suspensions are supplied to the web forming curtain, respectively. The sizing amount in the two headboxes is adjusted to control the density of the dense layer at 10-40 g / m² and the density of the skeleton layer at 40-80 g / m². The aim is to achieve a dry dense layer thickness of 20-60 μm and a dry skeleton layer thickness of 40-90 μm. The moisture content of the double-layer wet web is maintained at 90-98% after web forming, providing fluid-driven conditions for subsequent vacuum negative pressure lamination.

[0067] S3. Vacuum negative pressure composite: The double-layer wet web structure is transferred to a vacuum dehydration device. Negative pressure is applied to one side of the skeleton layer, driving water to carry some of the ultrafine fibers in the dense layer to migrate to the skeleton layer and embed into its pores, forming a gradient transition interlocking interface layer, while completing dehydration.

[0068] Negative pressure is applied to one side of the skeleton layer, driving water flow from the dense layer to the skeleton layer, thereby achieving the directional migration of ultrafine fibers into the skeleton layer. This step utilizes the negative pressure difference to drive water to rapidly penetrate from the dense layer to the skeleton layer, forming a directional high-speed water flow perpendicular to the mesh surface. The viscous dragging effect of this directional water flow on the ultrafine fibers causes some of the ultrafine fibers in the dense layer to migrate and embed into the pores of the skeleton layer, forming a gradient transition interlocking interface layer, while simultaneously completing the dehydration and curing of the wet mesh. After negative pressure dehydration, the moisture content of the double-layer wet mesh is reduced to 40-60%.

[0069] Specifically, in step S3, the negative pressure is achieved through 2-5 consecutively set vacuum dehydration zones, and the negative pressure intensity gradually increases from the initial 5 kPa to 60 kPa along the direction of the wet web operation.

[0070] More specifically, in step S3, the gradient increases as follows: Initially 5 kPa to 12 kPa: gentle dehydration to avoid damaging the wet web structure. This stage mainly achieves the initial bonding of the two layers, preventing the dense layer from being instantly ruptured under high negative pressure, forming pinhole defects.

[0071] Mid-term (12kPa~35kPa): Accelerated water infiltration drives the migration of ultrafine fibers. During this stage, the directional water flow velocity generated by the negative pressure is moderate, and the sulfonated modified ultrafine fibers begin to move into the pores of the skeleton layer under viscous drag.

[0072] Later stage (35kPa~60kPa): Intense dehydration allows the ultrafine fibers to deeply embed into the pores of the framework layer. During this stage, the high-speed water flow generates a strong drag force, enabling the ultrafine fibers to overcome interlayer resistance and ultimately embed into the pores of the framework layer to a depth of 20μm~60μm.

[0073] In this step, the interlocking interface formation mechanism is as follows: negative pressure difference drives water to rapidly penetrate from the dense layer to the skeleton layer, forming a directional high-speed water flow perpendicular to the mesh surface. Due to the sulfonation modification giving the ultrafine fibers in the dense layer good hydrophilicity (water contact angle ≤60°), the water flow generates a viscous dragging effect on the ultrafine fibers, causing some of the ultrafine fibers in the dense layer (about 5-10%) to overcome interlayer resistance, migrate along the water flow direction, and embed into the pores of the skeleton layer, forming a gradient transition interlocking interface layer with interwoven fibers, with a thickness of about 20μm~60μm.

[0074] Key Technology: The gradient-increasing negative pressure design is a process safety measure to prevent perforation of the dense layer, and it is also the core process for achieving "controlled migration" of ultrafine fibers. If a negative pressure of 60 kPa is applied directly, the dense layer will suffer local damage due to the instantaneous high pressure difference; if a low negative pressure (such as 20 kPa) is used throughout the process, the water flow velocity will be insufficient, and the ultrafine fibers will not be able to obtain enough drag force to migrate.

[0075] S4. Pre-drying and stepped hot pressing for shaping: The dehydrated wet web is pre-dried, followed by segmented hot pressing and cooling shaping.

[0076] The moisture content of the double-layer wet web is reduced to a level suitable for hot melt bonding by a drying device. The pre-dried wet web is then subjected to segmented high-temperature calendering using a multi-roll hot rolling mill. By utilizing the instantaneous rheological characteristics of polyester hot-bonding fibers under high temperature and high pressure, as well as the plastic deformation capability of low-crystallinity ultrafine fibers, fusion welding points are formed at the gradient transition interface, thereby achieving densification of the dense layer surface and high-strength bonding between layers.

[0077] (1) Pre-drying:

[0078] In step S4, the moisture content of the pre-dried double-layer wet net is reduced from 40-60% to 5-15% to prevent steam explosion during high-temperature hot pressing and avoid damage to the support structure.

[0079] (2) Stepwise hot pressing:

[0080] In this embodiment of the invention, a multi-roll hot rolling mill (equipped with 2 pairs of hot rolls) is used to perform segmented high-temperature calendering on the pre-dried wet web:

[0081] In step S4, the segmented hot pressing is as follows: In the rough pressing stage, the hot roller temperature is 140~170℃, and the linear pressure is 50kN / m~120kN / m. This gradually removes the air and small amount of water vapor remaining in the fiber network after pre-drying, preventing bubbling defects caused by instantaneous gas expansion in the fine pressing stage. At this temperature, the sheath of the core-sheath type adhesive fiber is completely melted. Under moderate pressure, the molten sheath forms a preliminary weld at the fiber intersections. However, due to the relatively light pressure, the melt will not excessively flow and block the three-dimensional pore structure of the skeleton layer, thus maintaining the high air permeability of the support.

[0082] Fine pressing section: Hot roller temperature 180~225℃, linear pressure 150kN / m~300kN / m, retention time within 1 second, causing plastic deformation and melting welding of low crystallinity microfiber and polyester thermal bonding fiber skin, forming a dense and smooth surface, and further reducing the moisture content to below 3%.

[0083] At the temperature provided by the fine pressing section, the molecular chain segments of the microfibers possess extremely high mobility. Under high linear pressure, the fibers undergo significant plastic deformation (rather than melt flow), flattening into flat ribbons that fuse together, filling in the microscopic unevenness of the surface and forming a mirror-like smooth surface (Ra≤3 μm). The skin layer of the bonding fibers is in a fully molten state at this temperature. Under high pressure, the melt fully penetrates to the fiber intersections and interlocking interfaces, forming numerous strong molten weld points, significantly improving interlayer peel strength. The microfibers on the surface of the dense layer fuse together under high temperature and pressure, forming a continuous dense surface layer, providing an ideal substrate for the interfacial polymerization of subsequent functional layers (such as the polyamide separation layer). The skeleton fibers (12μm~20μm in diameter) in the skeleton layer provide rigid support, preventing the complete collapse of the skeleton layer under the high pressure of the fine pressing section, maintaining the three-dimensional porous structure, thus achieving surface densification while still maintaining suitable air permeability.

[0084] The light pressing in the coarse pressing stage maintains the three-dimensional porosity of the skeleton layer (ensuring flux), while the heavy pressing in the fine pressing stage achieves a mirror-like surface finish in the dense layer (ensuring retention / coating properties). This segmented temperature and pressing matching is a key process for obtaining high peel strength, low surface roughness, and high air permeability. The residence time in the fine pressing stage is controlled to within 1 second, which is a "sudden high temperature" process. This avoids cold crystallization caused by prolonged heating of low-crystallinity fibers at high temperatures, preventing the fibers from becoming brittle or undergoing thermal shrinkage deformation.

[0085] (3) Cooling and shaping:

[0086] In step S4, after the support body is hot-pressed in stages, it immediately passes through the cooling roller after leaving the hot roller. The temperature of the cooling roller is 40~80℃, and the tension is maintained at 0.5kN / m~5.0kN / m. The cooling process allows the molten adhesive fibers to solidify rapidly, eliminates the internal stress of the fibers, prevents dimensional deformation caused by thermal shrinkage, and ensures the flatness of the support body.

[0087] The present invention also provides an interlocking separation membrane support, which is prepared by a method according to the present invention. The support includes a dense layer, a framework layer, and a gradient transition interlocking interface layer located between the two.

[0088] Specifically, the dense layer is composed of ultrafine polyester fibers and sulfonated modified ultrafine polyester fibers, with a smooth and dense surface, and is used for the composite of functional layers.

[0089] Specifically, the skeleton layer is composed of skeleton polyester fiber and polyester thermal bonding fiber, providing mechanical strength and high-throughput support.

[0090] Specifically, the thickness of the dense layer is 20μm~60μm.

[0091] Specifically, the thickness of the skeleton layer is 40μm~90μm.

[0092] Specifically, the gradient transition interlocking interface layer is formed by embedding some ultrafine fibers from the dense layer into the pores of the skeleton layer. The thickness of the gradient transition interlocking interface layer is 5μm~50μm, preferably 10μm~30μm, achieving a high-strength bond between the two layers.

[0093] Specifically, the total thickness of the support is 60μm~150μm, and the total amount is 50g / m²~120g / m²; preferably, the total thickness of the support is 80μm~120μm, and the total amount is 60g / m²~100g / m².

[0094] Specifically, the average pore size of the dense layer is 0.1 μm to 5 μm.

[0095] Specifically, the average pore size of the framework layer is 10μm~50μm.

[0096] Specifically, the surface roughness of the dense layer is Ra≤5μm, the interlayer peel strength is 30N / 50mm~55.6N / 50mm, and the air permeability is 65L / (m²·s)~280L / (m²·s); preferably, the surface roughness is Ra≤3μm and the interlayer peel strength is 40N / 50mm~55.6N / 50mm.

[0097] Example 1

[0098] The preparation of an interlocked separation membrane support includes the following steps:

[0099] S1. Preparation of heterogeneous slurry:

[0100] The first fiber suspension has a solid content controlled at 0.10 wt%. Based on the solid phase mass content, it consists of 80 wt% ultrafine polyester fiber and 20 wt% sulfonated modified ultrafine polyester fiber. The ultrafine polyester fiber has an average diameter of 2 μm, a length of 5 mm, and a crystallinity of 35% (determined by differential scanning calorimetry DSC). The sulfonation degree of the sulfonated modified ultrafine polyester fiber is controlled at 5% (reacted in 98% concentrated sulfuric acid at 80°C for 30 minutes). After sulfonation modification, the water contact angle of the dense layer is reduced to 55°.

[0101] The second fiber suspension has a solid content controlled at 0.15 wt%, and is composed of 75 wt% skeleton polyester fiber and 25 wt% polyester thermal bonding fiber based on the solid phase mass content. The skeleton polyester fiber is made of conventional PET short fiber with a linear density of 1.56 dtex and a diameter of approximately 15 μm (based on a linear density of 1.56 dtex and a PET density of 1.38 g / cm³). 3Calculated, the length is 6mm; the polyester thermal bonding fiber is a core-sheath composite low-melting-point fiber with a linear density of 4.4 dtex, a diameter of approximately 18μm, and a length of 6mm. This fiber is a bicomponent composite fiber, with a sheath of modified low-melting-point PET (melting point 110℃) and a core of conventional PET (melting point 250℃). The sheath accounts for approximately 30% of the total fiber mass.

[0102] S2, Dual-channel layered mesh formation:

[0103] A dual-channel wet web forming device is adopted, which includes a first headbox, a second headbox, and a web forming curtain (stainless steel mesh curtain with 80 mesh). The first fiber suspension and the second fiber suspension are supplied to the web forming curtain from two independent headboxes, and then laid on the web forming curtain to form a double-layer wet web structure.

[0104] Web forming requirements: The first headbox (upper channel) supplies the first fiber suspension at a rate of 25 g / m² to form a dense layer; the second headbox (lower channel) supplies the second fiber suspension at a rate of 55 g / m² to form a skeleton layer; the flow rate ratio (lower / upper) is controlled at 1.5 to ensure uniform laying of the two layers; the web forming speed is 10 m / min, and the moisture content of the double-layer wet web is maintained at 95% after web forming.

[0105] S3, Vacuum Negative Pressure Composite:

[0106] The double-layer wet web structure was transferred to a vacuum dehydration device. Three continuous vacuum dehydration zones were set on one side of the skeleton layer, and a gradient increasing negative pressure intensity was applied for dehydration. After negative pressure dehydration, the moisture content of the double-layer wet web was reduced to 50%, and the dehydration and curing of the wet web were completed simultaneously. The gradient increasing negative pressure intensity was: initial negative pressure intensity 10 kPa, intermediate negative pressure intensity 30 kPa, and final negative pressure intensity 60 kPa.

[0107] S4. Pre-drying and stepped hot pressing for characterization:

[0108] (1) Pre-drying: The wet net after dehydration is pre-dried by passing the wet net through 6 sets of drying cylinders (diameter 1.5 m, surface temperature 80-120℃), the total length of the drying cylinders is about 18 m, the residence time is about 2 minutes, and the moisture content of the double-layer wet net is reduced from 50% to 10%.

[0109] (2) Step-by-step hot pressing: A multi-roll hot rolling mill (equipped with 2 pairs of hot rolls) is used to perform segmented high-temperature calendering on the pre-dried wet web. After hot pressing, the moisture content drops to about 2%.

[0110] The hot pressing process is as follows: coarse pressing section: hot roller temperature: 160℃, linear pressure: 80kN / m, residence time: approximately 0.5 seconds.

[0111] Fine pressing section: Hot roller temperature: 210℃, linear pressure: 250kN / m, residence time: approximately 0.8 seconds.

[0112] (3) Cooling and shaping:

[0113] After being hot-pressed in stages, the support body immediately passes through the cooling roller after leaving the hot roller. The temperature of the cooling roller is controlled at 60℃, and the tension is maintained at 2.0kN / m.

[0114] Finally, an interlocked separation membrane support was obtained, with a total thickness of 95 μm, including a 25 μm thickness of the interlocked interface, an average pore size of 1.2 μm in the dense layer, and an average pore size of 25 μm in the framework layer.

[0115] The interlocked membrane support prepared in this embodiment has a smooth and clean surface, and the dense layer is milky white without defects such as cloudiness or bubbling. The support has excellent performance, and the specific performance test data is shown in Table 1. It is particularly suitable for the preparation of high-performance reverse osmosis membranes.

[0116] Example 2

[0117] This embodiment uses the same method as in Example 1 to prepare an interlocked separation membrane support, with the difference being:

[0118] S1. Preparation of heterogeneous slurry:

[0119] The first fiber suspension has a solid content controlled at 0.08 wt%. Based on the solid phase mass content, it consists of 60 wt% ultrafine polyester fiber and 40 wt% sulfonated modified ultrafine polyester fiber. The degree of sulfonation of the sulfonated modified ultrafine polyester fiber is controlled at 8% (reacted in 98% concentrated sulfuric acid at 80°C for 60 minutes). After sulfonation modification, the water contact angle of the dense layer is reduced to 38°.

[0120] The second fiber suspension has a solid content controlled at 0.12 wt%. Based on the solid phase mass content, it consists of 80 wt% skeleton polyester fiber and 20 wt% polyester thermal bonding fiber. The polyester thermal bonding fiber is unstretched polyester fiber (UDY): linear density 3.3 dtex, diameter approximately 16 μm, length 6 mm. It begins to soften significantly above the glass transition temperature (Tg≈75℃) and undergoes softening and shrinkage in the hot pressing section (150-195℃) and bonds with other fibers.

[0121] S2, Dual-channel layered mesh formation:

[0122] Web forming requirements: The first headbox (upper channel) supplies the first fiber suspension at a rate of 15 g / m² to form a dense layer; the second headbox (lower channel) supplies the second fiber suspension at a rate of 45 g / m² to form a skeleton layer; the flow rate ratio (lower / upper) is controlled at 1.8 to ensure uniform laying of the two layers; the web forming speed is 12 m / min, and the moisture content of the double-layer wet web is maintained at 96% after web forming.

[0123] S3, Vacuum Negative Pressure Composite:

[0124] The double-layer wet web structure was transferred to a vacuum dehydration device. Three continuous vacuum dehydration zones were set on one side of the skeleton layer, and a gradient increasing negative pressure intensity was applied for dehydration. After negative pressure dehydration, the moisture content of the double-layer wet web was reduced to 55%, and the dehydration and curing of the wet web were completed simultaneously. The gradient increasing negative pressure intensity was: 5 kPa for the initial stage, 20 kPa for the intermediate stage, and 50 kPa for the final stage.

[0125] S4. Pre-drying and stepped hot pressing for characterization:

[0126] (1) Pre-drying: Reduce the moisture content of the double-layer wet net from 55% to 12%.

[0127] (2) Step-by-step hot pressing: A multi-roll hot rolling mill (equipped with 2 pairs of hot rolls) is used to perform segmented high-temperature calendering on the pre-dried wet web. After hot pressing, the moisture content drops to about 2%.

[0128] The hot pressing process is as follows: coarse pressing section: hot roller temperature: 150℃, linear pressure: 60kN / m.

[0129] Precision pressing section: Hot roller temperature: 195℃, linear pressure: 200kN / m.

[0130] (3) Cooling and shaping:

[0131] After being hot-pressed in stages, the support body immediately passes through the cooling roller after leaving the hot roller. The temperature of the cooling roller is controlled at 50℃, and the tension is maintained at 1.5kN / m.

[0132] Finally, an interlocked separation membrane support was obtained with a total thickness of 75 μm, of which the thickness of the interlocked interface was 20 μm, the average pore size of the dense layer was 0.8 μm, and the average pore size of the skeleton layer was 30 μm.

[0133] The interlocked membrane support prepared in this embodiment has a smooth and translucent surface. The support is thin and has a high flux, making it particularly suitable for the preparation of low-pressure nanofiltration membranes. It can reduce operating pressure and save energy.

[0134] Example 3

[0135] This embodiment uses the same method as in Example 1 to prepare an interlocked separation membrane support, with the difference being:

[0136] S1. Preparation of heterogeneous slurry:

[0137] The first fiber suspension has a solid content controlled at 0.12 wt%. Based on the solid phase mass content, it consists of 90 wt% ultrafine polyester fiber and 10 wt% sulfonated modified ultrafine polyester fiber. The degree of sulfonation of the sulfonated modified ultrafine polyester fiber is controlled at 3% (reacted in 98% concentrated sulfuric acid at 80°C for 15 minutes). After sulfonation modification, the water contact angle of the dense layer is reduced to 52°.

[0138] The second fiber suspension has a solid content controlled at 0.20 wt%. Based on solid phase mass content, it consists of 70 wt% skeleton polyester fiber and 30 wt% polyester thermal bonding fiber. The skeleton polyester fiber has a linear density of 2.2 dtex, a diameter of approximately 17 μm, and a length of 8 mm. The polyester thermal bonding fiber is a core-sheath composite low-melting-point fiber with a linear density of 4.4 dtex, a diameter of approximately 18 μm, and a length of 8 mm. This fiber is a bicomponent composite fiber; the sheath is modified low-melting-point PET with a melting point of 110℃, and the core is conventional PET with a melting point of 250℃.

[0139] S2, Dual-channel layered mesh formation:

[0140] Web forming requirements: The first headbox (upper channel) supplies the first fiber suspension at a rate of 35 g / m² to form a dense layer; the second headbox (lower channel) supplies the second fiber suspension at a rate of 75 g / m² to form a skeleton layer; the flow rate ratio (lower / upper) is controlled at 1.2 to ensure uniform laying of the two layers; the web forming speed is 8 m / min, and the moisture content of the double-layer wet web is maintained at 94% after web forming.

[0141] S3, Vacuum Negative Pressure Composite:

[0142] The double-layer wet web structure was transferred to a vacuum dehydration device. Three continuous vacuum dehydration zones were set on one side of the skeleton layer, and a gradient increasing negative pressure intensity was applied for dehydration. After negative pressure dehydration, the moisture content of the double-layer wet web was reduced to 45%, and the dehydration and curing of the wet web were completed simultaneously. The gradient increasing negative pressure intensity was: initial negative pressure intensity 15 kPa, intermediate negative pressure intensity 40 kPa, and final negative pressure intensity 60 kPa.

[0143] S4. Pre-drying and stepped hot pressing for characterization:

[0144] (1) Pre-drying: Reduce the moisture content of the double-layer wet net from 45% to 8%.

[0145] (2) Step-by-step hot pressing: A multi-roll hot rolling mill (equipped with 2 pairs of hot rolls) is used to perform segmented high-temperature calendering on the pre-dried wet web. After hot pressing, the moisture content drops to about 2%.

[0146] The hot pressing process is as follows: Rough pressing section: Hot roller temperature: 170℃, Linear pressure: 120kN / m.

[0147] Precision pressing section: Hot roller temperature: 225℃, linear pressure: 300kN / m.

[0148] (3) Cooling and shaping:

[0149] After being hot-pressed in stages, the support body immediately passes through the cooling roller after leaving the hot roller. The temperature of the cooling roller is controlled at 70℃, and the tension is maintained at 3.5kN / m.

[0150] Finally, an interlocked separation membrane support was obtained with a total thickness of 125 μm, of which the thickness of the interlocked interface was 35 μm, the average pore size of the dense layer was 1.5 μm, and the average pore size of the skeleton layer was 22 μm.

[0151] The interlocked membrane support prepared in this embodiment has a dense, smooth, and clean surface with high mechanical strength. The support is thick and strong, and can withstand high operating pressures (such as 6-8 MPa in seawater desalination), making it particularly suitable for the preparation of high-pressure reverse osmosis membranes.

[0152] Example 4

[0153] This embodiment uses the same method as in Example 1 to prepare an interlocked separation membrane support, with the difference being:

[0154] S1. Preparation of heterogeneous slurry:

[0155] First fiber suspension: The solid content is controlled at 0.05 wt%. Based on the solid phase mass content, it consists of 90 wt% ultrafine polyester fiber and 10 wt% sulfonated modified ultrafine polyester fiber. The ultrafine polyester fiber has an average diameter of 0.5 μm, a length of 3 mm, and a crystallinity of 40%. The sulfonation degree of the sulfonated modified ultrafine polyester fiber is controlled at 3% (reacted in 98% concentrated sulfuric acid at 80°C for 15 minutes).

[0156] The second fiber suspension has a solid content controlled at 0.25 wt%. Based on the solid phase mass content, it consists of 85 wt% skeleton polyester fiber and 15 wt% polyester thermal bonding fiber. The skeleton polyester fiber has a linear density of 4.0 dtex, a diameter of about 20 μm, and a length of 12 mm. The polyester thermal bonding fiber is unstretched polyester fiber (UDY) with a linear density of 5.0 dtex.

[0157] S2, Dual-channel layered mesh formation:

[0158] Web formation requirements: The first headbox (upper channel) supplies the first fiber suspension at a rate of 40 g / m² to form a dense layer; the second headbox (lower channel) supplies the second fiber suspension at a rate of 80 g / m² to form a skeleton layer.

[0159] S3, Vacuum Negative Pressure Composite:

[0160] The double-layer wet web structure was transferred to a vacuum dehydration device. Five consecutive vacuum dehydration zones were set on one side of the skeleton layer, and a gradient of increasing negative pressure was applied for dehydration. After negative pressure dehydration, the moisture content of the double-layer wet web was reduced to 40%, and the dehydration and curing of the wet web were completed simultaneously. The gradient of increasing negative pressure was: 5 kPa → 12 kPa → 25 kPa → 45 kPa → 60 kPa.

[0161] S4. Pre-drying and stepped hot pressing for characterization:

[0162] (1) Pre-drying: Reduce the moisture content of the double-layer wet net from 40% to 15%.

[0163] (2) Step-by-step hot pressing: A multi-roll hot rolling mill (equipped with 2 pairs of hot rolls) is used to perform segmented high-temperature calendering on the pre-dried wet web. After hot pressing, the moisture content drops to about 3%.

[0164] The hot pressing process is as follows: coarse pressing section: hot roller temperature: 140℃, linear pressure: 50kN / m.

[0165] Precision pressing section: Hot roller temperature: 180℃, linear pressure: 150kN / m.

[0166] (3) Cooling and shaping:

[0167] After being hot-pressed in stages, the support body immediately passes through the cooling roller after leaving the hot roller. The temperature of the cooling roller is controlled at 40℃, and the tension is maintained at 0.5kN / m.

[0168] The final interlocked separation membrane support has a total thickness of 148 μm, of which the thickness of the interlocked interface is 50 μm, the average pore size of the dense layer is 0.6 μm, and the average pore size of the skeleton layer is 35 μm.

[0169] The surface of the interlocked membrane support prepared in this embodiment is slightly rough, but there are no obvious defects, and a support that meets the basic performance requirements can still be prepared.

[0170] Comparative Example 1

[0171] This comparative example uses the same method as Example 1 to prepare an interlocked separation membrane support, except that: in step S1, sulfonated modified fibers are not added to the first fiber suspension.

[0172] In step S3, conventional constant low negative pressure dehydration is used, with a negative pressure intensity of 20 kPa.

[0173] Finally, an interlocked separation membrane support was prepared with a total thickness of 105 μm. No interlocking interface was observed. The average pore size of the dense layer was 1.8 μm, and the average pore size of the skeleton layer was 25 μm.

[0174] As shown in Table 1, the interlocking interface formation failed, interlayer adhesion relied on hot melting, surface quality was poor, and the interlayer peel strength of the support was only 27% of that in Example 1, making delamination easy. This is because, due to the lack of hydrophilicity imparted by sulfonation modification, the ultrafine fibers had poor responsiveness to water flow (water contact angle 78°, water flow preferentially flows through the fiber gaps rather than dragging the fibers); at the same time, the constant low negative pressure (20kPa) generated a slow water flow velocity and weak dragging force, making it almost impossible for the ultrafine fibers to migrate into the pores of the skeleton layer, with only a small number of fibers (<1%) floating at the interlayer interface, and the interlocking depth <3μm. The two layers mainly relied on the fusion welding of the fibers in the fine pressing section (210℃) for bonding, but due to the lack of the "anchoring effect" of fiber interlocking, the number of fusion welding points was small, the distribution was uneven, and they only existed at the two-dimensional interface, resulting in weak interlayer bonding. Although ultrafine fibers with 35% crystallinity can undergo plastic deformation at 210℃, they lack the surface wettability improved by sulfonation modification. The dense layer surface exhibits disordered fiber arrangement, with tiny gaps between fibers forming cloud-like defects and high surface roughness. In peel strength tests, the support delaminates under relatively small external forces (the peel interface is flat, indicating few interfacial bonding points), and powdering occurs during edge trimming.

[0175] Comparative Example 2

[0176] This comparative example uses the same method as Example 1 to prepare an interlocked separation membrane support, except that in step S4, a single-temperature (200℃) one-step hot pressing with a linear pressure of 250 kN / m is used instead of process (2) gradient hot pressing.

[0177] Finally, an interlocked separation membrane support was obtained with a total thickness of 98 μm, of which the thickness of the interlocked interface was 22 μm, the average pore size of the dense layer was 0.6 μm, and the average pore size of the skeleton layer was 18 μm.

[0178] The separation membrane support prepared in this comparative example showed localized bubble marks and uneven surface smoothness upon external observation.

[0179] As shown in Table 1, the interlayer peel strength decreased significantly, air permeability was greatly reduced, and surface roughness was high. This is because, due to the lack of a "preheating and degassing" step in the coarse pressing section, residual air in the wet web after pre-drying, even at a moisture content of 10%, still contains a small amount of water vapor and air dispersed in the pores of the fiber network. At a high temperature of 200℃, the gas expands rapidly, with its volume increasing by about 1.6 times. Unable to escape in time, it forms microbubbles with a diameter of 50-200μm inside the support, resulting in a loose local structure. SEM observation reveals obvious void defects. Although a single temperature of 200℃ is higher than the glass transition temperature of PET (Tg≈75℃), for ultrafine fibers with a crystallinity of 35%, 200℃ is in the middle of the high elasticity state, and the plastic deformation capacity has not yet reached its optimal level. According to the rheological properties of PET, fibers with a crystallinity of 35% need to be above 210℃ to undergo significant plastic deformation and achieve surface densification. At 200℃, the fibers still maintain a certain rigidity, the surface fiber arrangement is not dense enough, and the surface roughness is relatively high (Ra 3.8 μm). Due to the lack of preheating of the wet web, the temperature distribution is uneven, with a high surface temperature and a low internal temperature, resulting in insufficient melting and welding of the bonding fibers. Some areas (near the surface of the hot roller) melt well, while some areas (the central layer) remain solid, leading to uneven interlayer bonding strength and reduced overall peel strength. During the one-step hot pressing, the skin of the bonding fibers flows excessively under high temperature and pressure (200℃, 250 kN / m), and the melt blocks some of the three-dimensional pores of the skeleton layer, resulting in a significant decrease in air permeability (from 120 L / (m²·s) in Example 1 to 85 L / (m²·s)), affecting the flux performance of the subsequent membrane. Although an interlocking interface was formed, the adhesion was not strong: Since an interlocking interface (about 22 μm) had been formed in S3, during the one-step hot pressing, due to unreasonable application of temperature and pressure, the number of molten welding points was small (without preheating and prepressing, the fiber contact area was small), and the "anchoring effect" of the interlocking interface was not fully utilized. The interlayer peel strength was only 63% of that in Example 1.

[0180] Comparative Example 3

[0181] This comparative example uses the same method as Example 1 to prepare an interlocked separation membrane support, except that in step S3, negative pressure is applied to the dense layer side instead of the skeleton layer side.

[0182] The final interlocked separation membrane support has a total thickness of 80 μm, of which the thickness of the interlocked interface is 18 μm, the average pore size of the dense layer is 3.5 μm, and the average pore size of the skeleton layer is 25 μm.

[0183] The separation membrane support prepared in this comparative example has a chaotic interlocking interface, and the surface of the dense layer is damaged by coarse fibers, resulting in a noticeably rough surface with visible coarse fiber protrusions, making it unsuitable for functional layer composites.

[0184] As can be seen from the data in Table 1, the interlayer peel strength is lower than that of Example 1, and the air permeability is significantly reduced.

[0185] This is because water permeates from the skeleton layer to the dense layer, and the coarse fibers and some fine fibers in the skeleton layer move towards the dense layer under the dragging effect of the water flow. Since the skeleton fibers are much coarser than the ultrafine fibers (15 μm vs 2 μm), some skeleton fibers are embedded in the surface of the dense layer or suspended above the dense layer, disrupting the uniformity of the dense layer. The embedded or suspended coarse fibers are pressed into the surface of the dense layer in the fine pressing section, forming obvious protrusions or pits, resulting in a significant increase in surface roughness. Although an interface of interwoven fibers is also formed, due to the reverse direction of the water flow, the composition of the interlocking interface becomes "skeleton fibers embedded in the dense layer + a small number of ultrafine fibers being pushed in the opposite direction", resulting in a chaotic structure that cannot form the ideal gradient transition structure of "ultrafine fibers embedded in the pores of the skeleton layer". Although fiber interlocking also exists in this comparative example, due to the chaotic interface structure and the uneven distribution of coarse fibers in the dense layer, the interlayer peel strength is slightly lower than that in Example 1. Due to the excessively high surface roughness (Ra 6.5 μm), the surface of the dense layer is not suitable for interfacial polymerization or coating, and a high-performance separation membrane cannot be prepared.

[0186] The performance test data of the separation membrane support prepared in the embodiments and comparative examples of the present invention are shown in Table 1, and the test methods involved are as follows:

[0187] (1) Peel strength: Refer to FZ / T 60011-2016 "Test Method for Peel Strength of Nonwoven Fabrics", with a sampling width of 50 mm and a peeling speed of 100 mm / min. Record the average peel force (unit: N / 50 mm) on an electronic tensile testing machine. Before testing, the sample needs to be equilibrated for 24 hours under standard atmospheric conditions (temperature 20±2℃, relative humidity 65±5%).

[0188] (2) Surface roughness (Ra): Using a Bruker Dektak XT surface roughness tester, in accordance with GB / T3505-2009, the sampling length was 10 mm and the scanning speed was 10 μm / s, the arithmetic mean roughness Ra value of the dense layer surface was measured. Five different locations were tested for each sample and the average value was taken.

[0189] (3) Gradient interlocking depth: After freezing the sample in liquid nitrogen, it was brittle and fractured. The cross section in the vertical direction was taken, and after being sputtered with gold, it was observed under a Hitachi SU8010 scanning electron microscope (SEM) with an accelerating voltage of 5kV and a magnification of 500-2000 times. The vertical depth of the dense layer fiber embedded in the pores of the skeleton layer was measured using Image J software, and the average value of 10 measurement points was taken.

[0190] (4) Water contact angle: Using a Dataphysics OCA 20 contact angle meter, the static drop method was used. 2 μL of deionized water was dropped onto the surface of the dense layer, and the contact angle was photographed and measured with a high-speed camera at the moment of contact (<1 second). Five different locations were tested for each sample, and the average value was taken.

[0191] (5) Air permeability: Refer to GB / T 5453-1997 "Determination of air permeability of textile fabrics", use YG461E fabric air permeability meter, test area 20cm², pressure difference 200Pa, test the gas flow rate per unit area (unit: L / (m²·s)). Each sample is tested 3 times and the average value is taken.

[0192] (6) Total mass: Refer to GB / T 24218.1-2009 Textiles - Test methods for nonwoven fabrics - Part 1: Determination of mass per unit area, weigh the 100mm×100mm sample using an electronic balance and convert it to mass per unit area (g / m²).

[0193] (7) Total thickness: Refer to GB / T 24218.2-2009, use YG141 fabric thickness gauge, presser foot area 2000mm², pressure 2kPa, test 5 different positions and take the average value.

[0194] Table 1. Performance test data of the separation membrane supports prepared in the examples and comparative examples.

[0195]

[0196] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0197] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing a separation membrane support with an interlocking structure, characterized in that, The preparation method includes the following steps: S1. Preparation of heterogeneous slurry: Prepare a first fiber suspension for constructing the dense layer and a second fiber suspension for constructing the skeleton layer, respectively; S2. Dual-channel layered web formation: A dual-channel wet web formation device is used to supply the first fiber suspension and the second fiber suspension from two independent headboxes to the web formation curtain, and lay them sequentially on the web formation curtain to form a double-layer wet web structure. S3, Vacuum negative pressure composite: The double-layer wet web structure is transferred to a vacuum dehydration device. Negative pressure is applied to one side of the skeleton layer, driving water to carry some of the ultrafine fibers in the dense layer to migrate to the skeleton layer and embed into its pores, forming a gradient transition interlocking interface layer, while completing dehydration. S4. Pre-drying and stepped hot pressing for shaping: The dehydrated wet web is pre-dried, followed by segmented hot pressing and cooling for shaping; In step S1, based on the solid phase mass content, the first fiber suspension consists of 60-90 wt% ultrafine polyester fiber and 10-40 wt% sulfonated modified ultrafine polyester fiber; wherein, in step S1, the crystallinity of the ultrafine polyester fiber is ≤40%, and the sulfonation degree of the sulfonated modified ultrafine polyester fiber is 3-8%; In step S1, the second fiber suspension is composed of 70-85 wt% skeleton polyester fiber and 15-30 wt% polyester thermal bonding fiber, based on the solid phase mass content. The polyester thermal bonding fiber is a core-sheath type composite low-melting-point fiber. The core-sheath composite low-melting-point fiber has a sheath melting point of 110~130℃ and a core melting point of 240~260℃. In step S3, the negative pressure is achieved through 2-5 consecutively set vacuum dehydration zones, and the negative pressure intensity gradually increases from the initial 5 kPa to 60 kPa along the direction of wet web operation. In step S4, the segmented hot pressing is as follows: coarse pressing section: hot roller temperature 140~170℃, linear pressure 50kN / m~120kN / m; fine pressing section: hot roller temperature 180~225℃, linear pressure 150kN / m~300kN / m. In step S4, the cooling and shaping process involves a cooling roller temperature of 40~80℃ and a tension of 0.5kN / m~5.0kN / m.

2. The method for preparing an interlocking separation membrane support according to claim 1, characterized in that, In step S1, the average diameter of the ultrafine polyester fiber is 0.5μm~3μm, and the length is 3mm~8mm; The sulfonated modified ultrafine polyester fiber has an average diameter of 0.5μm to 3μm and a length of 3mm to 8mm. The linear density of the skeleton polyester fiber is 1.5~4.0 dtex, the diameter is 12μm~20μm, and the length is 5mm~12mm; The linear density of the polyester thermal adhesive fiber is 1.5~5.0 dtex.

3. The method for preparing an interlocking separation membrane support according to claim 1, characterized in that, In step S1, the fiber solids content of the first fiber suspension is controlled at 0.05~0.15wt%, and the fiber solids content of the second fiber suspension is controlled at 0.08~0.25wt%.

4. The method for preparing an interlocked separation membrane support according to claim 1, characterized in that, In step S2, the dual-channel wet web forming device includes a first headbox and a second headbox. The amount of slurry applied to the two headboxes is adjusted to control the quantitative amount of the dense layer to be 10~40g / m² and the quantitative amount of the skeleton layer to be 40~80g / m².

5. The method for preparing an interlocking separation membrane support according to claim 1, characterized in that, In step S3, the gradient increases as follows: initial stage 5 kPa~12 kPa, middle stage 12 kPa~35 kPa, and later stage 35 kPa~60 kPa.

6. The method for preparing an interlocked separation membrane support according to claim 1, characterized in that, In step S4, the pre-drying process involves reducing the moisture content of the double-layer wet net from 40-60% to 5-15%.

7. A separation membrane support with an interlocking structure, characterized in that, The interlocking structure of the separation membrane support is prepared according to any one of claims 1-6. The support includes a dense layer, a skeleton layer, and a gradient transition interlocking interface layer located between the two. The dense layer is composed of ultrafine polyester fibers and sulfonated modified ultrafine polyester fibers; The skeleton layer is composed of skeleton polyester fiber and polyester thermal bonding fiber; The gradient transition interlock interface layer is formed by embedding some of the ultrafine fibers in the dense layer into the pores of the skeleton layer.

8. The interlocking structure of the separation membrane support according to claim 7, characterized in that, The thickness of the gradient transition interlock interface layer is 5μm~50μm; The total thickness of the support is 60μm~150μm, and the total amount is 50g / m²~120g / m².

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