A method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane

Abstract

The application provides a preparation method of a double-melting-point fiber reinforced glass fiber composite filter membrane, and relates to the technical field of filtering and separating materials.The method comprises the following steps: preparing slurry of superfine glass fibers, medium-fine glass fibers and medium-coarse glass fibers respectively, and distributing the double-melting-point fibers according to layers; and then performing continuous wet lamination, grading dehydration, first heat treatment, second heat treatment, node solidification and shaping in sequence.The first heat treatment forms point nodes, the second heat treatment forms bridging nodes, and after the node solidification, the glass fiber composite filter membrane with a surface node area, a bridging node area and a supporting node area along the thickness direction is obtained.

Description

Technical Field

[0001] This invention relates to the field of filtration and separation materials technology, specifically to a method for preparing a glass fiber composite filter membrane reinforced with dual melting point fibers. Background Technology

[0002] Glass fiber filter membranes use a three-dimensional network of glass fibers as the main filter element, featuring heat resistance, aging resistance, high porosity, and adjustable fiber diameter. In hydraulic oil filtration and industrial liquid purification processes, filter membranes must simultaneously meet requirements for filtration accuracy, differential pressure stability, resistance to fiber shedding, folding resistance, and post-processing compatibility. Existing glass fiber filter membranes typically employ ultrafine glass fibers to improve filtration accuracy and achieve consolidation through resin impregnation or single low-melting-point hot-melt fibers.

[0003] The above methods have the following technical defects: First, the ultrafine glass fibers are prone to surface migration during dehydration, drying, winding, and folding after wet web formation, resulting in uneven distribution of pore boundaries; Second, single low-melting-point hot-melt fibers are prone to forming continuous plasticized regions in local pores during high-temperature treatment, causing pore structure shrinkage; Third, although high-content resin impregnation can improve the bonding force between fibers, the resin will change the pore size distribution of the filter membrane after entering the pores; Fourth, existing processes usually treat the reinforcement treatment as a single consolidation process and do not establish a corresponding relationship between different thermal response stages and structural reconstruction in the thickness direction of the filter membrane. Summary of the Invention

[0004] Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a glass fiber composite filter membrane reinforced with dual melting point fibers, which solves the problems of insufficient surface node distribution, discontinuous bridging structure in the middle, simple pore structure in the bottom support layer, and alteration of pore structure by overall resin impregnation in the preparation of glass fiber composite filter membranes.

[0006] Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a glass fiber composite filter membrane reinforced with dual-melting-point fibers, comprising the following steps: preparing ultrafine glass fibers, medium-fine glass fibers, and medium-coarse glass fibers into dispersion slurries respectively; preparing dual-melting-point fibers into a fiber dispersion system, wherein the dual-melting-point fibers have a first response temperature zone and a second response temperature zone; mixing the ultrafine glass fiber dispersion slurry with a first portion of dual-melting-point fibers to form a first layer of slurry; mixing the ultrafine glass fiber dispersion slurry, the medium-fine glass fiber dispersion slurry, and a second portion of dual-melting-point fibers to form a second layer of slurry; and mixing the medium-coarse glass fiber dispersion slurry with a third portion of dual-melting-point fibers to form a second layer of slurry. A third layer of slurry is formed; the third layer of slurry, the second layer of slurry, and the first layer of slurry are sequentially laid using a continuous wet lamination method to form an integrated wet membrane; the integrated wet membrane is subjected to graded dehydration treatment; the integrated wet membrane after graded dehydration treatment is subjected to a first heat treatment, in which the first response temperature zone component of the dual-melting-point fibers forms discrete nodes in the first and second layers; the integrated wet membrane after the first heat treatment is subjected to a second heat treatment, in which the second response temperature zone component of the dual-melting-point fibers forms bridging nodes in the second and third layers; the membrane after the second heat treatment is subjected to node curing and shaping treatment to obtain a glass fiber composite filter membrane reinforced with dual-melting-point fibers.

[0008] Preferably, the average fiber diameter of the ultrafine glass fiber is 0.2–1.2 μm and the length is 0.5–3 mm, the average fiber diameter of the medium-fine glass fiber is 1.5–4 μm and the length is 1–6 mm, and the average fiber diameter of the medium-coarse glass fiber is 5–12 μm and the length is 2–8 mm.

[0009] Preferably, the dual-melting-point fiber is a core-sheath type bicomponent fiber, an eccentric core-sheath type bicomponent fiber, a parallel type bicomponent fiber, or a partially coated type bicomponent fiber, with the first response temperature range being 85–125°C and the second response temperature range being 145–190°C.

[0010] Preferably, the ultrafine glass fiber in the first layer of slurry accounts for 60-90% of the total mass of the first layer of fibers, the mass ratio of ultrafine glass fiber to medium-fine glass fiber in the second layer of slurry is 1:3 to 3:1, and the medium-coarse glass fiber in the third layer of slurry accounts for 50-90% of the total mass of the third layer of fibers.

[0011] Preferably, the dual-melting-point fibers account for 5-15% of the total fiber mass of the filter membrane, the first portion of dual-melting-point fibers accounts for 15-35% of the total mass of dual-melting-point fibers, the second portion of dual-melting-point fibers accounts for 35-60% of the total mass of dual-melting-point fibers, and the third portion of dual-melting-point fibers accounts for 15-35% of the total mass of dual-melting-point fibers.

[0012] Preferably, the solid content of the ultrafine glass fiber dispersion slurry is 0.02-0.10 wt%, the solid content of the medium-fine glass fiber dispersion slurry is 0.03-0.15 wt%, the solid content of the medium-coarse glass fiber dispersion slurry is 0.05-0.20 wt%, and the pH value of the three dispersion slurries is 3.8-4.8.

[0013] Preferably, the graded dehydration process includes a pre-dehydration stage, a mid-dehydration stage, and a post-shaping dehydration stage. The vacuum degree of the pre-dehydration stage is 5-15 kPa, the vacuum degree of the mid-dehydration stage is 15-30 kPa, and the vacuum degree of the post-shaping dehydration stage is 10-20 kPa. A light-pressure shaping roller is set during the post-shaping dehydration stage.

[0014] Preferably, the temperature of the first heat treatment is 90-120°C, the treatment time is 20-120s, the heat source is input from one side of the first layer, and the first response temperature zone component of the dual melting point fiber forms point nodes on the side of the first layer and the second layer near the first layer.

[0015] Preferably, the temperature of the second heat treatment is 150-185°C, the treatment time is 30-180s, the heat source is input from one side of the third layer, and a transverse tension of 2-10N / 5cm is applied during the second heat treatment. The second response temperature zone component of the dual melting point fiber forms a bridging node with span between the second and third layers.

[0016] Preferably, the node curing is performed using a node curing agent, which is one of water-based acrylic resin, epoxy-siloxane hybrid resin, or silica sol hybrid resin. The amount of the node curing agent added is 0.3-3 wt% based on the total mass of the finished filter membrane. The node curing agent is applied to the surface of the membrane after the second heat treatment by spraying and cured at 130-150°C for 30-90 seconds. After the node curing and shaping treatment, the glass fiber composite filter membrane sequentially forms a surface node area consisting of a first layer, a bridging node area consisting of a second layer, and a supporting node area consisting of a third layer along the thickness direction.

[0017] Beneficial effects

[0018] This invention provides a method for preparing a glass fiber composite filter membrane reinforced with dual melting point fibers. It has the following beneficial effects:

[0019] 1. This invention uses ultrafine glass fiber, medium-fine glass fiber and medium-coarse glass fiber to form a layered slurry, and then lays the third, second and first layers of slurry in sequence through continuous wet lamination, so that the raw materials have a thickness distribution relationship in the wet film formation stage; the finished filter membrane forms a surface node area, a bridging node area and a support node area along the thickness direction, avoiding random mixing of the three types of fibers in a single slurry.

[0020] 2. In this invention, dual-melting-point fibers are divided into a first part, a second part, and a third part and added to three layers of slurry, and the mass ratio of the first part, the second part, and the third part is limited; the dual-melting-point fibers have a stable distribution ratio in the first layer, the second layer, and the third layer, the first heat treatment forms dot-like nodes, the second heat treatment forms bridging nodes, and the node morphology corresponds to the layer distribution.

[0021] 3. The present invention uses a first-layer side-input heat source for the first heat treatment and a third-layer side-input heat source for the second heat treatment; the first response temperature zone component first forms point nodes in the region near the first layer, and the second response temperature zone component then forms bridging nodes between the second and third layers. The two types of nodes are formed in different temperature zones and different layers. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall process flow of the preparation method of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the integrated wet film formed by continuous wet lamination of the present invention;

[0024] Figure 3 This is a schematic diagram of the process of graded dehydration and two-stage heat treatment in this invention;

[0025] Figure 4 This is a schematic diagram illustrating the formation of point nodes and bridging nodes in this invention;

[0026] Figure 5 This is a schematic diagram of the cross-sectional structure of the finished filter membrane of the present invention;

[0027] Figure 6 This is a schematic diagram illustrating the industrialization implementation and data usage process of this invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation Example 1:

[0030] like Figures 1 to 6As shown, a method for preparing a glass fiber composite filter membrane reinforced with dual-melting-point fibers involves preparing ultrafine glass fibers, medium-fine glass fibers, and medium-coarse glass fibers into dispersion slurries, and preparing dual-melting-point fibers with first and second response temperature zones into a fiber dispersion system. Through layered slurry preparation, ultrafine glass fibers are mainly distributed in the first layer, medium-fine and ultrafine glass fibers are co-distributed in the second layer, and medium-coarse glass fibers are mainly distributed in the third layer. The dual-melting-point fibers are distributed in the three layers according to a predetermined mass ratio. The third layer is then laid sequentially using a continuous wet-laid mesh method. The first, second, and third layers of slurry form an integrated wet membrane; the wet membrane is then dehydrated in stages; subsequently, a first heat treatment is performed from the first layer side, causing the first response temperature zone component of the dual-melting-point fibers to form dot-like nodes in the first and second layers near the first layer; a second heat treatment is then performed from the third layer side, causing the second response temperature zone component of the dual-melting-point fibers to form bridging nodes between the second and third layers; finally, the membrane is subjected to node curing and shaping treatment to obtain a glass fiber composite filter membrane with surface node areas, bridging node areas, and support node areas sequentially along the thickness direction.

[0031] In the first slurry layer, ultrafine glass fibers account for 60–90% of the total fiber mass; in the second slurry layer, the mass ratio of ultrafine glass fibers to medium-fine glass fibers is 1:3–3:1; in the third slurry layer, medium-coarse glass fibers account for 50–90% of the total fiber mass. Dual-melting-point fibers account for 5–15% of the total fiber mass of the filter membrane, with the first, second, and third portions of dual-melting-point fibers accounting for 15–35%, 35–60%, and 15–35% of the total dual-melting-point fiber mass, respectively.

[0032] The first heat treatment is performed at 90–120℃ for 20–120 seconds, with the heat source input from one side of the first layer. The second heat treatment is performed at 150–185℃ for 30–180 seconds, with the heat source input from one side of the third layer. A transverse tension of 2–10 N / 5 cm is applied during the treatment. The node curing agent is one of water-based acrylic resin, epoxy-siloxane hybrid resin, or silica sol hybrid resin. The amount of node curing agent added is 0.3–3 wt% based on the total mass of the finished filter membrane. After spraying, it is cured at 130–150℃ for 30–90 seconds.

[0033] The core concept is the two-stage response of dual-melting-point fibers. The first response temperature zone corresponds to the low-temperature point node formation stage. In this stage, the heat source is input from one side of the first layer. The heat first acts on the first layer, which contains more ultrafine glass fibers, causing the components in the first response temperature zone to form point nodes at the fiber intersections. The second response temperature zone corresponds to the bridging node formation stage. In this stage, the heat source is input from one side of the third layer. The heat first acts on the third layer, which contains more medium-coarse glass fibers, and then is transferred to the interface between the second and third layers, causing the components in the second response temperature zone to form bridging nodes with spans between adjacent fibers.

[0034] The two-stage treatment described above is not a repeated heating process of the same thermosetting process. Instead, by using the opposite heat source input sequence and different temperature zones, the node formation locations are limited to different layers. The first layer yields point-like nodes, the second and third layers yield bridging nodes, and the third layer retains the supporting pore structure. Thus, each step in the preparation process corresponds to a clear layer reconstruction result: layered slurry preparation determines the spatial position of the raw materials, graded dehydration determines the initial morphology of the wet film pores, the first heat treatment determines the surface node morphology, the second heat treatment determines the bridging node morphology, and node curing determines the node's final shape.

[0035] The raw material dispersion unit consists of a fiber dispersion tank with speed control, a pH adjustment dosing pipeline, a slurry circulation pump, and a screen filter. The stirring speed of the ultrafine glass fiber dispersion tank is set to 800–1200 r / min, with a dispersion time of 15–30 min; the stirring speed of the medium-fine glass fiber dispersion tank is set to 500–900 r / min, with a dispersion time of 10–20 min; and the stirring speed of the medium-coarse glass fiber dispersion tank is set to 300–700 r / min, with a dispersion time of 8–15 min. The dual-melting-point fiber dispersion system is pre-wetted using a non-ionic wetting agent, with the wetting agent content being 0.05–0.30 wt% based on the mass of the dual-melting-point fibers.

[0036] The stratified slurry preparation unit consists of three sets of metering pumps, three sets of mixing tanks, and an online solids content analyzer. The first, second, and third layers of slurry are prepared in separate mixing tanks. The metering pumps deliver the glass fiber dispersion slurry and the dual-melting-point fiber dispersion system according to the calculated dry basis mass. Each mixing tank is equipped with a circulation reflux pipeline with a reflux time of 5–12 minutes. The slurry is filtered through an 80–150 mesh screen before being discharged.

[0037] The continuous wet lamination unit consists of three headboxes, a forming mesh belt, a vacuum box, and wet film guide rollers. The third layer of slurry is first laid on the forming mesh belt via the first headbox, the second layer of slurry is laid on top of the third wet layer via the second headbox, and the first layer of slurry is laid on top of the second wet layer via the third headbox. The three wet layers are continuously laminated on the same forming mesh belt without using an offline lamination process.

[0038] The grading and dewatering unit consists of a front vacuum chamber, a middle vacuum chamber, a rear vacuum chamber, and a light-pressure shaping roller. The vacuum degree of the front vacuum chamber is 5-15 kPa, the vacuum degree of the middle vacuum chamber is 15-30 kPa, the vacuum degree of the rear vacuum chamber is 10-20 kPa, and the linear pressure of the light-pressure shaping roller is 0.05-0.30 MPa.

[0039] The two-stage heat treatment unit consists of a first heat treatment zone and a second heat treatment zone. The first heat treatment zone is located on one side of the first layer and uses hot air penetration or heat radiation-assisted hot air, with a temperature control accuracy of ±2℃. The second heat treatment zone is located on one side of the third layer and uses hot air penetration, with a temperature control accuracy of ±2℃, and is equipped with tension detection rollers and width control devices.

[0040] The node curing unit consists of an atomizing nozzle, a curing agent storage tank, a liquid supply pump, a heat curing chamber, and a shaping and winding mechanism. The node curing agent is applied by atomization spraying at a pressure of 0.10–0.35 MPa. The spraying amount is 0.3–3 wt% based on the total mass of the finished filter membrane. The temperature of the heat curing chamber is 130–150℃, and the curing time is 30–90 seconds.

[0041] The core of this invention's algorithm is a process parameter conversion algorithm. This algorithm takes the target total areal density, interlayer areal density ratio, molding area, slurry solid content, total proportion of dual-melting-point fibers, layered proportion of dual-melting-point fibers, conveyor belt speed, effective length of the heat treatment zone, wet film inlet and outlet water quality, and node curing agent solid content as input data. It outputs the three-layer dry base feeding mass, three-layer slurry water addition amount, dual-melting-point fiber layered feeding mass, metering pump flow rate, heat treatment residence time, graded dehydration rate, and node curing agent spraying volume.

[0042] The relationship between the target total surface density and the three-layer surface density is determined according to formulas (1) and (2):

[0043] (1)

[0044] The target total areal density, in g / m²; , and The areal densities are the first, second, and third layers, respectively, in g / m². Formula (1) is used to decompose the target areal density of the finished filter membrane into the sum of the densities of the three layers.

[0045] (2)

[0046] Let be the density of the j-th layer, in g / m². Let be the density ratio of the j-th layer, which is dimensionless; Choose 1, 2, or 3. Set this before production. The density of each layer is obtained by taking the ratio of the three layers and then using formula (2).

[0047] The molding area and the mass of a single-layer dry base are determined according to formulas (3) and (4):

[0048] (3)

[0049] This refers to the molding area per batch, in m². This refers to the forming width, in meters (m). The forming length for a single batch is in meters. Formula (3) is used to determine the feeding area based on the production line width and batch length.

[0050] (4)

[0051] The mass of the dry base material for the j-th layer is expressed in grams. Let be the density of the j-th layer, in g / m². The area is the area formed in a single batch, in m². Formula (4) is used to convert the layer density into the actual dry base feed amount.

[0052] The solid content, water content, and total volume of the slurry are determined according to formulas (5) to (7):

[0053] (5)

[0054] The solid content of the j-th layer slurry is expressed in wt%; The dry basis solids mass of the j-th slurry layer is expressed in grams. Let be the water mass in the j-th layer of slurry, in grams. Formula (5) is used for online solids content detection and slurry preparation verification.

[0055] (6)

[0056] The mass of water required to be added for the j-th layer of slurry, in grams; The mass of the j-th dry base solid is expressed in grams. Substitute the value in wt%. Formula (6) is used to calculate the amount of water to be added based on the target solid content.

[0057] (7)

[0058] The total mass of the j-th layer of slurry is in grams. Formula (7) is used to determine the loading amount of the mixing tank and the total continuous slurry supply from the metering pump.

[0059] The amount of dual-melting-point fiber to be fed is determined according to formulas (8) and (9):

[0060] (8)

[0061] The total dry weight of dual-melting-point fiber in a single batch is expressed in grams. The proportion of dual-melting-point fibers to the total fiber mass of the filter membrane is dimensionless. , and The values ​​are the dry basis feed weights for the three layers, in grams. Formula (8) is used to determine the total feed weight of dual-melting-point fibers in a single batch.

[0062] (9)

[0063] The dry basis feed mass of the j-th layer of double-melting-point fiber is expressed in grams. The distribution ratio of the double-melting-point fibers in the j-th layer is dimensionless; the first, second, and third layers... The values ​​are taken as 0.15–0.35, 0.35–0.60, and 0.15–0.35, respectively. Formula (9) is used to define the mass distribution of the dual-melting-point fibers in the three layers.

[0064] The continuous production pump flow rate, heat treatment residence time, dehydration rate, and node curing agent spraying volume are determined according to formulas (10) to (14):

[0065] (10)

[0066] The volumetric pumping flow rate of the j-th layer of slurry is expressed in L / min. The speed of the forming conveyor belt is expressed in m / min. This refers to the forming width, in meters (m). Let be the density of the j-th layer, in g / m². The density of the j-th layer of slurry is expressed in kg / L. Let be the mass fraction of the solid content of the j-th layer slurry, dimensionless. Formula (10) is used to convert the target surface density into the metering pump flow rate setpoint.

[0067] (11)

[0068] The dwell time in the k-th heat treatment zone is expressed in seconds. The effective heating length of the kth heat treatment zone is expressed in meters. The speed of the formed mesh belt is expressed in m / s. Take 1 or 2, which correspond to the first heat treatment and the second heat treatment, respectively. Formula (11) is used to check whether the two heat treatment times fall within the set range.

[0069] (12)

[0070] The required forming conveyor belt speed is given in m / s. Formula (12) is used to calculate the conveyor belt speed from the target dwell time when the effective length of the heat treatment zone is fixed.

[0071] (13)

[0072] The dehydration rate is expressed as % (percentage not provided in the original text). The water content of the wet membrane before it enters the staged dehydration unit is expressed in grams. The water content of the wet film after leaving the staged dehydration unit is expressed in g. Formula (13) is used to set and verify the three-stage vacuum dehydration state.

[0073] (14)

[0074] The volume of the node curing agent sprayed is in liters (L). The proportion of the node curing agent added during curing is dimensionless. The total dry weight of the finished filter membrane is expressed in kg. Density of the node curing agent working fluid, in kg / L; The solid content of the working liquid of the node curing agent is expressed as a mass fraction and is dimensionless. Formula (14) is used to determine the amount of liquid to be prepared in the node curing agent storage tank, the amount to be sprayed, and the batch consumption.

[0075] The above formula is based on the conservation of mass, area density conversion, continuous network material balance, the length-speed-time relationship of the heat treatment zone, and the calculation of the difference in water content before and after dehydration. In application, production personnel first test the raw material and slurry data, then determine the target total surface density, interlayer ratio, and molding area, and then use formulas (1) to (14) in sequence to complete the calculation of layer density splitting, dry base feeding, water addition, double melting point fiber layer feeding, metering pump flow rate, mesh belt speed, dehydration rate, and curing agent spraying volume. The calculation results are written into the batch process card and production record table.

[0076] The input data sources are as follows: fiber diameter and length are obtained from microscopic images or fiber analyzer detection; slurry solids content is obtained from drying and weighing methods or online solids analyzers; forming width and conveyor belt speed are obtained from production line settings; effective length of the heat treatment zone is obtained from equipment structural dimensions; wet film inlet and outlet water quality is obtained from weighing records or moisture content conversion; node curing agent solids content and density are obtained from incoming material detection. The output data usage process is as follows: the three-layer feeding mass is used for weighing and feeding; the three-layer water addition amount is used for slurry preparation; the flow rate of the three metering pumps is used for continuous slurry supply; the conveyor belt speed is used to control the residence time of the two heat treatment stages; the dehydration rate is used to calibrate the three-stage vacuum degree; and the curing agent spraying volume is used to control atomized spraying.

[0077] The fiberglass composite filter membrane prepared by this invention is used in the preparation of hydraulic oil filter elements, industrial lubricating oil filter elements, precision cutting fluid filter elements, and circulating oil purification system filter elements. In practical applications, the finished filter membrane is cut to the filter element size, and then folded, end-cap sealed, frame assembled, and integrity tested to form the filter element. The folding direction of the filter membrane is consistent with the running direction of the forming conveyor belt, the folding distance is 2.5–6.0 mm, the folding temperature is room temperature to 60°C, and the end-cap sealing temperature is determined according to the end-cap adhesive material process.

[0078] During production line application, each batch of raw materials undergoes initial testing for fiber diameter, length, dual-melting-point fiber melting response temperature range, and slurry solids content. After slurry preparation, the solids content, pH value, feed mass, and reflow time of the three slurries are recorded. During web forming, the belt speed, width, three-stage vacuum level, and wet film moisture content are recorded. During heat treatment, the two-stage temperature, residence time, and transverse tension are recorded. During node curing, the solids content of the curing agent, spraying pressure, spraying amount, curing temperature, and curing time are recorded. In finished product testing, the areal density, thickness, appearance, pore size distribution, and node cross-sectional morphology are recorded. The above data forms a batch traceability record for subsequent production parameter verification.

[0079] If the target filter membrane surface density is 90–110 g / m², the density ratios of the first, second, and third layers are set to 25–35%, 35–45%, and 25–35%, respectively; if the target filter membrane surface density is 120–150 g / m², the density ratios of the first, second, and third layers are set to 20–30%, 35–45%, and 30–40%, respectively. The first heat treatment temperature is set based on the median of the first response temperature range of the dual-melting-point fiber, and the second heat treatment temperature is set based on the median of the second response temperature range. The deviation between the temperature setting and the actually measured response temperature range shall not exceed ±5℃.

[0080] The core of the algorithm of this invention is a process parameter conversion algorithm, which does not include a self-learning model, a neural network model, or an image recognition model. The algorithm is based on formulas (1) to (14) in the specification and is executed in the order of “target product parameter input—raw material data input—production line parameter input—formula calculation—equipment setting—process verification—finished product traceability”.

[0081] The target product parameters include target total areal density, target width, target batch length, density ratio of the first layer, density ratio of the second layer, density ratio of the third layer, and total proportion of dual-melting-point fibers; raw material data include moisture content of the three types of glass fibers, first and second response temperature zones of dual-melting-point fibers, solid content of node curing agent, density of node curing agent, and target solid content of the three-layer slurry; production line parameters include forming mesh belt speed range, vacuum degree range of the three-section vacuum chamber, effective length of the first heat treatment zone, effective length of the second heat treatment zone, spraying pressure range, and shaping and winding speed range.

[0082] The data usage process includes the following steps: First, calculate the density of the three layers according to the target surface density and interlayer ratio; second, calculate the dry base material feeding mass of the three layers according to the molding area; third, calculate the water addition mass and total slurry mass of the three layers according to the slurry solid content; fourth, calculate the feeding mass of the three layers of double-melting-point fibers according to the total proportion of double-melting-point fibers and the layer ratio; fifth, calculate the pumping flow rate of the three metering pumps according to the conveyor belt speed and layer density; sixth, calculate the residence time of the two heat treatment stages according to the effective length of the heat treatment zone; seventh, calculate the graded dehydration rate according to the moisture content of the wet film entering and leaving the dehydration unit; eighth, calculate the spraying volume according to the solid content and density of the node curing agent.

[0083] In production control, the formula calculation results are written into the batch process card. Raw material weighing personnel weigh according to the three-layer dry basis feeding mass and the dual-melting-point fiber layer feeding mass; slurry preparation personnel control the slurry according to the three-layer water addition mass and solid content; web forming personnel set the slurry supply according to the pumping flow rate of three metering pumps and the mesh belt speed; heat treatment personnel set the mesh belt speed and hot air temperature according to the two-stage residence time; dewatering personnel adjust the vacuum degree of the front, middle and rear stages according to the dewatering rate results; curing personnel control the application of curing agent at each node according to the spraying volume and spraying pressure.

[0084] Batch traceability data consists of raw material testing forms, slurry preparation records, web forming records, heat treatment records, dewatering records, curing records, and finished product testing forms. This data is used to verify the feed amount, heat treatment time, node curing agent dosage, and finished product structural state of each batch of filter membranes.

[0085] In the manufacturing of hydraulic oil filter elements, the finished filter membrane is cut along the height of the filter element using either a round or straight blade, ensuring the blade edges are burr-free. After cutting, the filter element is folded at a spacing of 2.5–6.0 mm, with the folding direction aligned with the running direction of the forming conveyor belt. After the folded filter media is assembled with the inner and outer frames, it is sealed with end cap adhesive. The cured filter element undergoes visual inspection, checks for end cap seal integrity, and inspection for filter media damage.

[0086] In industrial lubricating oil purification systems, the total areal density and three-layer ratio of the finished filter membrane are selected according to the target filtration accuracy. Low-viscosity oils use a total areal density of 90-110 g / m², medium-viscosity oils use a total areal density of 110-130 g / m², and high-viscosity oils use a total areal density of 130-150 g / m². Different total areal densities correspond to different first, second, and third layer density ratios. During production, the feed rate and equipment settings are recalculated according to formulas (6) to (11).

[0087] In quality control, raw material data, process data, and finished product data constitute a complete traceability chain for the same batch. Raw material data includes the average fiber diameter, fiber length, and dual-melting-point fiber response temperature range for the three types of glass fibers; process data includes slurry solids content, pH value, conveyor belt speed, three-stage vacuum degree, two-stage heat treatment temperature, residence time, transverse tension, spraying pressure, and curing time; finished product data includes areal density, thickness, cross-sectional layer position, node morphology, and appearance defect records.

[0088] In reproducing this invention, production personnel first select the target areal density and the proportion of dual-melting-point fibers, and then prepare the slurry layer by layer; after the slurry preparation is completed, an online solids content analyzer is used to verify the solids content of the three layers of slurry; during the web forming process, the conveyor belt speed and width are recorded; during the dewatering process, three stages of vacuum degree are recorded; during the heat treatment process, two stages of temperature and residence time are recorded; during the node curing process, the solids content of the curing agent, the spraying pressure, and the curing time are recorded; after sampling the finished product, the areal density, thickness, and cross-sectional node morphology are checked. The above records constitute the necessary process documents for reproducing this invention. Specific Implementation Example 2:

[0090] like Figures 1 to 6 As shown, this embodiment prepares a dual-melting-point fiber-reinforced glass fiber composite filter membrane with a total areal density of 110 g / m². The raw materials used are ultrafine glass fibers, medium-fine glass fibers, medium-coarse glass fibers, and eccentric core-sheath type bicomponent dual-melting-point fibers. The ultrafine glass fibers have an average fiber diameter of 0.5 μm and a length of 1.5 mm; the medium-fine glass fibers have an average fiber diameter of 2.5 μm and a length of 3 mm; and the medium-coarse glass fibers have an average fiber diameter of 7 μm and a length of 5 mm. The first response temperature range of the dual-melting-point fibers is 108–115 °C, the second response temperature range is 162–170 °C, and the high-melting-point portion has a melting point higher than 220 °C.

[0091] During slurry preparation, ultrafine glass fibers were added to deionized water to obtain an ultrafine glass fiber dispersion slurry with a solid content of 0.05 wt%; medium-fine glass fibers were added to deionized water to obtain a medium-fine glass fiber dispersion slurry with a solid content of 0.08 wt%; and medium-coarse glass fibers were added to deionized water to obtain a medium-coarse glass fiber dispersion slurry with a solid content of 0.12 wt%. The pH value of all three slurries was adjusted to 4.2. The ultrafine glass fiber slurry was dispersed at a speed of 1000 r / min for 25 min; the medium-fine glass fiber slurry was dispersed at a speed of 700 r / min for 18 min; and the medium-coarse glass fiber slurry was dispersed at a speed of 500 r / min for 12 min.

[0092] The first, second, and third layers of slurry were prepared according to dry basis weight. The first layer of slurry contained 82% ultrafine glass fiber and 18% dual-melting-point fiber; the second layer contained 30% ultrafine glass fiber, 55% medium-fine glass fiber, and 15% dual-melting-point fiber; and the third layer contained 72% medium-coarse glass fiber and 28% dual-melting-point fiber. The areal densities of the first, second, and third layers were set to 30 g / m², 45 g / m², and 35 g / m², respectively.

[0093] During the forming process, the third layer of slurry is first laid on the forming mesh belt, followed by the second layer, and finally the first layer, forming an integrated wet film. The wet film enters the grading and dewatering unit, with the vacuum level set at 10 kPa in the front section, 22 kPa in the middle section, and 15 kPa in the rear section. The pressure of the rear light-pressure shaping roller line is set to 0.12 MPa.

[0094] The first heat treatment involved hot air input from one side of the first layer, with a temperature set at 112℃ and a treatment time of 55 seconds. The second heat treatment involved hot air input from one side of the third layer, with a temperature set at 168℃ and a treatment time of 80 seconds, while the transverse tension was set at 5 N / 5 cm. Subsequently, epoxy-siloxane hybrid resin was used as the node curing agent, with a solid content of 1.2 wt% and an application rate of 1.0 wt% based on the total mass of the finished filter membrane. The curing temperature was 140℃, and the curing time was 60 seconds. After curing, the membrane was shaped and wound to obtain the finished filter membrane.

[0095] The batch production records in this embodiment include the solid content of the three-layer slurry, the surface density of the three layers, the amount of dual-melting-point fiber fed, the vacuum level in three stages, the heat treatment temperature in two stages, the treatment time, the transverse tension, the amount of curing agent sprayed, and the surface density of the finished product. Production personnel calculate the feeding amount and the conveyor belt speed according to the formula and check the set values ​​according to the record sheet. Specific Implementation Example 3:

[0097] This embodiment prepares a dual-melting-point fiber-reinforced glass fiber composite filter membrane with a total areal density of 90 g / m². The areal densities of the first, second, and third layers are set to 25 g / m², 35 g / m², and 30 g / m², respectively. The first layer slurry contains 86% ultrafine glass fiber and 14% dual-melting-point fiber; the second layer slurry contains 40% ultrafine glass fiber, 48% medium-fine glass fiber, and 12% dual-melting-point fiber; and the third layer slurry contains 80% medium-coarse glass fiber and 20% dual-melting-point fiber. The first heat treatment temperature is 102℃, and the treatment time is 40 s; the second heat treatment temperature is 158℃, and the treatment time is 65 s, with a transverse tension of 3 N / 5 cm. The node curing agent is water-based acrylic resin with a solid content of 0.8 wt%, and the spraying amount is 0.6 wt% based on the total mass of the finished filter membrane. The curing temperature is 135℃, and the curing time is 45 s. The remaining steps are the same as in Example 1. Specific Implementation Example 4:

[0099] This embodiment prepares a dual-melting-point fiber-reinforced glass fiber composite filter membrane with a total areal density of 135 g / m². The areal densities of the first, second, and third layers are set to 35 g / m², 55 g / m², and 45 g / m², respectively. The first layer slurry contains 78% ultrafine glass fiber and 22% dual-melting-point fiber; the second layer slurry contains 28% ultrafine glass fiber, 56% medium-fine glass fiber, and 16% dual-melting-point fiber; and the third layer slurry contains 78% medium-coarse glass fiber and 22% dual-melting-point fiber. The first heat treatment temperature is 118℃, and the treatment time is 70 s; the second heat treatment temperature is 175℃, and the treatment time is 110 s, with a transverse tension of 8 N / 5 cm. The node curing agent is a silica sol hybrid resin with a solid content of 1.5 wt%, and the spraying amount is 1.5 wt% based on the total mass of the finished filter membrane. The curing temperature is 148℃, and the curing time is 75 s. The remaining steps are the same as in Example 1.

[0100] To ensure the reproducibility of this invention in industrial production lines, the preparation process is implemented in the following order: "raw material testing—formula calculation—layered slurry preparation—continuous wire mesh formation—graded dewatering—two-stage heat treatment—node curing—finished product testing—batch traceability." A correspondence is established between each step using areal density, solid content, conveyor belt speed, vacuum level, heat treatment residence time, and node curing agent application rate. Production personnel input test data and equipment parameters according to the batch record sheet, and then calculate the feed rate, pumping rate, wire mesh speed, and heat treatment time using the formula.

[0101] During the raw material testing phase, the average fiber diameter, length distribution, and moisture content of ultrafine glass fiber, medium-fine glass fiber, and medium-coarse glass fiber were tested; the first response temperature zone, second response temperature zone, and fiber length of the dual-melting-point fiber were tested; and the solid content, viscosity, and spray atomization state of the node curing agent were tested. The test data are used as input data for formulation calculations and are not replaced by empirical material additions.

[0102] In the formulation calculation stage, the target total areal density and the density ratio of the three layers are first determined, and then the dry basis mass of the three layers is calculated. After that, the dry basis mass of the three layers of double melting point fiber is calculated according to the total proportion of double melting point fiber and the layer ratio. Then, the water addition mass and total slurry volume are calculated according to the target solid content of each layer of slurry. Finally, the conveyor belt speed is determined according to the effective length of the heat treatment zone.

[0103] During the web forming and heat treatment stages, the third layer of slurry first enters the first headbox and forms the bottom wet layer. The second layer of slurry enters the second headbox and covers the bottom wet layer. The first layer of slurry enters the third headbox and covers the second wet layer. After three stages of vacuum dehydration, the wet film enters the first heat treatment zone, with the first heat source input from one side of the first layer. It then enters the second heat treatment zone, with the second heat source input from one side of the third layer. No offline handling or secondary bonding is performed between the two heat treatments.

[0104] During the node curing stage, the node curing agent is applied to the surface of the membrane that has undergone the second heat treatment via an atomizing nozzle. The spraying pressure, spraying amount, and curing temperature are determined based on the solid content of the curing agent. After curing, the membrane is shaped and wound to obtain the finished filter membrane. The finished filter membranes are tested in batches for areal density, thickness, appearance, pore size distribution, cross-sectional node morphology, and cleanliness. Specific Implementation Example 5:

[0106] This embodiment provides a method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane using decommissioned glass fiber wind turbine blades as the glass fiber source. The decommissioned glass fiber wind turbine blades are glass fiber reinforced epoxy resin composite blade scraps or cut materials from decommissioned blades. The recycled blade material contains glass fiber, cured epoxy resin, fillers, coating fragments, and metallic impurities. To ensure that the recycled glass fiber meets the requirements for wet film formation, this embodiment first performs resin removal, impurity removal, grading, shortening, and micronization treatment on the recycled blade material. Then, the obtained recycled glass fiber is classified into three categories according to fiber size: ultrafine glass fiber, medium-fine glass fiber, and medium-coarse glass fiber, and combined with dual-melting-point fibers to prepare the composite filter membrane.

[0107] First, retired fiberglass wind turbine blades are cut into sheet-like recycled materials with a length of 30–80 mm and a width of 10–40 mm. Obvious coating blocks, adhesive blocks, metal connectors, and core materials are removed. The sheet-like recycled materials are then placed in a crusher for low-speed shearing and crushing at a speed controlled at 300–800 r / min, yielding blade fragments with a particle size of 3–15 mm. Subsequently, the blade fragments are subjected to magnetic separation and air separation to remove metal particles, coating powder, and low-density core fragments, resulting in fiberglass resin composite fragments.

[0108] Glass fiber resin composite fragments were placed in a pyrolysis furnace for resin removal. Nitrogen gas was introduced into the furnace as a protective gas, with a flow rate controlled at 1.0–3.0 L / min. The heating rate was controlled at 3–8 °C / min. After heating to 450–520 °C, the temperature was held for 40–120 min to allow the cured resin matrix to thermally decompose and separate from the glass fiber. After pyrolysis, the mixture was naturally cooled to below 80 °C, and the pyrolysis product was removed. Carbonized resin powder was removed by airflow dispersion and sieving. To reduce the impact of residual carbon from pyrolysis on subsequent wet film formation, the sieved glass fiber was immersed in a 1–3 wt% hydrogen peroxide aqueous solution for 20–60 min, then washed with deionized water until the pH of the washing solution reached 6.5–7.5. Subsequently, it was dried at 90–110 °C for 60–120 min to obtain clean recycled glass fiber.

[0109] Clean recycled glass fibers are chopped and graded. First, a fiber cutter is used to cut the recycled glass fibers to a length of 1–8 mm. Then, a combination of air classifier and sieve classification is used for particle size and length sorting. After grading, fine fibers with an average fiber diameter of 0.5–1.2 μm and a length of 0.5–3 mm are defined as ultrafine recycled glass fibers; fibers with an average fiber diameter of 1.5–4 μm and a length of 1–6 mm are defined as medium-fine recycled glass fibers; and fibers with an average fiber diameter of 5–12 μm and a length of 2–8 mm are defined as medium-coarse recycled glass fibers. Coarse particles with a diameter greater than 12 μm or containing resin lumps or carbon powder agglomerates are not included in the filter membrane preparation process of this embodiment.

[0110] To improve the water dispersibility of the recycled glass fibers, the three types of recycled glass fibers were subjected to surface activation treatment. Based on the dry weight of the fibers, recycled ultrafine glass fibers, recycled medium-fine glass fibers, and recycled medium-coarse glass fibers were added to deionized water, and the pH of the slurry was adjusted to 4.0–4.5. Then, 0.2–0.6 wt% of γ-glycidoxypropyltrimethoxysilane was added, and the mixture was stirred for 30–60 min and allowed to stand for 20–40 min to allow the silane coupling agent to form an activated layer on the surface of the recycled glass fibers. Subsequently, the fibers were dispersed using a fiber dissociator. The dispersion speed for the ultrafine glass fiber slurry was 1200–1800 r / min, and the dispersion time was 15–30 min; the dispersion speed for the medium-fine glass fiber slurry was 800–1200 r / min, and the dispersion time was 10–20 min; the dispersion speed for the medium-coarse glass fiber slurry was 500–900 r / min, and the dispersion time was 5–15 min.

[0111] In this embodiment, an eccentric core-sheath type dual-melting-point fiber is used as the reinforcing fiber. The softening temperature range of the low-melting-point sheath layer of the dual-melting-point fiber is 105-115℃, and the melting point of the high-melting-point core layer is higher than 220℃. The average fiber diameter is 10-18μm, and the length is 3-6mm. To prepare the dual-melting-point fiber dispersion system, the dual-melting-point fiber is first pre-wetted in an aqueous solution containing 0.05-0.15wt% nonionic dispersant for 10-20 minutes, and then stirred at 500-800 r / min for 5-10 minutes to obtain a uniform dual-melting-point fiber suspension.

[0112] Based on the dry basis weight of the finished filter membrane, 45 parts of recycled ultrafine glass fiber, 22 parts of recycled medium-fine glass fiber, 18 parts of recycled medium-coarse glass fiber, 10 parts of dual-melting-point fiber, 2 parts of node curing agent (consolidation weight), and 3 parts for process loss are taken. The recycled ultrafine glass fiber is mixed with a portion of the dual-melting-point fiber to form the first slurry, wherein the recycled ultrafine glass fiber accounts for 82% of the dry basis weight of the first slurry, and the dual-melting-point fiber accounts for 18%. The recycled ultrafine glass fiber, recycled medium-fine glass fiber, and a portion of the dual-melting-point fiber are mixed to form the second slurry, wherein the recycled ultrafine glass fiber accounts for 28%, the recycled medium-fine glass fiber accounts for 57%, and the dual-melting-point fiber accounts for 15%. The recycled medium-coarse glass fiber and a portion of the dual-melting-point fiber are mixed to form the third slurry, wherein the recycled medium-coarse glass fiber accounts for 75% and the dual-melting-point fiber accounts for 25%. The solid content of the three-layer slurry is controlled at 0.04–0.08 wt%, 0.06–0.12 wt%, and 0.08–0.18 wt%, respectively.

[0113] A continuous wet-layout membrane formation process is employed. First, the third layer of slurry is laid on a conveyor belt to form the bottom supporting wet layer. Then, the second layer of slurry is laid on top of the bottom supporting wet layer to form the middle bridging wet layer. Finally, the first layer of slurry is laid on top of the middle bridging wet layer to form the surface pore-stabilizing wet layer, resulting in an integrated wet membrane. The dry basis areal densities of the first, second, and third layers are controlled to be 28–35 g / m², 40–50 g / m², and 30–40 g / m², respectively, with the total areal density of the finished filter membrane controlled to be 100–125 g / m².

[0114] The integrated wet film undergoes a graded dehydration process. The vacuum degree is controlled at 6–12 kPa in the first stage, 18–26 kPa in the middle stage, and 12–18 kPa in the final stage. The wet film thickness is initially controlled using a light-pressure shaping roller, with the linear pressure controlled at 0.05–0.20 MPa. After graded dehydration, the moisture content of the wet film is controlled at 55–70%.

[0115] The wet film is then subjected to a first heat treatment. The wet film is fed into the first heat treatment zone, with the first heat source input from one side of the first layer. The heat treatment temperature is controlled at 108–115°C, and the treatment time is 45–75 seconds, causing the low-melting-point fiber skin layer of the dual-melting-point fibers to form dot-like nodes on the side of the first and second layers closest to the first layer. After the first heat treatment, the wet film is not subjected to high-pressure compaction and is directly introduced into the second heat treatment zone.

[0116] During the second heat treatment, the second heat source is input from one side of the third layer. The heat treatment temperature is controlled at 162–175℃, and the treatment time is 70–120 seconds. Simultaneously, a transverse tension of 4–8 N / 5 cm is applied, causing the low-melting-point portion of the dual-melting-point fiber to form a span-span bridging node between the second and third layers, while the high-melting-point core layer maintains the fiber ridge shape. After the second heat treatment, the membrane forms a surface node region composed of the first layer, a bridging node region composed of the second layer, and a support node region composed of the third layer along the thickness direction.

[0117] Node curing was performed using epoxy-siloxane hybrid resin. An epoxy-siloxane hybrid resin with a solid content of 1.0–1.5 wt% was applied to the membrane after its second heat treatment via spraying. The spraying amount was 1.0–2.0 wt% based on the dry basis weight of the finished filter membrane. After spraying, the membrane was cured at 135–145℃ for 45–80 seconds, then shaped and wound using a shaping roller to obtain a dual-melting-point fiber-reinforced fiberglass composite filter membrane made from recycled fiberglass wind turbine blades.

[0118] In this embodiment, the recycled material from decommissioned fiberglass wind turbine blades undergoes thermal descaling, oxidative cleaning, grading and screening, shaving and micronization, and surface activation to form recycled ultrafine, medium-fine, and medium-coarse glass fibers suitable for wet membrane formation. Through three-layer slurry separation and continuous wet lamination, the recycled glass fibers with different particle size distributions are layered in the thickness direction of the filter membrane. A first and second heat treatment cause the dual-melting-point fibers to form dot-like nodes and bridging nodes in the first, second, and third layers, respectively. Low-load node curing results in a stable three-layer node structure in the finished filter membrane. This embodiment can convert glass fibers from decommissioned fiberglass wind turbine blades into fiber raw materials for composite filter membranes and is suitable for the preparation of hydraulic oil filtration, industrial liquid purification, and high-precision separation filter media.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a reference structure" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0120] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a glass fiber composite filter membrane reinforced with dual melting point fibers, characterized in that, The process includes the following steps: preparing ultrafine glass fibers, medium-fine glass fibers, and medium-coarse glass fibers into dispersion slurries; preparing dual-melting-point fibers into a fiber dispersion system, wherein the dual-melting-point fibers have a first response temperature zone and a second response temperature zone; mixing the ultrafine glass fiber dispersion slurry with a first portion of dual-melting-point fibers to form a first layer of slurry; mixing the ultrafine glass fiber dispersion slurry, the medium-fine glass fiber dispersion slurry, and a second portion of dual-melting-point fibers to form a second layer of slurry; and mixing the medium-coarse glass fiber dispersion slurry with a third portion of dual-melting-point fibers to form a third layer of slurry. The third layer of slurry, the second layer of slurry, and the first layer of slurry are laid sequentially using a continuous wet overlay method to form an integrated wet membrane; the integrated wet membrane is then subjected to graded dewatering treatment. The integrated wet membrane after graded dehydration is subjected to a first heat treatment, and the first response temperature zone component of the dual melting point fiber forms discrete nodes in the first and second layers. A second heat treatment is performed on the integrated wet film after the first heat treatment, and the second response temperature zone component of the dual melting point fiber forms bridging nodes in the second and third layers. After the second heat treatment, the membrane is subjected to node curing and shaping to obtain a glass fiber composite filter membrane reinforced with dual melting point fibers.

2. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The average fiber diameter of the ultrafine glass fiber is 0.2–1.2 μm and the length is 0.5–3 mm; the average fiber diameter of the medium-fine glass fiber is 1.5–4 μm and the length is 1–6 mm; and the average fiber diameter of the medium-coarse glass fiber is 5–12 μm and the length is 2–8 mm.

3. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The dual-melting-point fiber is a core-sheath type bicomponent fiber, an eccentric core-sheath type bicomponent fiber, a parallel type bicomponent fiber, or a partially coated type bicomponent fiber. The first response temperature range is 85–125°C, and the second response temperature range is 145–190°C.

4. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, In the first layer of slurry, ultrafine glass fibers account for 60-90% of the total mass of the first layer of fibers. In the second layer of slurry, the mass ratio of ultrafine glass fibers to medium-fine glass fibers is 1:3 to 3:

1. In the third layer of slurry, medium-coarse glass fibers account for 50-90% of the total mass of the third layer of fibers.

5. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The dual-melting-point fibers account for 5-15% of the total fiber mass of the filter membrane, the first portion of dual-melting-point fibers accounts for 15-35% of the total dual-melting-point fibers, the second portion of dual-melting-point fibers accounts for 35-60% of the total dual-melting-point fibers, and the third portion of dual-melting-point fibers accounts for 15-35% of the total dual-melting-point fibers.

6. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The solid content of the ultrafine glass fiber dispersion slurry is 0.02–0.10 wt%, the solid content of the medium-fine glass fiber dispersion slurry is 0.03–0.15 wt%, and the solid content of the medium-coarse glass fiber dispersion slurry is 0.05–0.20 wt%. The pH value of all three dispersion slurries is 3.8–4.

8.

7. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The graded dehydration process includes a front-stage dehydration, a middle-stage dehydration, and a rear-stage shaping dehydration. The vacuum degree of the front-stage dehydration is 5-15 kPa, the vacuum degree of the middle-stage dehydration is 15-30 kPa, and the vacuum degree of the rear-stage shaping dehydration is 10-20 kPa. A light-pressure shaping roller is set during the rear-stage shaping dehydration process.

8. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The temperature of the first heat treatment is 90-120℃, the treatment time is 20-120s, the heat source is input from one side of the first layer, and the first response temperature zone component of the dual melting point fiber forms point nodes on the side of the first layer and the second layer near the first layer.

9. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The second heat treatment is performed at a temperature of 150–185°C for 30–180 seconds. The heat source is input from one side of the third layer. During the second heat treatment, a transverse tension of 2–10 N / 5 cm is applied. The second response temperature zone component of the dual-melting-point fiber forms a bridging node with a span between the second and third layers.

10. The method for preparing a dual-melting-point fiber-reinforced glass fiber composite filter membrane according to claim 1, characterized in that, The node curing is carried out using a node curing agent, which is one of water-based acrylic resin, epoxy-siloxane hybrid resin or silica sol hybrid resin. The amount of node curing agent added is 0.3 to 3 wt% based on the total mass of the finished filter membrane. The node curing agent is applied to the surface of the membrane after the second heat treatment by spraying and cured at 130 to 150°C for 30 to 90 seconds. After the node curing and shaping process, the fiberglass composite filter membrane sequentially forms a surface node area consisting of a first layer, a bridging node area consisting of a second layer, and a support node area consisting of a third layer along the thickness direction.

Images