A fiber composite hydraulic defoaming filter element and a preparation method thereof

Abstract

The application belongs to the technical field of hydraulic pressure filtration, and provides a fiber composite hydraulic pressure defoaming filter element and a preparation method thereof.The application adopts a three-layer gradient precision filtration membrane design, and comprises an L1 bubble trapping layer of polyvinylidene fluoride nanofiber and metal fiber co-structure, an L2 synergistic coalescence layer of glass fiber framework and PA66 microfiber composite, and a L3 stable flow particle trapping layer of melt-blown polypropylene, combines a grid-shaped bubble breaking cover and an annular gap structure to form a gas discharge channel, prepares the composite fiber through electrospinning, orientation, annealing process regulation of beta phase content and in-situ polymerization technology, realizes a bubble removal rate of more than 91%, a pressure drop of less than 0.2 MPa, and a service life of more than 5000 hours, solves the technical problems of low defoaming efficiency and large flow resistance of the traditional filter element, and has wide industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic filtration technology and provides a fiber composite hydraulic defoaming filter element and its preparation method. Background Technology

[0002] In modern industrial hydraulic systems, especially in high-end equipment fields such as engineering machinery, aerospace, and shipbuilding, hydraulic oil plays a crucial role as the power transmission medium. The presence of air bubbles in the oil can cause a series of serious problems, including cavitation, pressure fluctuations, and system vibration, directly affecting the working accuracy and service life of hydraulic components. Therefore, hydraulic systems place extremely stringent performance requirements on defoaming filter elements. They must not only possess highly efficient bubble separation capabilities to ensure oil quality but also maintain extremely low flow resistance to sustain system efficiency and stability. As hydraulic technology develops towards higher pressure, higher precision, and longer lifespan, higher standards are being set for the reliability and durability of defoaming filter elements under complex operating conditions. This requires filter element materials to possess excellent mechanical strength, chemical stability, and fatigue resistance. The development and application of high-performance fiber composite defoaming filter elements can not only significantly improve the overall performance and reliability of hydraulic systems and reduce equipment failure rates and maintenance costs, but also serve as a key technological support for driving hydraulic technology to a higher level, holding significant strategic importance for promoting technological progress and product upgrades in related industries.

[0003] While hydraulic defoaming filter technology has made some progress in achieving basic functions, it still has significant shortcomings in meeting the needs of high-end applications. These shortcomings are mainly manifested in two core issues: low defoaming efficiency and excessive flow resistance. Traditional filter elements often use single materials or simple composite structures, lacking specialized designs for the characteristics of bubbles, resulting in an imperfect bubble capture mechanism and an inability to effectively achieve gas-liquid separation. For example, Chinese patent CN119900748A discloses a hydraulic oil filter element, but it suffers from low defoaming efficiency. Furthermore, existing filter elements often neglect flow resistance control in the pursuit of filtration precision, resulting in unreasonable pore structure design and a lack of effective flow channel optimization, leading to increased system energy consumption and decreased operating efficiency. For instance, Chinese patent CN118512808A discloses a multi-layer lubricating oil filter element structure, but it suffers from excessive flow resistance. The root cause of these technological limitations lies in the lack of in-depth understanding of the mechanism of bubble behavior, the lack of systematic optimization in material selection and structural design, especially in key technical aspects such as the control of surface properties of fiber materials, the collaborative design of multi-layer structures, and the rational construction of gas exhaust channels, which have obvious shortcomings and make it difficult to achieve a balance between defoaming efficiency and low flow resistance. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a fiber composite hydraulic defoaming filter element and its preparation method, which solves the problems of low defoaming efficiency and excessive flow resistance in current filter elements.

[0006] (2) Technical solution

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

[0008] A fiber composite hydraulic defoaming filter element, comprising:

[0009] The top cover is made of nylon.

[0010] The outer mesh sleeve is made of stainless steel.

[0011] Fine filtration membrane;

[0012] Bubble wrap, made of stainless steel;

[0013] The lower end cap is made of nylon.

[0014] The fine filter membrane has a cylindrical structure, and the outer mesh sleeve covers the outer surface of the fine filter membrane and forms a pressure-bearing filtration unit with it; the bubble fragmentation cover has a grid-like structure, axially penetrates and is located in the center of the inner cavity of the fine filter membrane, forming an annular gap structure with the inner wall of the fine filter membrane; the upper end cover is provided with a gas collection cavity and communicates with the annular gap structure; the upper end cover and the lower end cover are respectively sealed and connected to both ends of the fine filter membrane, applying an axial pre-tightening force to the fine filter membrane, assembling the outer mesh sleeve, the fine filter membrane and the bubble fragmentation cover into a whole;

[0015] The fine filtration membrane comprises, from the outside to the inside, an L1 bubble trapping layer, an L2 co-aggregation layer, and an L3 flow stabilizing and particle intercepting layer.

[0016] Furthermore, the L1 bubble trapping layer is co-constructed from polyvinylidene fluoride nanofibers and metal fibers, wherein the polyvinylidene fluoride is obtained through electrospinning, orientation, and annealing processes to achieve a β phase content that satisfies β / (α+β)≥0.60, and the volume fraction of the metal fibers is 10 vol%-30 vol%.

[0017] The L2 co-polymerization layer is formed by a composite of a glass fiber skeleton and PA66 microfibers, wherein the PA66 microfibers are grown on the glass fiber skeleton through an in-situ polymerization process; the bubbles captured by the L1 bubble trapping layer are guided to the L2 co-polymerization layer through the pore size gradient for polymerization, and the polymerized bubbles are discharged through the annular gap structure.

[0018] This invention employs a three-layer gradient fiber composite structure combined with a grid-like bubble-breaking cap design, primarily to enhance the defoaming separation and low flow resistance performance of hydraulic filter elements. From a material synergy perspective, the composite configuration of polyvinylidene fluoride nanofibers and metal fibers in the L1 bubble-catching layer achieves functional complementarity. The polyvinylidene fluoride nanofibers, after undergoing electrospinning, orientation, and annealing processes to control the β-phase content, possess excellent oleophobic and gas-loving properties and a high specific surface area. The metal fibers provide structural support and electrical conductivity; their synergistic effect significantly enhances the bubble-capturing capability. From a structural design perspective, the L2 synergistic aggregation layer adopts a composite configuration of glass fiber skeleton and PA66 microfibers. The strong interfacial bond formed by the in-situ polymerization process of PA66 microfibers on the glass fiber surface organically integrates the mechanical strength of the glass fiber with the flexibility of the PA66 microfibers, synergistically promoting the aggregation process of captured bubbles. From a flow control perspective, the pore size gradient design formed by the three-layer structure, combined with the grid-like bubble fragmentation cap and annular structure, constructs a complete gas separation channel. The L3 flow stabilizing and particle-retaining layer ensures uniform fluid distribution, while the annular structure provides an efficient discharge path for large bubbles after aggregation. The synergistic cooperation of multiple structures achieves a balance between high defoaming efficiency and low flow resistance. The overall design, through multi-level synergistic optimization of material properties, structural configuration, and flow mechanism, overcomes the limitations of traditional single-function filter cartridges.

[0019] Furthermore, the L1 bubble-catching layer is prepared through the following steps:

[0020] Step A1: Electrospinning to prepare polyvinylidene fluoride nanofibers, with an electric field strength of 12kV-22kV and a collection distance of 12cm-22cm;

[0021] Step A2: The polyvinylidene fluoride nanofibers are subjected to a stretching and orientation treatment, with a stretching-orientation ratio λ of 1.3-2.0;

[0022] Step A3: Perform annealing treatment to control the crystal phase. The annealing temperature is 110℃-135℃ and the annealing time is 5min-20min, so that β / (α+β)≥0.60.

[0023] Furthermore, the L2 collaborative aggregation layer is prepared through the following steps:

[0024] Step B1: Prepare a glass fiber skeleton with a nominal pore size of 10μm-25μm;

[0025] Step B2: Prepare a prepolymerization solution by mixing hexamethylenediamine and adipic acid monomers in a molar ratio of 1:(1.0-1.05), impregnate the glass fiber skeleton, and then carry out in-situ polymerization under an inert atmosphere. The polymerization temperature is 260℃-280℃ and the holding time is 10min-30min, so that PA66 microfibers grow in situ on the glass fiber surface.

[0026] Step B3: Control the crystallinity of PA66 microfibers to reach 25%-40%, and the microfiber diameter to be 1μm-5μm.

[0027] Furthermore, in step A1, the mass fraction of polyvinylidene fluoride in N,N-dimethylformamide is 8wt%-15wt%, and the electrospinning environment temperature is 20℃-30℃.

[0028] After step A3, the polyvinylidene fluoride nanofibers are subjected to plasma activation treatment with a power of 30W-80W and a time of 30s-120s.

[0029] Furthermore, in step B2, the mass ratio of microfiber to glass fiber is 1:3 to 1:8.

[0030] Furthermore, the polyvinylidene fluoride fiber of the L1 bubble trapping layer has a diameter of 200nm-600nm and a surface energy γs≤22mN / m;

[0031] The metal fibers in the L1 bubble trapping layer are stainless steel fibers;

[0032] The L1 bubble trapping layer, L2 synergistic aggregation layer, and L3 flow stabilizing and particle intercepting layer work together to form a pore size gradient with an outer equivalent pore size of 40μm-80μm and an inner equivalent pore size of 8μm-20μm.

[0033] The L3 flow stabilizing and particle-removing layer is a meltblown polypropylene fiber layer with a nominal pore size of 5μm-15μm;

[0034] The thickness ratio of the L1 bubble trapping layer, the L2 co-aggregation layer, and the L3 flow stabilizing and particle intercepting layer is 1:(1.5-3):(0.5-1.0);

[0035] Furthermore, the opening ratio of the broken blister pack is 20%-35%; the width of the annular gap is 0.4mm-1.2mm;

[0036] The upper end cover is provided with a gas collection cavity and an exhaust channel to realize the coordinated gas discharge of the L1 bubble trapping layer and the L2 co-aggregation layer.

[0037] This invention employs a multi-stage synergistic process design primarily to enhance the defoaming separation and structural stability of fiber composite filter elements. From a crystal phase control perspective, the L1 defoaming layer achieves precise control of the β-phase content of polyvinylidene fluoride (PVDF) through a combined process of electrospinning, stretching and orientation, and annealing. The electrospinning process forms nanoscale fiber structures in an N,N-dimethylformamide solvent system, the stretching and orientation process further optimizes the molecular chain arrangement, and the annealing process promotes the β-phase crystal transformation. The synergistic effect of these multiple processes endows the fibers with excellent oleophobic and gas-loving properties and low surface energy characteristics. From an interface engineering perspective, the L2 synergistic polymerization layer utilizes in-situ polymerization technology of hexamethylenediamine and adipic acid monomers to achieve controllable growth of PA66 microfibers on the surface of the glass fiber skeleton under an inert atmosphere, forming strong interfacial bonding and ideal microfiber crystallinity. The in-situ polymerization mechanism ensures the synergistic effect of glass fiber mechanical strength and PA66 flexibility. From a structural optimization perspective, plasma activation treatment further improves the surface activity of polyvinylidene fluoride fibers. Combined with the composite reinforcement of stainless steel fibers, the three-layer structure forms a synergistic filtration system through precise design of thickness ratio and pore size gradient. The control of the opening rate of the broken bubble cap and the design of the annular gap width provide an optimized channel for gas discharge. The configuration of the gas collection chamber and the exhaust channel realizes the effective connection between capture and aggregation functions. The multi-level synergistic design breaks through the performance limitations of a single functional layer.

[0038] This invention also discloses a method for preparing a fiber composite hydraulic defoaming filter element, comprising the following steps:

[0039] Step S1: The L1 bubble trapping layer, L2 co-aggregating layer, and L3 flow stabilizing and particle intercepting layer are sequentially composited to form a fine filtration membrane at a composite temperature of 60℃-80℃; the composite interface between the L1 bubble trapping layer and the L2 co-aggregating layer is achieved by hot pressing, with a composite pressure of 0.5MPa-1.5MPa.

[0040] Step S2: Insert the broken bubble cap into the fine filter membrane, and then install it into the outer mesh sleeve;

[0041] Step S3: Seal both ends of the fine filter membrane with the upper and lower end caps respectively.

[0042] A fiber composite hydraulic defoaming filter element is used in hydraulic systems for defoaming and filtering hydraulic oil.

[0043] In the fiber composite hydraulic defoaming filter system, the L1 bubble-capturing layer primarily focuses on the initial bubble capture function. It achieves efficient bubble adsorption through the low surface energy characteristics of polyvinylidene fluoride (PVDF) nanofibers and the structural support of metal fibers. The microscopic mechanism lies in the oleophobic and gas-loving interface provided by the PVDF β-phase crystal structure, which facilitates preferential bubble adsorption on the fiber surface. Meanwhile, the metal fibers enhance bubble capture capability through electrostatic effects. The L2 synergistic aggregation layer focuses on capturing the aggregation and growth process of bubbles. The glass fiber skeleton provides a stable three-dimensional network structure, and the strong interfacial bonding formed by in-situ polymerization of PA66 microfibers creates a suitable aggregation environment. Its mechanism is reflected in the synergistic construction of a microscopic space conducive to the collision and fusion of small bubbles by the rigid skeleton of the glass fiber and the flexible interface of the PA66 microfibers. The L3 flow-stabilizing and particle-retaining layer ensures uniform fluid distribution and particle retention. The regular pore structure of meltblown polypropylene fibers effectively stabilizes the flow field distribution. The synergistic effect of the three-layer structure is manifested in the pore size gradient design formed from the outside to the inside, which realizes the stepwise separation and coalescence of bubbles. The initial capture of the L1 layer provides an abundant bubble source for the L2 layer, and the coalescence treatment of the L2 layer creates stable flow conditions for the L3 layer. The multi-layer synergistic effect breaks through the performance bottleneck of single-layer materials in terms of defoaming efficiency and flow resistance control. However, the understanding of the bubble transfer dynamics mechanism between the three-layer interfaces still needs to be deepened.

[0044] (3) Beneficial technical effects

[0045] 1. Significantly improves defoaming and separation efficiency: Through the oil-repellent and gas-friendly design of the L1 bubble-catching layer, which is composed of polyvinylidene fluoride nanofibers and metal fibers, combined with the strong interfacial bonding structure of the L2 synergistic polymerization layer glass fiber skeleton and PA66 microfibers, efficient separation is achieved throughout the entire process from bubble capture to polymerization. At the same time, the gas discharge channel constructed by the grid-shaped bubble-breaking cap and the annular gap structure significantly improves the removal efficiency of bubbles in hydraulic oil through multi-level synergistic effect.

[0046] 2. Effectively reduce flow resistance: The three-layer structure forms an outer layer with a pore size gradient of 40μm-80μm and an inner layer with a pore size gradient of 8μm-20μm. Combined with the regular pore structure of the L3 flow-stabilizing granulation layer meltblown polypropylene fiber and the 20%-35% open porosity control of the broken bubble cap, the fluid is uniformly distributed and the flow field is stabilized, effectively reducing pressure loss during the flow process and reducing system energy consumption.

[0047] 3. Enhanced structural stability and service life: The content of polyvinylidene fluoride β phase is precisely controlled through electrospinning, orientation, and annealing processes. Combined with in-situ polymerization technology, strong interfacial bonding of PA66 microfibers on the glass fiber surface is achieved. With the mechanical support of stainless steel outer mesh sleeve and broken blister cap, multiple reinforcement mechanisms significantly improve the mechanical strength and fatigue resistance of the filter element and extend its service life.

[0048] 4. Achieve multi-functional integrated design: The configuration of the gas collection chamber and the exhaust channel effectively connects the capture and aggregation functions. Combined with the optimized configuration of the three-layer thickness ratio of 1:(1.5-3):(0.5-1.0) and the overall structure formed by the hot pressing process, multiple functions such as defoaming, filtration and flow stabilization are achieved in a single filter element, simplifying the system structure and improving the overall performance. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the fiber composite hydraulic defoaming filter element structure of the present invention.

[0050] Figure 2 This invention relates to the effect of annealing temperature on the crystal phase of polyvinylidene fluoride nanofibers.

[0051] Figure 3 This invention illustrates the influence of the stretching orientation ratio λ on the bubble removal rate and pressure drop.

[0052] Figure 4 This invention illustrates the influence of polymerization temperature on bubble removal rate and pressure drop.

[0053] Figure 5 This invention illustrates the effect of annealing temperature on β phase content and bubble removal rate.

[0054] Figure 6 This invention illustrates the influence of PA66 crystallinity on bubble removal rate and pressure drop.

[0055] Figure 7 This is a comparative analysis of the bubble removal rate and initial bubble point pressure in the embodiments and comparative examples of the present invention.

[0056] Figure 8 This is a comparative analysis of the voltage drop and performance retention rate over 500 hours in the embodiments and comparative examples of the present invention.

[0057] Figure 9 This is a comparative analysis of the chemical compatibility change rate and temperature adaptability of the embodiments and comparative examples of the present invention.

[0058] Figure 10 This is a comparative analysis of the fatigue life performance of the embodiments and comparative examples of the present invention.

[0059] In the diagram: 1. Top cover; 2. Outer mesh sleeve; 3. Fine filter membrane; 4. Bubble cap; 5. Bottom cover. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0061] Example 1:

[0062] A fiber composite hydraulic defoaming filter element includes: an upper end cap 1 made of nylon; an outer mesh sleeve 2 made of stainless steel; a fine filter membrane 3; a bubble-breaking cover 4 made of stainless steel; and a lower end cap 5 made of nylon. In this embodiment, the fine filter membrane 3 has a cylindrical structure, and the outer mesh sleeve 2 covers the outer surface of the fine filter membrane 3 and forms a pressure-bearing filtration unit with it. The bubble-breaking cover 4 has a grid-like structure, axially penetrates through and is located in the center of the inner cavity of the fine filter membrane 3, forming an annular gap structure with the inner wall of the fine filter membrane 3. The upper end cap 1 is provided with a gas collection cavity and communicates with the annular gap structure. The upper end cap 1 and the lower end cap 5 are respectively sealed and connected to both ends of the fine filter membrane 3, applying an axial pre-tightening force to the fine filter membrane 3, assembling the outer mesh sleeve 2, the fine filter membrane 3, and the bubble-breaking cover 4 into a whole. The fine filter membrane 3 in this embodiment includes an L1 bubble-catching layer, an L2 co-aggregating layer, and an L3 flow-stabilizing and particle-removing layer arranged sequentially from the outside to the inside. The L1 bubble trapping layer in this embodiment is co-constructed from polyvinylidene fluoride (PVDF) nanofibers and stainless steel fibers. The PVDF is obtained through electrospinning, orientation, and annealing processes, resulting in a β-phase content of 0.65%, and the metal fibers have a volume fraction of 20 vol%. The L2 co-polymerization layer in this embodiment is composed of a glass fiber skeleton and PA66 microfibers, with the PA66 microfibers grown on the glass fiber skeleton through in-situ polymerization. The L1 bubble trapping layer in this embodiment is prepared through the following steps: Step A1: Electrospinning to prepare PVDF nanofibers at an electric field strength of 16 kV and a collection distance of 17 cm; Step A2: Stretching and oriented the PVDF nanofibers in this embodiment, with a stretching-orientation ratio λ of 1.6; Step A3: Annealing to control the crystal phase at a temperature of 120°C for 12 min. The L2 synergistic polymerization layer of this embodiment is prepared through the following steps: Step B1: Prepare a glass fiber skeleton with a nominal pore size of 17 μm; Step B2: Prepare a prepolymerization solution by mixing hexamethylenediamine and adipic acid monomers in a molar ratio of 1:1.02, impregnate the glass fiber skeleton, and then carry out in-situ polymerization under an inert atmosphere at a polymerization temperature of 270°C for 20 min, so that PA66 microfibers grow in situ on the glass fiber surface; Step B3: Control the crystallinity of PA66 microfibers to reach 32% and the microfiber diameter to be 3 μm. In step A1 of this embodiment, the mass fraction of polyvinylidene fluoride in N,N-dimethylformamide is 11 wt%, and the electrospinning environment temperature is 25°C; After step A3 of this embodiment, the polyvinylidene fluoride nanofibers are subjected to plasma activation treatment at a power of 50 W for 75 s. In step B2 of this embodiment, the mass ratio of microfibers to glass fiber is 1:5.In this embodiment, the L1 bubble-catching layer has a polyvinylidene fluoride fiber diameter of 400 nm and a surface energy γs of 20 mN / m. The L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer synergistically form a pore size gradient with an outer equivalent pore size of 60 μm and an inner equivalent pore size of 14 μm. The L3 flow-stabilizing and particle-reducing layer is a melt-blown polypropylene fiber layer with a nominal pore size of 10 μm. The thickness ratio of the L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer is 1:2:0.75. The open area of ​​the bubble-breaking cap 4 in this embodiment is 27%. The width of the annular gap in this embodiment is 0.8 mm. The preparation method of this embodiment includes the following steps: Step S1: The L1 bubble trapping layer, the L2 co-aggregating layer, and the L3 flow stabilizing and particle intercepting layer are sequentially composited to form a fine filter membrane 3 at a composite temperature of 70°C; wherein the composite interface between the L1 bubble trapping layer and the L2 co-aggregating layer is achieved by hot pressing, and the composite pressure is 1.0 MPa; Step S2: The bubble crushing cap 4 is inserted into the fine filter membrane 3 and then installed in the outer mesh sleeve 2; Step S3: The two ends of the fine filter membrane 3 are sealed with the upper end cap 1 and the lower end cap 5 respectively.

[0063] Features of this embodiment: It adopts moderate parameter configuration, with mild and stable process conditions, suitable for large-scale industrial production. It has a good balance between defoaming efficiency and flow resistance control, and its structure is stable and reliable. Application scenarios: Suitable for medium-sized hydraulic systems, such as hydraulic oil filtration in forklifts, excavators, and other construction machinery, in situations where high stability and reliability are required.

[0064] Example 2:

[0065] A fiber composite hydraulic defoaming filter element includes: an upper end cap 1 made of nylon; an outer mesh sleeve 2 made of stainless steel; a fine filter membrane 3; a bubble-breaking cover 4 made of stainless steel; and a lower end cap 5 made of nylon. In this embodiment, the fine filter membrane 3 has a cylindrical structure, and the outer mesh sleeve 2 covers the outer surface of the fine filter membrane 3 and forms a pressure-bearing filtration unit with it. The bubble-breaking cover 4 has a grid-like structure, axially penetrates through and is located in the center of the inner cavity of the fine filter membrane 3, forming an annular gap structure with the inner wall of the fine filter membrane 3. The upper end cap 1 is provided with a gas collection cavity and communicates with the annular gap structure. The upper end cap 1 and the lower end cap 5 are respectively sealed and connected to both ends of the fine filter membrane 3, applying an axial pre-tightening force to the fine filter membrane 3, assembling the outer mesh sleeve 2, the fine filter membrane 3, and the bubble-breaking cover 4 into a whole. The fine filter membrane 3 in this embodiment includes an L1 bubble-catching layer, an L2 co-aggregating layer, and an L3 flow-stabilizing and particle-removing layer arranged sequentially from the outside to the inside. The L1 bubble-trapping layer of this embodiment is formed by the co-construction of polyvinylidene fluoride (PVDF) nanofibers and stainless steel fibers. The PVDF is obtained through electrospinning, orientation, and annealing processes, resulting in a β-phase content of 0.75%, and the metal fibers have a volume fraction of 30 vol%. The L2 co-polymerization layer of this embodiment is formed by the composite of a glass fiber skeleton and PA66 microfibers. The PA66 microfibers are grown on the glass fiber skeleton through in-situ polymerization. The L1 bubble-trapping layer of this embodiment is prepared through the following steps: Step A1: Electrospinning to prepare PVDF nanofibers, with an electric field strength of 20 kV and a collection distance of 22 cm; Step A2: Stretching and oriented treatment of the PVDF nanofibers in this embodiment, with a stretching-orientation ratio λ of 1.9; Step A3: Annealing treatment to control the crystal phase, with an annealing temperature of 135°C and an annealing time of 18 min. The L2 synergistic polymerization layer of this embodiment is prepared through the following steps: Step B1: Prepare a glass fiber skeleton with a nominal pore size of 10 μm; Step B2: Prepare a prepolymerization solution by mixing hexamethylenediamine and adipic acid monomers in a molar ratio of 1:1.0, impregnate the glass fiber skeleton, and then carry out in-situ polymerization under an inert atmosphere at a polymerization temperature of 280℃ for 30 min, so that PA66 microfibers grow in situ on the glass fiber surface; Step B3: Control the crystallinity of PA66 microfibers to reach 40% and the microfiber diameter to be 1 μm. In step A1 of this embodiment, the mass fraction of polyvinylidene fluoride in N,N-dimethylformamide is 15 wt%, and the electrospinning environment temperature is 30℃; After step A3 of this embodiment, the polyvinylidene fluoride nanofibers are subjected to plasma activation treatment at a power of 80 W for 120 s. In step B2 of this embodiment, the mass ratio of microfibers to glass fiber is 1:3.In this embodiment, the L1 bubble-catching layer has a polyvinylidene fluoride fiber diameter of 200 nm and a surface energy γs of 18 mN / m. The L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer synergistically form a pore size gradient with an outer equivalent pore size of 80 μm and an inner equivalent pore size of 8 μm. The L3 flow-stabilizing and particle-reducing layer is a melt-blown polypropylene fiber layer with a nominal pore size of 5 μm. The thickness ratio of the L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer is 1:3:0.5. The open area of ​​the bubble-breaking cap 4 in this embodiment is 35%. The width of the annular gap in this embodiment is 1.2 mm. The preparation method of this embodiment includes the following steps: Step S1: The L1 bubble trapping layer, the L2 co-aggregating layer, and the L3 flow stabilizing and particle intercepting layer are sequentially composited to form a fine filter membrane 3 at a composite temperature of 80°C; wherein the composite interface between the L1 bubble trapping layer and the L2 co-aggregating layer is achieved by hot pressing, and the composite pressure is 1.5 MPa; Step S2: The bubble fragmentation cap 4 is inserted into the fine filter membrane 3 and then installed in the outer mesh sleeve 2; Step S3: The two ends of the fine filter membrane 3 are sealed with the upper end cap 1 and the lower end cap 5 respectively.

[0066] Features of this embodiment: Optimized for high defoaming efficiency, the high β-phase content and large gradient pore size structure significantly enhance bubble capture and separation capabilities. Minimized nanofiber diameter increases specific surface area, making it suitable for applications with extremely high defoaming performance requirements. Application scenarios: Suitable for precision hydraulic systems, such as hydraulic oil filtration in high-precision equipment like CNC machine tools and injection molding machines, and industrial applications with extremely strict requirements for bubble content.

[0067] Example 3:

[0068] A fiber composite hydraulic defoaming filter element includes: an upper end cap 1 made of nylon; an outer mesh sleeve 2 made of stainless steel; a fine filter membrane 3; a bubble-breaking cover 4 made of stainless steel; and a lower end cap 5 made of nylon. In this embodiment, the fine filter membrane 3 has a cylindrical structure, and the outer mesh sleeve 2 covers the outer surface of the fine filter membrane 3 and forms a pressure-bearing filtration unit with it. The bubble-breaking cover 4 has a grid-like structure, axially penetrates through and is located in the center of the inner cavity of the fine filter membrane 3, forming an annular gap structure with the inner wall of the fine filter membrane 3. The upper end cap 1 is provided with a gas collection cavity and communicates with the annular gap structure. The upper end cap 1 and the lower end cap 5 are respectively sealed and connected to both ends of the fine filter membrane 3, applying an axial pre-tightening force to the fine filter membrane 3, assembling the outer mesh sleeve 2, the fine filter membrane 3, and the bubble-breaking cover 4 into a whole. The fine filter membrane 3 in this embodiment includes an L1 bubble-catching layer, an L2 co-aggregating layer, and an L3 flow-stabilizing and particle-removing layer arranged sequentially from the outside to the inside. The L1 bubble trapping layer in this embodiment is formed by the co-construction of polyvinylidene fluoride (PVDF) nanofibers and stainless steel fibers. The PVDF is obtained through electrospinning, orientation, and annealing processes, resulting in a β-phase content of 0.60%, and the metal fibers have a volume fraction of 10 vol%. The L2 co-polymerization layer in this embodiment is formed by the composite of a glass fiber skeleton and PA66 microfibers. The PA66 microfibers are grown on the glass fiber skeleton through in-situ polymerization. The L1 bubble trapping layer in this embodiment is prepared through the following steps: Step A1: Electrospinning to prepare PVDF nanofibers, with an electric field strength of 12 kV and a collection distance of 12 cm; Step A2: Stretching and orientation treatment of the PVDF nanofibers in this embodiment, with a stretching-orientation ratio λ of 1.3; Step A3: Annealing treatment to control the crystal phase, with an annealing temperature of 110°C and an annealing time of 5 min. The L2 synergistic polymerization layer of this embodiment is prepared through the following steps: Step B1: Prepare a glass fiber skeleton with a nominal pore size of 25 μm; Step B2: Prepare a prepolymerization solution by mixing hexamethylenediamine and adipic acid monomers in a molar ratio of 1:1.05, impregnate the glass fiber skeleton, and then carry out in-situ polymerization under an inert atmosphere at a polymerization temperature of 260℃ for 10 min, so that PA66 microfibers grow in situ on the glass fiber surface; Step B3: Control the crystallinity of PA66 microfibers to reach 25% and the microfiber diameter to be 5 μm. In step A1 of this embodiment, the mass fraction of polyvinylidene fluoride in N,N-dimethylformamide is 8 wt%, and the electrospinning environment temperature is 20℃; After step A3 of this embodiment, the polyvinylidene fluoride nanofibers are subjected to plasma activation treatment at a power of 30 W for 30 s. In step B2 of this embodiment, the mass ratio of microfibers to glass fiber is 1:8.In this embodiment, the L1 bubble-catching layer has a polyvinylidene fluoride fiber diameter of 600 nm and a surface energy γs of 22 mN / m. The L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer synergistically form a pore size gradient with an outer equivalent pore size of 40 μm and an inner equivalent pore size of 20 μm. The L3 flow-stabilizing and particle-reducing layer is a melt-blown polypropylene fiber layer with a nominal pore size of 15 μm. The thickness ratio of the L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer is 1:1.5:1.0. The open area of ​​the bubble-breaking cap 4 in this embodiment is 20%. The width of the annular gap in this embodiment is 0.4 mm. The preparation method of this embodiment includes the following steps: Step S1: The L1 bubble trapping layer, the L2 co-aggregating layer, and the L3 flow stabilizing and particle intercepting layer are sequentially composited to form a fine filter membrane 3 at a composite temperature of 60°C; wherein the composite interface between the L1 bubble trapping layer and the L2 co-aggregating layer is achieved by hot pressing, and the composite pressure is 0.5 MPa; Step S2: The bubble fragmentation cap 4 is inserted into the fine filter membrane 3 and then installed in the outer mesh sleeve 2; Step S3: The two ends of the fine filter membrane 3 are sealed with the upper end cap 1 and the lower end cap 5 respectively.

[0069] Features of this embodiment: Optimized for low flow resistance, employing a large pore size gradient and low porosity control, with mild process conditions ensuring a loose and porous structure, effectively reducing flow resistance, making it suitable for hydraulic systems with high flow rate requirements. Application scenarios: Suitable for high-flow-rate hydraulic systems, such as heavy-duty construction machinery and marine hydraulic systems, in applications sensitive to flow resistance, and industrial environments requiring high flow rate and low pressure drop.

[0070] Example 4:

[0071] A fiber composite hydraulic defoaming filter element includes: an upper end cap 1 made of nylon; an outer mesh sleeve 2 made of stainless steel; a fine filter membrane 3; a bubble-breaking cover 4 made of stainless steel; and a lower end cap 5 made of nylon. In this embodiment, the fine filter membrane 3 has a cylindrical structure, and the outer mesh sleeve 2 covers the outer surface of the fine filter membrane 3 and forms a pressure-bearing filtration unit with it. The bubble-breaking cover 4 has a grid-like structure, axially penetrates through and is located in the center of the inner cavity of the fine filter membrane 3, forming an annular gap structure with the inner wall of the fine filter membrane 3. The upper end cap 1 is provided with a gas collection cavity and communicates with the annular gap structure. The upper end cap 1 and the lower end cap 5 are respectively sealed and connected to both ends of the fine filter membrane 3, applying an axial pre-tightening force to the fine filter membrane 3, assembling the outer mesh sleeve 2, the fine filter membrane 3, and the bubble-breaking cover 4 into a whole. The fine filter membrane 3 in this embodiment includes an L1 bubble-catching layer, an L2 co-aggregating layer, and an L3 flow-stabilizing and particle-removing layer arranged sequentially from the outside to the inside. The L1 bubble trapping layer in this embodiment is formed by the co-construction of polyvinylidene fluoride (PVDF) nanofibers and stainless steel fibers. The PVDF is obtained through electrospinning, orientation, and annealing processes, resulting in a β-phase content of 0.70%, and the metal fibers have a volume fraction of 25 vol%. The L2 co-polymerization layer in this embodiment is formed by the composite of a glass fiber skeleton and PA66 microfibers. The PA66 microfibers are grown on the glass fiber skeleton through in-situ polymerization. The L1 bubble trapping layer in this embodiment is prepared through the following steps: Step A1: Electrospinning to prepare PVDF nanofibers, with an electric field strength of 18 kV and a collection distance of 20 cm; Step A2: Stretching and oriented treatment of the PVDF nanofibers in this embodiment, with a stretching-orientation ratio λ of 2.0; Step A3: Annealing treatment to control the crystal phase, with an annealing temperature of 130°C and an annealing time of 20 min. The L2 synergistic polymerization layer of this embodiment is prepared through the following steps: Step B1: Prepare a glass fiber skeleton with a nominal pore size of 20 μm; Step B2: Prepare a prepolymerization solution by mixing hexamethylenediamine and adipic acid monomers in a molar ratio of 1:1.03, impregnate the glass fiber skeleton, and then carry out in-situ polymerization under an inert atmosphere at a polymerization temperature of 275°C and a holding time of 25 min, so that PA66 microfibers grow in situ on the glass fiber surface; Step B3: Control the crystallinity of PA66 microfibers to reach 35% and the microfiber diameter to be 2 μm. In step A1 of this embodiment, the mass fraction of polyvinylidene fluoride in N,N-dimethylformamide is 12 wt%, and the electrospinning environment temperature is 28°C; After step A3 of this embodiment, the polyvinylidene fluoride nanofibers are subjected to plasma activation treatment at a power of 65 W for 90 s. In step B2 of this embodiment, the mass ratio of microfibers to glass fiber is 1:6.In this embodiment, the L1 bubble-catching layer has a polyvinylidene fluoride fiber diameter of 300 nm and a surface energy γs of 19 mN / m. The L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer synergistically form a pore size gradient with an outer equivalent pore size of 70 μm and an inner equivalent pore size of 12 μm. The L3 flow-stabilizing and particle-reducing layer is a melt-blown polypropylene fiber layer with a nominal pore size of 8 μm. The thickness ratio of the L1 bubble-catching layer, L2 synergistic polymerization layer, and L3 flow-stabilizing and particle-reducing layer is 1:2.5:0.8. The open area of ​​the bubble-breaking cap 4 in this embodiment is 30%. The width of the annular gap in this embodiment is 1.0 mm. The preparation method of this embodiment includes the following steps: Step S1: The L1 bubble trapping layer, the L2 co-aggregating layer, and the L3 flow stabilizing and particle intercepting layer are sequentially composited to form a fine filter membrane 3 at a composite temperature of 75°C; wherein the composite interface between the L1 bubble trapping layer and the L2 co-aggregating layer is achieved by hot pressing, and the composite pressure is 1.2 MPa; Step S2: The bubble crushing cap 4 is inserted into the fine filter membrane 3 and then installed in the outer mesh sleeve 2; Step S3: The two ends of the fine filter membrane 3 are sealed with the upper end cap 1 and the lower end cap 5 respectively.

[0072] Features of this embodiment: It employs a combination of boundary parameters, with a high draw-to-orientation ratio and a longer annealing time to enhance fiber properties. The moderately high parameter configurations ensure stability while pursuing performance limits, resulting in excellent overall performance. Application scenarios: Suitable for high-end hydraulic systems in aerospace, military, and other special application environments with extremely high requirements for product performance and reliability, where stable operation under extreme conditions is necessary.

[0073] Comparative Example 1: It is basically the same as Example 1, except that the annealing temperature in step A3 is 90°C and the annealing time is 12 min, so that the β phase content in the polyvinylidene fluoride fiber is only 0.45.

[0074] Comparative Example 2: It is basically the same as Example 1, except that the stretching orientation ratio λ of the polyvinylidene fluoride nanofibers in step A2 is 1.0, and no effective orientation treatment is performed.

[0075] Comparative Example 3: It is basically the same as Example 1, except that the volume fraction of metal fibers in the L1 bubble trapping layer is 5 vol%, which is significantly lower than the 20 vol% ratio in Example 1.

[0076] Comparative Example 4: It is basically the same as Example 1, except that the polymerization temperature in step B2 is 220°C and the holding time is 20 min, which results in a weaker interfacial bonding strength between PA66 microfibers and glass fiber skeleton.

[0077] Comparative Example 5: It is basically the same as Example 1, except that in step B2, the hexamethylenediamine and adipic acid monomers are prepared in a molar ratio of 1:0.8 to form a prepolymer solution, which deviates from the stoichiometric ratio.

[0078] Comparative Example 6: It is basically the same as Example 1, except that in step B3, the crystallinity of PA66 microfibers is controlled at 15% and the microfiber diameter is 3μm, which is significantly lower than the crystallinity.

[0079] Comparative Example 7: Basically the same as Example 1, except that the plasma activation treatment step after step A3 was omitted, and the surface activity of polyvinylidene fluoride nanofibers was not improved.

[0080] Comparative Example 8: It is basically the same as Example 1, except that the thickness ratio of L1 bubble trapping layer, L2 co-aggregation layer and L3 flow stabilizing and particle intercepting layer is 1:1:1, which deviates from the optimal thickness ratio.

[0081] Comparative Example 9: It is basically the same as Example 1, except that the opening ratio of the broken blister pack 4 is 15%, which is significantly lower than the 27% opening ratio of Example 1.

[0082] Comparative Example 10: It is basically the same as Example 1, except that the fine filter membrane 3 only contains two layers: L1 bubble trapping layer and L3 flow stabilizing and particle intercepting layer. The L2 co-aggregation layer is omitted, so it cannot achieve effective bubble aggregation treatment.

[0083] Performance testing:

[0084] Bubble Removal Efficiency Test Experiment: The test object is the defoaming and separation performance of a fiber composite hydraulic defoaming filter element in standard hydraulic oil. The purpose of the test is to evaluate the filter element's removal efficiency and separation capability for bubbles of different sizes in hydraulic oil. The test principle is based on the gas-liquid two-phase separation mechanism, quantifying the defoaming effect by measuring the change in bubble content in the hydraulic oil before and after filter element treatment. The experimental method uses an oil circulation system to simulate actual working conditions (flow rate 10L / min, pressure 0.5MPa). An optical bubble detector is used to measure the number of bubbles at the inlet and outlet, and the defoaming performance is evaluated by calculating the bubble removal rate. The test standard is based on the test method specified in GB / Z 44946-2024 "Test Methods for Hydraulic Transmission Filter Elements - Actual Life Assessment". Key parameters include test flow rates of 5L / min, 10L / min, and 15L / min, working pressure of 0.5MPa, use of ISO VG46 hydraulic oil, and inlet bubble concentration controlled within the range of 1200-1300 bubbles / ml.

[0085] Flow Resistance Test Experiment: The test object is the pressure loss characteristics of a fiber composite hydraulic defoaming filter element under different flow conditions. The purpose of the test is to evaluate the influence of the filter element on the flow performance of the hydraulic system and its flow resistance characteristics. The test principle is based on the pressure loss theory in fluid mechanics, characterizing the flow resistance by measuring the pressure difference between the inlet and outlet of the filter element. The experimental method involves recording the filter element pressure drop under different flow conditions in a standard hydraulic test system. Test flow points include 5 L / min, 10 L / min, and 15 L / min. After each flow point has stabilized, the corresponding pressure loss data is recorded. The test standard follows the testing requirements for low flow resistance filter elements in GB / Z44946-2024 "Test Methods for Hydraulic Transmission Filter Elements - Actual Life Assessment". Key parameters include a test flow range of 5-15 L / min, the use of ISO VG46 hydraulic oil, a working pressure of 0.5 MPa, and test temperature controlled according to standard environmental conditions.

[0086] Structural Integrity Test Experiment: The test object is the structural integrity and pore size characteristics of a fiber composite hydraulic defoaming filter element. The purpose of the test is to evaluate the structural stability and filtration accuracy of the filter element. The test principle is based on the bubble point test method, which characterizes the structural integrity and maximum pore size of the filter element by measuring its initial bubble point pressure. The experimental method uses a bubble point tester (LT-F968 model) to gradually increase the gas pressure until the first stable bubble appears on the filter element, and the pressure value at this point is recorded as the initial bubble point pressure. The test standard is based on the method specified in GB / T 14041.1-2007 "Filter Element Structural Integrity Verification (Initial Bubble Point Test)". Key parameters include the test medium being a standard test liquid, the pressure increase rate being controlled according to standard requirements, the test temperature being room temperature, and the observation time and judgment criteria being performed according to GB / T 14041.1-2007.

[0087] Service Life Assessment Experiment: The test object is the performance degradation characteristics of a fiber composite hydraulic defoaming filter element under long-term operating conditions. The purpose of the test is to evaluate the actual service life and performance stability of the filter element. The test principle is based on the filter element life assessment method, monitoring the change in filter element performance over time through continuous operation tests. The experimental method adopts a durability test with continuous operation for 500 hours, periodically monitoring changes in bubble removal rate and pressure drop, and recording performance degradation data. The test standard is based on the life assessment method specified in GB / Z 44946-2024 "Test Method for Hydraulic Transmission Filter Elements - Actual Life Assessment". Key parameters include continuous operation time of 500 hours, test conditions maintaining a flow rate of 10 L / min and a pressure of 0.5 MPa, using ISO VG46 hydraulic oil, and data collection at monitoring intervals of 0h, 100h, 300h, and 500h.

[0088] Chemical compatibility test experiment: The test object is the chemical compatibility between fiber composite hydraulic defoaming filter element material and hydraulic oil. The purpose of the test is to evaluate the chemical stability and long-term applicability of the filter element material in hydraulic media. The test principle is based on the material immersion test method, which evaluates compatibility by observing the physical and chemical changes of the material in hydraulic oil. Experimental method: The filter element is immersed in ISO VG46 hydraulic oil and kept at 80℃ for 72 hours. The expansion, degumming, and other changes of the filter element material are observed, and the bubbling point is retested. The test standard is based on the method specified in ISO 2943-1998 "Filter element material – Test for compatibility with hydraulic fluids". Key parameters include immersion temperature 80±2℃, immersion time 72 hours, use of ISO VG46 standard hydraulic oil, and cooling and drying treatment after immersion are performed according to standard requirements.

[0089] Temperature Adaptability Test: The test subject is the performance of a fiber composite hydraulic defoaming filter element under different operating temperatures. The purpose of the test is to evaluate the filter element's adaptability and performance stability in environments with temperature variations. The test principle is based on thermodynamic theory, testing the temperature dependence of the filter element's performance by changing the operating temperature. Experimental Method: In a temperature-controlled test environment, the defoaming efficiency and flow resistance of the filter element were tested at -20℃, 0℃, 40℃, 80℃, and 100℃, respectively, and the changes in performance parameters with temperature were observed. Key parameters include temperature control accuracy ±2℃, temperature stabilization time 60 minutes, test time at each temperature point 30 minutes, and heating / cooling rate 5℃ / min.

[0090] Fatigue Performance Testing Experiment: The test object is the fatigue durability of a fiber composite hydraulic defoaming filter element under cyclic loading. The purpose of the test is to evaluate the structural stability and reliability of the filter element under repeated pressure changes. The test principle is based on the theory of material fatigue mechanics, simulating pressure fluctuations in actual working conditions by applying cyclic pressure loads. The experimental method uses a fatigue testing machine to apply a sinusoidal pressure load of 0.1-1.0 MPa to the filter element, with the frequency set at 1 Hz, for 1 million consecutive cycles. The structural integrity and performance changes of the filter element are periodically checked. Key parameters include load amplitude of 0.9 MPa, average load of 0.55 MPa, loading frequency of 1 ± 0.1 Hz, test temperature of 40 ± 2℃, and a test interval of every 100,000 cycles.

[0091] Table 1 shows that deviations from the various technical solutions in the comparative examples led to varying degrees of performance degradation. In Comparative Example 1, the β-phase content decreased to 0.45%, resulting in a significant reduction in the piezoelectric properties and surface activity of the polyvinylidene fluoride fiber. According to crystal structure theory, the β-phase content is positively correlated with the bubble adsorption capacity. Furthermore, the excessively low annealing temperature failed to fully activate the molecular chain rearrangement, affecting long-term stability. In Comparative Example 2, the draw orientation ratio λ=1.0 indicates that the fiber was not effectively oriented. According to the principles of polymer physics, low molecular chain orientation leads to insufficient fiber strength and surface energy. Unoriented fibers are easily damaged by fluid impact. Deformation reduces defoaming stability; in Comparative Example 3, the metal fiber volume fraction was only 5 vol%, far below the effective conductivity threshold. According to percolation theory, it could not form a continuous conductive network, weakening its ability to electrostatically capture bubbles; the polymerization temperature of Comparative Example 4, 220℃, was far below the optimal polymerization temperature of PA66. According to polymerization kinetics, low-temperature polymerization leads to insufficient molecular weight and low interfacial bonding strength. The weak bond between microfibers and the glass fiber skeleton seriously affects chemical compatibility and long-term stability; in Comparative Example 5, the molar ratio of hexamethylenediamine to adipic acid, 1:0.8, deviated significantly from the stoichiometric ratio. According to the stepwise polymerization mechanism, the monomer ratio imbalance leads to… The decrease in polymerization degree and end-group imbalance affect the crystallinity and chemical stability of PA66 microfibers. In Comparative Example 6, the PA66 microfiber crystallinity was only 15%, far below the optimal range. According to polymer crystallization theory, low crystallinity leads to insufficient mechanical strength of the microfibers, making them prone to plastic deformation under fluid shear. Comparative Example 7 lacked plasma activation treatment, resulting in insufficient fiber surface energy and wettability. According to surface chemistry theory, the unactivated polyvinylidene fluoride surface is highly hydrophobic and has a large contact angle with oil, which is not conducive to bubble capture. The thickness ratio of Comparative Example 8 (1:1:1) deviates from the optimal ratio. According to porous media flow theory, the thickness ratio of each layer affects… The deviations from these technical solutions have negatively impacted the flow field distribution and bubble separation efficiency. In Comparative Example 9, the open area ratio of the broken bubble cap is only 15%. According to fluid mechanics principles, the low open area ratio leads to a significant increase in flow resistance and restricts the channels for bubbles to enter the separation chamber. In Comparative Example 10, the double-layer structure lacking the L2 synergistic coalescence layer cannot achieve an effective bubble coalescence mechanism. According to interface science theory, small bubbles are difficult to coalesce into large bubbles and separate from the oil. These deviations from the technical solutions have disrupted the coordination and unity of the microstructure and macroscopic properties of the material from different angles, resulting in a comprehensive deterioration of key performance indicators such as bubble removal efficiency, flow resistance control, structural stability, and chemical compatibility.

[0092] Table 1 Summary of performance of examples and comparative examples

[0093]

[0094] based on Figures 1-6 The systematic experimental verification results show that the fiber composite hydraulic defoaming filter element technology of the present invention demonstrates significant rationality, reliability and effectiveness. Figure 1 The fiber composite hydraulic defoaming filter element structure design shown is illustrated. Figure 2 A systematic study of the effect of annealing temperature on the crystalline phase of polyvinylidene fluoride nanofibers revealed the precise influence mechanism of temperature control on the microstructure of the material and verified the theoretical feasibility of performance optimization through process parameter adjustment. Figure 3 As the mid-drawing orientation ratio λ increased from 1.0 to 1.8, the bubble removal rate significantly improved from 84.7% to 92.6%, while the pressure drop decreased from 0.16MPa to 0.114MPa, showing a clear performance optimization trend. This proves that λ=1.8 is the optimal process parameter, and this optimal point is located in the middle 71.4% of the patent protection range, reflecting the scientific and forward-looking nature of the parameter design. Figure 4 The demonstration of the effect of polymerization temperature shows that when the temperature increases from 220℃ to 275℃, the bubble removal rate increases from 87.1% to 92.1%, and the pressure drop decreases from 0.17MPa to 0.115MPa. The optimal point is located in the middle 75% of the patent range, which further verifies the rationality of the process window design. Figure 5 Through in-depth analysis of the dual effects of annealing temperature on β phase content and bubble removal rate, the optimal performance of β phase content reaching 0.71 and bubble removal rate reaching 93.1% at 130℃ was found. This point is located in the middle 80% of the patent scope, which fully demonstrates the intrinsic correlation between microstructure control and macro performance improvement. Figure 6 The research results on the crystallinity of PA66 show that the optimal bubble removal rate (92.3-92.6%) and the lowest pressure drop (0.113-0.115 MPa) are achieved when the crystallinity is in the range of 35-38%. This optimal range is located within the middle 76.7% of the patent protection range, demonstrating the accuracy and reproducibility of parameter optimization. The systematic verification results of the six charts confirm that the optimal values ​​of all key process parameters are stably located within the patent protection range, forming a complete technical protection system. This not only proves the theoretical scientific nature and practical operability of the invention's technical solution, but more importantly, it verifies that precise control of process parameters can achieve directional adjustment of the material's microstructure and significant improvement of its macroscopic properties. This provides a reliable technical path and sufficient process margin for industrial production, fully demonstrating the innovative and practical value of the invention's technical solution.

[0095] based on Figures 7-10 The systematic comparative experimental results show that the fiber composite hydraulic defoaming filter element technology of the present invention has demonstrated outstanding technical advantages and significant performance improvement in a comprehensive comparison with traditional technologies, fully proving the rationality, reliability and effectiveness of the solution. Figure 7The comparative analysis of bubble removal rate and initial bubble point pressure clearly shows that the bubble removal rate of Examples 1-4 of the present invention is consistently maintained at a high level of 88.6%-94.8%, which is a significant improvement compared with the performance range of 79.5%-87.1% of Comparative Examples 1-10, with an average performance advantage of 7-10 percentage points. At the same time, the initial bubble point pressure shows good stability and controllability in the range of 0.38-0.52 MPa, verifying the technological leadership and process stability of the present invention in core functional indicators. Figure 8 The long-term reliability of the invention was verified by comparing the voltage drop and the 500-hour performance retention rate. The voltage drop of the embodiment was controlled at a low level of 0.08-0.15 MPa, which is significantly better than the 0.13-0.25 MPa range of the comparative example. More importantly, the 500-hour performance retention rate was maintained at an excellent level of 95.2%-97.8%, which is significantly better than the 82.2%-92.1% range of the comparative example. This demonstrates the superior long-term stability and durability, fully proving the reliability and continued effectiveness of the technical solution of the invention in practical applications. Figure 9 The comparative analysis of the chemical compatibility change rate and temperature adaptability further verified the environmental adaptability of the present invention. The chemical compatibility change rate of all embodiments was controlled at an excellent level of less than 2%, which is far lower than the change range of 2.3%-4.8% of the comparative examples. At the same time, the temperature adaptability can still maintain a high performance level of 85.2%-92.1% in an environment of 80℃, which is significantly better than the range of 75.8%-82.8% of the comparative examples. This proves the stability and adaptability of the present invention in complex working conditions. Figure 10 The fatigue life performance comparison analysis, a key indicator of durability, shows that all examples achieved excellent fatigue life of 1.1 million to 1.35 million cycles, representing a 30%-50% improvement compared to the 650,000 to 950,000 cycles range of the comparative examples. This significant performance improvement not only verifies the scientific nature of the material structure design and the effectiveness of the process optimization in this invention, but more importantly, it provides longer service cycles and higher economic benefits for practical engineering applications. The comprehensive comparison results of the four charts systematically demonstrate that this invention achieves comprehensive superiority in key technical indicators such as bubble removal efficiency, pressure loss control, long-term stability, environmental adaptability, and service life, forming a complete system of technical advantages. This fully verifies that a revolutionary improvement in the performance of hydraulic defoaming filter elements can be achieved through precise material design, optimized process parameters, and reasonable structural configuration, providing a reliable and innovative solution for related industrial fields.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fiber composite hydraulic defoaming filter element, characterized in that, include: The upper cap (1) is made of nylon; The outer mesh sleeve (2) is made of stainless steel; Fine filtration membrane (3); The broken bubble cap (4) is made of stainless steel; The lower end cap (5) is made of nylon; The fine filter membrane (3) has a cylindrical structure. The outer mesh sleeve (2) covers the outer surface of the fine filter membrane (3) and forms a pressure-bearing filtration unit with it. The bubble fragmentation cover (4) has a grid-like structure, penetrates axially and is located in the center of the inner cavity of the fine filter membrane (3), forming an annular gap structure with the inner wall of the fine filter membrane (3). The upper end cover (1) is provided with a gas collection cavity and communicates with the annular gap structure. The upper end cover (1) and the lower end cover (5) are respectively sealed and connected to the two ends of the fine filter membrane (3), applying axial pre-tightening force to the fine filter membrane (3) and assembling the outer mesh sleeve (2), the fine filter membrane (3) and the bubble fragmentation cover (4) into one unit. The fine filtration membrane (3) comprises, from the outside to the inside, an L1 bubble trapping layer, an L2 co-aggregation layer and an L3 flow stabilizing and particle intercepting layer; The L1 bubble-trapping layer is formed by the co-construction of polyvinylidene fluoride nanofibers and metal fibers. The polyvinylidene fluoride is obtained by electrospinning, orientation and annealing processes to obtain a β phase content that meets the requirement of β / (α+β)≥0.

60. The volume fraction of the metal fibers is 10vol%-30vol%. The L2 co-polymerization layer is formed by the composite of glass fiber skeleton and PA66 microfibers. The PA66 microfibers are grown on the glass fiber skeleton by in-situ polymerization. The bubbles captured by the L1 bubble-trapping layer are guided to the L2 co-polymerization layer through the pore size gradient for polymerization. The polymerized bubbles are discharged through the annular structure.

2. The fiber composite hydraulic defoaming filter element as described in claim 1, characterized in that, The L1 bubble-catching layer is prepared by the following steps: Step A1: Electrospinning to prepare polyvinylidene fluoride nanofibers, with an electric field strength of 12kV-22kV and a collection distance of 12cm-22cm; Step A2: The polyvinylidene fluoride nanofibers are subjected to a stretching and orientation treatment, with a stretching-orientation ratio λ of 1.3-2.0; Step A3: Perform annealing treatment to control the crystal phase. The annealing temperature is 110℃-135℃ and the annealing time is 5min-20min, so that β / (α+β)≥0.

60.

3. The fiber composite hydraulic defoaming filter element as described in claim 1, characterized in that, The L2 synergistic aggregation layer is prepared through the following steps: Step B1: Prepare a glass fiber skeleton with a nominal pore size of 10μm-25μm; Step B2: Prepare a prepolymerization solution by mixing hexamethylenediamine and adipic acid monomers in a molar ratio of 1:(1.0-1.05), impregnate the glass fiber skeleton, and then carry out in-situ polymerization under an inert atmosphere. The polymerization temperature is 260℃-280℃ and the holding time is 10min-30min, so that PA66 microfibers grow in situ on the glass fiber surface. Step B3: Control the crystallinity of PA66 microfibers to reach 25%-40%, and the microfiber diameter to be 1μm-5μm.

4. The fiber composite hydraulic defoaming filter element as described in claim 2, characterized in that, In step A1, the mass fraction of polyvinylidene fluoride in N,N-dimethylformamide is 8wt%-15wt%, and the electrospinning environment temperature is 20℃-30℃. After step A3, the polyvinylidene fluoride nanofibers are subjected to plasma activation treatment with a power of 30W-80W and a time of 30s-120s.

5. The fiber composite hydraulic defoaming filter element as described in claim 3, characterized in that, In step B2, the mass ratio of microfiber to glass fiber is 1:3 to 1:

8.

6. The fiber composite hydraulic defoaming filter element as described in claim 1, characterized in that, The polyvinylidene fluoride fibers of the L1 bubble trap layer have a diameter of 200nm-600nm and a surface energy γs≤22mN / m; The metal fibers in the L1 bubble trapping layer are stainless steel fibers; The L1 bubble trapping layer, L2 synergistic aggregation layer, and L3 flow stabilizing and particle intercepting layer work together to form a pore size gradient with an outer equivalent pore size of 40μm-80μm and an inner equivalent pore size of 8μm-20μm. The L3 flow stabilizing and particle-removing layer is a meltblown polypropylene fiber layer with a nominal pore size of 5μm-15μm; The thickness ratio of the L1 bubble trapping layer, the L2 co-aggregation layer, and the L3 flow stabilizing and particle intercepting layer is 1:(1.5-3):(0.5-1.0).

7. The fiber composite hydraulic defoaming filter element as described in claim 1, characterized in that, The opening ratio of the broken blister pack (4) is 20%-35%; the width of the annular gap is 0.4mm-1.2mm; The upper end cover (1) is provided with a gas collection cavity and an exhaust channel to realize the coordinated gas discharge of the L1 bubble trapping layer and the L2 co-aggregation layer.

8. A method for preparing a fiber composite hydraulic defoaming filter element as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step S1: The L1 bubble trapping layer, L2 co-aggregating layer and L3 flow stabilizing and particle intercepting layer are sequentially composited to form a fine filtration membrane (3) at a composite temperature of 60℃-80℃; the composite interface between the L1 bubble trapping layer and the L2 co-aggregating layer is achieved by hot pressing, with a composite pressure of 0.5MPa-1.5MPa. Step S2: Insert the broken bubble cap (4) into the fine filter membrane (3), and then put it into the outer mesh sleeve (2); Step S3: Seal both ends of the fine filter membrane (3) with the upper end cap (1) and the lower end cap (5) respectively.

9. The use of the filter element as described in any one of claims 1-7 in a hydraulic system for defoaming and filtering hydraulic oil.

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