An antibacterial diaphragm for diaphragm valves and its preparation method

Abstract

This invention discloses an antibacterial diaphragm for diaphragm valves and its preparation method, relating to the technical field of diaphragm valve components. The diaphragm consists of a surface layer, a backing layer, and reinforcing ribs: the surface layer is a PEEK physically blended modified high-temperature PTFE, solving the cold flow deformation problem of traditional PTFE; the backing layer contains EPDM rubber, chitosan nanofibers, and nano-zinc oxide, achieving long-lasting antibacterial properties through synergistic effects; the reinforcing ribs are radially carbon fiber reinforced polyimide, improving structural stability. The preparation employs a stepped molding process to ensure a firm bond between each layer. This invention improves the diaphragm's cold flow resistance, antibacterial durability, and structural strength, making it suitable for biopharmaceutical, food processing, and other fields, and possessing significant practical value.

Description

Technical Field

[0001] This invention relates to the field of diaphragm valve accessories technology, specifically to an antibacterial diaphragm for diaphragm valves and its preparation method. Background Technology

[0002] As a key device in fluid control, the diaphragm valve's core component, the diaphragm, must simultaneously meet multiple performance requirements, including dynamic sealing, resistance to media corrosion, anti-aging, and antibacterial properties. Especially in fields such as biopharmaceuticals and food processing, the diaphragm comes into direct contact with high-value process media, and its performance directly affects production safety and equipment lifespan.

[0003] While traditional PTFE diaphragms possess excellent corrosion resistance, they suffer from significant cold-flow deformation—gradually changing shape under continuous pressure, leading to seal failure. This deformation is exacerbated by alternating hot and cold temperatures, especially in intermittent steam sterilization scenarios, potentially causing process media leakage, contaminating the production environment, or affecting product quality. Ordinary rubber diaphragms (such as EPDM) offer good elasticity and excellent sealing performance, but their temperature resistance is limited. Prolonged exposure to high-temperature media can cause them to age and harden, and their antibacterial properties often rely on single antibacterial agents, resulting in a significant decrease in antibacterial effectiveness after a period of use. In fields with extremely high hygiene requirements, such as biopharmaceuticals, this can easily lead to bacterial growth and cross-contamination.

[0004] Furthermore, some improvement schemes attempt to form a double-layer structure by combining PTFE and rubber. However, due to the poor compatibility of the two materials, delamination often occurs under high temperature and high pressure conditions, resulting in weak interlayer bonding. This not only affects the sealing effect but also shortens the diaphragm's service life. At the same time, these composite diaphragms often lack effective structural reinforcement designs. During frequent opening and closing operations, excessive local stress can easily lead to permanent deformation, further reducing the valve's reliability.

[0005] Therefore, in order to solve the above problems, a membrane that can simultaneously solve the problems of cold flow deformation, short antibacterial time, easy structural damage and easy separation between layers is proposed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an antibacterial diaphragm for diaphragm valves and its preparation method, aiming to solve problems such as large cold flow deformation, poor antibacterial durability, and insufficient reliability under high-temperature conditions in traditional diaphragms. Through multi-component synergistic modification and composite structure design, the overall performance of the diaphragm is improved.

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

[0008] The technical solution provided by this invention is:

[0009] An antibacterial diaphragm for a diaphragm valve, characterized in that it comprises a surface layer, a backing layer, and reinforcing ribs, the parts of which are in parts by weight as follows:

[0010] The surface layer consists of 35-55 parts of polyether ether ketone (PEEK) physically blended modified high-temperature PTFE, of which PEEK accounts for 5-15% of the total weight of the surface layer and high-temperature PTFE accounts for 85-95% of the total weight of the surface layer. The modification is achieved through melt blending.

[0011] The backrest layer consists of 25-45 parts EPDM rubber, 1-3 parts chitosan nanofibers, 2-4 parts nano zinc oxide, 3-6 parts graphene nanosheets, 1.2-2.2 parts vulcanizing agent, and 0.8-1.8 parts accelerator.

[0012] The vulcanizing agent is dicumyl peroxide;

[0013] The accelerator is 2-thiol benzothiazole;

[0014] The reinforcing ribs are composed of 8-18 parts of short-cut carbon fiber reinforced polyimide, of which carbon fiber accounts for 10-20% of the total weight of the reinforcing ribs. The reinforcement is achieved by resin impregnation.

[0015] Furthermore, the particle size of high-temperature PTFE is 5-10 μm.

[0016] Furthermore, the chitosan nanofibers have a diameter of 50-200 nm and a length of 5-20 μm, and are prepared by cryogenic milling.

[0017] Furthermore, the cryogenic grinding method includes the following steps: pulverizing chitosan raw material into 100-200 mesh powder, mixing it with deionized water at a mass ratio of 1:5-1:8 to form a suspension, freezing it at -40 to -30℃ for 2-4 hours until completely frozen; placing the frozen material in a planetary ball mill, grinding it at a speed of 300-500 r / min for 3-5 times at a low temperature of -20 to -10℃, each time for 15-20 minutes, with a 5-minute interval; after grinding, passing it through a 500 mesh sieve, and collecting the sieve material to obtain chitosan nanofibers.

[0018] A method for preparing an antibacterial diaphragm for a diaphragm valve includes the following steps:

[0019] S1: Surface layer preparation: PEEK is vacuum dried at 120℃ for 4 hours, and high-temperature PTFE is dried at 80℃ for 2 hours; PEEK accounts for 5-15% of the total weight of the surface layer, and high-temperature PTFE accounts for 85-95%, and is added to a high-speed mixer and premixed at 80-100℃ and 800-1000r / min for 5-8 minutes; the premix is ​​added to a twin-screw extruder, which has five temperature zones along the material conveying direction: Zone 1 180-200℃, Zone 2 250-280℃, Zone 3 320-340℃, Zone 4 360-380℃, and Zone 5 340-360℃, with a screw speed of 180-220r / min. After extrusion, water cooling, and pelletizing, the blend is pressed by a tablet press at 340-380℃ and 12-15MPa for 5-8 minutes to obtain the surface layer preform;

[0020] S2: Backrest layer rubber compound preparation: Plasticize EPDM rubber on a two-roll mill for 5 minutes at 70℃, add chitosan nanofibers, nano zinc oxide, and graphene nanosheets, mix in an internal mixer at 90-110℃ for 12-18 minutes, then add vulcanizing agent dicumyl peroxide and accelerator 2-mercaptobenzothiazole, and continue mixing for 6-10 minutes to obtain the backrest layer rubber compound;

[0021] S3: Preparation of reinforcing ribs: Short carbon fibers with a length of 3-5mm are mixed with polyimide resin in a certain proportion, and then molded into radial reinforcing ribs at 300-320℃ and 8-10MPa using a compression molding machine. After molding, the mixture is naturally cooled to room temperature to obtain radial reinforcing ribs.

[0022] S4: Composite molding: Using stepped molding technology, the surface layer blank is first laid flat on the lower mold, and the backrest layer material is laid to the preset thickness. It is pre-composite at 180-200℃ and 8-10MPa for 5-7 minutes. The mold is opened, and the reinforcing ribs are embedded radially into the center of the backrest layer material. After the mold is closed, the temperature is raised to 280-300℃ at a rate of 5-8℃ / min, and the pressure is increased to 15-18MPa. The temperature and pressure are maintained for 20-25 minutes to obtain the S4: composite molded diaphragm blank.

[0023] S5: Post-processing: After cooling to below 80℃, open the mold and remove the product. Remove edge burrs and overflow. Clean with deionized water using ultrasonic cleaning 2-3 times, 10-15 minutes each time. Dry in a vacuum drying oven at 60-80℃ for 2-3 hours. After dimensional calibration, the finished antibacterial diaphragm for diaphragm valves with a three-layer composite structure is obtained. The surface layer of the finished product is a dense and smooth modified PTFE layer, the backrest layer is an elastic EPDM rubber layer, and radial reinforcing ribs are embedded inside.

[0024] Furthermore, the rotor speed of the internal mixer in S2 is 60-80 r / min.

[0025] Furthermore, the positioning of the reinforcing rib in S4 is achieved through a pre-set positioning slot within the mold.

[0026] The beneficial effects of this technical solution are:

[0027] (1) The surface layer is made by melting and blending PEEK with high-temperature PTFE, so that the rigid PEEK molecular chains are evenly dispersed in PTFE to form a "rigid support network". This not only retains the advantages of PTFE in resisting acid and alkali corrosion, but also utilizes the creep resistance of PEEK to prevent PTFE from slowly deforming under continuous pressure and temperature changes, ensuring that the diaphragm can still fit tightly against the sealing surface after long-term use, and avoid media leakage caused by deformation.

[0028] (2) The backrest layer innovatively combines chitosan nanofibers with nano zinc oxide. Chitosan, as a natural antibacterial substance, can form a "protective film" that continuously inhibits bacteria on the surface of the membrane. Nano zinc oxide exerts a long-lasting bactericidal effect by slowly releasing zinc ions. The two work together to solve the problem of "good initial effect but rapid decline in the later stage" in the use of traditional single antibacterial agents. Even after repeated steam sterilization, it can still maintain the ability to inhibit common bacteria such as Escherichia coli and Staphylococcus aureus.

[0029] (3) The radially distributed carbon fiber reinforced polyimide reinforcing ribs are embedded in the middle of the backrest layer like "umbrella ribs". When the diaphragm is closed, the reinforcing ribs can evenly distribute the external force to the entire diaphragm surface, avoiding wrinkles or tears caused by excessive local stress; at the same time, they guide the sealing pressure to concentrate in the valve weir area to ensure tight sealing. This design greatly reduces the permanent deformation of the diaphragm after frequent opening and closing operations and significantly extends its service life.

[0030] (4) A stepped molding process is adopted. First, the surface layer and the backrest layer are pre-composite at low temperature. Then, the molecules of each layer of materials diffuse and permeate each other through high temperature and high pressure to form a "gradient fusion interface". This solves the delamination problem caused by poor material compatibility of traditional composite membranes. Even if it is used repeatedly in a wide temperature range of -40℃ to 150℃, the surface layer and the backrest layer will not peel off, ensuring the overall structure of the membrane is stable.

[0031] (5) The surface layer is modified PTFE, which is resistant to steam and organic solvents and can come into contact with various process media; the backing layer EPDM rubber has excellent elasticity to ensure a tight seal; coupled with the overall antibacterial design and anti-deformation ability, the diaphragm can meet the sanitary requirements of the biopharmaceutical field, adapt to high-temperature cleaning in food processing, and can also be used for the control of corrosive media in the chemical field, with a wide range of applications. Attached Figure Description

[0032] Figure 1This is a step diagram illustrating the antibacterial diaphragm for a diaphragm valve and its preparation method proposed in this invention;

[0033] Figure 2 This is a parameter difference table for an antibacterial diaphragm for a diaphragm valve and its preparation method proposed in this invention;

[0034] Figure 3 This is a comparative table of experimental data for an antibacterial diaphragm for a diaphragm valve and its preparation method proposed in this invention. Detailed Implementation

[0035] 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.

[0036] The specific implementation process is as follows:

[0037] Example 1:

[0038] Please see Figure 1-3 The present invention provides a technical solution: an antibacterial diaphragm for a diaphragm valve and its preparation method, comprising the following components:

[0039] Surface layer: PEEK 50g, high-temperature PTFE 450g (total 500g);

[0040] Backrest layer: 300g EPDM rubber, 10g chitosan nanofibers, 20g nano zinc oxide, 30g graphene nanosheets, 12g vulcanizing agent (diisopropylbenzene peroxide), 8g accelerator (2-mercaptobenzothiazole);

[0041] Reinforcing ribs: 15g chopped carbon fiber, 135g polyimide resin (total 150g);

[0042] The preparation steps are as follows:

[0043] S1: Surface layer preparation: PEEK was vacuum dried at 120℃ for 4 hours, and high-temperature PTFE was dried at 80℃ for 2 hours; the mixture was added to a high-speed mixer in proportion and premixed at 80℃ and 800r / min for 8 minutes; the premix was added to a twin-screw extruder (temperature zones: 180℃, 250℃, 320℃, 360℃, 340℃), with a screw speed of 180r / min. After water cooling and pelletizing, the extrudate was pressed into sheets at 340℃ and 12MPa for 5 minutes to obtain the surface layer preform;

[0044] S2: Backrest layer rubber compound preparation: EPDM is plasticized in a 70℃ open mill for 5 minutes, chitosan nanofibers, nano zinc oxide and graphene nanosheets are added, and the mixture is mixed in a 90℃ internal mixer (rotor speed 60r / min) for 18 minutes. Then vulcanizing agent and accelerator are added, and the mixture is continued to be mixed for 10 minutes to obtain the backrest layer rubber compound.

[0045] S3: Preparation of reinforcing ribs: Short carbon fibers are mixed with polyimide resin, molded into radial reinforcing ribs at 300℃ and 8MPa, and then naturally cooled to room temperature;

[0046] S4: Composite molding: The surface layer blank is laid on the lower mold, the backing layer material is laid, and pre-composite at 180℃ and 8MPa for 7min; the reinforcing rib is embedded (through the positioning slot), the temperature is increased to 280℃ at 5℃ / min, the pressure is applied to 15MPa, and the temperature and pressure are maintained for 25min to obtain the diaphragm blank.

[0047] S5: Post-processing: Cool to below 80℃, remove, deburr, ultrasonically clean with deionized water 3 times (10min each time), vacuum dry at 60℃ for 3h, and calibrate the dimensions to obtain the finished product;

[0048] In this embodiment, the surface layer contains 10% PEEK, forming a basic support network in high-temperature PTFE. After 1000 hours of testing at 120°C and 1.5MPa, the cold flow deformation is only 0.45%, which is better than the more than 3% of traditional PTFE membranes. In the backrest layer, 10g of chitosan nanofibers and 20nm zinc oxide work synergistically to achieve an initial antibacterial rate of 99.8% against E. coli, which remains at 99.2% after 6 months. This is because the natural antibacterial film of chitosan and the slow-release bactericidal effect of zinc oxide provide continuous protection. The 10% carbon fiber content in the reinforcing ribs is sufficient to disperse the closing load. After 100 cycles of steam cycling at 150°C, the permanent compression deformation is only 2.8%, and the elasticity of the backrest layer is not affected by the positioning slot embedding. The interlayer peel strength is 5.2N / mm. The stepped pre-composite process effectively avoids the delamination of the surface layer and the backrest layer, resulting in balanced overall performance suitable for conventional biopharmaceutical working conditions.

[0049] Example 2:

[0050] Please see Figure 1-3 The present invention provides a technical solution: an antibacterial diaphragm for a diaphragm valve and its preparation method, comprising the following components:

[0051] Surface layer: PEEK 75g, high-temperature PTFE 425g (total 500g);

[0052] Backrest layer: 350g EPDM rubber, 20g chitosan nanofibers, 30g nano zinc oxide, 40g graphene nanosheets, 18g vulcanizing agent, 12g accelerator;

[0053] Reinforcing ribs: 20g chopped carbon fiber, 130g polyimide resin (total 150g);

[0054] The preparation steps are as follows:

[0055] S1: Surface layer preparation: PEEK and high-temperature PTFE are dried and premixed at 90℃ and 900r / min for 6min; the temperature of each zone of the twin-screw extruder is 200℃, 260℃, 330℃, 370℃ and 350℃, the screw speed is 200r / min, and the extruder is pressed at 360℃ and 13MPa for 6min.

[0056] S2: Backrest layer rubber compound preparation: After EPDM plasticizing, mix in a 100℃ internal mixer (70r / min) for 15min, add vulcanizing agent and accelerator and mix for 8min;

[0057] S3: Preparation of reinforcing ribs: Molding at 310℃ and 9MPa;

[0058] S4: Composite molding: Pre-composite at 200℃ and 9MPa for 6min, then heat up to 290℃ at 6℃ / min and hold at 16MPa for 22min;

[0059] S5: Post-treatment: Ultrasonic cleaning twice (12 min / time), vacuum drying at 70℃ for 2.5 h;

[0060] This embodiment increases the proportion of PEEK in the surface layer (15%), increasing its rigid molecular chain density and reducing cold flow deformation to 0.38%, making it more suitable for high-pressure conditions. The backrest layer increases chitosan nanofibers to 20g, forming a stronger antibacterial synergy with 30g of nano zinc oxide, achieving an initial antibacterial rate of 99.9%, which remains at 99.3% after 6 months. Furthermore, the addition of chitosan does not affect the vulcanization crosslinking of EPDM (1.8kg of vulcanizing agent is suitable for 35kg of EPDM). The reinforcing carbon fiber accounts for 13.3%, and its radial structure distributes stress more evenly when closed, reducing compression set by 2.5%. The 100℃ mixing temperature promotes the dispersion of graphene nanosheets in EPDM, improving the thermal conductivity of the backrest layer and preventing local overheating and aging during steam sterilization. The interlayer peel strength is 5.5N / mm, and the high-temperature pre-composite stage enhances molecular diffusion between the surface layer and the backrest layer, making it suitable for scenarios requiring frequent high-temperature sterilization.

[0061] Example 3:

[0062] Please see Figure 1-3 The present invention provides a technical solution: an antibacterial diaphragm for a diaphragm valve and its preparation method, comprising the following components:

[0063] Surface layer: PEEK 55g, high-temperature PTFE 395g (total 450g);

[0064] Backrest layer: 250g EPDM rubber, 30g chitosan nanofibers, 40g nano zinc oxide, 60g graphene nanosheets, 22g vulcanizing agent, 18g accelerator;

[0065] Reinforcing ribs: 18g of chopped carbon fiber and 102g of polyimide resin (total 120g).

[0066] The preparation steps are as follows:

[0067] S1: Surface layer preparation: Premix at 100℃ and 1000r / min for 5min; Twin-screw extruder temperatures in each zone are 200℃, 280℃, 340℃, 380℃, and 360℃, screw speed is 220r / min, and tableting is performed at 380℃ and 15MPa for 5min.

[0068] S2: Preparation of backrest layer rubber compound: Mix in a 110℃ internal mixer (80r / min) for 12min, then mix for 6min after adding vulcanizing agent and accelerator;

[0069] S3: Preparation of reinforcing ribs: Molding at 320℃ and 10MPa;

[0070] S4: Composite molding: Pre-composite at 200℃ and 10MPa for 5min, then heat up to 300℃ at 8℃ / min, and hold at 18MPa for 20min.

[0071] S5: Post-treatment: Ultrasonic cleaning twice (15 min / time), vacuum drying at 80℃ for 2 h;

[0072] In this embodiment, the surface layer contains 12.2% PEEK. High-pressure pressing at 380℃ makes the blend more compact, with a cold flow deformation of 0.32%. At the same time, the reduced proportion of PTFE at high temperature does not affect the corrosion resistance (it can still withstand immersion in 10% nitric acid solution for 30 days without swelling). The backrest layer contains 30g of chitosan nanofibers, forming a continuous antibacterial network. Combined with 40g of nano zinc oxide, the initial antibacterial rate is 100%, and it reaches 99.5% after 6 months. However, it should be noted that 30g of chitosan may increase the viscosity of the adhesive. Therefore, high-temperature mixing at 110℃ (high speed of 80r / min) ensures uniform dispersion. 60g of graphene nanosheets significantly improves the wear resistance of the backrest layer. After 1000 opening and closing cycles, there are no obvious scratches on the surface. The reinforcing ribs contain 15% (15% carbon fiber). Molding at 320℃ fully cures the polyimide resin, making it more firmly embedded with the backrest layer. The compression set is 2.2%, which is suitable for valves with high-frequency operation.

[0073] Example 4:

[0074] Please see Figure 1-3 The present invention provides a technical solution: an antibacterial diaphragm for a diaphragm valve and its preparation method, comprising the following components:

[0075] Surface layer: PEEK 40g, high-temperature PTFE 360g (total 400g);

[0076] Backrest layer: 400g EPDM rubber, 20g chitosan nanofibers, 30g nano zinc oxide, 50g graphene nanosheets, 20g vulcanizing agent, 15g accelerator;

[0077] Reinforcing ribs: 10g of chopped carbon fiber and 90g of polyimide resin (total 100g).

[0078] The preparation steps are as follows:

[0079] S1: Surface layer preparation: Premix at 90℃ and 900r / min for 7min; Twin-screw extruder temperatures in each zone are 190℃, 270℃, 330℃, 370℃, and 350℃, screw speed is 200r / min, and tableting is performed at 350℃ and 14MPa for 7min.

[0080] S2: Preparation of backrest layer rubber compound: Mix in a 100℃ internal mixer (75r / min) for 16min, then mix for 7min after adding vulcanizing agent and accelerator;

[0081] S3: Reinforcing rib preparation: compression molding at 315℃ and 9.5MPa;

[0082] S4: Composite molding: Pre-composite at 190℃ and 9.5MPa for 6min, then heat up to 295℃ at 7℃ / min and hold at 17MPa for 23min;

[0083] S5: Post-treatment: Ultrasonic cleaning twice (13 min / time), vacuum drying at 75℃ for 2.5 h;

[0084] In this embodiment, the surface layer contains 10% PEEK, balancing cold flow resistance (0.42% deformation) with flexibility, making it suitable for sealing surfaces requiring a certain degree of elasticity compensation. The backrest layer contains 40kg of EPDM, combined with 15g of accelerator for more complete vulcanization, achieving an elastic recovery rate of 92% and a tighter fit when opening and closing. The ratio of 20g chitosan to 30g nano zinc oxide avoids material compatibility issues caused by excessive antibacterial agents, achieving a 99.0% antibacterial rate after 6 months. Furthermore, 50g of graphene nanosheets improves thermal conductivity, reducing thermal stress during steam sterilization. The reinforcing ribs contain 10% (10% carbon fiber), which, although low in content, ensures structural strength through precise molding at 315℃, with a compression set of 2.5%, making it suitable for low-pressure but high-frequency elastic deformation applications. The overall cost is lower than that of Embodiment 3.

[0085] Example 5:

[0086] Please see Figure 1-3 The present invention provides a technical solution: an antibacterial diaphragm for a diaphragm valve and its preparation method, comprising the following components:

[0087] Surface layer: PEEK 35g, high-temperature PTFE 315g (total 350g);

[0088] Backrest layer: 450g EPDM rubber, 15g chitosan nanofibers, 25g nano zinc oxide, 45g graphene nanosheets, 15g vulcanizing agent, 10g accelerator;

[0089] Reinforcing ribs: 12g of chopped carbon fiber and 68g of polyimide resin (total 80g).

[0090] The preparation steps are as follows:

[0091] S1: Surface layer preparation: Premix at 85℃ and 850r / min for 7.5min; Twin-screw extruder temperatures in each zone are 185℃, 260℃, 325℃, 365℃, and 345℃, screw speed is 190r / min, and tableting is performed at 345℃ and 13MPa for 6.5min.

[0092] S2: Backrest layer rubber compound preparation: Mix in a 95℃ internal mixer (65r / min) for 17min, then add vulcanizing agent and accelerator and mix for 8min;

[0093] S3: Preparation of reinforcing ribs: compression molding at 305℃ and 8.5MPa;

[0094] S4: Composite molding: Pre-composite at 185℃ and 8.5MPa for 6.5min, then heat up to 285℃ at 6.5℃ / min and hold at 16MPa for 24min;

[0095] S5: Post-treatment: Ultrasonic cleaning 3 times (12min / time), vacuum drying at 65℃ for 2.8h;

[0096] In this embodiment, the surface layer contains 10% PEEK, totaling 350g, reducing the amount of high-cost materials used. The cold flow deformation is 0.48%, meeting the requirements of general working conditions. The backrest layer contains 450g of EPDM, which has excellent elasticity and is suitable for sealing surfaces with large unevenness. The synergistic antibacterial rate of 15g chitosan and 25g nano zinc oxide remains at 98.8% after 6 months. 45g of graphene nanosheets improves aging resistance (hardness change ≤5 Shore A after 72h of hot air aging at 150℃). The reinforcing ribs contain only 80g (15% carbon fiber). Molding at 305℃ ensures that polyimide fully impregnates the carbon fiber. Although the overall reinforcement effect is weaker than that of Examples 1-4, it is sufficient to cope with low-to-medium frequency operation, with a significant cost advantage. The interlayer peel strength is 5.1N / mm, and the pre-composite temperature of 185℃ avoids poor interlayer bonding caused by premature vulcanization of EPDM.

[0097] Example 6:

[0098] Please see Figure 1-3 The present invention provides a technical solution: an antibacterial diaphragm for a diaphragm valve and its preparation method, comprising the following components:

[0099] Surface layer: PEEK 82.5g, high-temperature PTFE 467.5g (total 550g);

[0100] Backrest layer: 250g EPDM rubber, 25g chitosan nanofibers, 35g nano zinc oxide, 55g graphene nanosheets, 21g vulcanizing agent, 17g accelerator;

[0101] Reinforcing ribs: 36g of chopped carbon fiber and 144g of polyimide resin (total 180g).

[0102] The preparation steps are as follows:

[0103] S1: Surface layer preparation: Premix at 95℃ and 950r / min for 5.5min; Twin-screw extruder zone temperatures of 195℃, 275℃, 335℃, 375℃, and 355℃, screw speed of 210r / min, and tableting at 375℃ and 14.5MPa for 5.5min.

[0104] S2: Backrest layer rubber compound preparation: Mix in a 105℃ internal mixer (75r / min) for 14min, then add vulcanizing agent and accelerator and mix for 6.5min;

[0105] S3: Reinforcing rib preparation: compression molding at 315℃ and 9.5MPa;

[0106] S4: Composite molding: Pre-composite at 195℃ and 9.5MPa for 5.5min, then heat up to 295℃ at 7.5℃ / min and hold at 17.5MPa for 21min;

[0107] S5: Post-treatment: Ultrasonic cleaning twice (14 min / time), vacuum drying at 75℃ for 2.2 h;

[0108] In this embodiment, the surface layer has the highest PEEK content (15%) among all embodiments, with a cold flow deformation as low as 0.30%. High-pressure pressing at 375℃ increases the surface layer density and enhances solvent resistance (no weight change after 30 days of acetone immersion). The backrest layer contains 25g of chitosan and 35g of nano-zinc oxide, forming a powerful antibacterial system with an antibacterial rate of 99.6% after 6 months. 55g of graphene nanosheets improve wear resistance and thermal conductivity, making it suitable for media containing trace particles. The reinforcing ribs reach 180g (20% carbon fiber), and molding at 315℃ ensures a strong bond between the carbon fiber and polyimide, with a compression set of only 2.0%, enabling it to withstand high-frequency and high-pressure operations, although the overall weight increases slightly. The interlayer peel strength is 5.7N / mm, and the 195℃ pre-composite and stepped heating process ensures the interfacial fusion between the surface layer (high-temperature material) and the backrest layer (medium-temperature material), making it suitable for long-term use under harsh conditions.

[0109] Comparative Example 1:

[0110] Please see Figure 1-3 The present invention provides a comparative scheme comprising the following components:

[0111] Surface layer: High-temperature PTFE 500g;

[0112] The backrest layer and reinforcing ribs are the same as in Example 1;

[0113] The preparation steps are as follows:

[0114] Except for the surface layer, which is directly pressed into a high-temperature PTFE sheet (340℃, 12MPa, 5min), the other steps are the same as in Example 1;

[0115] Because the surface layer of this comparative example does not contain PEEK, the high-temperature PTFE molecular chains lack rigid support. After 1000 hours at 120℃ and 1.5MPa, the cold flow deformation reached 4.8%, far exceeding the 0.45% of Example 1. After 50 steam sterilization cycles, local bulges appeared on the surface layer, and gaps were formed at the joint with the backrest layer due to deformation. The peel strength dropped to 3.2N / mm, and the sealing performance failed. This shows that the addition of PEEK is the key to solving the cold flow defect of PTFE. A simple PTFE surface layer cannot meet the long-term high-pressure sealing requirements, which confirms the necessity of the surface layer modification scheme of this invention.

[0116] Comparative Example 2:

[0117] Please see Figure 1-3 The present invention provides a comparative scheme comprising the following components:

[0118] The surface layer is the same as in Example 2;

[0119] Backrest layer: Chitosan nanofibers removed, otherwise the same as in Example 2;

[0120] The reinforcing ribs are the same as in Example 2;

[0121] The preparation steps are as follows:

[0122] Same as Example 2;

[0123] The comparative example backrest layer contained only 30g of nano-zinc oxide as an antibacterial agent, with an initial antibacterial rate of 98.5%. However, after 3 months, the antibacterial rate dropped to 85.2% due to the gradual passivation of the zinc oxide surface, and further decreased to 72.3% after 6 months, with bacterial biofilm appearing on the surface. In contrast, Example 2, due to the continuous antibacterial film formed by chitosan nanofibers, still achieved an antibacterial rate of 99.3% after 6 months. The comparison shows that the synergistic effect of chitosan and nano-zinc oxide can effectively solve the time-limited problem of single antibacterial agents, which is especially suitable for the long-term antibacterial requirements in the biopharmaceutical field, highlighting the inventiveness of the antibacterial system of this invention.

[0124] Comparative Example 3:

[0125] Please see Figure 1-3 The present invention provides a comparative scheme comprising the following components:

[0126] The surface layer and backrest layer are the same as in Example 3, but without reinforcing ribs;

[0127] The preparation steps are as follows:

[0128] S4: During composite molding, the surface layer and the backrest layer are directly laminated together, and the remaining steps are the same as in Example 3;

[0129] Because this comparative example lacks reinforcing ribs, the load is concentrated in the central area when the diaphragm is closed. After 100 switching cycles, local wrinkles appear, and the permanent compression deformation reaches 15.6%, far exceeding the 2.2% of Example 3. After steam sterilization, microcracks appear in the deformed areas due to stress concentration, leading to seal leakage. The radial reinforcing ribs of Example 3 evenly distribute stress through positioning slots, avoiding excessive local deformation. This proves that the design of reinforcing ribs is crucial to improving the stability of the diaphragm structure, solving the problem of short lifespan caused by the lack of reinforcement structure in traditional composite diaphragms, and demonstrating the advantages of the structural design of this invention.

[0130] Please see Figure 1-3 :

[0131] This technical solution, through synergistic innovation in materials, structural design, and process optimization, has formed an advanced antibacterial diaphragm technology system for diaphragm valves. Its core advantages can be fully demonstrated through a systematic comparison between Examples 1-6 and Comparative Examples 1-3. From the perspective of surface layer modification, Examples 1-6 all adopt a melt blending system of PEEK and high-temperature PTFE. By constructing a "support network" with 5%-15% rigid PEEK molecular chains, the problem of cold flow deformation of traditional PTFE is effectively solved. In Example 1, the combination of 50g PEEK and 450g high-temperature PTFE controls the cold flow deformation at 0.45%. In Example 6, the deformation is reduced to 0.30% with 82.5g PEEK (accounting for 15%). However, in Comparative Example 1, without the addition of PEEK, the deformation reaches 4.8% when using only 500g of high-temperature PTFE, and bulging and sealing failure occur after steam circulation. This fully demonstrates that the introduction of PEEK is not a simple material superposition, but rather inhibits the creep characteristics of PTFE through molecular-level synergistic effects. This modification approach breaks through the limitations of traditional single-material improvement.

[0132] Regarding antibacterial properties, Examples 1-6 innovatively constructed a synergistic system of chitosan nanofibers and nano-zinc oxide. By combining natural antibacterial and sustained-release bactericidal mechanisms, a long-lasting antibacterial effect was achieved. In Example 1, the ratio of 10g chitosan to 20g nano-zinc oxide maintained an antibacterial rate of 99.2% after 6 months. In Example 3, 30g chitosan formed a continuous antibacterial network, which, combined with 40g nano-zinc oxide, maintained an antibacterial rate of 99.5%. In contrast, in Comparative Example 2, due to the removal of chitosan, the antibacterial rate dropped to 85.2% after 3 months with only 30g nano-zinc oxide, and bacterial biofilm appeared after 6 months, highlighting the beneficial effect of the synergistic effect of the two antibacterial agents. The film-forming properties of chitosan provided a sustained-release carrier for nano-zinc oxide, while the ionic bactericidal effect of nano-zinc oxide compensated for the lack of rapid action of chitosan. This complementary design far exceeds the technical effect of a single antibacterial agent and solves the long-standing problem of short-lasting antibacterial effects in the biopharmaceutical field.

[0133] Examples 1-6 all employ radial carbon fiber reinforced polyimide reinforcing ribs, with stress dispersion achieved through positioning slots embedded in the backrest layer. In Example 1, the combination of 15g carbon fiber and 135g polyimide resulted in a compression set of only 2.8% after 100 steam cycles. In Example 6, 36g carbon fiber (20% of the total) controlled the deformation to 2.0%, while Comparative Example 3, lacking reinforcing ribs, exhibited a deformation of 15.6% under the same conditions, along with microcrack leakage. The radial structure evenly transmits the closing load to the valve weir area, preventing localized stress concentration. The composite of carbon fiber and polyimide retains the high strength of the reinforcing phase while ensuring compatibility with the backrest layer through resin impregnation. The positioning slot design solves the problem of bonding the reinforcing ribs to the elastic matrix. The synergy of these three elements allows the diaphragm to maintain structural integrity even under high-frequency operation, overcoming the contradiction of "increased rigidity leading to decreased elasticity" in traditional composite diaphragms.

[0134] In terms of process, Examples 1-6 achieve preliminary bonding between the surface layer and the backrest layer through low-temperature pre-composite (180-200℃), followed by high temperature and high pressure (280-300℃, 15-18MPa) to promote molecular diffusion, so that the interlayer peel strength is maintained above 5.1N / mm. In contrast, the interlayer bonding strength of composite membranes prepared by traditional processes is generally lower than 4N / mm due to the lack of gradient temperature control. Example 2 achieves a peel strength of 5.5N / mm through step control of 200℃ pre-composite and 290℃ final composite, and no delamination occurs even after 100 cold and hot cycles. This process innovation solves the industry pain point of poor compatibility between PTFE and EPDM materials and provides a new path for heterogeneous material composites.

[0135] From the perspective of overall performance synergy, this technical solution integrates three dimensions of "materials-structure-process": the PEEK modified surface layer solves the cold flow resistance, the synergistic antibacterial backrest layer solves the hygiene and safety, the radial reinforcing ribs solve the structural stability, and the stepped molding solves the interlayer bonding. The four elements support each other to form an organic whole. Example 5, with a ratio of 350g surface layer, 450g backrest layer, and 80g reinforcing ribs, achieves balanced performance of 0.48% cold flow deformation, 98.8% antibacterial rate after 6 months, and peel strength of 5.1N / mm while controlling costs. This proves that the technical system has a wide range of working conditions adaptability. Compared with the existing technology, the traditional PTFE diaphragm has large cold flow deformation, the rubber diaphragm has poor antibacterial properties, and the ordinary composite diaphragm is prone to delamination. These multiple defects are systematically solved in this solution. For example, the rigidity of PEEK does not affect the corrosion resistance of the surface layer, the addition of antibacterial agent does not reduce the elasticity of the backrest layer, and the reinforcement of the reinforcing ribs does not damage the sealing and adhesion of the diaphragm.

[0136] The testing method is as follows:

[0137] (I) Cold Flow Deformation Test: A custom-made fixture was used to continuously load the diaphragm sample. The specific steps are as follows:

[0138] Sampling: Cut a 50mm×50mm square sample from the surface layer of the finished diaphragm, keeping the original thickness (3-5mm).

[0139] Pretreatment: Place the sample in an environment of 23℃ and 50% relative humidity for 24 hours;

[0140] Loading conditions: The sample was placed in a constant temperature chamber at 120℃ and a constant pressure of 1.5MPa was applied by weights (the pressure was calculated based on the contact area of ​​the sample) for 1000h.

[0141] Measurement: Before and after the test, the thickness of the sample center and four corners was measured with a laser thickness gauge with an accuracy of 0.001 mm. The average deformation was calculated as follows: cold flow deformation = (initial thickness - thickness after test) / initial thickness × 100%.

[0142] (II) Antibacterial performance test: Tests were conducted against Escherichia coli and Staphylococcus aureus.

[0143] Preparation of bacterial culture: The bacterial strain was cultured on nutrient agar medium at 37°C for 24 hours, and then diluted with 0.85% physiological saline to prepare a culture with a concentration of 1×10⁻⁶. 6 CFU / mL bacterial suspension;

[0144] Sample preparation: Take a 30mm×30mm diaphragm sample, sterilize it with ultraviolet light for 30 minutes, and then place it in a sterile petri dish;

[0145] Inoculation and cultivation: Add 0.2 mL of bacterial suspension to each sample, cover with a sterile polyethylene film to ensure uniform contact of the bacterial suspension with the sample surface, and incubate at 37℃ and 90% relative humidity for 24 h;

[0146] Viable bacteria count: After culturing, add 10 mL of physiological saline containing 0.05% Tween 80, shake to wash away viable bacteria, and calculate the viable bacteria count using the plate count method. Antibacterial rate = (Viable bacteria count in blank control group - Viable bacteria count in sample group) / Viable bacteria count in blank control group × 100%;

[0147] Long-term test: Immerse the sample in deionized water at 37°C for 180 days (simulating long-term use), and repeat the above steps to determine the antibacterial rate.

[0148] (III) Compression set test: The test was designed in conjunction with steam sterilization conditions.

[0149] Sampling: Prepare cylindrical samples with a diameter of 29 mm and a thickness of 12.5 mm (taken from the back layer area of ​​the diaphragm).

[0150] Compression conditions: Place the sample in a compression device, apply a compression rate of 25% (i.e., compress to 9.375 mm), and place it in a 150°C saturated steam sterilizer for 100 cycles (each cycle: heat to 150°C and hold for 30 min, then cool to 23°C and hold for 30 min).

[0151] Recovery and Measurement: After the test, release the compression and place it in a 23℃ environment for 30 minutes. Measure the thickness with a micrometer. The permanent compression deformation is calculated as (initial thickness - recovered thickness) / (initial thickness × compression ratio) × 100%.

[0152] (iv) Interlayer peel strength test:

[0153] Sample preparation: The diaphragm is pre-peeled 50 mm along the interlayer interface. The peeled part is fixed on the upper and lower clamps of the tensile testing machine. The sample width is 25 mm and the effective peel length is 100 mm.

[0154] Test conditions: Tensile speed of 100 mm / min, record the maximum force value during the peeling process;

[0155] Calculation: Peel strength = maximum force / specimen width (unit: N / mm), take the average value of 5 parallel specimens.

[0156] (v) Aging resistance test:

[0157] Sampling: Take dumbbell-shaped specimens from the backrest layer (meeting the requirements for Type I specimens);

[0158] Aging conditions: Place the sample in a 150℃ hot air aging chamber and age for 72 hours;

[0159] Performance testing: Shore A hardness and tensile strength were tested before and after aging, and the change in hardness and the retention rate of tensile strength were calculated.

[0160] (vi) Abrasion resistance test:

[0161] Sample preparation: Cylindrical sample with a diameter of 16 mm and a thickness of 6 mm (taken from the surface layer);

[0162] Test conditions: load 10N, grinding wheel speed 40r / min, grinding distance 40m, abrasive is 80 mesh diamond;

[0163] Calculation: Wear amount = (mass before test - mass after test) / mass before test × 100% (mass is weighed using an electronic balance with an accuracy of 0.1 mg).

[0164] (vii) Chemical resistance test:

[0165] Media selection: 10% nitric acid solution, acetone, physiological saline (simulating common media in the pharmaceutical industry);

[0166] Test conditions: The 30mm×30mm sample was completely immersed in the medium at 23℃ for 30 days;

[0167] Measurement: The changes in mass, volume and appearance of the sample were measured before and after the test. The mass change rate = (mass after test - initial mass) / initial mass × 100%. The volume change rate was determined by the water displacement method.

[0168] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An antibacterial diaphragm for a diaphragm valve, characterized in that, It consists of a surface layer, a backrest layer, and reinforcing ribs, with each part in parts by weight as follows: The surface layer is 35-55 parts of polyether ether ketone (PEEK) physically blended modified high-temperature PTFE, wherein PEEK accounts for 5-15% of the total weight of the surface layer and high-temperature PTFE accounts for 85-95% of the total weight of the surface layer. The modification is achieved by melt blending. The backrest layer consists of 25-45 parts EPDM rubber, 1-3 parts chitosan nanofibers, 2-4 parts nano zinc oxide, 3-6 parts graphene nanosheets, 1.2-2.2 parts vulcanizing agent, and 0.8-1.8 parts accelerator. The vulcanizing agent is dicumyl peroxide; The accelerator is 2-thiol benzothiazole; The reinforcing rib is composed of 8-18 parts of short-cut carbon fiber reinforced polyimide, wherein the carbon fiber accounts for 10-20% of the total weight of the reinforcing rib, and the reinforcement is achieved by resin impregnation. The particle size of the high-temperature PTFE is 5-10 μm; The chitosan nanofibers have a diameter of 50-200 nm and a length of 5-20 μm, and are prepared by cryogenic milling. The cryogenic grinding method includes the following steps: pulverizing chitosan raw material into 100-200 mesh powder, mixing it with deionized water at a mass ratio of 1:5-1:8 to form a suspension, freezing it at -40 to -30℃ for 2-4 hours until completely frozen; placing the frozen material in a planetary ball mill, grinding it at a speed of 300-500 r / min for 3-5 times at a low temperature of -20 to -10℃, each time for 15-20 minutes, with a 5-minute interval; passing the material through a 500 mesh sieve after grinding, and collecting the material passing through the sieve to obtain chitosan nanofibers.

2. A method for preparing an antibacterial diaphragm for a diaphragm valve as described in claim 1, characterized in that, Includes the following steps: S1: Surface layer preparation: PEEK is vacuum dried at 120℃ for 4 hours, and high-temperature PTFE is dried at 80℃ for 2 hours; PEEK accounts for 5-15% of the total weight of the surface layer, and high-temperature PTFE accounts for 85-95%, and is added to a high-speed mixer and premixed at 80-100℃ and 800-1000 r / min for 5-8 minutes; the premix is ​​added to a twin-screw extruder, which has five temperature zones along the material conveying direction: zone 1 180-200℃, zone 2 250-280℃, zone 3 320-340℃, zone 4 360-380℃, and zone 5 340-360℃, with a screw speed of 180-220 r / min. After extrusion, water cooling, and pelletizing, the blend is pressed by a tablet press at 340-380℃ and 12-15 MPa for 5-8 minutes to obtain the surface layer preform; S2: Backrest layer rubber compound preparation: Plasticize EPDM rubber on a two-roll mill for 5 minutes at 70℃, add chitosan nanofibers, nano zinc oxide, and graphene nanosheets, mix in an internal mixer at 90-110℃ for 12-18 minutes, then add vulcanizing agent dicumyl peroxide and accelerator 2-mercaptobenzothiazole, and continue mixing for 6-10 minutes to obtain the backrest layer rubber compound; S3: Preparation of reinforcing ribs: Short carbon fibers with a length of 3-5mm are mixed with polyimide resin in a certain proportion, and then molded into radial reinforcing ribs at 300-320℃ and 8-10MPa using a compression molding machine. After molding, the mixture is naturally cooled to room temperature to obtain radial reinforcing ribs. S4: Composite molding: Using stepped molding technology, the surface layer blank is first laid flat on the lower mold, and the backrest layer material is laid to the preset thickness. It is pre-composite at 180-200℃ and 8-10MPa for 5-7 minutes. The mold is opened, and the reinforcing ribs are embedded radially into the center of the backrest layer material. After the mold is closed, the temperature is raised to 280-300℃ at a rate of 5-8℃ / min, and the pressure is increased to 15-18MPa. The temperature and pressure are maintained for 20-25 minutes to obtain the S4: composite molded diaphragm blank. S5: Post-processing: After cooling to below 80℃, open the mold and remove the product. Remove edge burrs and overflow. Clean with deionized water using ultrasonic cleaning 2-3 times, 10-15 minutes each time. Dry in a vacuum drying oven at 60-80℃ for 2-3 hours. After dimensional calibration, the finished antibacterial diaphragm for diaphragm valves with a three-layer composite structure is obtained. The surface layer of the finished product is a dense and smooth modified PTFE layer, the backing layer is an elastic EPDM rubber layer, and radial reinforcing ribs are embedded inside.

3. The preparation method according to claim 2, characterized in that, The rotor speed of the internal mixer in S2 is 60-80 r / min.

4. The preparation method according to claim 2, characterized in that, The positioning of the reinforcing rib in S4 is achieved through a pre-set positioning slot inside the mold.

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