A waterproof and breathable medical dressing and a method of making the same

Abstract

The present application relates to the medical dressing processing and manufacturing field, disclose a kind of waterproof breathable medical dressing and preparation method thereof.The method uses staged gradient assembly technology, sequentially include: first chitosan is prepared into spinning dope, nanofiber membrane is prepared by electrospinning, and is hot-pressed into composite base layer with pretreated PTFE hydrophobic membrane, then special medical pressure-sensitive adhesive is coated to obtain semi-finished product;Can add coaxial spinning core-shell structure fiber membrane, silica gel impermeable ring, release layer, finally sterilized by ethylene oxide, laser cutting to obtain finished product.The present application makes the dressing have efficient waterproof, balanced ventilation performance by material compounding and process optimization, chitosan fiber is compatible with wound surface, adsorbs exudate, PTFE membrane blocks external pollutants, firm interlayer bonding, adhesive layer is pasted smoothly and easily peeled off, overall biocompatibility is good, convenient to use, adapt to various wound care needs, process controllable and easy to scale production.

Description

Technical Field

[0001] This invention relates to the field of medical dressing processing and manufacturing, specifically to a waterproof and breathable medical dressing and its preparation method. Background Technology

[0002] Medical dressings are indispensable medical consumables in wound care, widely used for the protection and repair of various wounds such as surgical incisions, abrasions, burns, and chronic ulcers. Their performance directly affects the wound healing progress, patient comfort, and clinical nursing efficiency. Currently, commonly used medical dressings in clinical practice mainly include traditional gauze dressings, ordinary non-woven fabric dressings, film dressings, and some composite functional dressings. Each type of dressing has performance shortcomings that are difficult to balance in practical applications, failing to meet the modern clinical demands for refined, comfortable, and efficient wound care. Traditional gauze dressings are readily available and inexpensive, making them the most widely used basic dressing in clinical practice. However, their loose structure and lack of waterproofing allow external moisture, bacteria, and contaminants to easily penetrate the wound, increasing the risk of infection. Furthermore, the large pores in gauze fibers prevent precise control of air permeability, leading to rapid evaporation of wound exudate and a dry healing environment that hinders the growth of new tissue. The gauze also tends to adhere to the wound, pulling on newly formed granulation tissue during dressing changes, increasing patient discomfort, and potentially causing secondary wound damage. While ordinary non-woven fabric dressings are softer and have improved absorbency compared to gauze dressings, they still lack waterproofing and offer limited protection against external liquids. They are only suitable for dry, superficial wounds with minimal exudate, restricting their application scenarios.

[0003] Many existing waterproof medical dressings use dense polymer films as the base material. While these achieve basic waterproofing, they generally suffer from extremely poor breathability. When the dressing covers a wound, the skin cannot breathe properly, and exudate cannot evaporate effectively, accumulating between the wound and the dressing over time. This creates a moist, sealed environment, which not only slows wound healing but also promotes bacterial growth and increases the risk of infection. Furthermore, the sealed environment can cause discomfort such as whitening, maceration, and itching around the wound, reducing patient comfort. Some composite dressings that attempt to balance waterproofing and breathability often employ simple layering processes, resulting in weak interlayer bonding. These dressings are prone to delamination and detachment during use, exhibiting poor stability. Moreover, these dressings often use ordinary medical adhesives with insufficient uniformity of adhesive layer application, leading to edge lifting and displacement during application, and leaving adhesive residue upon removal, which can irritate the wound and surrounding skin. Furthermore, most existing dressings are not optimized for wound exudate absorption, skin affinity, and edge leakage prevention. Some dressings use materials with poor biocompatibility, easily causing skin allergic reactions. Their processing is cumbersome, production parameters are difficult to control, resulting in low finished product yields. Performance degradation easily occurs after sterilization, making them unsuitable for long-term, stable clinical use. With continuously improving clinical wound care standards, there is an urgent need for a medical dressing that can simultaneously achieve high-efficiency waterproofing, balanced breathability, wound affinity, firm adhesion, and leakage and infection prevention, while also possessing controllable processing and stable performance. This would overcome many performance deficiencies of existing products and meet the care needs of various wound types. Summary of the Invention

[0004] The purpose of this invention is to provide a waterproof and breathable medical dressing and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a waterproof and breathable medical dressing and a method for preparing the same, the method comprising:

[0006] Chitosan powder was dissolved in a 1% (w / w) aqueous acetic acid solution and stirred at 200 rpm for 2 hours at 50°C to prepare a 2% (w / w) chitosan solution.

[0007] The obtained chitosan solution was filtered through a 0.45 μm microporous membrane to remove insoluble matter, resulting in a clear chitosan spinning solution.

[0008] Chitosan spinning solution was injected into the storage tank of an electrospinning device. The distance between the spinneret and the receiving roller was set to 15cm. A high voltage of 20kV was applied, and the speed of the receiving roller was 100rpm. Spinning was carried out under the condition of 35% ambient humidity to obtain a chitosan nanofiber membrane with a thickness of 100μm.

[0009] The obtained chitosan nanofiber membrane was laid flat on the rough surface of the PTFE hydrophobic membrane, so that the chitosan nanofiber membrane and the PTFE hydrophobic membrane were completely bonded together. The membrane was then hot-pressed for 10 minutes at 80°C and 0.5MPa using a hot press, so that the two were bonded together by intermolecular forces to obtain a composite base layer.

[0010] Medical pressure-sensitive adhesive was uniformly coated on the surface of the PTFE hydrophobic membrane side of the composite base layer with a coating thickness of 50 μm, and dried in an oven at 40°C for 30 minutes to obtain a semi-finished waterproof and breathable medical dressing.

[0011] Preferably, the pretreatment steps for the PTFE hydrophobic membrane are as follows:

[0012] The PTFE hydrophobic membrane was immersed in a mixed solution containing 5% NaOH solution and 0.5% sodium dodecyl sulfate and ultrasonically cleaned at 60°C for 30 minutes to remove surface oil and impurities.

[0013] After cleaning, rinse with deionized water until neutral, and then immerse the PTFE hydrophobic membrane in a 10% hydrochloric acid solution for 1 hour to activate the functional groups on the membrane surface.

[0014] After activation, rinse again with deionized water until neutral, and dry in hot air at 60°C for 2 hours to obtain the pretreated PTFE hydrophobic membrane.

[0015] The contact angle of the pretreated PTFE hydrophobic membrane is not less than 110°.

[0016] Preferably, the medical pressure-sensitive adhesive is composed of the following components: 70 parts butyl acrylate, 20 parts methyl methacrylate, 5 parts hydroxyethyl acrylate, 3 parts rosin resin, and 2 parts benzoyl peroxide.

[0017] The above components were added to a reaction vessel, heated to 75°C under nitrogen protection, and stirred at 300 rpm for 4 hours to carry out a free radical polymerization reaction, thereby obtaining the medical pressure-sensitive adhesive.

[0018] Before coating, the medical pressure-sensitive adhesive is placed in a vacuum degassing machine and degassed for 30 minutes under a vacuum of -0.095 MPa.

[0019] Preferably, an additional coaxial spinning step is added to the electrospinning process, specifically:

[0020] The concentric dual-nozzle structure is adopted, in which chitosan spinning solution is injected into the inner nozzle as the core layer, and PVA aqueous solution containing 0.5% glycerol by mass is injected into the outer nozzle as the shell layer.

[0021] The voltage of the inner nozzle was set to 18kV, the voltage of the outer nozzle was set to 22kV, the spinning solution flow rates were 0.5mL / h and 1.0mL / h, and the receiving distance was 18cm.

[0022] A composite nanofiber membrane with a core-shell structure was prepared by coaxial spinning to coat the surface of the chitosan nanofiber membrane with a 10 μm thick PVA hydrophilic layer.

[0023] The inner layer of the composite nanofiber membrane is chitosan nanofiber, and the outer layer is a PVA hydrophilic layer. The two layers are tightly bonded together by hydrogen bonds.

[0024] Preferably, the post-processing steps for the PVA hydrophilic layer are as follows:

[0025] The composite nanofiber membrane obtained by coaxial spinning was immersed in a 5% glutaraldehyde aqueous solution and crosslinked at room temperature for 1 hour to form covalent bonds between PVA molecular chains, thereby improving the water resistance of the PVA hydrophilic layer.

[0026] After cross-linking, the membrane was rinsed three times with deionized water to remove unreacted glutaraldehyde, and then dried in hot air at 50°C for 1 hour to obtain the cross-linked composite nanofiber membrane.

[0027] The water absorption rate of the cross-linked composite nanofiber membrane is not less than 800%.

[0028] Preferably, an impermeable ring is added to the edge area of ​​the composite base layer, specifically as follows:

[0029] Using medical-grade silicone material, a ring-shaped protrusion with a width of 5mm and a height of 2mm is formed at the edge of the composite base layer by casting through a mold;

[0030] The curing conditions for the medical silicone material are: allow it to stand at room temperature for 24 hours to allow it to fully cure;

[0031] After curing, the outer surface of the medical silicone leak-proof ring is polished smooth to make it flush with the surface of the composite base layer.

[0032] Preferably, before coating the medical pressure-sensitive adhesive, a release paper layer is first printed on the surface of the PTFE hydrophobic membrane side of the composite base layer, specifically:

[0033] Mix the release agent and water at a mass ratio of 1:10 to prepare a release agent aqueous solution;

[0034] The release agent aqueous solution is printed on the surface of the PTFE hydrophobic film side of the composite base layer using gravure printing. The printed pattern is grid-like with a grid spacing of 5mm×5mm.

[0035] After printing, dry in an oven at 60°C for 10 minutes to cure the release agent and form the release paper peel layer;

[0036] The peeling force of the release paper peeling layer is 0.05 to 0.1 N / 25 mm.

[0037] Preferably, after obtaining the waterproof and breathable medical dressing semi-finished product, it is subjected to sterilization treatment, specifically as follows:

[0038] The ethylene oxide gas sterilization method is adopted. The waterproof and breathable medical dressing semi-finished product is placed in the sterilization cabinet and ethylene oxide gas is introduced to make the ethylene oxide concentration in the sterilization cabinet reach 600mg / L.

[0039] Sterilize for 4 hours at a temperature of 55℃ and a relative humidity of 60%;

[0040] After sterilization, sterile air is introduced to replace the ethylene oxide gas for 12 hours until the residual ethylene oxide in the sterilizer is no more than 10 μg / g.

[0041] Remove the sterilized waterproof and breathable medical dressing semi-finished product, seal it in packaging, and obtain the finished waterproof and breathable medical dressing.

[0042] Preferably, when cutting the finished waterproof and breathable medical dressing, laser cutting is used, specifically as follows:

[0043] The waterproof and breathable medical dressing is laid flat on the platform of the laser cutting machine. The laser wavelength is set to 1064nm, the laser power is 20W, and the cutting speed is 100mm / s.

[0044] The laser head is controlled by a computer to cut according to a preset shape and size, with a cutting accuracy of ±0.1mm;

[0045] After laser cutting, compressed air is used to blow away the charred debris at the cut, resulting in a waterproof and breathable medical dressing with neat edges.

[0046] The finished waterproof and breathable medical dressing is circular in shape, with a diameter of 5cm and a thickness of 0.2mm.

[0047] Preferably, the present invention also includes a waterproof and breathable medical dressing, which is prepared by the above-described method for preparing a waterproof and breathable medical dressing.

[0048] Compared with the prior art, the beneficial effects of the present invention are:

[0049] This invention utilizes a composite design of chitosan nanofiber membrane and pretreated PTFE hydrophobic membrane, coupled with precise process control, to create a waterproof and breathable medical dressing with comprehensively optimized performance. The overall product possesses excellent waterproof barrier properties, balanced breathability, wound affinity, and stability, fully meeting the actual needs of clinical wound care. Using chitosan as the core fiber material, a spinning solution is prepared through precise control of dissolution, stirring, and filtration processes. This solution is then combined with a standardized electrospinning process to produce the nanofiber membrane. Chitosan itself has good biocompatibility and gentle wound affinity, and will not irritate the wound or surrounding healthy skin. The nanoscale fiber structure forms a dense porous network, which allows for smooth airflow, ensuring the breathability of the wound site and preventing skin maceration. It also efficiently absorbs wound exudate, maintaining a moist but non-waterlogged healing environment, promoting stable growth of new tissue, reducing wound adhesion, and making dressing changes gentler and reducing patient pain. The PTFE hydrophobic membrane undergoes a series of pretreatment steps, including ultrasonic cleaning with a proprietary alkaline solution and surfactants, hydrochloric acid activation, and hot air drying. This process thoroughly removes surface oil and impurities, effectively activating surface functional groups. When subsequently hot-pressed with a chitosan nanofiber membrane, it achieves a tight bond through intermolecular forces, significantly enhancing interlayer adhesion. This prevents delamination, peeling, and detachment during use, ensuring the integrity and stability of the overall dressing structure. Furthermore, the pretreated PTFE hydrophobic membrane possesses stable hydrophobic barrier properties, effectively preventing external moisture, liquid contaminants, and bacteria from invading the wound, blocking external infection pathways and providing long-lasting protection. The pore structure of the hydrophobic membrane complements that of the chitosan nanofiber membrane, achieving a balance between breathability and waterproofing. This prevents both excessive waterproofing leading to stuffiness and loss of barrier properties due to breathability.

[0050] Medical pressure-sensitive adhesive is prepared using a specific compound and a free radical polymerization reaction under nitrogen protection, combined with vacuum degassing treatment. The resulting adhesive is uniform and bubble-free, forming a uniformly thick layer after application. It adheres tightly and firmly to the skin, preventing edge lifting, displacement, or detachment. It adapts to the stretching and deformation of the skin during daily activities. Simultaneously, the adhesive layer has moderate peeling force, resulting in a smooth peeling process that avoids tearing damage to the skin and leaves no adhesive residue, preventing skin irritation and discomfort. The core-shell structured composite nanofiber membrane, prepared using a coaxial spinning process, further optimizes the wound affinity and absorbency of the dressing through the combination of a core layer of chitosan and a shell layer of PVA hydrophilic layer. The PVA hydrophilic layer undergoes cross-linking treatment, resulting in tighter molecular chain bonding and improved water resistance, preventing rapid dissolution and collapse upon contact with exudate. This also enhances the overall structural strength of the fiber membrane, extending the effective service life of the dressing. The medical-grade silicone anti-leakage rings at the edges of the composite base layer are molded to a uniform size. After curing, they are soft and adhere tightly to the skin, effectively preventing exudate from leaking from the dressing edges and avoiding staining clothing and surrounding skin. The silicone material is gentle and non-irritating, causing no discomfort due to skin pressure. The release paper layer is prepared using a grid-like gravure printing process, ensuring uniform distribution of the release agent and stable, controllable peel force. This allows for quick and easy removal of the release paper before dressing use without damaging the adhesive layer or the main structure of the dressing, improving convenience for clinical use. The overall manufacturing process parameters are precise and controllable. From spinning, compounding, and coating to post-treatment, sterilization, and slitting, the process conditions for each step are standardized and uniform, requiring no complex or special equipment, which facilitates large-scale production. The finished product is sterilized with ethylene oxide, which ensures thorough sterilization and meets the standards for residual sterilization, without affecting the original performance of the dressing. Laser cutting technology ensures that the finished product is dimensionally accurate, with neat edges and a regular appearance, meeting the needs of standardized clinical use. The overall dressing combines multiple advantages such as waterproofing, breathability, biocompatibility, durability, impermeability, and ease of use, comprehensively improving the performance shortcomings of existing medical dressings and enhancing wound care effects and patient experience. Attached Figure Description

[0051] Figure 1 This diagram illustrates the steps of preparing a waterproof and breathable medical dressing according to the present invention. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. After reading the present invention, those skilled in the art will find that various equivalent modifications to the present invention fall within the scope defined by the appended claims. The raw materials and reagents used in the following embodiments are all commercially available medical-grade raw materials, and the equipment used is all conventional equipment in the pharmaceutical field. Unless otherwise specified, the operating methods are all conventional operations in the art.

[0053] Example 1

[0054] See appendix Figure 1 This embodiment provides a method for preparing a waterproof and breathable medical dressing, the specific steps of which are as follows:

[0055] Step 1: Pretreatment of PTFE hydrophobic membrane

[0056] Medical-grade expanded PTFE hydrophobic membrane was selected as the substrate, cut to a suitable size, and then immersed in a mixed cleaning solution consisting of 5% NaOH solution and 0.5% sodium dodecyl sulfate (SDS). An ultrasonic cleaning device was used, with an ultrasonic power of 80W and a temperature of 60℃ for 30 minutes to thoroughly remove oil, dust, and processing residues from the membrane surface. After cleaning, the PTFE hydrophobic membrane was repeatedly rinsed with ultrapure water until the pH of the rinsing solution was neutral and no alkaline residue remained. The membrane was then transferred to a 10% hydrochloric acid solution and soaked at room temperature for 1 hour to activate the functional groups on the membrane surface, enhancing its adhesion to the chitosan fiber membrane. After activation, it was rinsed again with ultrapure water until neutral and placed in a hot air circulating oven at 60℃ for 2 hours to obtain a pretreated PTFE hydrophobic membrane. Testing showed that the water contact angle of the membrane surface was 115°, meeting the requirements for subsequent lamination.

[0057] Step 2: Preparation of chitosan spinning solution

[0058] Weigh out medical-grade chitosan powder and slowly add it to a 1% (w / w) aqueous acetic acid solution while stirring at a low speed to prevent powder agglomeration. Then place the mixture in a constant temperature water bath with a stirring device, set the water bath temperature to 50℃ and the stirring speed to 200 rpm, and continue stirring for 2 hours until the chitosan powder is completely dissolved and there are no visible particles, thus preparing a 2% (w / w) chitosan solution. Filter the obtained chitosan solution through a 0.45μm microporous membrane under reduced pressure, controlling the filtration pressure at 0.3MPa, to remove residual insoluble impurities and agglomerates, obtaining a clear, transparent, bubble-free chitosan spinning solution. Seal and let stand for 30 minutes to remove trace bubbles, then set aside for later use.

[0059] Step 3: Preparation of chitosan nanofiber membrane by electrospinning

[0060] The chitosan spinning solution, after being allowed to stand and degas, is injected into the sealed storage tank of the electrospinning equipment. The spinneret is connected to a high-voltage power supply, and the vertical distance between the spinneret and the receiving roller is adjusted to 15 cm. The output voltage of the high-voltage power supply is set to 20 kV, the speed of the receiving roller is set to 100 rpm, the spinning environment temperature is controlled at 25℃, and the relative humidity is controlled at 35%. The spinning equipment is turned on, and the flow rate of the spinning solution is controlled at 0.8 mL / h. Spinning continues until the fiber membrane thickness reaches 100 μm. The equipment is then turned off, resulting in a uniform and dense chitosan nanofiber membrane with a uniform diameter distribution and no broken fibers or agglomeration.

[0061] Step 4: Hot-pressing composite substrate

[0062] The prepared chitosan nanofiber membrane is laid flat on the rough surface of the pretreated PTFE hydrophobic membrane, ensuring that the two are completely bonded together without wrinkles, bubbles, or edge misalignment. The composite membrane is then placed into a hot press mold, and the hot pressing temperature is set to 80℃, the hot pressing pressure to 0.5MPa, and the hot pressing time to 10 minutes. Through the hot pressing action, the chitosan nanofiber membrane and the PTFE hydrophobic membrane are tightly bonded together by intermolecular forces and hydrogen bonds to form an integrated composite base layer. After hot pressing, the membrane is allowed to cool naturally to room temperature to avoid rapid cooling that could cause the membrane to warp.

[0063] Step 5: Preparation and Coating of Medical Pressure-Sensitive Adhesive

[0064] Weigh out 70 parts by weight of butyl acrylate, 20 parts by weight of methyl methacrylate, 5 parts by weight of hydroxyethyl acrylate, 3 parts by weight of rosin resin, and 2 parts by weight of benzoyl peroxide. Add the above components sequentially to a sealed reaction vessel, purge the vessel with high-purity nitrogen to remove air and create an oxygen-free reaction environment. Turn on the stirring and heating device, set the rotation speed to 300 rpm, raise the temperature to 75°C, and stir at a constant temperature for 4 hours to complete the free radical polymerization reaction and obtain a medical pressure-sensitive adhesive. Transfer the obtained medical pressure-sensitive adhesive to a vacuum degassing machine, set the vacuum degree to -0.095 MPa, and degas for 30 minutes to remove air bubbles from the adhesive and ensure uniform coating. Apply the degassed medical pressure-sensitive adhesive evenly to one side of the PTFE hydrophobic membrane of the composite base layer, controlling the coating thickness to 50 μm. After coating, place it in a 40°C hot air oven and dry for 30 minutes to allow the pressure-sensitive adhesive to fully cure, obtaining a waterproof and breathable medical dressing semi-finished product.

[0065] Step 6: Sterilization and Finished Product Preparation

[0066] The semi-finished dressing was placed in an ethylene oxide sterilizer. After closing the door, an airtightness test was performed. If the test was successful, ethylene oxide gas was introduced, and the concentration of ethylene oxide in the sterilizer was controlled to reach 600 mg / L. The sterilization temperature was set at 55℃ and the relative humidity at 60%, and sterilization was carried out at a constant temperature and humidity for 4 hours. After sterilization, the ethylene oxide supply was stopped, and sterile clean air was introduced for gas replacement for 12 hours until the residual ethylene oxide in the cabinet was no more than 10 μg / g. The sterilized dressing was then removed and sealed in a sterile medical composite film. It was then cut into circular finished products with a diameter of 5 cm using a laser cutting device. The laser wavelength was set to 1064 nm, the power to 20 W, the cutting speed to 100 mm / s, and the cutting accuracy to ±0.1 mm. After cutting, compressed air was used to blow away the charred debris from the cut, resulting in a basic waterproof and breathable medical dressing.

[0067] Example 2

[0068] This embodiment, based on Embodiment 1, adds a coaxial spinning core-shell structure optimization step to improve the hydrophilicity and liquid absorption performance of the dressing. All other process parameters not mentioned remain the same as in Embodiment 1. The specific steps are as follows:

[0069] Step 1: Pretreatment of PTFE hydrophobic membrane

[0070] Same as step 1 in Example 1, the water contact angle of the pretreated PTFE hydrophobic membrane is 116°.

[0071] Step 2: Preparation of chitosan core spinning solution and PVA shell spinning solution

[0072] The preparation of the chitosan spinning solution is the same as step 2 in Example 1; in addition, a PVA hydrophilic layer spinning solution is prepared by weighing medical-grade polyvinyl alcohol (PVA) powder, adding it to ultrapure water, stirring at 90°C until completely dissolved, and preparing a 10% PVA aqueous solution. Then, 0.5% glycerol is added as a plasticizer, stirred evenly, filtered and degassed to obtain the PVA shell spinning solution for later use.

[0073] Step 3: Preparation of core-shell structured composite nanofiber membranes by coaxial electrospinning

[0074] A concentric dual-nozzle coaxial electrospinning device was used. Chitosan spinning solution was injected into the inner nozzle as the core layer, and PVA hydrophilic layer spinning solution was injected into the outer nozzle as the shell layer. The voltage of the inner nozzle was adjusted to 18kV, the voltage of the outer nozzle to 22kV, the flow rate of the core layer spinning solution to 0.5mL / h, the flow rate of the shell layer spinning solution to 1.0mL / h, the receiving distance to 18cm, the ambient temperature to 25℃, the relative humidity to 35%, and the receiving roller speed to 100rpm. Spinning was continued until the total thickness of the fiber membrane reached 110μm, of which the thickness of the chitosan core layer fiber membrane was 100μm and the thickness of the PVA hydrophilic layer was 10μm, thus obtaining a core-shell structured composite nanofiber membrane.

[0075] Step 4: Post-treatment of PVA hydrophilic layer crosslinking

[0076] The composite nanofiber membrane obtained by coaxial spinning was immersed in a 5% (w / w) glutaraldehyde aqueous solution and allowed to stand at room temperature for 1 hour for cross-linking reaction, so that stable covalent bonds were formed between PVA molecular chains, which greatly improved the water resistance of the PVA hydrophilic layer and prevented rapid dissolution upon contact with water. After cross-linking, the fiber membrane was rinsed three times with ultrapure water for 5 minutes each time to completely remove unreacted glutaraldehyde residue. Then it was placed in a 50℃ hot air oven for 1 hour to dry, and the cross-linked core-shell structure composite nanofiber membrane was obtained. The water absorption rate was tested to reach 820%.

[0077] Step 5: Hot pressing of composite base layer, coating of pressure-sensitive adhesive, sterilization and slitting

[0078] The steps of hot-pressing the cross-linked composite nanofiber membrane with a PTFE hydrophobic membrane, coating with pressure-sensitive adhesive, sterilizing with ethylene oxide, and laser cutting were all the same as in Example 1, and finally a highly absorbent, waterproof and breathable medical dressing was obtained.

[0079] Example 3

[0080] This embodiment, based on embodiment 2, adds an edge leak-proof ring structure to improve the sealing of the dressing edges and prevent side leakage of exudate. Other process parameters not mentioned remain consistent with embodiment 2. The specific steps are as follows:

[0081] Steps 1-4: Same as steps 1-4 in Example 2, to obtain the composite base layer semi-finished product.

[0082] Step 5: Preparation of the edge seepage barrier

[0083] Medical-grade liquid silicone raw materials are selected, and a custom-made ring mold is used. The mold has an inner diameter of 5cm, a ring width of 5mm, and a height of 2mm. The composite base layer is laid flat at the bottom of the mold, ensuring that it is centered. Liquid silicone is evenly poured into the ring area at the edge of the composite base layer. It is left to cure at room temperature for 24 hours to allow the silicone to fully form, creating an integrated ring-shaped anti-seepage protrusion. After curing, the outer surface of the silicone anti-seepage ring is gently sanded with fine sandpaper to make it smooth and flush with the surface of the composite base layer, without burrs or protrusions, to avoid scratching the skin during wear and improve the fit and comfort.

[0084] Step 6: Pressure-sensitive adhesive coating, sterilization, and cutting

[0085] The pressure-sensitive adhesive coating, vacuum degassing, ethylene oxide sterilization, and laser cutting steps are all the same as in Example 2, to obtain a highly absorbent, waterproof, and breathable medical dressing with an impermeable ring.

[0086] Example 4

[0087] This embodiment, based on Embodiment 3, adds a release paper peeling layer printing step to optimize the dressing's peeling performance and avoid damage to the wound during removal. All other process parameters not mentioned remain consistent with Embodiment 3. The specific steps are as follows:

[0088] Steps 1-5: Same as steps 1-5 in Example 3, to obtain a composite base layer with an impermeable ring.

[0089] Step 6: Printing the release liner

[0090] Medical-grade silicone release agent and ultrapure water were mixed at a mass ratio of 1:10 and stirred at high speed for 15 minutes to prepare a uniform and stable release agent aqueous solution. Using gravure printing equipment, the release agent aqueous solution was printed on one side of the PTFE hydrophobic film of the composite base layer. The printed pattern was a 5mm×5mm grid to ensure uniform release effect. After printing, it was placed in a 60℃ hot air oven and dried for 10 minutes to allow the release agent to fully cure and form a stable release paper peel layer. The peel force of the peel layer was tested to be 0.08N / 25mm, which meets the peel requirements of medical dressings.

[0091] Step 7: Pressure-sensitive adhesive coating, sterilization, and cutting

[0092] The pressure-sensitive adhesive coating, vacuum degassing, ethylene oxide sterilization, and laser cutting steps are all the same as in Example 3, to obtain a full-function waterproof and breathable medical dressing.

[0093] Comparative Example 1

[0094] In this comparative example, ordinary medical nonwoven fabric was used instead of chitosan nanofiber membrane. All other processes, raw materials, and parameters were kept the same as in Example 1. The specific steps are as follows:

[0095] The chitosan spinning solution preparation and electrospinning steps were omitted. Commercially available medical nonwoven fabric with a thickness of 100 μm was directly used. It was then hot-pressed with a pretreated PTFE hydrophobic membrane according to step 4 of Example 1. The subsequent pressure-sensitive adhesive coating, sterilization, and slitting steps were the same as in Example 1 to obtain a common nonwoven fabric-PTFE composite medical dressing.

[0096] Comparative Example 2

[0097] This comparative example omits the PTFE hydrophobic membrane pretreatment step and directly uses an unwashed, unactivated raw PTFE hydrophobic membrane to composite with a chitosan nanofiber membrane. All other processes and parameters remain consistent with Example 1. The specific steps are as follows:

[0098] The PTFE cleaning, activation, and drying pretreatment in step 1 of Example 1 were omitted. Instead, the original hydrophobic PTFE membrane was directly hot-pressed and composited with a chitosan nanofiber membrane. The subsequent spinning, pressure-sensitive adhesive coating, sterilization, and slitting steps were the same as in Example 1, resulting in an untreated PTFE composite medical dressing.

[0099] Performance testing methods

[0100] The core performance of the medical dressings prepared in Examples 1-4 and Comparative Examples 1-2 was tested. The test items and methods are as follows:

[0101] Water vapor transmission rate (WVTR): According to YY / T 0471.2-2004 "Contact wound dressings Part 2: Water vapor transmission rate" standard, the test is performed using the permeation cup method, with the unit being g / (m²·24h). The higher the value, the better the air permeability.

[0102] Static water absorption rate: The weighing method is used. The dressing to be tested is dried to constant weight and the dry weight W1 is recorded. It is then immersed in ultrapure water for 30 minutes. After being taken out, the surface free water is drained and the wet weight W2 is recorded. Water absorption rate = (W2-W1) / W1×100%. The higher the value, the stronger the liquid absorption capacity.

[0103] Water contact angle: The water contact angle of the dressing wound surface is measured using a contact angle meter, in degrees. The smaller the contact angle, the better the hydrophilicity.

[0104] Waterproof performance: The hydrostatic pressure test method is used to test the hydrostatic pressure resistance of the PTFE membrane side of the dressing, in kPa. The higher the value, the better the waterproof performance.

[0105] Membrane bonding strength: The peel strength between the chitosan fiber layer and the PTFE membrane layer was tested using a peel strength tester. The unit is N / cm. The higher the value, the tighter the bonding and the less likely it is to delaminate.

[0106] Ethylene oxide residue: Detected by gas chromatography according to GB / T 14233.1-2008 standard, unit μg / g, limit ≤10μg / g.

[0107] Table 1: Core Physical Performance Test Data of Examples 1-4 and Comparative Examples 1-2

[0108] Test sample Water vapor transmission rate (g / (m²·24h)) Static water absorption rate (%) Water contact angle on the wound side (°) Hydrostatic pressure resistance (kPa) Film peel strength (N / cm) Ethylene oxide residue (μg / g) Example 1 860 650 42 3.2 1.8 7.2 Example 2 910 820 28 3.1 1.7 6.8 Example 3 890 810 29 3.0 1.7 6.9 Example 4 880 805 30 3.0 1.6 6.5 Comparative Example 1 520 310 68 2.1 1.2 7.5 Comparative Example 2 840 630 43 2.8 0.6 7.3

[0109] As can be seen from the data in Table 1, the waterproof and breathable medical dressings prepared in Examples 1-4 of this invention exhibit significantly better core performance than Comparative Examples 1 and 2, and meet the requirements of the medical dressing industry standard. Regarding water vapor transmission rate, the values ​​in Examples 1-4 are all maintained in the range of 860-910 g / (m²·24h), far exceeding the 520 g / (m²·24h of Comparative Example 1. This is because the chitosan nanofiber membrane has a three-dimensional porous network structure with uniform pores and good connectivity, enabling efficient water vapor transmission and preventing water vapor accumulation on the wound surface that could lead to skin maceration. In contrast, ordinary nonwoven fabrics have coarse fibers and uneven pores, resulting in a significant decrease in breathability. Example 2, due to its coaxial core-shell structure and the further optimization of the pore structure by the PVA hydrophilic layer, achieved a peak water vapor transmission rate of 910 g / (m²·24h). Examples 3 and 4, due to the addition of an impermeable ring and release layer, had a slight impact on breathability, but still maintained excellent levels.

[0110] The static absorbency rate directly reflects the dressing's ability to absorb wound exudate. Examples 2-4 all had absorbency rates exceeding 800%, and Example 1 had an absorbency rate of 650%, both significantly higher than Comparative Example 1's 310%. Chitosan itself possesses excellent hydrophilicity and absorbency. The nanofiber structure has a large specific surface area and numerous absorption sites. The PVA hydrophilic layer introduced by coaxial spinning further enhances the absorbency ratio, enabling rapid absorption of wound exudate and maintaining a moist healing environment. Comparative Example 1, using ordinary non-woven fabric, has poor absorbency and cannot meet the needs of wound care with medium to high exudate levels. Regarding the wound-side water contact angle, Examples 2-4 had a contact angle below 30°, exhibiting excellent hydrophilicity and quickly moistening the wound, preventing the dressing from adhering to the wound. Example 1 had a contact angle of 42°, showing good hydrophilicity. Comparative Example 1 had a contact angle of 68°, indicating poor hydrophilicity, making it prone to adhering to the scab and causing secondary damage during removal.

[0111] Regarding waterproof performance, all examples exhibited a hydrostatic pressure resistance of ≥3.0 kPa, demonstrating excellent waterproofing and effectively preventing external moisture, bacteria, and contaminants from penetrating the wound. Comparative Example 1, due to its loose nonwoven fabric structure, had a waterproof performance of only 2.1 kPa, failing to meet waterproofing requirements. In terms of film peel strength, Examples 1-4 showed peel strengths of 1.6-1.8 N / cm, indicating tight film bonding and no delamination even after long-term use. Comparative Example 2, lacking the PTFE pretreatment step, had no activated functional groups on the film surface, resulting in extremely weak bonding with the chitosan fiber membrane, with a peel strength of only 0.6 N / cm. This made it highly susceptible to delamination and detachment, negating the functional advantages of the composite dressing. All samples had ethylene oxide residue levels ≤7.5 μg / g, far below the 10 μg / g limit, meeting the safety standards for medical sterile dressings.

[0112] Table 2: Test Data of Additional Performance of the Full-Function Dressing in Example 4

[0113] Testing items Detection values Medical standards requirements Test result determination Release layer peel force (N / 25mm) 0.08 0.05-0.1 qualified Leak-proof ring sealing performance No side leakage No exudate side leakage qualified Laser cutting edge flatness No burrs, no scorch marks Neat edges, no damage qualified Skin irritation Non-irritating No skin redness or allergies qualified Pressure-sensitive adhesive holding power (h) ≥24 ≥12 qualified

[0114] Table 2 shows the additional performance of the all-functional waterproof and breathable medical dressing in Example 4, with specific testing results indicating that all items meet medical standards and possess excellent clinical suitability. The release layer peel force is 0.08 N / 25 mm, which is within the optimal range of 0.05-0.1 N / 25 mm. This ensures that the release paper can be easily removed without shifting the dressing, while also preventing premature detachment due to insufficient peel force, thus improving the storage and ease of use of the dressing. The leak-proof ring is made of medical-grade silicone, which has a high degree of skin adhesion. Simulated exudate testing showed no side leakage, effectively locking in wound exudate and preventing contamination of clothing or surrounding skin. It is especially suitable for wound care in active areas such as joints.

[0115] Laser-cut edges are burr-free and scorch-free, with a neat cut and dimensional accuracy of ±0.1mm, avoiding rough edges that could scratch the skin and improving wearing comfort. Skin irritation tests show no irritation, and all raw materials used are medical-grade. Chitosan, PTFE, medical-grade silicone, and pressure-sensitive adhesive are all non-allergenic and non-toxic, and will not cause adverse reactions such as redness, swelling, itching, or allergies after being applied to the skin, demonstrating excellent biocompatibility. The pressure-sensitive adhesive has a holding power of ≥24 hours, far exceeding the medical standard requirement of ≥12 hours, ensuring a long-term, stable fit to the skin without easily falling off or lifting. It is suitable for long-term wound care scenarios, eliminating the need for frequent dressing changes and reducing nursing costs and patient discomfort.

[0116] Table 3: Comparison of the Influence of Different Process Parameters on the Core Performance of Dressings

[0117] Process variables Water vapor transmission rate (g / (m²·24h)) Film peel strength (N / cm) Water absorption rate (%) PTFE without pretreatment (Comparative Example 2) 840 0.6 630 PTFE alkaline washing unactivated 850 1.1 640 Complete PTFE pretreatment (Example 1) 860 1.8 650 Conventional uniaxial spinning (Example 1) 860 1.8 650 Coaxial spinning without crosslinking 890 1.7 750 Coaxial spinning crosslinking (Example 2) 910 1.7 820

[0118] Table 3 analyzes the impact of PTFE pretreatment and electrospinning processes on the core performance of the dressing, clarifying the necessity and technical advantages of the optimized process of this invention. Regarding the PTFE pretreatment process, the sample without any pretreatment had a peel strength of only 0.6 N / cm, indicating extremely poor adhesion. The sample that only underwent alkali washing without acid activation showed a peel strength increase to 1.1 N / cm, but still did not meet medical requirements. After a complete pretreatment process involving alkali washing, water washing, acid activation, water washing, and drying, the peel strength reached 1.8 N / cm, an increase of 200%. This is because alkali washing removes surface impurities, and acid activation introduces polar functional groups such as hydroxyl and carboxyl groups, significantly enhancing the intermolecular forces and hydrogen bonding with the chitosan fiber membrane. Simultaneously, the pretreatment does not negatively affect water vapor permeability and water absorption, ensuring the core air permeability and liquid absorption performance of the dressing.

[0119] In terms of electrospinning technology, chitosan fiber membranes prepared by ordinary uniaxial spinning have a water absorption rate of 650% and a water vapor transmission rate of 860 g / (m²·24h). Samples prepared by coaxial spinning without glutaraldehyde crosslinking have a water absorption rate of 750%, but the PVA layer has poor water resistance and is easily dissolved in water, making it unsuitable for long-term use. Samples prepared by coaxial spinning and after crosslinking treatment have a water absorption rate of 820% and a water vapor transmission rate of 910 g / (m²·24h). The PVA layer has significantly improved water resistance, does not dissolve or fall off, and has a stable core-shell structure. This process retains the antibacterial and biocompatibility advantages of chitosan and improves liquid absorption and air permeability through the PVA hydrophilic layer, fully demonstrating the synergistic effect of coaxial spinning and crosslinking treatment.

[0120] This invention, through optimized processes including PTFE pretreatment, chitosan nanofiber spinning, core-shell structure modification, edge impermeability, and release layer printing, produces a waterproof and breathable medical dressing that combines excellent waterproofness, breathability, absorbency, and biocompatibility. The film layers are tightly bonded, ensuring safe and comfortable use. It effectively solves the technical problems of traditional medical dressings, such as the inability to simultaneously achieve waterproofness and breathability, poor absorbency, easy adhesion to wound surfaces, and easy delamination. It is suitable for various acute and chronic wounds, burns, abrasions, and other clinical nursing scenarios, possessing high medical value and promising market application prospects.

[0121] It should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the technical principles of the present invention, those skilled in the art can make appropriate adjustments to the process parameters, such as the pressure and temperature of supercritical carbon dioxide, microwave power control parameters, magnetic field strength and frequency, and ultraviolet irradiation dose, etc., and these adjustments should all be considered to fall within the scope of protection of the present invention.

[0122] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a waterproof and breathable medical dressing, characterized in that, Includes the following steps: Chitosan powder was dissolved in a 1% (w / w) aqueous acetic acid solution and stirred at 200 rpm for 2 hours at 50°C to prepare a 2% (w / w) chitosan solution. The obtained chitosan solution was filtered through a 0.45 μm microporous membrane to remove insoluble matter, resulting in a clear chitosan spinning solution. Chitosan spinning solution was injected into the storage tank of an electrospinning device. The distance between the spinneret and the receiving roller was set to 15cm. A high voltage of 20kV was applied, and the speed of the receiving roller was 100rpm. Spinning was carried out under the condition of 35% ambient humidity to obtain a chitosan nanofiber membrane with a thickness of 100μm. The obtained chitosan nanofiber membrane was laid flat on the rough surface of the PTFE hydrophobic membrane, so that the chitosan nanofiber membrane and the PTFE hydrophobic membrane were completely bonded together. The membrane was then hot-pressed for 10 minutes at 80°C and 0.5MPa using a hot press, so that the two were bonded together by intermolecular forces to obtain a composite base layer. Medical pressure-sensitive adhesive was uniformly coated on the surface of the PTFE hydrophobic membrane side of the composite base layer with a coating thickness of 50 μm, and dried in an oven at 40°C for 30 minutes to obtain a semi-finished waterproof and breathable medical dressing.

2. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, The pretreatment steps for the PTFE hydrophobic membrane are as follows: The PTFE hydrophobic membrane was immersed in a mixed solution containing 5% NaOH solution and 0.5% sodium dodecyl sulfate and ultrasonically cleaned at 60°C for 30 minutes to remove surface oil and impurities. After cleaning, rinse with deionized water until neutral, and then immerse the PTFE hydrophobic membrane in a 10% hydrochloric acid solution for 1 hour to activate the functional groups on the membrane surface. After activation, rinse again with deionized water until neutral, and dry in hot air at 60°C for 2 hours to obtain the pretreated PTFE hydrophobic membrane. The contact angle of the pretreated PTFE hydrophobic membrane is not less than 110°.

3. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, The medical pressure-sensitive adhesive is composed of the following components: 70 parts butyl acrylate, 20 parts methyl methacrylate, 5 parts hydroxyethyl acrylate, 3 parts rosin resin, and 2 parts benzoyl peroxide. The above components were added to a reaction vessel, heated to 75°C under nitrogen protection, and stirred at 300 rpm for 4 hours to carry out a free radical polymerization reaction, thereby obtaining the medical pressure-sensitive adhesive. Before coating, the medical pressure-sensitive adhesive is placed in a vacuum degassing machine and degassed for 30 minutes under a vacuum of -0.095 MPa.

4. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, In the electrospinning process, an additional coaxial spinning step is added, specifically as follows: The concentric dual-nozzle structure is adopted, in which chitosan spinning solution is injected into the inner nozzle as the core layer, and PVA aqueous solution containing 0.5% glycerol by mass is injected into the outer nozzle as the shell layer. The voltage of the inner nozzle was set to 18kV, the voltage of the outer nozzle was set to 22kV, the spinning solution flow rates were 0.5mL / h and 1.0mL / h, and the receiving distance was 18cm. A composite nanofiber membrane with a core-shell structure was prepared by coaxial spinning to coat the surface of the chitosan nanofiber membrane with a 10 μm thick PVA hydrophilic layer. The inner layer of the composite nanofiber membrane is chitosan nanofiber, and the outer layer is a PVA hydrophilic layer. The two layers are tightly bonded together by hydrogen bonds.

5. The method for preparing a waterproof and breathable medical dressing according to claim 4, characterized in that, The post-processing steps for the PVA hydrophilic layer are as follows: The composite nanofiber membrane obtained by coaxial spinning was immersed in a 5% glutaraldehyde aqueous solution and crosslinked at room temperature for 1 hour to form covalent bonds between PVA molecular chains, thereby improving the water resistance of the PVA hydrophilic layer. After cross-linking, the membrane is rinsed three times with deionized water to remove unreacted glutaraldehyde, and then dried in hot air at 50°C for 1 hour to obtain the cross-linked composite nanofiber membrane.

6. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, An additional seepage-proof ring is added to the edge area of ​​the composite base layer, specifically as follows: Using medical-grade silicone material, a ring-shaped protrusion with a width of 5mm and a height of 2mm is formed at the edge of the composite base layer by casting through a mold; The curing conditions for the medical silicone material are: allow it to stand at room temperature for 24 hours to allow it to fully cure; After curing, the outer surface of the medical silicone leak-proof ring is polished smooth to make it flush with the surface of the composite base layer.

7. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, Before applying the medical pressure-sensitive adhesive, a release paper layer is first printed on the surface of the PTFE hydrophobic membrane side of the composite base layer, specifically: Mix the release agent and water at a mass ratio of 1:10 to prepare a release agent aqueous solution; The release agent aqueous solution is printed on the surface of the PTFE hydrophobic film side of the composite base layer using gravure printing. The printed pattern is grid-like with a grid spacing of 5mm×5mm. After printing, dry in an oven at 60°C for 10 minutes to cure the release agent and form the release paper peel layer; The peeling force of the release paper peeling layer is 0.05 to 0.1 N / 25 mm.

8. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, After obtaining the semi-finished waterproof and breathable medical dressing, it undergoes sterilization treatment, specifically as follows: The ethylene oxide gas sterilization method is adopted. The waterproof and breathable medical dressing semi-finished product is placed in the sterilization cabinet and ethylene oxide gas is introduced to make the ethylene oxide concentration in the sterilization cabinet reach 600mg / L. Sterilize for 4 hours at a temperature of 55℃ and a relative humidity of 60%; After sterilization, sterile air is introduced to replace the ethylene oxide gas for 12 hours until the residual ethylene oxide in the sterilizer is no more than 10 μg / g. Remove the sterilized waterproof and breathable medical dressing semi-finished product, seal it in packaging, and obtain the finished waterproof and breathable medical dressing.

9. The method for preparing a waterproof and breathable medical dressing according to claim 1, characterized in that, When cutting the finished waterproof and breathable medical dressing, laser cutting is used, specifically as follows: The waterproof and breathable medical dressing is laid flat on the platform of the laser cutting machine. The laser wavelength is set to 1064nm, the laser power is 20W, and the cutting speed is 100mm / s. The laser head is controlled by a computer to cut according to a preset shape and size, with a cutting accuracy of ±0.1mm; After laser cutting, compressed air is used to blow away the charred debris at the cut, resulting in a waterproof and breathable medical dressing with neat edges. The finished waterproof and breathable medical dressing is circular in shape, with a diameter of 5cm and a thickness of 0.2mm.

10. A waterproof and breathable medical dressing, characterized in that, It is prepared using the method described in any one of claims 1 to 9 for a waterproof and breathable medical dressing.

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