A method for preparing a low-allergenic medical protective pad material

Abstract

This invention discloses a method for preparing a low-allergenic medical protective liner material, belonging to the field of biomedical materials technology, and solves the problem of allergenicity in materials with high barrier properties and high moisture permeability. The key technical points are: using high molecular weight polyethylene as a substrate, a gradient-pore-size microporous base membrane is constructed through biaxial stretching and supercritical carbon dioxide extraction; the base membrane is surface-treated using argon plasma activation technology to generate active free radical sites; subsequently, hydrophilic monomers and antibacterial monomers are covalently grafted onto the membrane surface and pore walls sequentially through water bath polymerization to form a stable hydrophilic antibacterial layer; the modified base membrane is then laminated with medical nonwoven fabric via adhesive-free hot pressing, and finally sterilized by electron beam irradiation. The process avoids the risks of allergens such as residual organic solvents, shedding of physically coated components, sensitization by chemical adhesives, and ethylene oxide sterilization residues. This invention is applicable to medical protective liners used in wound care, postoperative protection, and other scenarios requiring prolonged skin contact.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, and in particular to a method for preparing a low-allergenic medical protective liner material. Background Technology

[0002] Medical protective liner materials are key medical consumables in wound care, postoperative protection, and skin trauma repair. They must simultaneously meet two core performance requirements: high barrier properties and high breathability, to adapt to the physiological repair needs of human wounds. Currently, most protective liners on the market with high barrier and high breathability properties are made of polymer base materials such as polyurethane. Although they can achieve a basic balance between protection and breathability, long-term clinical application has revealed that these materials commonly cause adverse reactions such as skin sensitization, irritation, redness, swelling, and itching. The risk of sensitization is particularly prominent in infants, people with sensitive skin, and in long-term wound care scenarios, seriously affecting the safety of use and patient comfort.

[0003] The sensitizing properties of existing high-barrier, high-permeability padding materials mainly stem from inherent defects in the manufacturing process and material composition. To improve permeability, traditional processes often employ wet phase inversion film formation, which requires the introduction of organic solvents such as N,N-dimethylformamide. Solvent residues can continuously irritate the skin. To achieve hydrophilic and antibacterial modifications, surfactants and nano-silver particles are commonly used for physical coating. However, these coating components are prone to detachment and are themselves allergens. Material bonding relies on acrylate chemical adhesives, and adhesive curing residues and degradation products are the main allergens. Final sterilization commonly uses ethylene oxide, which easily leaves ethylene oxide derivatives that are both cytotoxic and sensitizing. The combination of multiple sensitizing factors makes it difficult for existing materials to balance performance and safety.

[0004] Existing technologies reduce the risk of sensitization by optimizing formulations and adjusting process parameters, but these only alleviate the degree of sensitization and cannot solve the problem at its root. A comprehensive protective liner material that simultaneously possesses high barrier properties, high permeability, low sensitization, antibacterial properties, and sterility has yet to be developed, failing to meet the urgent clinical demand for high-safety, high-performance medical consumables. Current technologies use traditional wet phase inversion, physical coating, chemical adhesive bonding, and ethylene oxide sterilization processes to prepare high-barrier, high-permeability liner materials, which cannot fundamentally avoid the risk of sensitization. These shortcomings severely restrict the widespread application of high-barrier, high-permeability medical protective liners in high-end medical scenarios such as sensitive skin care, chronic wound repair, and long-term postoperative protection. Summary of the Invention

[0005] To address the above shortcomings, this invention provides a method for preparing a low-allergenic medical protective pad material, which can solve the problem of allergenicity in materials with high barrier properties and high moisture permeability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a hypoallergenic medical protective liner material: S1: High molecular weight polyethylene powder, pore-forming agent, and antioxidant are placed in a high-speed mixer at 25~30℃ and stirred continuously at 500~1000rpm for 15~30min. Then the mixture is placed in a twin-screw extruder and melt-blended in a gradient heating range of 200~230℃ and extruded into cast sheets. The mixture is then cooled to 25℃ to obtain nascent cast sheets. S2: The nascent film obtained in S1 is placed in a biaxial stretching machine. The biaxial stretching machine is set to stretch the nascent film at 125°C with a transverse stretching ratio of 7-9 times and a longitudinal stretching ratio of 6-7 times. Then, the stretched nascent film is placed in a supercritical fluid extraction vessel for cyclic extraction. After extraction, the pressure is released and the material is placed in a vacuum dryer at 40°C to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 is placed in a low-temperature plasma reaction chamber. The reaction chamber is then evacuated to an environment of 6~10 Pa. High-purity argon gas is then introduced into the chamber and the chamber pressure is maintained at 30~50 Pa. The power of the radio frequency power supply is then set to 80~100 W and the plasma activation treatment is set to 90~120 s. Finally, the microporous substrate membrane is cooled to room temperature of 25°C under an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add hydrophilic monomers, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2-7.5 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50-60℃ in a water bath for 90-150 min. Finally, wash the base membrane with deionized water at 100℃ for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add antibacterial monomer and ammonium persulfate to deionized water, then add an adjuster to adjust the pH of the system to 7.2~7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55~60℃ for water bath reaction for 90~120min. Finally, wash the base membrane with 100℃ deionized water for 60~120min to obtain the antibacterial modified base membrane. S6: The medical nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes, and then dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 120~135°C and a hot pressing pressure of 0.3~0.5MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation to obtain a low-allergenic medical protective liner material.

[0007] Preferably, the pore-forming agent in S1 is medical-grade paraffin oil without aromatic residues.

[0008] Preferably, the antioxidant in S1 is medical-grade antioxidant 1010, which is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0009] Preferably, the supercritical fluid in S2 is supercritical carbon dioxide, and the ambient temperature of the supercritical carbon dioxide is 45~50℃, the pressure is 12~15MPa, and the circulation extraction time is 120min.

[0010] Preferably, the hydrophilic monomer in S4 is medical-grade hydroxyethyl methacrylate with a concentration of 15~25 g / L.

[0011] Preferably, the antibacterial monomer in S5 is methacryloyloxyethyl dimethyl benzyl ammonium chloride, and its concentration is 10~20g / L.

[0012] Preferably, the regulator in S5 is sodium dihydrogen phosphate-disodium hydrogen phosphate.

[0013] Preferably, the medical-grade nonwoven fabric mentioned in S6 is a polypropylene spunbond nonwoven fabric.

[0014] Preferably, the irradiation dose in S7 is electron beam irradiation sterilization of 25~30kGy.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, ammonium sulfate used in S4 is an ion regulator, free radical stabilizer, and auxiliary adsorbent. In S4, hydrophilic monomers are covalently grafted onto the plasma-activated base film. The plasma activation has already generated stable active free radicals on the base film surface, eliminating the need for an initiator. Ammonium sulfate, as a strong electrolyte, regulates the ionic strength of the reaction solution, promoting the directional adsorption of hydrophilic monomers on the base film surface and stabilizing the active free radicals on the base film surface, thus preventing premature quenching of free radicals.

[0016] 2. In this invention, the ammonium persulfate used in S5 is a water-soluble free radical initiator. It is used to covalently graft antibacterial monomers onto the hydrophilic modified base film in S5. Since the activity of free radicals formed on the surface of the base film after hydrophilic modification in S4 is weakened, it is necessary to introduce an external initiator to generate free radicals. The ammonium persulfate is a thermally decomposable initiator. Under a water bath at 55~60℃, the persulfate ions decompose to generate sulfate free radicals. The free radicals initiate the polymerization reaction of the antibacterial monomers, so that the antibacterial monomers are covalently grafted onto the surface of the base film.

[0017] 3. This invention employs a glue-free hot-pressing composite process, which achieves composite bonding through material melting and bonding at 120~135℃ and 0.3~0.5MPa, completely avoiding the risk of sensitization introduced by chemical adhesives.

[0018] 4. This invention uses supercritical CO2 extraction to create pores on the surface of the base membrane. CO2 is non-toxic and has strong diffusion properties, which can efficiently remove pore-forming agents without solvent residue, and can accurately preserve the gradient interconnected microporous structure. This ensures stable high moisture permeability and high barrier properties, and avoids the defects of micropore collapse and uneven pore size in traditional processes.

[0019] 5. This invention uses 25~30kGy electron beam irradiation for sterilization. This sterilization process leaves no chemical residue and causes no secondary pollution. It can completely kill microorganisms and pathogens without introducing new allergens, further enhancing the low allergenicity of the material. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0021] Figure 1 This is a flowchart of a method for preparing a low-allergenic medical protective liner material according to the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0023] Example 1 This embodiment provides a method for preparing a low-allergenic medical protective liner material, the specific implementation steps of which include: Experimental materials: 100 parts by weight of high molecular weight polyethylene (UHMWPE), 360 parts by weight of medical-grade paraffin oil without aromatic residue, 0.2 parts by weight of medical-grade antioxidant 1010, supercritical CO2, 20 g / L medical-grade hydroxyethyl methacrylate, 1.0 g / L ammonium sulfate, 0.6 g / L ammonium persulfate, sodium dihydrogen phosphate-disodium hydrogen phosphate, and 15 g / L methacryloyloxyethyl dimethyl benzyl ammonium chloride.

[0024] Experimental objective: Prepare a low-allergenic medical protective pad material.

[0025] Experimental steps: S1: High molecular weight polyethylene powder, medical grade paraffin oil without aromatic residue, and medical grade antioxidant 1010 are placed in a high-speed mixer at 25°C and stirred continuously at 1000 rpm for 15 minutes. The mixture is then placed in a twin-screw extruder and melt-blended in a gradient heating range of 215°C and extruded into a cast sheet. The cast sheet is then cooled to 25°C to obtain the nascent cast sheet. S2: The nascent film obtained in S1 was placed in a biaxial stretching machine. The biaxial stretching machine was set to stretch the nascent film at 125℃ with a 9x transverse stretching ratio and a 7x longitudinal stretching ratio. Then, the stretched nascent film was placed in a supercritical CO2 extraction vessel at 45℃ and 12MPa for 120min for cyclic extraction. After extraction, the pressure was released and the material was placed in a vacuum dryer at 40℃ to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 is placed in a low-temperature plasma reaction chamber. The reaction chamber is then evacuated to a vacuum environment of 8 Pa. High-purity argon gas is then introduced into the chamber and the chamber pressure is maintained at 40 Pa. The power of the radio frequency power supply is then set to 100 W and the plasma activation treatment is set to 90 s. Finally, the microporous substrate membrane is cooled to room temperature in an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add medical-grade hydroxyethyl methacrylate, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50°C in a water bath for 120 min. Finally, wash the base membrane with deionized water at 100°C for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add methacryloyloxyethyl dimethyl benzyl ammonium chloride and ammonium persulfate to deionized water, then add sodium dihydrogen phosphate-disodium hydrogen phosphate to adjust the pH of the system to 7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55°C for 90 min in a water bath. Finally, wash the base membrane with deionized water at 100°C for 90 min to obtain the antibacterial modified base membrane. S6: The medical polypropylene spunbond nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes. Then, the nonwoven fabric is dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 130°C and a hot pressing pressure of 0.4MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation with an irradiation dose of 25~30kGy to obtain a low-allergenic medical protective liner material.

[0026] Experimental results: See Table 1 for details.

[0027] Table 1: Test Results of Example 1 refer to Figure 1 The flowchart illustrates how this embodiment separates UHMWPE flakes through high-ratio biaxial stretching, forming numerous through-hole microporous channels. Supercritical CO2 fluid is then used to extract the paraffin oil porogen. CO2's excellent diffusivity and dissolving power efficiently remove the porogen without damaging the pore structure, resulting in a clean microporous membrane with high porosity and a gradient pore size distribution. Argon plasma is used to activate the membrane surface with an inert gas, generating numerous stable free radical sites on the membrane surface and pore walls, providing high-density reaction anchors for subsequent grafting. Grafting the hydrophilic monomer hydroxyethyl methacrylate forms a covalently bonded, strongly hydrophilic layer on the inner wall of the micropores. This significantly accelerates water molecule adsorption-diffusion by lowering the water molecule transport energy barrier, giving the material high moisture permeability. Covalent grafting of the quaternary ammonium salt monomer methacryloyloxyethyl dimethyl benzyl ammonium chloride creates positively charged molecular brushes on the membrane surface. These brushes disrupt the cell membranes of contacting bacteria through electrostatic and hydrophobic interactions, achieving highly efficient contact antibacterial action. By using glue-free hot-press melt bonding and electron beam irradiation sterilization, the final sterility and integrity of the material are ensured while avoiding the introduction of sensitizing chemical adhesives.

[0028] Example 2 This embodiment provides a method for preparing a low-allergenic medical protective liner material, the specific implementation steps of which include: Experimental materials: 100 parts by weight of high molecular weight polyethylene (UHMWPE), 360 parts by weight of medical-grade paraffin oil without aromatic residue, 0.2 parts by weight of medical-grade antioxidant 1010, supercritical CO2, 20 g / L medical-grade hydroxyethyl methacrylate, 1.0 g / L ammonium sulfate, 0.6 g / L ammonium persulfate, sodium dihydrogen phosphate-disodium hydrogen phosphate, and 15 g / L methacryloyloxyethyl dimethyl benzyl ammonium chloride.

[0029] Experimental objective: To investigate the effect of low stretching ratio on the micropores of the base film.

[0030] Experimental steps: S1: High molecular weight polyethylene (UHMWPE) powder, medical-grade paraffin oil without aromatic residue, and medical-grade antioxidant 1010 are placed in a high-speed mixer at 25°C and stirred continuously at 1000 rpm for 15 minutes. The mixture is then placed in a twin-screw extruder and melt-blended in a gradient heating range of 215°C and extruded into cast sheets. The cast sheets are then cooled to 25°C to obtain nascent cast sheets. S2: The nascent film obtained in S1 was placed in a biaxial stretching machine. The biaxial stretching machine was set to stretch the nascent film at 125℃ with a transverse stretching ratio of 8 times and a longitudinal stretching ratio of 6 times. Then, the stretched nascent film was placed in a supercritical CO2 extraction vessel at 45℃ and 12MPa for 120min for cyclic extraction. After extraction, the pressure was released and the material was placed in a vacuum dryer at 40℃ to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 is placed in a low-temperature plasma reaction chamber. The reaction chamber is then evacuated to a vacuum environment of 8 Pa. High-purity argon gas is then introduced into the chamber and the chamber pressure is maintained at 40 Pa. The power of the radio frequency power supply is then set to 100 W and the plasma activation treatment is set to 90 s. Finally, the microporous substrate membrane is cooled to room temperature in an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add medical-grade hydroxyethyl methacrylate, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50°C in a water bath for 120 min. Finally, wash the base membrane with deionized water at 100°C for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add methacryloyloxyethyl dimethyl benzyl ammonium chloride and ammonium persulfate to deionized water, then add sodium dihydrogen phosphate-disodium hydrogen phosphate to adjust the pH of the system to 7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55°C for 90 min in a water bath. Finally, wash the base membrane with deionized water at 100°C for 90 min to obtain the antibacterial modified base membrane. S6: The medical polypropylene spunbond nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes. Then, the nonwoven fabric is dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 130°C and a hot pressing pressure of 0.4MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation with an irradiation dose of 25~30kGy to obtain a low-allergenic medical protective liner material.

[0031] Experimental results: See Table 2 for details.

[0032] Table 2: Test Results of Example 2 This embodiment reduces the stretching ratio compared to Example 1. The core mechanism lies in altering the geometric characteristics and formation process of the microporous structure. The lower lateral and longitudinal stretching ratios reduce the separation between UHMWPE flakes, leading to a simultaneous decrease in pore size and porosity during micropore formation, resulting in a denser and finer pore structure. This denser, interconnected microporous network significantly increases the breakthrough pressure required for liquid water penetration, thus increasing hydrostatic pressure. Simultaneously, the narrower and more tortuous pores increase the resistance to water vapor molecule diffusion, leading to a decrease in water vapor permeability. Since the surface grafting modification and sterilization process remain unchanged, the mechanisms of its interfacial hydrophilicity, antibacterial activity, and final sterilization effect are consistent with those of Example 1.

[0033] Example 3 This embodiment provides a method for preparing a low-allergenic medical protective liner material, the specific implementation steps of which include: Experimental materials: 100 parts by weight of high molecular weight polyethylene (UHMWPE), 360 parts by weight of medical-grade paraffin oil without aromatic residue, 0.2 parts by weight of medical-grade antioxidant 1010, supercritical CO2, 15 g / L medical-grade hydroxyethyl methacrylate, 1.0 g / L ammonium sulfate, 0.6 g / L ammonium persulfate, sodium dihydrogen phosphate-disodium hydrogen phosphate, and 10 g / L methacryloyloxyethyl dimethyl benzyl ammonium chloride.

[0034] Experimental objective: The effects of low concentrations of hydroxyethyl methacrylate and methacryloyloxyethyl dimethyl benzyl ammonium chloride on the final protective gasket during a short immersion in a water bath reaction were investigated.

[0035] Experimental steps: S1: High molecular weight polyethylene (UHMWPE) powder, medical-grade paraffin oil without aromatic residue, and medical-grade antioxidant 1010 are placed in a high-speed mixer at 25°C and stirred continuously at 1000 rpm for 15 minutes. The mixture is then placed in a twin-screw extruder and melt-blended in a gradient heating range of 215°C and extruded into cast sheets. The cast sheets are then cooled to 25°C to obtain nascent cast sheets. S2: The nascent film obtained in S1 was placed in a biaxial stretching machine. The biaxial stretching machine was set to stretch the nascent film at 125℃ with a 9x transverse stretching ratio and a 7x longitudinal stretching ratio. Then, the stretched nascent film was placed in a supercritical CO2 extraction vessel at 45℃ and 12MPa for 120min for cyclic extraction. After extraction, the pressure was released and the material was placed in a vacuum dryer at 40℃ to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 is placed in a low-temperature plasma reaction chamber. The reaction chamber is then evacuated to a vacuum environment of 8 Pa. High-purity argon gas is then introduced into the chamber and the chamber pressure is maintained at 40 Pa. The power of the radio frequency power supply is then set to 100 W and the plasma activation treatment is set to 90 s. Finally, the microporous substrate membrane is cooled to room temperature in an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add medical-grade hydroxyethyl methacrylate, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50°C in a water bath for 90 min. Finally, wash the base membrane with deionized water at 100°C for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add methacryloyloxyethyl dimethyl benzyl ammonium chloride and ammonium persulfate to deionized water, then add sodium dihydrogen phosphate-disodium hydrogen phosphate to adjust the pH of the system to 7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55°C in a water bath for 60 min. Finally, wash the base membrane with deionized water at 100°C for 90 min to obtain the antibacterial modified base membrane. S6: The medical polypropylene spunbond nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes. Then, the nonwoven fabric is dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 130°C and a hot pressing pressure of 0.4MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation with an irradiation dose of 25~30kGy to obtain a low-allergenic medical protective liner material.

[0036] Experimental results: See Table 3 for details.

[0037] Table 3: Test Results of Example 3 This embodiment reduces the concentrations of hydrophilic and antibacterial monomers and shortens the grafting reaction time. Its core impact lies in reducing the grafting density and chain length of the modified layer on the base membrane surface. The lower monomer concentration slows down the free radical polymerization reaction rate, while the shorter reaction time causes the polymerization process to terminate prematurely. The coupling of these two factors results in the inability to form sufficiently dense and extended hydrophilic and antibacterial polymer molecular brushes on the microporous base membrane surface. This leads to insufficient hydrophilic modification of the microporous inner walls, weakened interaction between water molecules and the pore walls, and insufficient diffusion driving force under capillary effect, resulting in reduced moisture permeability. Simultaneously, insufficient surface positive charge density and sparse antibacterial molecular chains weaken electrostatic adsorption and physical penetration capabilities, resulting in unsatisfactory barrier and moisture permeability performance.

[0038] Example 4 This embodiment provides a method for preparing a low-allergenic medical protective liner material, the specific implementation steps of which include: Experimental materials: 100 parts by weight of high molecular weight polyethylene (UHMWPE), 360 parts by weight of medical-grade paraffin oil without aromatic residue, 0.2 parts by weight of medical-grade antioxidant 1010, supercritical CO2, 25 g / L medical-grade hydroxyethyl methacrylate, 1.0 g / L ammonium sulfate, 0.6 g / L ammonium persulfate, sodium dihydrogen phosphate-disodium hydrogen phosphate, 20 g / L methacryloyloxyethyl dimethyl benzyl ammonium chloride.

[0039] Experimental objective: The effects of prolonged immersion in a water bath with high concentrations of hydroxyethyl methacrylate and methacryloyloxyethyl dimethyl benzyl ammonium chloride on the final protective gasket were investigated.

[0040] Experimental steps: S1: High molecular weight polyethylene (UHMWPE) powder, medical-grade paraffin oil without aromatic residue, and medical-grade antioxidant 1010 are placed in a high-speed mixer at 25°C and stirred continuously at 1000 rpm for 15 minutes. The mixture is then placed in a twin-screw extruder and melt-blended in a gradient heating range of 215°C and extruded into cast sheets. The cast sheets are then cooled to 25°C to obtain nascent cast sheets. S2: The nascent film obtained in S1 was placed in a biaxial stretching machine. The biaxial stretching machine was set to stretch the nascent film at 125℃ with a 9x transverse stretching ratio and a 7x longitudinal stretching ratio. Then, the stretched nascent film was placed in a supercritical CO2 extraction vessel at 45℃ and 12MPa for 120min for cyclic extraction. After extraction, the pressure was released and the material was placed in a vacuum dryer at 40℃ to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 is placed in a low-temperature plasma reaction chamber. The reaction chamber is then evacuated to a vacuum environment of 8 Pa. High-purity argon gas is then introduced into the chamber and the chamber pressure is maintained at 40 Pa. The power of the radio frequency power supply is then set to 100 W and the plasma activation treatment is set to 90 s. Finally, the microporous substrate membrane is cooled to room temperature in an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add medical-grade hydroxyethyl methacrylate, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50°C in a water bath for 150 min. Finally, wash the base membrane with deionized water at 100°C for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add methacryloyloxyethyl dimethyl benzyl ammonium chloride and ammonium persulfate to deionized water, then add sodium dihydrogen phosphate-disodium hydrogen phosphate to adjust the pH of the system to 7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55°C in a water bath for 120 min. Finally, wash the base membrane with deionized water at 100°C for 90 min to obtain the antibacterial modified base membrane. S6: The medical polypropylene spunbond nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes. Then, the nonwoven fabric is dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 130°C and a hot pressing pressure of 0.4MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation with an irradiation dose of 25~30kGy to obtain a low-allergenic medical protective liner material.

[0041] Experimental results: See Table 4 for details.

[0042] Table 4: Test Results of Example 4 This embodiment increases the concentration of grafted monomers while extending the reaction time, transforming the grafting mechanism from insufficient grafting density to potential overgrafting. Theoretically, high monomer concentration and sufficient reaction time should result in a thicker, higher-density grafted polymer layer. The high-density hydrophilic molecular chains significantly enhance the affinity of the pore wall interface for water molecules and the capillary condensation effect, resulting in a significant increase in water vapor permeability. However, an excessively thick grafted layer may microscopically block the original UHMWPE micropores, reducing the effective pore size and pore volume. This, in turn, reduces the material's resistance to liquid water penetration, manifesting as a decrease in hydrostatic pressure. The enhanced antibacterial properties are similar to those of the hydrophilic properties, attributed to the increased density and chain activity of surface quaternary ammonium salt cations.

[0043] Example 5 This embodiment provides a method for preparing a low-allergenic medical protective liner material, the specific implementation steps of which include: Experimental materials: 100 parts by weight of high molecular weight polyethylene (UHMWPE), 360 parts by weight of medical-grade paraffin oil without aromatic residue, 0.2 parts by weight of medical-grade antioxidant 1010, supercritical CO2, 20 g / L medical-grade hydroxyethyl methacrylate, 1.0 g / L ammonium sulfate, 0.6 g / L ammonium persulfate, sodium dihydrogen phosphate-disodium hydrogen phosphate, and 15 g / L methacryloyloxyethyl dimethyl benzyl ammonium chloride.

[0044] Experimental objective: The effects of low-power radio frequency power supply, short-duration plasma activation treatment, and different hot-pressing temperatures and pressures on the padding material were investigated.

[0045] Experimental steps: S1: High molecular weight polyethylene (UHMWPE) powder, medical-grade paraffin oil without aromatic residue, and medical-grade antioxidant 1010 are placed in a high-speed mixer at 25°C and stirred continuously at 1000 rpm for 15 minutes. The mixture is then placed in a twin-screw extruder and melt-blended in a gradient heating range of 215°C and extruded into cast sheets. The cast sheets are then cooled to 25°C to obtain nascent cast sheets. S2: The nascent film obtained in S1 was placed in a biaxial stretching machine. The biaxial stretching machine was set to stretch the nascent film at 125℃ with a 9x transverse stretching ratio and a 7x longitudinal stretching ratio. Then, the stretched nascent film was placed in a supercritical CO2 extraction vessel at 45℃ and 12MPa for 120min for cyclic extraction. After extraction, the pressure was released and the material was placed in a vacuum dryer at 40℃ to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 was placed in a low-temperature plasma reaction chamber. The reaction chamber was then evacuated to a vacuum environment of 8 Pa. High-purity argon gas was then introduced into the chamber and the chamber pressure was maintained at 40 Pa. The power of the radio frequency power supply was then set to 80 W and the plasma activation treatment was performed for 120 s. Finally, the microporous substrate membrane was cooled to room temperature in an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add medical-grade hydroxyethyl methacrylate, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50°C in a water bath for 120 min. Finally, wash the base membrane with deionized water at 100°C for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add methacryloyloxyethyl dimethyl benzyl ammonium chloride and ammonium persulfate to deionized water, then add sodium dihydrogen phosphate-disodium hydrogen phosphate to adjust the pH of the system to 7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55°C for 90 min in a water bath. Finally, wash the base membrane with deionized water at 100°C for 90 min to obtain the antibacterial modified base membrane. S6: The medical polypropylene spunbond nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes. Then, the nonwoven fabric is dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 125°C and a hot pressing pressure of 0.5MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation with an irradiation dose of 25~30kGy to obtain a low-allergenic medical protective liner material.

[0046] Experimental results: See Table 5 for details.

[0047] Table 5: Test Results of Example 5 This embodiment is an optimization case involving multivariate coupling, and its mechanism involves balancing plasma processing efficiency and hot-pressing composite conditions. Reducing the radio frequency power weakens the energy and density of plasma active particles, but appropriately extending the processing time can compensate for the insufficient activation efficiency through continuous particle bombardment, while still effectively generating sufficient surface free radical sites to ensure subsequent grafting. In the hot-pressing composite stage, lowering the temperature and appropriately increasing the pressure avoids excessive melting that could cause the microporous structure of the base film to collapse and close at high temperatures, while the slightly increased pressure ensures the interfacial bonding strength. These mild yet effective hot-pressing and activation conditions together achieve a good composite effect while maintaining good moisture permeability and barrier properties.

[0048] Comparative Example 1 This embodiment provides a method for preparing a traditional medical protective liner material, the specific implementation steps of which include: Experimental materials: Medical-grade polyether polyurethane granules (PU), N,N-dimethylformamide (DMF), nonionic surfactant fatty alcohol polyoxyethylene ether (AEO), nano silver antibacterial dispersion, medical-grade acrylate pressure-sensitive adhesive, medical-grade polypropylene spunbond nonwoven fabric (PP), deionized water, ethyl acetate.

[0049] Experimental objective: Prepare a traditional medical protective padding material.

[0050] Experimental steps: S1: Medical-grade polyether PU granules and DMF solvent are added to a closed reactor at a mass ratio of 1:4. The mixture is stirred at 300 rpm for 4 hours at a constant temperature of 60℃ until the PU is completely dissolved, thus preparing a homogeneous PU casting solution. After standing and vacuum degassing for 2 hours, the casting solution is coated onto a PET release film using a doctor blade. The wet film thickness is controlled to be 80 μm. The coated film is then immersed in a 25℃ deionized water coagulation bath for 10 minutes to complete the phase inversion and film formation. The film is then washed three times with 60℃ deionized water for 20 minutes each time. Finally, it is dried in an 80℃ hot air oven for 30 minutes to obtain a PU barrier base film with a thickness of 20 μm. S2: Prepare a modified coating solution using deionized water as a solvent, add 30 g / L AEO-9 and 50 g / L nano-silver antibacterial dispersion to it, stir at 500 rpm for 30 min at room temperature until the system is uniformly dispersed, completely immerse the PU barrier base film obtained in S1 in the modified coating solution, soak at room temperature for 30 min, take it out, use a rubber roller to squeeze out excess coating solution on the surface at a uniform speed, and put it into a 60℃ hot air oven to dry for 20 min to obtain a hydrophilic antibacterial modified PU film; S3: Dilute the acrylic pressure-sensitive adhesive with ethyl acetate at a mass ratio of 3:1, stir at room temperature for 20 minutes until uniform, and use a comma-shaped scraper to evenly coat the diluted pressure-sensitive adhesive onto the uncoated side of the modified PU film prepared in S2, controlling the dry adhesive thickness to 5μm. Dry in a 50℃ oven for 10 minutes to remove residual solvent. Then, flatly bond the coated side with medical PP spunbond nonwoven fabric and send it into a roller laminating machine for lamination at 0.3MPa pressure and room temperature. After curing at room temperature for 24 hours, a composite liner semi-finished product is obtained. S4: Cut the composite liner semi-finished product obtained in S3 according to clinical use specifications, package it with medical dialysis paper and composite film, and put it into an ethylene oxide sterilizer for sterilization. Control the ethylene oxide concentration at 600mg / L, the sterilization temperature at 40℃, and the sterilization time at 6h. After sterilization, desorb at room temperature for 7 days to obtain the finished traditional medical protective liner material.

[0051] Experimental results: See Table 6 for details.

[0052] Table 6: Test Results of Comparative Example 1 This comparative example employs the traditional wet phase transformation pore-forming and physical coating modification technique, which introduces inherent defects. Firstly, the micropores of the PU film are formed through instantaneous mass transfer and solidification between solvent and non-solvent. This rapid phase separation often results in a structure combining a dense skin layer with finger-like or sponge-like pores, exhibiting poor pore size uniformity and limited porosity, fundamentally restricting the balance between moisture permeability and barrier properties. Improvements in hydrophilicity and antibacterial properties rely solely on the physical coating of surfactants and silver nanoparticles. These components lack strong chemical bonds with the substrate, are easily lost during use, leading to rapid performance degradation. Furthermore, the AEO-9 surfactant itself is a common skin irritant and allergen. The use of chemical solvents such as DMF, pressure-sensitive adhesives, and ethylene oxide for sterilization leaves residues and precipitates that become major sources of cytotoxicity and skin sensitization. This is the most fundamental difference in biosafety mechanism between this invention and the technique of plasma covalent grafting, adhesive-free composite, and irradiation sterilization.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a low-allergenic medical protective liner material, characterized in that, Specifically, the following steps are included: S1: High molecular weight polyethylene powder, pore-forming agent, and antioxidant are placed in a high-speed mixer at 25~30℃ and stirred continuously at 500~1000rpm for 15~30min. Then the mixture is placed in a twin-screw extruder and melt-blended in a gradient heating range of 200~230℃ and extruded into cast sheets. The mixture is then cooled to 25℃ to obtain nascent cast sheets. S2: The nascent film obtained in S1 is placed in a biaxial stretching machine. The biaxial stretching machine is set to stretch the nascent film at 125°C with a transverse stretching ratio of 7-9 times and a longitudinal stretching ratio of 6-7 times. Then, the stretched nascent film is placed in a supercritical fluid extraction vessel for cyclic extraction. After extraction, the pressure is released and the material is placed in a vacuum dryer at 40°C to constant weight to obtain a gradient pore size UHMWPE microporous base membrane. S3: The gradient pore size UHMWPE microporous substrate membrane obtained in S2 is placed in a low-temperature plasma reaction chamber. The reaction chamber is then evacuated to an environment of 6~10 Pa. High-purity argon gas is then introduced into the chamber and the chamber pressure is maintained at 30~50 Pa. The power of the radio frequency power supply is then set to 80~100 W and the plasma activation treatment is set to 90~120 s. Finally, the microporous substrate membrane is cooled to room temperature of 25°C under an argon atmosphere to obtain an activated substrate membrane with a surface rich in active free radicals. S4: Add hydrophilic monomers, ammonium sulfate, and sodium dihydrogen phosphate-disodium hydrogen phosphate to deionized water. Then adjust the pH of the system to 7.2-7.5 and purge with high-purity nitrogen to remove oxygen. Then place the activated base membrane with a surface rich in active free radicals obtained in S3 into the reaction solution and raise the reaction solution to 50-60℃ in a water bath for 90-150 min. Finally, wash the base membrane with deionized water at 100℃ for 120 min and dry to constant weight to obtain a covalently grafted hydrophilic modified microporous base membrane. S5: Add antibacterial monomer and ammonium persulfate to deionized water, then add an adjuster to adjust the pH of the system to 7.2~7.5 and purge with high-purity nitrogen to remove oxygen. Then place the covalently grafted hydrophilic modified microporous base membrane obtained in S4 into the solution and raise the solution to 55~60℃ for water bath reaction for 90~120min. Finally, wash the base membrane with 100℃ deionized water for 60~120min to obtain the antibacterial modified base membrane. S6: The medical nonwoven fabric is ultrasonically cleaned with deionized water for 30 minutes, and then dried in a vacuum drying oven at 40°C to constant weight. The antibacterial modified base film obtained in S5 and the nonwoven fabric are flatly laminated and sent into a roller hot press at 120~135°C and a hot pressing pressure of 0.3~0.5MPa for continuous glue-free hot pressing composite to obtain a composite pad. S7: The composite liner obtained in S6 is sterilized by electron beam irradiation to obtain a low-allergenic medical protective liner material.

2. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The pore-forming agent mentioned in S1 is medical-grade paraffin oil without aromatic residue.

3. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The antioxidant mentioned in S1 is medical-grade antioxidant 1010, which is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

4. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The supercritical fluid mentioned in S2 is supercritical carbon dioxide, and the ambient temperature of the supercritical carbon dioxide is 45~50℃, the pressure is 12~15MPa, and the circulation extraction time is 120min.

5. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The hydrophilic monomer mentioned in S4 is medical-grade hydroxyethyl methacrylate, with a concentration of 15~25g / L.

6. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The antibacterial monomer mentioned in S5 is methacryloyloxyethyl dimethyl benzyl ammonium chloride, with a concentration of 10~20 g / L.

7. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The regulator mentioned in S5 is sodium dihydrogen phosphate-disodium hydrogen phosphate.

8. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, The medical-grade nonwoven fabric mentioned in S6 is polypropylene spunbond nonwoven fabric.

9. The method for preparing a low-allergenic medical protective liner material as described in claim 1, characterized in that, S7 describes electron beam irradiation sterilization with an irradiation dose of 25-30 kGy.

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