A repellent water-resistant medical dressing and a method of making the same

Abstract

This invention relates to the field of medical dressing technology, and discloses a tensile-resistant hydrophobic medical dressing and its preparation method. The method includes the following steps: sequentially mixing a polyvinyl alcohol aqueous solution, a polyamino chitosan acetic acid aqueous solution, and a drug to obtain a hydrophilic layer spinning solution; electrospinning to obtain a hydrophilic layer; sequentially mixing a polyvinyl alcohol aqueous solution, a chitosan acetic acid aqueous solution, a polyvinyl alcohol-g-polylactic acid aqueous solution, and a drug to obtain a weakly hydrophobic layer spinning solution; electrospinning to form a weakly hydrophobic layer on the surface of the hydrophilic layer; sequentially mixing a polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution to obtain a highly hydrophobic layer spinning solution; electrospinning to form a highly hydrophobic layer on the surface of the weakly hydrophobic layer; and vacuum drying to obtain the tensile-resistant hydrophobic medical dressing. The tensile-resistant hydrophobic medical dressing obtained in this method exhibits good tensile strength and hydrophobicity.

Description

Technical Field

[0001] This invention relates to the field of medical dressing technology, specifically a tensile-resistant and water-repellent medical dressing and its preparation method. Background Technology

[0002] Medical dressings are the core materials for wound care. Dressings that combine excellent absorbency, moisture wicking, waterproofing, and antibacterial properties with high tensile strength are crucial for maintaining a moist healing environment, preventing wound infection, and avoiding secondary damage during dressing changes. Currently, commonly used traditional dressings tend to stick to the wound and have poor water resistance. Hydrogel dressings have low wet strength and are easily damaged, making them unsuitable for use on active wounds. Conventional multilayer dressings are simply stacked structures without a gradient wetting system, resulting in poor unidirectional moisture wicking, easy backflow of exudate, and loose interlayer bonding with insufficient tensile stability.

[0003] Existing technologies, such as CN120899977A, disclose a biodegradable chitosan medical dressing. It has excellent hydrophilicity but is very easy to adhere to the wound. Simple surface hydrophobic modification can easily cause the dressing to absorb liquid and separate into layers and fail structurally. Adding an additional functional layer will greatly increase the complexity of preparation.

[0004] To address the shortcomings of existing technologies, this invention designs a hydrophilic-weakly hydrophobic-highly hydrophobic three-layer gradient structure, combined with a modified chitosan and grafted polymer composite system, which balances tensile strength, water repellency, and unidirectional flow conduction properties, and has good application value. Summary of the Invention

[0005] The purpose of this invention is to provide a tensile-resistant and water-repellent medical dressing and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a tensile-resistant and water-repellent medical dressing includes the following steps: S1: Modified chitosan was obtained by modifying polyamino chitosan with carboxylated β-cyclodextrin and palmitic acid; alkylated chitosan was obtained by modifying polyamino chitosan with lauraldehyde. S2: (1) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug sequentially to obtain hydrophilic spinning solution, electrospinning to obtain hydrophilic layer; (2) Polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution and drug are stirred and mixed in sequence to obtain a weak hydrophobic layer spinning solution. Electrospinning is performed to form a weak hydrophobic layer on the surface of the hydrophilic layer. (3) Polyvinyl alcohol aqueous solution, alkylated chitosan acetic acid aqueous solution and polyvinyl alcohol-g-polylactic acid aqueous solution are stirred and mixed in sequence to obtain a high hydrophobic layer spinning solution. Electrospinning is performed to form a high hydrophobic layer on the surface of the weak hydrophobic layer. Vacuum drying yields a tensile-resistant, water-repellent medical dressing.

[0007] In a more optimized manner, the mass ratio of polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution, and drug in the raw materials of the hydrophilic layer spinning solution is (3~5):1:(0.2~0.5). In the raw materials of the weak hydrophobic layer spinning solution, the mass ratio of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug is 3~5:(1~2):(1~1.5):(0.8~1); In the raw materials of the high hydrophobic layer spinning solution, the mass ratio of polyvinyl alcohol aqueous solution, alkylated chitosan acetic acid aqueous solution, and polyvinyl alcohol-g-polylactic acid aqueous solution is (3~5):(1~3):2.

[0008] More optimized, the concentration of the polyvinyl alcohol aqueous solution is 10-15 wt%; the concentration of the polyamino chitosan acetic acid aqueous solution is 4-6 wt%; the solid content of the chitosan acetic acid aqueous solution is 7-9 wt%, which includes modified chitosan and alkylated chitosan in a mass ratio of 3:(1-2); the concentration of the polyvinyl alcohol-g-polylactic acid aqueous solution is 5-10 wt%; and the concentration of the alkylated chitosan acetic acid aqueous solution is 8-10 wt%.

[0009] A more optimized method for preparing modified chitosan is as follows: (1) Mix carboxylated β-cyclodextrin evenly, add EDC·HCl and stir to obtain a mixture; add palmitic acid to methanol and mix, add EDC·HCl and stir to obtain a palmitic acid mixture; (2) Add the polyamino chitosan to an aqueous acetic acid solution to swell, add methanol to dilute, add the mixture, stir at 37°C for 5 hours, add palmitic acid mixture, continue stirring for 6 hours, remove methanol by rotary evaporation, purify, freeze dry to obtain modified chitosan.

[0010] In a more optimized form, the raw material for the modified chitosan includes the following components: by mass parts, 2-4 parts carboxylated β-cyclodextrin, 4-7 parts palmitic acid, 3-5 parts EDC·HCl, 10-15 parts polyamino chitosan, 60-80 parts aqueous acetic acid solution, and 100-200 parts methanol.

[0011] A more optimized method for preparing alkylated chitosan is as follows: Polyamino chitosan is added to an aqueous acetic acid solution and mixed. The pH is adjusted to 10-12. The precipitate is filtered and washed to obtain a filter cake. The filter cake is placed in N,N-dimethylformamide and mixed. Lauryl aldehyde is added, and the pH is adjusted to 6-6.5 with acetic acid. The mixture is stirred for 5-7 hours, and sodium triacetoxyborohydride is added and mixed. The mixture is stirred for 10-12 hours under nitrogen protection. After washing and drying, alkylated chitosan is obtained.

[0012] In a more optimized form, the raw material for the alkylated chitosan includes the following components: by mass, 5 parts of polyamino chitosan, 1-3 parts of lauraldehyde, and 1-3 parts of sodium triacetoxyborohydride.

[0013] The optimal grafting rate of lactic acid in polyvinyl alcohol-g-polylactic acid is 37%~42%.

[0014] In a more optimized configuration, the thickness of the hydrophilic layer is 120~150µm; the thickness of the weakly hydrophobic layer is 110~130µm; and the thickness of the highly hydrophobic layer is 40~60µm.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention prepares a water-repellent medical dressing with a three-layer gradient fiber structure consisting of a drug-loaded hydrophilic bottom layer, a drug-loaded weakly hydrophobic transition layer, and a highly hydrophobic surface layer. By combining polyvinyl alcohol-g-polylactic acid with different lactic acid grafting rates and modified chitosan, the dressing possesses excellent mechanical properties, water repellency, and gradient drug release performance.

[0016] The hydrophilic layer adheres to the wound surface, rapidly absorbing wound exudate, stabilizing drug loading, and enabling burst drug release for rapid onset of action. It also maintains a moist microenvironment on the wound surface, preventing the dressing from drying and sticking to the wound. The weakly hydrophobic transition layer disperses tensile stress, improves the delamination problem between the hydrophilic bottom layer and the highly hydrophobic top layer, and enhances the overall tensile strength of the dressing. At the same time, it enables sustained drug release, buffers excess exudate, forms a gradient drug release effect, prolongs the duration of antibacterial treatment, and allows for one-way exudate drainage, preventing wound maceration.

[0017] The highly hydrophobic surface layer forms a dense hydrophobic barrier, effectively blocking the intrusion of external sewage, bacteria, and dust, reducing the risk of wound infection. It also retains the microporous structure of the fibers, allowing for breathability and moisture wicking, achieving water repellency without causing skin suffocation. This invention effectively solves the problems of traditional dressings, such as easy delamination leading to poor mechanical properties, limited drug release, and poor waterproof compatibility. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments; at the same time, the parts in the embodiments are parts by weight. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] The lactic acid grafting rate in polyvinyl alcohol-g-polylactic acid (PVA-g-PLA) was 40.6%. The preparation was carried out using existing technology, specifically as follows: deionized water was heated to 95°C, 1 part of polyvinyl alcohol was added and mixed, 30 parts of lactic acid (LA) and EDC·HCl were added and stirring was continued for 3 hours under a pressure of 16 kPa; the temperature was raised to 130°C, and the reaction was continued for 6 hours under a pressure of 2.7 kPa. After cooling, the mixture was added to tetrahydrofuran and homogenized, then added to diethyl ether to precipitate the product. The precipitate was filtered, collected, and dried to obtain PVA-g-PLA with a lactic acid grafting rate of 40.6%. The amount of EDC·HCl added was 0.5 wt% of the lactic acid.

[0020] Example 1: A method for preparing a tensile-resistant and water-repellent medical dressing, comprising the following steps: S1: The preparation method of modified chitosan is as follows: (1) Add 3 parts of carboxylated β-cyclodextrin to 30 parts of methanol and mix evenly, add 1.5 parts of EDC·HCl and stir to mix, and obtain a mixture; add 7 parts of palmitic acid to 60 parts of methanol and mix, add 3 parts of EDC·HCl and stir to mix, and obtain a palmitic acid mixture; (2) Add 10 parts of polyamino chitosan to 80 parts of acetic acid aqueous solution to swell, add 30 parts of methanol to dilute, add the mixture, stir at 37°C for 5 hours, add palmitic acid mixture, continue stirring for 6 hours, remove methanol by rotary evaporation, purify, freeze dry to obtain modified chitosan. The preparation method of alkylated chitosan is as follows: 5 parts of polyamino chitosan are added to an aqueous acetic acid solution and mixed. The pH is adjusted to 12 with 1M sodium hydroxide. The precipitate is filtered and washed to obtain a filter cake. The filter cake is placed in 30 parts of N,N-dimethylformamide and mixed. 3 parts of lauraldehyde are added. The pH is adjusted to 6.5 with acetic acid and stirred for 6 hours. 3 parts of sodium triacetoxyborohydride are added and mixed. The mixture is stirred for 10 hours under nitrogen protection. After washing and drying, alkylated chitosan is obtained. S2: (1) Add polyvinyl alcohol to deionized water, stir and dissolve at 90°C, cool to room temperature, and obtain a polyvinyl alcohol aqueous solution with a concentration of 12wt%; Polyvinyl alcohol-g-polylactic acid was added to deionized water, stirred and dissolved at 90°C, and cooled to room temperature to obtain an 8wt% polyvinyl alcohol-g-polylactic acid aqueous solution. Adding polyamino chitosan to a 1 wt% aqueous acetic acid solution yields a 4 wt% polyamino chitosan-acetic acid aqueous solution. A 1 wt% aqueous acetic acid solution was used as a solvent, and modified chitosan and alkylated chitosan in a mass ratio of 4:1 were added and stirred until homogeneous to obtain a chitosan-acetic acid aqueous solution with a solid content of 7 wt%. Alkylated chitosan was added to a 1 wt% aqueous acetic acid solution to obtain a 10 wt% alkylated chitosan-acetic acid aqueous solution. (2) A polyvinyl alcohol aqueous solution, a polyamino chitosan acetic acid aqueous solution and the drug were stirred and mixed in sequence at a mass ratio of 3:1:0.2 to obtain a hydrophilic layer spinning solution. The voltage was set to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm, and electrospinning was performed to obtain a hydrophilic layer with a thickness of 120µm. A mixture of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug in a mass ratio of 3:1.5:1:0.8 was stirred and mixed sequentially to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 130µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant, water-repellent medical dressing. In this embodiment, polyvinyl alcohol has a weight average molecular weight of 124,000; the drug is mupirocin hydrochloride; carboxylated β-cyclodextrin is carboxymethyl-β-cyclodextrin; EDC·HCl is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; and palmitic acid is commercially available.

[0021] Example 2 is based on Example 1; the difference is that the thickness of the hydrophilic layer is 150 μm; the other operating steps are the same. S2: (2) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug in a mass ratio of 3:1:0.2 to obtain hydrophilic spinning solution. Set the voltage to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm and perform electrospinning to obtain a hydrophilic layer with a thickness of 150µm. A mixture of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug in a mass ratio of 3:1.5:1:0.8 was stirred and mixed sequentially to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 130µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0022] Example 3 is based on Example 1: the difference is that the thickness of the weak hydrophobic layer is 110 μm; the other operation steps are the same. S2: (2) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug in sequence with a mass ratio of 3:1:0.2 to obtain hydrophilic spinning solution. Set the voltage to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm and perform electrospinning to obtain a hydrophilic layer with a thickness of 120µm. A mixture of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug in a mass ratio of 3:1.5:1:0.8 was stirred and mixed sequentially to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 110µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0023] Comparative Example 1 is based on Example 2; the difference is that a weak hydrophobic layer was not provided; the other operating steps are the same. S2: (2) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug in a mass ratio of 3:1:0.2 to obtain hydrophilic spinning solution. Set the voltage to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm and perform electrospinning to obtain a hydrophilic layer with a thickness of 150µm. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the hydrophilic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0024] Comparative Example 2 is based on Example 2; the difference is that polyvinyl alcohol-g-polylactic acid was not introduced; the other operating steps are the same. S2: (2) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug in a mass ratio of 3:1:0.2 to obtain hydrophilic spinning solution. Set the voltage to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm and perform electrospinning to obtain a hydrophilic layer with a thickness of 150µm. A polyvinyl alcohol aqueous solution, a chitosan acetic acid aqueous solution, and a drug were sequentially stirred and mixed in a mass ratio of 3:1.5:0.8 to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 130µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution and an alkylated chitosan acetic acid aqueous solution with a mass ratio of 3:2.5 were stirred and mixed sequentially to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0025] Comparative Example 3 is based on Example 2; the difference is that the grafting rate of polyvinyl alcohol-g-polylactic acid was reduced to 31.8%; the other operating steps are the same. The lactic acid grafting rate in polyvinyl alcohol-g-polylactic acid (PVA-g-PLA) was 31.8%. The preparation method was as follows: deionized water was heated to 95°C, 1 part of PVA was added and mixed, then 10 parts of lactic acid (LA) and EDC·HCl were added and stirred continuously at 16 kPa for 3 hours; the temperature was then raised to 130°C and the reaction was continued at 2.7 kPa for 6 hours. After cooling, the mixture was added to tetrahydrofuran and homogenized, then added to diethyl ether to precipitate the product. The precipitate was filtered, collected, and dried to obtain PVA-g-PLA with a lactic acid grafting rate of 31.8%. The amount of EDC·HCl added was 0.5 wt% of the lactic acid. S2: (2) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug in a mass ratio of 3:1:0.2 to obtain hydrophilic spinning solution. Set the voltage to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm and perform electrospinning to obtain a hydrophilic layer with a thickness of 150µm. A mixture of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug in a mass ratio of 3:1.5:1:0.8 was stirred and mixed sequentially to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 130µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0026] Comparative Example 4 is based on Example 2; the difference is that palmitic acid was not introduced; the other operating steps are the same. S1: The preparation method of modified chitosan is as follows: (1) Add 3 parts of carboxylated β-cyclodextrin to 30 parts of methanol and mix evenly, add 1.5 parts of EDC·HCl and stir to mix, and obtain a mixture; (2) Add 10 parts of polyamino chitosan to 80 parts of acetic acid aqueous solution to swell, add 30 parts of methanol to dilute, add the mixture, stir at 37°C for 6 hours, remove methanol by rotary evaporation, purify, freeze dry to obtain modified chitosan; The preparation method of alkylated chitosan is as follows: 5 parts of polyamino chitosan are added to an aqueous acetic acid solution and mixed. The pH is adjusted to 12 with 1M sodium hydroxide. The precipitate is filtered and washed to obtain a filter cake. The filter cake is placed in 30 parts of N,N-dimethylformamide and mixed. 3 parts of lauraldehyde are added. The pH is adjusted to 6.5 with acetic acid and stirred for 6 hours. 3 parts of sodium triacetoxyborohydride are added and mixed. The mixture is stirred for 10 hours under nitrogen protection. After washing and drying, alkylated chitosan is obtained. S2: (2) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug in a mass ratio of 3:1:0.2 to obtain hydrophilic spinning solution. Set the voltage to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm and perform electrospinning to obtain a hydrophilic layer with a thickness of 150µm. A mixture of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug in a mass ratio of 3:1.5:1:0.8 was stirred and mixed sequentially to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 130µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0027] Comparative Example 5 is based on Example 2; the difference is that the mass ratio of modified chitosan to alkylated chitosan is 1:5; the other operating steps are the same. S2: (1) Add polyvinyl alcohol to deionized water, stir and dissolve at 90°C, cool to room temperature, and obtain a polyvinyl alcohol aqueous solution with a concentration of 12wt%; Polyvinyl alcohol-g-polylactic acid was added to deionized water, stirred and dissolved at 90°C, and cooled to room temperature to obtain an 8wt% polyvinyl alcohol-g-polylactic acid aqueous solution. Adding polyamino chitosan to a 1 wt% aqueous acetic acid solution yields a 4 wt% polyamino chitosan-acetic acid aqueous solution. A 1 wt% aqueous acetic acid solution was used as a solvent, and modified chitosan and alkylated chitosan in a mass ratio of 1:5 were added and stirred until homogeneous to obtain a chitosan-acetic acid aqueous solution with a solid content of 7 wt%. Alkylated chitosan was added to a 1 wt% aqueous acetic acid solution to obtain a 10 wt% alkylated chitosan-acetic acid aqueous solution. (2) A polyvinyl alcohol aqueous solution, a polyamino chitosan acetic acid aqueous solution and the drug were stirred and mixed in sequence at a mass ratio of 3:1:0.2 to obtain a hydrophilic layer spinning solution. The voltage was set to 16kV, the feed speed to 0.8mL / h and the receiving distance to 15cm, and electrospinning was performed to obtain a hydrophilic layer with a thickness of 150µm. A mixture of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug in a mass ratio of 3:1.5:1:0.8 was stirred and mixed sequentially to obtain a weakly hydrophobic spinning solution. Electrospinning was performed with a voltage of 18kV, a feed speed of 0.8mL / h, and a receiving distance of 15cm to form a weakly hydrophobic layer with a thickness of 130µm on the surface of the hydrophilic layer. A polyvinyl alcohol aqueous solution, an alkylated chitosan acetic acid aqueous solution, and a polyvinyl alcohol-g-polylactic acid aqueous solution in a mass ratio of 3:2.5:2 were sequentially stirred and mixed to obtain a high hydrophobic spinning solution. Electrospinning was performed with a voltage of 20kV, a feed speed of 0.7mL / h, and a receiving distance of 17cm to form a high hydrophobic layer with a thickness of 50µm on the surface of the weak hydrophobic layer. The material was vacuum dried at 40°C to obtain a tensile-resistant and water-repellent medical dressing.

[0028] Tests; (1) Testing the tensile strength (MPa) of Examples 1-3 and Comparative Examples 1-5; (2) Testing the contact angle (°) of the weak hydrophobic layer and the highly hydrophobic layer of Examples 2 and Comparative Examples 2-5. Table 1

[0029] Table 2

[0030] Conclusions: Thickness has a significant impact on tensile strength; Comparative Example 2 is based on Example 2; polyvinyl alcohol-g-polylactic acid was not introduced, resulting in a decrease in the contact angle of the weak hydrophobic layer and the highly hydrophobic layer; Comparative Example 3 is based on Example 2; the grafting rate of polyvinyl alcohol-g-polylactic acid was reduced to 31.8%; polylactic acid has a certain degree of hydrophobicity, and the hydrophobicity decreases when the grafting rate decreases; Comparative Example 4 is based on Example 2; palmitic acid was not introduced, resulting in a decrease in the contact angle and tensile strength of the weak hydrophobic layer.

[0031] Test 2: The tensile hydrophobic medical dressings prepared in Example 2 and Comparative Examples 2-5 were tested according to GB / T 21655.2-2019 for the unidirectional transfer index along the high hydrophobic-weak hydrophobic-hydrophilic direction and the hydrophilic-weak hydrophobic-high hydrophobic direction; the contact angle of the hydrophilic layer was tested to be 42°. Table 3

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a tensile-resistant and water-repellent medical dressing, characterized in that: The following steps are included: S1: Modified chitosan was obtained by modifying polyamino chitosan with carboxylated β-cyclodextrin and palmitic acid; alkylated chitosan was obtained by modifying polyamino chitosan with lauraldehyde. S2: (1) Mix polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution and drug sequentially to obtain hydrophilic spinning solution, electrospinning to obtain hydrophilic layer; (2) Polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution and drug are stirred and mixed in sequence to obtain a weak hydrophobic layer spinning solution. Electrospinning is performed to form a weak hydrophobic layer on the surface of the hydrophilic layer. (3) Polyvinyl alcohol aqueous solution, alkylated chitosan acetic acid aqueous solution and polyvinyl alcohol-g-polylactic acid aqueous solution are stirred and mixed in sequence to obtain a high hydrophobic layer spinning solution. Electrospinning is performed to form a high hydrophobic layer on the surface of the weak hydrophobic layer. Vacuum drying yields a tensile-resistant, water-repellent medical dressing.

2. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 1, characterized in that: In the raw materials of the hydrophilic layer spinning solution, the mass ratio of polyvinyl alcohol aqueous solution, polyamino chitosan acetic acid aqueous solution, and drug is (3~5):1:(0.2~0.5); In the raw materials of the weak hydrophobic layer spinning solution, the mass ratio of polyvinyl alcohol aqueous solution, chitosan acetic acid aqueous solution, polyvinyl alcohol-g-polylactic acid aqueous solution, and drug is 3~5:(1~2):(1~1.5):(0.8~1); In the raw materials of the high hydrophobic layer spinning solution, the mass ratio of polyvinyl alcohol aqueous solution, alkylated chitosan acetic acid aqueous solution, and polyvinyl alcohol-g-polylactic acid aqueous solution is (3~5):(1~3):

2.

3. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 1, characterized in that: The concentration of the polyvinyl alcohol aqueous solution is 10-15 wt%; the concentration of the polyamino chitosan acetic acid aqueous solution is 4-6 wt%; the solid content of the chitosan acetic acid aqueous solution is 7-9 wt%, which includes modified chitosan and alkylated chitosan in a mass ratio of 3:(1-2); the concentration of the polyvinyl alcohol-g-polylactic acid aqueous solution is 5-10 wt%; and the concentration of the alkylated chitosan acetic acid aqueous solution is 8-10 wt%.

4. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 1, characterized in that: The preparation method of the modified chitosan is as follows: (1) Mix carboxylated β-cyclodextrin evenly, add EDC·HCl and stir to obtain a mixture; add palmitic acid to methanol and mix, add EDC·HCl and stir to obtain a palmitic acid mixture; (2) Add the polyamino chitosan to an aqueous acetic acid solution to swell, add methanol to dilute, add the mixture, stir at 37°C for 5 hours, add palmitic acid mixture, continue stirring for 6 hours, remove methanol by rotary evaporation, purify, freeze dry to obtain modified chitosan.

5. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 4, characterized in that: The modified chitosan raw materials include the following components: by mass parts, 2-4 parts carboxylated β-cyclodextrin, 4-7 parts palmitic acid, 3-5 parts EDC·HCl, 10-15 parts polyamino chitosan, 60-80 parts aqueous acetic acid solution, and 100-200 parts methanol.

6. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 1, characterized in that: The preparation method of alkylated chitosan is as follows: polyamino chitosan is added to an aqueous acetic acid solution and mixed. The pH is adjusted to 10-12. The precipitate is filtered and washed to obtain a filter cake. The filter cake is placed in N,N-dimethylformamide and mixed. Lauraldehyde is added, and the pH is adjusted to 6-6.5 with acetic acid. The mixture is stirred for 5-7 hours. Sodium triacetoxyborohydride is added and mixed. The mixture is stirred for 10-12 hours under nitrogen protection. The mixture is washed and dried to obtain alkylated chitosan.

7. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 6, characterized in that: The raw materials for the alkylated chitosan include the following components: by mass, 5 parts of polyamino chitosan, 1-3 parts of lauraldehyde, and 1-3 parts of sodium triacetoxyborohydride.

8. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 1, characterized in that: The lactic acid grafting rate in polyvinyl alcohol-g-polylactic acid is 37%~42%.

9. The method for preparing a tensile-resistant and water-repellent medical dressing according to claim 1, characterized in that: The thickness of the hydrophilic layer is 120~150µm; the thickness of the weakly hydrophobic layer is 110~130µm; and the thickness of the highly hydrophobic layer is 40~60µm.

10. The tensile water-repellent medical dressing prepared by the method of preparing a tensile water-repellent medical dressing according to any one of claims 1 to 9.

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