A porous insole loaded with a nano-silver-chitosan composite antibacterial agent and its preparation process

Abstract

This invention relates to a porous insole loaded with a nano-silver-chitosan composite antibacterial agent and its preparation process in the field of insole manufacturing technology. The insole is composed of a porous substrate, in which a nano-silver-chitosan composite antibacterial agent is loaded. The composite antibacterial agent is fixed on the pore wall surface of the porous substrate through in-situ reduction or physical adsorption, giving the insole broad-spectrum antibacterial properties. The preparation process consists of three steps: using highly deacetylated chitosan as a stabilizer and reducing agent, uniformly dispersed nano-silver is synthesized in situ, maintaining high activity. It has an inhibition rate of ≥99% against common foot pathogens such as Staphylococcus aureus and Escherichia coli, effectively inhibiting foot odor, athlete's foot, and mold growth. This solution solves the problem of traditional insoles easily breeding bacteria, producing odors, and causing skin infections. This solution blocks the microbial breeding environment at the source.

Description

Technical Field

[0001] This invention relates to the field of insole production technology, specifically to a porous insole loaded with a nano-silver-chitosan composite antibacterial agent and its preparation process. Background Technology

[0002] Insoles are functional pads placed inside shoes, between the sole of the foot and the insole. While seemingly simple, they play a crucial role in comfort, health protection, and athletic performance. Most commercially available antibacterial insoles use surface spraying or simple impregnation to load antibacterial agents, such as quaternary ammonium salts, triclosan, nano-silver, and ordinary silver ions. These agents are not firmly bonded to the substrate. Furthermore, if nano-silver is not stabilized, it easily agglomerates into large particles >100 nm during preparation or use, reducing the specific surface area and significantly decreasing antibacterial activity. Some products directly add silver powder or silver salts without forming an effective nanostructure, resulting in actual sterilization efficiency far lower than theoretical values. This can lead to skin irritation or environmental pollution due to silver particle shedding. In pursuit of antibacterial effects, some products use dense materials such as coated fabrics. While this structure can prevent bacterial growth inside the insole, it sacrifices breathability, exacerbating stuffiness and humidity, and promoting the growth of anaerobic bacteria. Therefore, the inventors have proposed a porous insole loaded with a nano-silver-chitosan composite antibacterial agent and its preparation process to solve the aforementioned technical problems. Summary of the Invention

[0003] To overcome the shortcomings mentioned above, the invention aims to provide a technical solution that can solve the above problems.

[0004] A porous insole loaded with a nano-silver-chitosan composite antibacterial agent is disclosed. The insole is composed of a porous substrate, and the nano-silver-chitosan composite antibacterial agent is loaded inside the porous substrate. The composite antibacterial agent is fixed on the pore wall surface of the porous substrate by in-situ reduction or physical adsorption, so that the insole has broad-spectrum antibacterial properties.

[0005] Furthermore, the porous substrate is selected from one or more of EVA foam material, TPU foam material, PU sponge, natural latex or porous fiber nonwoven fabric, and its porosity is 40%-85% and the average pore size is 50-500 μm.

[0006] Furthermore, in the nano-silver-chitosan composite antibacterial agent, the nano-silver particles have a particle size of 5-50 nm, the degree of deacetylation of chitosan is ≥85%, and the mass ratio of nano-silver to chitosan is 1:5-1:50.

[0007] Furthermore, the insole surface or interior has at least one color zone, which is achieved by adding food-grade or medical-grade organic / inorganic pigments, and the pigments are mixed with antibacterial agents during the insole preparation process without reducing antibacterial activity.

[0008] Furthermore, the color zoning includes at least one of the arch area, forefoot area, or heel area, and the color depth does not affect the release kinetics of the nano-silver-chitosan composite antibacterial agent.

[0009] A process for preparing porous insoles loaded with a nano-silver-chitosan composite antibacterial agent, the process comprising the following steps: S1: Dissolve chitosan in dilute acetic acid solution, add silver nitrate solution, stir and then add reducing agent to react and generate nano-silver-chitosan composite solution; S2: The porous substrate is immersed in the composite liquid, and the composite liquid is fully penetrated into the pores by vacuum negative pressure treatment. Color powder is added in this step to form a colored antibacterial insole. S3: After removal, dry and solidify to ensure that the nano-silver-chitosan complex adheres firmly to the pore wall.

[0010] Furthermore, the reducing agent in S1 is one of ascorbic acid, glucose, or tea polyphenols, the reaction temperature is 25-60℃, and the reaction time is 1-4 hours.

[0011] Furthermore, the vacuum negative pressure in S2 is -0.05 to -0.09 MPa, and the pressure holding time is 10 to 30 minutes, to ensure that the antibacterial agent is evenly distributed in the three-dimensional pore network.

[0012] Furthermore, the drying temperature in S3 is 40-70℃, and the drying time is 2-12 hours, to avoid high temperature causing chitosan degradation or nano-silver agglomeration.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. Nano silver has a strong ability to kill bacteria and fungi, while chitosan itself is positively charged, which can destroy the cell membrane of microorganisms and synergistically enhance the release of silver ions. The antibacterial agent is firmly fixed to the pore wall through in-situ reduction or physical adsorption, avoiding rapid loss during use. Using chitosan with high degree of deacetylation as a stabilizer and reducing agent, uniformly dispersed nano silver is synthesized in situ, maintaining high activity. It has an antibacterial rate of ≥99% against common foot pathogens such as Staphylococcus aureus and Escherichia coli, effectively inhibiting foot odor, tinea pedis, and mold. It solves the problem that traditional insoles are prone to bacterial growth, odor, and skin infections. This solution blocks the microbial breeding environment from the root. 2. Made with mature shoe materials such as EVA, TPU, PU, ​​natural latex, or non-woven fabric, ensuring softness, resilience, breathability, and environmental friendliness. It ensures air circulation, reduces stuffiness and humidity, and the average pore size facilitates sweat evaporation. It also provides sufficient specific surface area to load antibacterial agents, rather than just the surface, improving contact efficiency and durability. It has porosity and pore size structure, providing sufficient load space while ensuring sweat / air circulation. 3. Using color as a secondary zoning element, different colors are set in functional areas such as the arch, forefoot, and heel to mark high antibacterial areas and cushioning areas, helping users prevent left-right installation and improving product recognizability and aesthetics. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to specific embodiments.

[0015] Example 1: Please refer to a specific embodiment of a porous insole loaded with a nano-silver-chitosan composite antibacterial agent. The insole is composed of a porous substrate, and the nano-silver-chitosan composite antibacterial agent is loaded inside the porous substrate. The composite antibacterial agent is fixed on the pore wall surface of the porous substrate by in-situ reduction or physical adsorption, so that the insole has broad-spectrum antibacterial properties. The nano-silver-chitosan composite antibacterial agent combines the broad-spectrum bactericidal properties of nano-silver, which is effective against both bacteria and fungi; chitosan is a natural cationic polysaccharide with biocompatibility, film-forming properties and synergistic antibacterial effects, and can stabilize nano-silver, prevent aggregation, reduce in situ or physically adsorb and fix it to the pore wall, so that the antibacterial agent is firmly loaded in the three-dimensional porous network and avoids rapid loss during use. The nano-silver particles with a diameter of 25 nm and ≥85% chitosan with a high degree of deacetylation, when used in a mass ratio of 1:5–1:50, can ensure a high specific surface area and achieve a strong bactericidal effect. The full protonation of chitosan can enhance its interaction with microbial cell membranes and prevent excessive silver precipitation, thereby achieving a ≥99% antibacterial rate against common foot pathogens such as Staphylococcus aureus and Escherichia coli in the insole.

[0016] The porous substrate is selected from one or more of EVA foam, TPU foam, PU sponge, natural latex, or porous fiber nonwoven fabric, with a porosity of 55% and an average pore size of 220 μm. In the nano-silver-chitosan composite antibacterial agent, the nano-silver particles have a particle size of 35 nm, the chitosan has a deacetylation degree ≥85%, and the mass ratio of nano-silver to chitosan is 1:5-1:50. Using mature shoe materials such as EVA, TPU, PU, ​​latex, or nonwoven fabric ensures softness, resilience, cushioning, and breathability. The combination of a 61% porosity and an average pore size of 55 μm allows for sufficient porosity to ensure air / sweat circulation, inhibiting anaerobic bacterial growth. Within a reasonable pore size range, it facilitates the penetration and impregnation of the antibacterial agent solution and provides sufficient specific surface area for load-bearing. The microporous structure itself can physically block the migration of some microorganisms. This structure maximizes the distribution density and contact efficiency of the antibacterial agent while maintaining basic insole comfort.

[0017] The insole has at least one color zone on its surface or inside. The color zone is achieved by adding food-grade or medical-grade organic / inorganic pigments, and the pigments are mixed with antibacterial agents during the insole manufacturing process without reducing antibacterial activity. The color zone includes at least one of the arch, forefoot, or heel areas, and the color depth does not affect the release kinetics of the nano-silver-chitosan composite antibacterial agent. The color is introduced by mixing pigments rather than surface spraying to avoid pore blockage, maintain breathability, reduce dye leaching to ensure skin safety, and ensure unobstructed release channels by covering the antibacterial agent. The color zones are located in functional areas such as the arch, forefoot, and heel to identify different functions such as high antibacterial areas and high cushioning areas, helping users to correctly install the insole.

[0018] A process for preparing porous insoles loaded with a nano-silver-chitosan composite antibacterial agent, the process comprising the following steps: S1: Chitosan is dissolved in dilute acetic acid solution, silver nitrate solution is added, and after stirring, a reducing agent is added to react and generate nano-silver-chitosan composite solution. The reducing agent in S1 is one of ascorbic acid, glucose or tea polyphenols. The reaction temperature is 37°C and the reaction time is 2 hours. Chitosan with a degree of deacetylation ≥85% was dissolved in a 1% dilute acetic acid aqueous solution to form a 1% w / v transparent or slightly turbid colloid. Silver nitrate (AgNO3) aqueous solution was then slowly added dropwise with stirring to allow the AgNO3 solution to dissolve. + The ions complex with the amino / hydroxyl groups in the chitosan molecules, and ascorbic acid is added as a reducing agent to transform Ag under mild conditions. + In-situ restoration to Ag 0 Nano-silver particles are generated and stabilized by chitosan coating, forming a uniformly dispersed brownish-yellow composite liquid. S2: The porous substrate is immersed in the composite liquid, and the composite liquid is fully penetrated into the pores by vacuum negative pressure treatment. Color powder is added in this step to form a colored antibacterial insole. The vacuum negative pressure in S2 is -0.07 MPa and the pressure holding time is 15 minutes to ensure that the antibacterial agent is evenly distributed in the three-dimensional pore network. The pre-formed porous insole substrate is immersed in the above-mentioned composite liquid and placed in a vacuum chamber / room. The vacuum is evacuated to a negative pressure of -0.07 MPa and maintained for 15 minutes. The negative pressure causes the air inside the substrate to be expelled. When the vacuum is released, the liquid rapidly fills the pores under atmospheric pressure. This step can overcome the capillary resistance of porous materials and ensure that the antibacterial liquid penetrates deeply and uniformly into the three-dimensional pore network, rather than just adhering to the surface. When preparing the composite liquid, food-grade color powders such as iron oxide red, titanium dioxide white, and ultramarine blue can be added and mixed and dispersed. S3: After removal, dry and solidify to ensure that the nano-silver-chitosan composite adheres firmly to the pore wall. The drying temperature in S3 is 60℃ and the drying time is 8 hours to avoid high temperature causing chitosan degradation or nano-silver agglomeration. Remove the soaked insole, drain excess liquid, and place it in a 50℃ oven to dry for 8 hours. During the drying process, the moisture evaporates, and the chitosan can firmly anchor the nano-silver to the pore wall, avoiding excessive dehydration and cross-linking of chitosan or sintering and agglomeration of nano-silver caused by high temperature >70℃, thus maintaining antibacterial activity and structural stability. Before drying, the soaked insole is locally sprayed or overall blended with color to ensure that the color powder does not clog the pores.

[0019] Example 2: Please refer to a specific embodiment of a porous insole loaded with a nano-silver-chitosan composite antibacterial agent. The insole is composed of a porous substrate, and the nano-silver-chitosan composite antibacterial agent is loaded inside the porous substrate. The composite antibacterial agent is fixed on the pore wall surface of the porous substrate by in-situ reduction or physical adsorption, so that the insole has broad-spectrum antibacterial properties. The nano-silver-chitosan composite antibacterial agent combines the broad-spectrum bactericidal properties of nano-silver, which is effective against both bacteria and fungi; chitosan is a natural cationic polysaccharide with biocompatibility, film-forming properties and synergistic antibacterial effects, and can stabilize nano-silver, prevent aggregation, reduce in situ or physically adsorb and fix it to the pore wall, so that the antibacterial agent is firmly loaded in the three-dimensional porous network and avoids rapid loss during use. The nano-silver particles have a diameter of 46 nm and a high degree of deacetylation of ≥85% chitosan. When the mass ratio is 1:5–1:50, a high specific surface area can be ensured, resulting in a strong bactericidal activity. The full protonation of chitosan can enhance its interaction with microbial cell membranes and prevent excessive silver precipitation. As a result, the insole has an antibacterial rate of ≥99% against common foot pathogens such as Staphylococcus aureus and Escherichia coli.

[0020] The porous substrate is selected from one or more of EVA foam, TPU foam, PU sponge, natural latex, or porous fiber nonwoven fabric, with a porosity of 80% and an average pore size of 450 μm. In the nano-silver-chitosan composite antibacterial agent, the nano-silver particles have a particle size of 40 nm, the degree of deacetylation of chitosan is ≥85%, and the mass ratio of nano-silver to chitosan is 1:5-1:50. Using mature shoe materials such as EVA, TPU, PU, ​​latex, or nonwoven fabric ensures softness, resilience, cushioning, and breathability. The combination of a 78% porosity and an average pore size of 470 μm allows for sufficient porosity to ensure air / sweat circulation, inhibit anaerobic bacterial growth, and facilitates the penetration and impregnation of the antibacterial agent solution within a reasonable pore size range. It also provides sufficient specific surface area for load-bearing, and the microporous structure itself physically blocks the migration of some microorganisms. This structure maximizes the distribution density and contact efficiency of the antibacterial agent while maintaining basic insole comfort.

[0021] The insole has at least one color zone on its surface or inside. The color zone is achieved by adding food-grade or medical-grade organic / inorganic pigments, and the pigments are mixed with antibacterial agents during the insole manufacturing process without reducing antibacterial activity. The color zone includes at least one of the arch, forefoot, or heel areas, and the color depth does not affect the release kinetics of the nano-silver-chitosan composite antibacterial agent. The color is introduced by mixing pigments rather than surface spraying to avoid pore blockage, maintain breathability, reduce dye leaching to ensure skin safety, and ensure unobstructed release channels by covering the antibacterial agent. The color zones are located in functional areas such as the arch, forefoot, and heel to identify different functions such as high antibacterial areas and high cushioning areas, helping users to correctly install the insole.

[0022] A process for preparing porous insoles loaded with a nano-silver-chitosan composite antibacterial agent, the process comprising the following steps: S1: Chitosan is dissolved in dilute acetic acid solution, silver nitrate solution is added, and after stirring, a reducing agent is added to react and generate nano-silver-chitosan composite solution. The reducing agent in S1 is one of ascorbic acid, glucose or tea polyphenols. The reaction temperature is 55℃ and the reaction time is 3 hours. Chitosan with a degree of deacetylation ≥85% was dissolved in a 2% dilute acetic acid aqueous solution to form a transparent or slightly turbid colloid with a concentration of 1.8% w / v. Silver nitrate (AgNO3) aqueous solution was then slowly added dropwise with stirring to allow the AgNO3 solution to precipitate. + The ions complex with the amino / hydroxyl groups in the chitosan molecules, and ascorbic acid is added as a reducing agent to transform Ag under mild conditions. + In-situ restoration to Ag 0 Nano-silver particles are generated and stabilized by chitosan coating, forming a uniformly dispersed brownish-yellow composite liquid. S2: The porous substrate is immersed in the composite liquid, and the composite liquid is fully penetrated into the pores by vacuum negative pressure treatment. Color powder is added in this step to form a colored antibacterial insole. The vacuum negative pressure in S2 is -0.08 MPa and the pressure holding time is 25 minutes to ensure that the antibacterial agent is evenly distributed in the three-dimensional pore network. The pre-formed porous insole substrate is immersed in the above-mentioned composite liquid and placed in a vacuum chamber / room. The vacuum is evacuated to a negative pressure of -0.08 MPa and maintained for 25 minutes. The negative pressure causes the air inside the substrate to be expelled. When the vacuum is released, the liquid rapidly fills the pores under atmospheric pressure. This step can overcome the capillary resistance of porous materials and ensure that the antibacterial liquid penetrates deeply and uniformly into the three-dimensional pore network, rather than just adhering to the surface. When preparing the composite liquid, food-grade color powders such as iron oxide red, titanium dioxide white, and ultramarine blue can be added and mixed and dispersed. S3: After removal, dry and solidify to ensure the nano-silver-chitosan composite adheres firmly to the pore walls. The drying temperature in S3 is 66℃, and the drying time is 11 hours to avoid chitosan degradation or nano-silver agglomeration caused by high temperatures. Remove the soaked insole, drain excess liquid, and place it in a 66℃ oven to dry for 11 hours. During drying, moisture evaporates, and the chitosan can firmly anchor the nano-silver to the pore walls, preventing excessive dehydration and cross-linking of chitosan or sintering and agglomeration of nano-silver caused by temperatures above 70℃, thus maintaining antibacterial activity and structural stability. Before drying, locally spray or overall blend coloring is applied to the soaked insole to ensure the color powder does not clog the pores. The foregoing description provides a further detailed explanation of the present invention in conjunction with specific preferred embodiments, but it should not be construed as limiting the specific implementation of the invention to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A porous insole loaded with a nano-silver-chitosan composite antibacterial agent, characterized in that, The insole is made of a porous substrate, and the porous substrate is loaded with a nano-silver-chitosan composite antibacterial agent. The composite antibacterial agent is fixed on the surface of the pore walls of the porous substrate by in-situ reduction or physical adsorption, so that the insole has broad-spectrum antibacterial properties.

2. The porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 1, characterized in that, The porous substrate is selected from one or more of EVA foam, TPU foam, PU sponge, natural latex or porous fiber nonwoven fabric, and its porosity is 40%-85% and the average pore size is 50-500 μm.

3. The porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 1, characterized in that, In the nano-silver-chitosan composite antibacterial agent, the nano-silver particles have a particle size of 5-50 nm, the degree of deacetylation of chitosan is ≥85%, and the mass ratio of nano-silver to chitosan is 1:5-1:

50.

4. The porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 1, characterized in that, The insole has at least one color zone on its surface or inside. The color zone is achieved by adding food-grade or medical-grade organic / inorganic pigments. The pigments are mixed with antibacterial agents during the insole preparation process without reducing antibacterial activity.

5. The porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 4, characterized in that, The color zones include at least one of the arch area, forefoot area, or heel area, and the color depth does not affect the release kinetics of the nano-silver-chitosan composite antibacterial agent.

6. A process for preparing porous insoles loaded with nano-silver-chitosan composite antibacterial agents, characterized in that: This preparation process is used for the porous insole according to any one of claims 1-5, and the preparation process includes the following steps: S1: Dissolve chitosan in dilute acetic acid solution, add silver nitrate solution, stir and then add reducing agent to react and generate nano-silver-chitosan composite solution; S2: The porous substrate is immersed in the composite liquid, and the composite liquid is fully penetrated into the pores by vacuum negative pressure treatment. Color powder is added in this step to form a colored antibacterial insole. S3: After removal, dry and solidify to ensure that the nano-silver-chitosan complex adheres firmly to the pore wall.

7. The process for preparing a porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 6, characterized in that: The reducing agent in S1 is one of ascorbic acid, glucose, or tea polyphenols, the reaction temperature is 25-60℃, and the reaction time is 1-4 hours.

8. The process for preparing a porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 6, characterized in that: The vacuum negative pressure in S2 is -0.05 to 0.09 MPa, and the pressure holding time is 10 to 30 minutes, to ensure that the antibacterial agent is evenly distributed in the three-dimensional pore network.

9. The preparation process of a porous insole loaded with a nano-silver-chitosan composite antibacterial agent according to claim 6, characterized in that: The drying temperature in S3 is 40-70℃, and the drying time is 2-12 hours to avoid high temperature causing chitosan degradation or nano-silver agglomeration.