Activated carbon deodorization insole

Abstract

The invention relates to the technical field of footwear products, in particular to an activated carbon deodorization insole, discloses an insole named as an activated carbon deodorization insole, and aims at overcoming the defects of an existing activated carbon deodorization insole in the aspects of adsorption performance, structural stability, air permeability and wearing comfort. The insole is characterized by comprising the following components in percentage by weight: 20% of bamboo charcoal, 45% of cassava starch and 15% of a plasticizer, cassava starch is gelatinized through high-temperature and high-pressure water vapor treatment; by the adoption of the technical scheme, efficient and lasting adsorption performance and excellent structural stability and durability can be achieved, and air permeability, comfort, environment friendliness and biological safety are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of insole technology, and more specifically to an activated carbon deodorizing insole. Background Technology

[0002] Foot health and comfort are receiving increasing attention from the public, especially in situations involving prolonged standing, walking, or exercise, where foot breathability and hygiene significantly impact individual experience. Foot odor not only affects the wearer's psychological well-being but can also cause distress in social situations, thus creating an urgent demand for insoles with excellent odor-resistant properties. As a functional component inside footwear that comes into direct contact with the foot, insoles play a crucial role in providing cushioning, support, and regulating the foot's microenvironment. Therefore, developing insoles with highly effective odor-resistant and antibacterial functions has become an important development direction in the current functional insole field, and market demand continues to grow.

[0003] To effectively address foot odor problems, those skilled in the art have made numerous attempts and proposed various solutions. Among them, activated carbon deodorizing insoles, based on the principle of physical adsorption, are highly favored due to their broad-spectrum adsorption capacity. Activated carbon, with its unique microporous structure and huge specific surface area, can efficiently adsorb odor molecules in the air, including volatile organic compounds, thereby achieving a deodorizing effect. Early activated carbon deodorizing insoles typically achieved this by directly adding activated carbon powder to the insole substrate or by sandwiching activated carbon granules between the fabric layers of the insole. The basic working principle is that activated carbon captures and fixes odor molecules within its porous structure through van der Waals forces, hydrogen bonds, and other forces, thus purifying the air. This approach alleviates foot odor problems to a certain extent. Compared to simple fragrance masking or chemical neutralization methods, its deodorizing effect is more lasting and less likely to cause secondary pollution, thus gaining some market recognition and application.

[0004] However, as consumers' demands for comfort, durability, functional sustainability, and environmental friendliness in insoles continue to rise, the inherent characteristics of traditional activated carbon-based odor-resistant insoles are gradually revealing their limitations in addressing new challenges. Specifically, the core technological dilemma facing existing activated carbon insoles lies in how to effectively and stably integrate highly porous activated carbon into the insole substrate while maximizing its adsorption properties and ensuring the insole's structural stability, breathability, and wearing comfort, without introducing additional environmental or health risks. The reason for this is that existing technologies often compromise one aspect for another when trying to solve this dilemma: if a small amount of binder is used or only physical layering is employed, the activated carbon powder or particles are prone to detachment and uneven distribution, leading to a rapid decline in odor-resistant effect, and the insole is easily worn during use, losing structural integrity and exhibiting poor durability. Conversely, if conventional synthetic polymer adhesives (such as various resins or adhesives) are used in large quantities for mixing or coating to enhance the structural strength and bonding firmness of the activated carbon, a series of new problems inevitably arise.

[0005] Furthermore, during the curing process, the molecular chains of these conventional synthetic binders fill or even block the microporous structure of activated carbon, significantly reducing its effective specific surface area and directly weakening its adsorption capacity for odor molecules. This results in a substantial reduction in its deodorizing effect, making it difficult for it to realize its full potential as a highly efficient adsorbent. Simultaneously, many synthetic binders themselves lack good breathability, forming a relatively dense film inside the insole that hinders air circulation and moisture dissipation. This may exacerbate the stuffiness and humid environment of the feet, indirectly providing conditions for bacterial growth and odor production, thus contradicting its original purpose of deodorization. In addition, some synthetic materials may have irritating odors or potential allergy risks, conflicting with current consumer demands for natural, environmentally friendly, and skin-friendly materials. This irreconcilable contradiction between the functionality of activated carbon and the structural integrity, breathability, and skin-friendliness of insoles constitutes the fundamental bottleneck currently facing the development of activated carbon deodorizing insole technology. How to effectively solve the comprehensive technical challenges of maintaining the high adsorption performance of activated carbon while ensuring its stable integration, breathability, and comfort in the insole structure through innovative material selection and preparation processes has become a key challenge and an urgent technical problem for those skilled in the art. Summary of the Invention

[0006] To address the inherent contradictions in existing activated carbon odor-resistant insoles regarding activated carbon adsorption performance, insole structural stability, breathability, and wearing comfort—specifically, how to effectively and stably integrate highly porous activated carbon into the insole substrate while maximizing its adsorption performance and ensuring the insole's structural stability, breathability, and wearing comfort without introducing additional environmental or health risks—this invention discloses an activated carbon odor-resistant insole. This invention utilizes a specific ratio of bamboo charcoal, cassava starch, and plasticizers, combined with a precisely controlled high-temperature, high-pressure steam treatment process, to construct a bio-based composite material insole with excellent adsorption performance, structural stability, and good breathability. This effectively overcomes the technical challenges of activated carbon micropore clogging, poor insole breathability, and insufficient comfort in existing technologies.

[0007] An activated carbon deodorizing insole, the main body of which is composed of the following components:

[0008] a. Bamboo charcoal, comprising 20% ​​of the total solid weight of the insole, wherein the bamboo charcoal is prepared by high-temperature pyrolysis of selected bamboo materials in an oxygen-free or low-oxygen environment at 600°C to 800°C, forming a carbonaceous material with a highly developed microporous and mesoporous structure, wherein the bamboo charcoal is used to efficiently remove volatile organic compounds from the feet through the principle of physical adsorption.

[0009] b. Cassava starch, comprising 45% of the total solid weight of the insole, wherein the cassava starch, as a bio-based adhesive and matrix material for the insole, is derived from edible cassava tubers and has an amylose content of 15% to 25% and an amylopectin content of 75% to 85%; the cassava starch undergoes a specific gelatinization treatment, specifically: the cassava starch is mixed with purified water at a mass ratio of 1:3 to 1:5 to form a starch suspension, and then the starch suspension is heated in a closed high-pressure steam environment by introducing saturated steam at a temperature of 200 degrees Celsius (±5 degrees Celsius) for 5 to 15 minutes to promote complete gelatinization and partial hydrolysis of the cassava starch particles, forming an elastic gel network structure with porosity. This structure provides excellent mechanical strength and elasticity after curing, while minimizing clogging of the bamboo charcoal micropores;

[0010] c. A plasticizer comprising 15% of the total solid weight of the insole, the plasticizer being used to adjust the flexibility and elasticity of the cassava starch matrix to improve the wearing comfort and fatigue resistance of the insole.

[0011] A method for preparing activated carbon deodorizing insoles includes the following steps:

[0012] a. Pretreatment of bamboo charcoal: The raw bamboo charcoal is dried at 105 degrees Celsius (±2 degrees Celsius) until its moisture content is less than 2%. Then it is ultra-finely ground by a vibratory mill or air jet mill to ensure that its particle size distribution is between 5 micrometers and 50 micrometers. The ground bamboo charcoal powder is stored in a sealed container.

[0013] b. Preparation of cassava starch paste: Cassava starch and purified water are mixed at a mass ratio of 1:3 to 1:5 to form a uniform starch suspension, which is then added to a high-pressure mixing vessel. Saturated steam at 200°C (±5°C) is then injected into the mixing vessel through a high-pressure steam generator to maintain the pressure inside the vessel between 1.5 MPa and 2.0 MPa. This high-temperature, high-pressure steam treatment condition is maintained for 5 to 15 minutes to promote complete gelatinization and partial hydrolysis of the cassava starch granules, forming a viscous starch paste. After the treatment is completed, the pressure inside the vessel is slowly released through a pressure relief valve.

[0014] c. Mixing of plasticizer: Transfer the starch paste prepared in step b to a cooling kettle with a stirring function. Under continuous stirring, slowly add the bamboo charcoal powder pretreated in step a and the pre-weighed plasticizer. The amount of bamboo charcoal powder added to the starch paste is 20% of the total weight of the insole solids, and the amount of plasticizer added is 15% of the total weight of the insole solids. Continue stirring for 30 to 60 minutes to ensure that all components are uniformly and fully mixed to form a composite slurry that is non-agglomerated and rheologically stable.

[0015] d. Insole molding: The composite slurry prepared in step c is precisely delivered to the insole mold preheated to 60 degrees Celsius (±2 degrees Celsius) by a metering pump. Then, the surface of the slurry is smoothed by a scraper or calendering roller to ensure uniform thickness.

[0016] e. Drying and Curing: The mold filled with slurry is placed in a drying chamber with precise temperature and humidity control. First, it is pre-dried at 50 degrees Celsius (±2 degrees Celsius) and 60% (±5%) relative humidity for 4 hours. Then, the temperature is gradually increased to 70 degrees Celsius (±2 degrees Celsius) and the relative humidity is reduced to 40% (±5%) for 12 hours. Finally, it is naturally air-dried at room temperature (25 degrees Celsius ±2 degrees Celsius) and 50% (±5%) relative humidity for 24 hours to completely remove residual moisture and bring the insole to a stable moisture content.

[0017] f. Post-processing and inspection: After drying and curing, the insoles are removed from the mold, their edges are trimmed, and the finished insoles are subjected to quality tests on multiple indicators such as appearance, size, thickness, hardness, flexibility, tensile strength and adsorption performance.

[0018] The activated carbon deodorizing insole and its preparation method provided by this invention have the following advantages compared with the prior art:

[0019] 1. Highly Efficient and Durable Adsorption Performance: This invention achieves moderate hydrolysis and rearrangement of starch molecular chains through precise control of the gelatinization process of cassava starch under saturated water vapor conditions at 200 degrees Celsius, forming an open three-dimensional gel network structure. This structure effectively encapsulates bamboo charcoal particles while minimizing clogging of the bamboo charcoal micropores, ensuring full utilization of the bamboo charcoal's large specific surface area and abundant pore structure. Compared with traditional synthetic adhesives, the starch matrix of this invention significantly reduces the negative impact on the adsorption performance of activated carbon, resulting in high adsorption efficiency and large adsorption capacity for foot odor molecules in the insole, thus providing a more durable deodorizing effect.

[0020] 2. Excellent Structural Stability and Durability: Under the action of plasticizers, the cassava starch matrix forms a polymer network that combines elasticity and toughness. This network can firmly bind the bamboo charcoal particles, effectively preventing the bamboo charcoal powder from falling off and leaking during use, maintaining the long-lasting odor-resistant function. At the same time, the addition of plasticizers significantly improves the insole material's resistance to bending, compression, and abrasion, enabling the insole to maintain its structural integrity and functionality even under high-intensity foot activity and long-term wear, significantly extending the product's lifespan.

[0021] 3. Significantly Improved Breathability and Comfort: The cassava starch matrix used in this invention, under a specific processing technique, avoids the formation of a dense, non-porous film structure. It, along with the uniformly dispersed bamboo charcoal particles, constitutes a microporous network within the insole material, greatly promoting air circulation and moisture dissipation. This high breathability effectively solves the problems of stuffy feet and excessive sweating associated with traditional synthetic insoles, helping to maintain a dry and comfortable microenvironment for the feet, thereby physically reducing conditions for bacterial growth and odor. The introduction of plasticizers further ensures the insole's softness and cushioning performance, enhancing wearing comfort.

[0022] 4. Environmentally Friendly and Biosafety: All major components of this invention (bamboo charcoal, cassava starch, glycerin, etc.) are derived from natural biomass, exhibiting excellent biodegradability and environmental friendliness. The entire preparation process does not use toxic or harmful chemical adhesives or solvents, has no irritating odor, and poses no risk of skin irritation or allergies, meeting modern consumers' pursuit of green, healthy, and environmentally friendly products. Discarded insoles can naturally degrade, reducing environmental pollution.

[0023] 5. Process Controllability and Production Efficiency: The preparation method proposed in this invention achieves a high degree of standardization and repeatability of the process flow by precisely controlling the particle size of bamboo charcoal, the temperature, pressure, and time of starch gelatinization, as well as the proportions and mixing conditions of each component. High-temperature, high-pressure steam treatment of starch gelatinization is highly efficient, shortening the reaction time, which is beneficial for large-scale production, improving production efficiency, and reducing production costs.

[0024] In summary, through systematic innovation in material selection, component ratio, and preparation process, this invention has successfully constructed a highly efficient, stable, comfortable, and environmentally friendly activated carbon odor-resistant insole. It effectively solves the core technical contradictions faced by existing activated carbon odor-resistant insoles and provides a brand-new solution for the field of functional insoles. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0026] This invention provides an activated carbon odor-resistant insole that, through innovative material composition, precise formulation, and rigorous manufacturing process, effectively resolves the inherent technical contradictions between adsorption performance, structural stability, breathability, and wearing comfort in existing odor-resistant insoles. The overall design of the activated carbon odor-resistant insole of this invention aims to achieve highly efficient adsorption and decomposition of foot odors, while providing excellent foot microenvironment regulation capabilities, structural support, and lasting wearing comfort.

[0027] The activated carbon deodorizing insole of this invention is mainly composed of bamboo charcoal, cassava starch, and a plasticizer. Each component occupies a specific mass proportion in the total solid weight of the insole. Specifically, the bamboo charcoal content is 20%, the cassava starch content is 45%, and the plasticizer content is 15%. The remaining 20% ​​by mass is auxiliary filling material or other functional additives, such as a small amount of natural cellulose fiber to further enhance toughness, or a trace amount of nano-silver ions to enhance the antibacterial effect. The specific amount can be adjusted according to actual needs, but it must be ensured that it does not affect the functionality of the core components. The synergistic effect between the components and their unique physicochemical properties constitute the basis for the superior performance of the insole of this invention.

[0028] The bamboo charcoal, as the core adsorption and antibacterial component of the insole of this invention, is crucial to the performance of the final product due to its preparation process. It is made from carefully selected fast-growing moso bamboo (e.g., diameter between 8cm and 12cm, age 3-5 years), which undergoes pre-drying and high-temperature pyrolysis carbonization. The carbonization process is carried out under a precisely controlled inert gas atmosphere (such as high-purity nitrogen) or vacuum environment, with the initial heating rate controlled at 5-10℃ / min, and the final pyrolysis temperature maintained between 600℃ and 800℃, preferably 700℃, and isothermal pyrolysis at this temperature for 2 to 4 hours. This process ensures the formation of a highly developed and uniformly distributed microporous and mesoporous structure within the bamboo charcoal. The BET specific surface area of ​​the bamboo charcoal used is preferably 800 m², as determined by the nitrogen adsorption-desorption isotherm method (BET method). 2 / g to 1500m 2 / g, which can reach 1200m in one specific implementation. 2 / g. Its total pore volume is preferably 0.4 cm³. 3 / g to 0.8cm 3 The bamboo charcoal has a micropore volume ratio of 60% to 80% and an average pore size of 1.5 nm to 3 nm, ensuring effective capture of small-molecule odor gases such as acetic acid and ammonia. To ensure uniform dispersion of bamboo charcoal in the insole substrate and effective adsorption capacity for odor molecules, while avoiding discomfort due to excessively large particles or easy loss due to excessively small particles, the particle diameter of the bamboo charcoal is preferably in the range of 5 micrometers to 50 micrometers, and is precisely controlled by a laser particle size analyzer. Its cumulative distribution D10 value is not higher than 10 micrometers, the D50 value (median particle size) is preferably 20 micrometers, and the D90 value is not higher than 45 micrometers. This bamboo charcoal efficiently captures and fixes volatile organic compounds (VOCs) emitted from the feet through various physical adsorption mechanisms such as van der Waals forces, hydrogen bonds, and π-π stacking, including but not limited to typical foot odor components such as acetic acid, isovaleric acid, propionic acid, butyric acid, hydrogen sulfide, and ammonia. Furthermore, bamboo charcoal, due to its unique microstructure, abundant negative ion release capacity, and weakly alkaline surface properties (pH value typically between 7.5 and 9.0), can help inhibit the growth and reproduction of bacteria and fungi in the foot environment, thereby reducing odor generation at its source. The porous structure of bamboo charcoal also promotes air circulation and moisture diffusion within the insole, helping to maintain a dry foot microenvironment, further enhancing wearing comfort and inhibiting microbial growth.

[0029] The cassava starch, used as the core bio-based adhesive and matrix material for the insole of this invention, is derived from edible cassava tubers and, after purification, is a white or off-white powder. To ensure that it can form an elastic matrix with a unique microporous network structure after specific treatment, the selected cassava starch preferably has an amylose content of 15% to 25% and an amylopectin content of 75% to 85%. In a preferred embodiment, the amylose content is about 20% and the amylopectin content is about 80%. This ratio provides suitable viscosity and gel strength after starch gelatinization. Its functional conversion as an adhesive is achieved through the following precisely controlled process steps: the cassava starch is precisely mixed with softened and filtered purified water at a mass ratio of 1:3 to 1:5 to form a uniform starch suspension, with a preferred mixing ratio of 1 part cassava starch to 4 parts purified water. This suspension is then transferred to a sealed, high-pressure reactor. Saturated steam at a temperature of 200 degrees Celsius (±5 degrees Celsius) is precisely introduced into the reactor through a high-pressure steam generator. Under this high temperature, the pressure inside the reactor is automatically maintained between 1.5 MPa and 2.0 MPa. This high-temperature, high-pressure steam treatment process preferably lasts for 5 to 15 minutes, and in a preferred embodiment, is precisely controlled for 10 minutes (±1 minute). These extreme gelatinization conditions significantly exceed the conventional starch gelatinization temperature (typically below 100 degrees Celsius), resulting in rapid and complete gelatinization of the cassava starch granules, with their internal semi-crystalline regions rapidly melting. Simultaneously, under the influence of high temperature (200 degrees Celsius) and high shear stress (generated by high-speed steam impact and friction between starch granules), the starch molecular chains, especially amylopectin molecules, undergo moderate mechanical shearing and partial hydrolysis, leading to a narrower molecular weight distribution and increased molecular flexibility. A large amount of amylose molecules dissolve and, together with partially sheared amylopectin, form a highly expanded gel network structure with specific rheological properties (e.g., lower gel viscosity and higher extensibility). This unique molecular conformation and network formation mechanism allows the starch matrix to form a three-dimensional open structure with a certain porosity during subsequent drying and curing, rather than a traditional dense film. This minimizes the encapsulation and blockage of the bamboo charcoal micropores, preserving the adsorption activity of the bamboo charcoal. The cured starch matrix provides excellent mechanical strength and elasticity, ensuring the structural stability of the insole during long-term use and effectively resisting repeated pressure and bending of the foot.

[0030] The plasticizer is used to finely adjust the flexibility and elasticity of the cassava starch matrix, thereby significantly improving the wearing comfort and anti-fatigue performance of the insole. This invention preferentially uses biodegradable, non-toxic polyol compounds with good compatibility with starch. Specifically, the plasticizer is preferably at least one of pharmaceutical-grade glycerol, food-grade sorbitol, or polyethylene glycol (PEG) with a molecular weight range of 200 to 600. Glycerol is a preferred plasticizer due to its good hygroscopicity, biocompatibility, and low toxicity. The plasticizer effectively inserts itself into the starch molecular chain segments by forming numerous hydrogen bonds with the hydroxyl groups in the starch polymer chain. This change in intermolecular interaction weakens the hydrogen bonding between starch molecular chains, increases the free volume of the polymer chains, thereby lowering the glass transition temperature (Tg) of the starch matrix and significantly increasing its segmental mobility and macroscopic flexibility. This endows the insole material with excellent flexibility, extensibility, and elasticity, effectively preventing cracking and breakage caused by material embrittlement during drying or long-term use, significantly improving the insole's durability and wearing comfort. The plasticizer content in the total solid weight of the insole is 15%. This content ratio has been precisely optimized to maintain sufficient toughness in the insole while avoiding excessive plasticization that could lead to a significant decrease in material strength or a sticky surface.

[0031] The preparation method of the activated carbon deodorizing insole described in this invention aims to ensure the full utilization of the performance of each component and achieve high quality in the final product through systematic process control. The preparation steps include:

[0032] The first step is the pretreatment of bamboo charcoal. First, obtain the bamboo charcoal raw material prepared by the above-mentioned high-temperature pyrolysis process. Its initial moisture content may be between 5% and 10%. To ensure the stability of subsequent grinding and mixing with starch paste, precise drying is required. Spread the bamboo charcoal raw material evenly on a stainless steel tray and place it in an oven with forced convection and temperature and humidity control. Drying is carried out at a constant temperature of 105 degrees Celsius (±2 degrees Celsius) for a duration typically of 4 to 8 hours, until its moisture content is below 2% (preferably below 0.5%) as detected by an infrared moisture analyzer or Karl Fischer titration, to avoid agglomeration or energy loss due to moisture during grinding and to improve grinding efficiency. Subsequently, the dried bamboo charcoal is ultrafinely ground using a vibratory mill or an air jet mill. An air jet mill system under nitrogen protection is preferred to avoid oxidation of the bamboo charcoal due to high temperatures generated by friction during grinding and to precisely control the airflow speed and feed rate in the grinding chamber. During the grinding process, real-time monitoring is performed using an online laser particle size analyzer to ensure that the particle size distribution is between 5 and 50 micrometers, with a median particle size (D50) preferably of 20 micrometers and a D90 value not exceeding 45 micrometers, ensuring uniform fineness. The ground bamboo charcoal powder should maintain a stable specific surface area and pore structure and be stored in a sealed container filled with dry nitrogen to prevent re-hygroscopicity and oxidation, thus ensuring its activity.

[0033] The second step is the preparation of the cassava starch paste. Food-grade cassava starch that has passed quality testing is mixed with purified water that meets drinking water standards (preferably deionized water treated by reverse osmosis with a conductivity of less than 5 μS / cm) at a precise mass ratio of 1:4 (i.e., 1 part cassava starch to 4 parts water) in a stainless steel high-pressure mixing vessel equipped with an anchor-type or paddle-type stirrer. The mixing device is started and stirred at 150 rpm (±10 rpm) for 15 to 20 minutes to ensure the starch powder is fully dispersed in the water, forming a uniform suspension without significant agglomeration. The mixing vessel is then closed and tightly sealed, and all sealing points are checked for leaks. Saturated steam at a temperature precisely controlled at 200 degrees Celsius (±5 degrees Celsius) is injected into the jacket of the mixing vessel and / or directly into the vessel using a high-pressure steam generator. The steam injection rate needs to be precisely controlled so that the pressure inside the vessel rises slowly over 5 minutes and is maintained between 1.5 MPa and 2.0 MPa, preferably 1.8 MPa. Maintain this high-temperature, high-pressure steam treatment condition for 10 minutes (±1 minute). During this process, the cassava starch granules undergo rapid and thorough gelatinization, accompanied by moderate molecular chain hydrolysis and rearrangement, forming a transparent or translucent viscous starch paste with specific rheological properties. This process is monitored in real time using an online viscometer and temperature and pressure sensors. After treatment, the pressure inside the vessel is slowly released at a controlled rate (e.g., 0.2 MPa per minute) through a high-pressure relief valve. Once the pressure returns to atmospheric pressure and the starch paste has cooled to approximately 70 degrees Celsius, it is transferred to the cooling and mixing vessel for the next step.

[0034] The third step is the mixing of the plasticizer. The starch paste prepared in the second step, at approximately 70 degrees Celsius, is transferred to a cooling vessel equipped with a stirring function and a jacketed cooling system. Under continuous stirring (preferably at a speed of 80 rpm ± 5 rpm), the pre-treated bamboo charcoal powder from the first step and the pre-weighed plasticizer (e.g., food-grade glycerin, with a purity higher than 99.5%) are slowly and uniformly added. The amount of glycerin added is 15% of the total solid weight of the insole, and the amount of bamboo charcoal powder added is 20% of the total solid weight of the insole. The addition process must be carried out under vacuum or inert gas protection to avoid air ingress that could cause bubbles. Stirring continues for 30 to 60 minutes to ensure uniform and thorough mixing of the bamboo charcoal powder, plasticizer, and starch paste, forming a composite slurry that is free of agglomeration, rheologically stable, and free of obvious bubbles. This mixing process requires precise control of the stirring shear force. A planetary mixer or a mixer with a scraper is preferred to avoid excessive shearing that could damage the molecular network structure of the starch. Simultaneously, it ensures that the bamboo charcoal particles are evenly dispersed in the slurry, minimizing the risk of their pores being completely encapsulated and blocked by starch. The temperature during mixing is controlled between 40 and 50 degrees Celsius using a cooling jacket to maintain the appropriate viscosity of the slurry and prevent premature retrogradation of the starch paste.

[0035] Step four, insole molding. The composite slurry prepared in step three is precisely delivered via a metering pump (e.g., a peristaltic pump or screw pump, suitable for high-viscosity fluids) into an insole mold preheated to 60 degrees Celsius (±2 degrees Celsius). The mold is made of high-temperature resistant silicone or aluminum alloy with a polytetrafluoroethylene (PTFE) coating, and has the precise geometry and texture of the insole. Mold preheating helps improve the flowability and surface smoothness of the slurry. After slurry injection, the surface of the slurry is smoothed using a precision scraper or calendering roller system to ensure uniform distribution of the slurry within the mold, with thickness consistency controlled within ±0.2 mm. For molds with complex arch support or heel cups, vacuum-assisted molding can be used to ensure that the slurry fully fills every detail of the mold and eliminates internal air bubbles.

[0036] Step 5: Drying and Curing. The mold filled with slurry is placed into a drying chamber with precise temperature and humidity control. The entire drying and curing process is divided into three stages to achieve uniform removal of moisture from the material and stable curing of the starch matrix:

[0037] First, pre-drying is carried out at 50°C (±2°C) and 60% (±5%) relative humidity for 4 to 6 hours. This stage aims to slowly remove free water from the composite material, preventing the surface from drying too quickly and forming a hard shell that would hinder internal moisture diffusion or cause internal stress cracking due to inconsistent drying rates. Airflow speed is controlled between 0.5 m / s and 1.0 m / s to ensure uniform drying.

[0038] Subsequently, the temperature was gradually increased to 70 degrees Celsius (±2 degrees Celsius), and the relative humidity was reduced to 40% (±5%) for 12 to 16 hours. This stage accelerates moisture removal and promotes further cross-linking and solidification of the starch molecular network under the synergistic effect of the plasticizer, forming a stable three-dimensional structure. The glass transition temperature of the starch matrix is ​​above this stage, ensuring sufficient movement and rearrangement of molecular chain segments.

[0039] Finally, the insoles are allowed to air dry or undergo humidification treatment for 24 to 48 hours at room temperature (25°C ± 2°C) and relative humidity of 50% (± 5%). This stage aims to thoroughly remove residual moisture, allowing the insoles to reach a stable equilibrium moisture content (preferably 8% to 12%), preventing deformation due to changes in ambient humidity during use. Throughout the drying and curing process, the degree of drying is precisely controlled by continuously monitoring the weight changes of the insoles, ensuring that the starch molecular network firmly anchors the bamboo charcoal particles while maintaining the material's permeability at both the macroscopic and microscopic levels.

[0040] Step 6: Post-processing and Inspection. After drying and curing, the insole is removed from the mold, and its edges are precisely trimmed to remove any burrs or flash. This step can be done using automated punching equipment or a laser cutting machine to ensure dimensional accuracy and edge smoothness. The finished insole undergoes multiple quality tests to ensure that the product meets design requirements and performance standards.

[0041] Visual inspection: Check the surface flatness, color uniformity, and for the presence of cracks, bubbles, or foreign objects.

[0042] Dimensional accuracy: Use digital calipers or a coordinate measuring machine to measure the length, width and thickness of the insole to ensure that it is consistent with the mold design dimensions, with a deviation within ±1mm.

[0043] Hardness testing: The hardness of different areas of the insole is measured using a Shore A hardness tester (according to ASTM D2240 standard), with a preferred range of 25 to 35 to ensure appropriate softness and support.

[0044] Flexibility and fatigue resistance: A flexural fatigue testing machine is used to simulate the bending of the foot during daily movement. Cyclic tests are conducted at a specific bending radius, requiring the insole to show no obvious cracks or structural damage after 100,000 bends.

[0045] Tensile strength and elongation at break: The tensile strength and elongation at break of the insole material were measured using a universal testing machine (according to ASTM D412) to ensure that it has sufficient mechanical strength and toughness.

[0046] Adsorption performance test:

[0047] Adsorption rate of acetic acid: A certain mass of insole sample was placed in a sealed container, and acetic acid gas of known concentration was injected. The container was allowed to stand for 2 hours at constant temperature and humidity. The residual acetic acid concentration was measured by gas chromatography-mass spectrometry (GC-MS), and the adsorption rate was calculated. An adsorption rate higher than 80% is preferred.

[0048] Adsorption rate for ammonia: Using a similar method, ammonia is used as the test gas. The ammonia concentration is measured by a semiconductor gas sensor or ion chromatography, and the adsorption rate is calculated. An adsorption rate higher than 80% is preferred.

[0049] Breathability testing: Using a fabric breathability tester (e.g., according to ASTM D737), the airflow rate of the insole material under a specific pressure differential is measured to evaluate its breathability. A preferred breathability index should be higher than 0.5 L / (m²). 2 ·s)@100Pa.

[0050] Water vapor transmission rate: Tested according to ISO 15496 or similar standards to ensure that the insole can effectively dissipate moisture from the feet.

[0051] All test indicators must meet the preset standards to be considered a qualified product, and then it will be individually packaged for moisture and dust protection.

[0052] Example 1: Preparation and performance testing of the activated carbon deodorizing insole of the present invention

[0053] In this embodiment, activated carbon odor-resistant insoles are prepared according to the preferred method and parameters described in this invention.

[0054] 1. Pretreatment of bamboo charcoal:

[0055] Bamboo charcoal powder with a D50 of 20 microns was selected. The bamboo charcoal powder was placed in a forced convection oven and dried at 105℃ for 6 hours until the moisture content dropped to 0.4%. The dried bamboo charcoal powder was then stored for later use.

[0056] 2. Preparation of cassava starch paste:

[0057] Accurately weigh 1000g of food-grade tapioca starch with an amylose content of 20% and an amylopectin content of 80%, and mix it with 4000g of deionized water (mass ratio 1:4). Add the mixture to a 5L stainless steel autoclave and stir at 150rpm for 20 minutes to form a homogeneous suspension. Seal the autoclave and inject 200℃ saturated steam through a steam generator, raising the pressure inside the autoclave to 1.8MPa within 5 minutes. Maintain this high-temperature and high-pressure condition for 10 minutes. Then, slowly depressurize at a rate of 0.2MPa / min until the temperature inside the autoclave drops to approximately 70℃, and remove the starch paste. The resulting starch paste is translucent and viscous with moderate viscosity and good rheological properties.

[0058] 3. Mixing of plasticizers:

[0059] The starch paste, heated to approximately 70°C, was transferred to a planetary mixer with a cooling jacket. At a mixing speed of 80 rpm, 200 g (15% of total solids weight) of pharmaceutical-grade glycerin and 266.7 g (20% of total solids weight) of pretreated bamboo charcoal powder were slowly added. The mixture was stirred for 30 minutes, while the jacket temperature was maintained at 45°C to ensure uniform mixing of all components, forming a cohesive slurry free of agglomerates and bubbles.

[0060] 4. Insole molding:

[0061] The composite slurry is pumped via a screw pump into a PTFE-coated aluminum alloy mold preheated to 60°C. An automated scraper system is used to smooth the slurry surface, ensuring the insole thickness is 3.5mm.

[0062] 5. Drying and curing:

[0063] Place the mold into a temperature and humidity controlled drying chamber:

[0064] Pre-drying: 50℃, 60% relative humidity, for 5 hours.

[0065] Main drying: 70℃, relative humidity 40%, for 14 hours.

[0066] Natural air drying: 25℃, 50% relative humidity, for 24 hours.

[0067] After drying and curing, the moisture content of the insole stabilizes at 10.5%.

[0068] 6. Post-processing and inspection:

[0069] The insoles are removed and trimmed using automated punching equipment. Performance testing is performed on the finished insoles, and the results are as follows:

[0070] Appearance: Smooth surface, no cracks, uniform color.

[0071] Size: Designed to conform to standard shoe sizes, with uniform thickness.

[0072] Shore A hardness: 30.

[0073] Bending fatigue cycles: Over 150,000 cycles, with no obvious damage.

[0074] Tensile strength: 5.2 MPa.

[0075] Elongation at break: 180%.

[0076] Acetic acid adsorption rate: 92%.

[0077] Ammonia adsorption rate: 88%.

[0078] Breathability: 0.75L / (m 2 ·s)@100Pa.

[0079] Water vapor transmission rate: 1500g / (m 2 •24h).

[0080] Comparative Example 1: Traditional low-temperature starch gelatinization and activated carbon odor-resistant insoles with low plasticizer content

[0081] In this comparative example, the preparation conditions of cassava starch paste and the content of plasticizer were changed to simulate the traditional or suboptimal process.

[0082] 1. Pretreatment of bamboo charcoal:

[0083] Similar to Example 1, bamboo charcoal powder with a D50 of 20 micrometers was selected and dried to a moisture content of 0.4%.

[0084] 2. Preparation of cassava starch paste:

[0085] Accurately weigh 1000g of tapioca starch (20% amylose content) and mix with 4000g of deionized water. Add the mixture to a 5L stainless steel mixing vessel and stir at 150rpm for 20 minutes. Seal the vessel and heat it to 90°C using a jacket, maintaining this temperature at atmospheric pressure for 30 minutes. The resulting starch paste will have high viscosity, low transparency, and may contain incompletely gelatinized particles.

[0086] 3. Mixing of plasticizers:

[0087] The starch paste, heated to approximately 90°C, was transferred to a mixer. While mixing at 80 rpm, 66.7 g (5% of total solids weight) of pharmaceutical-grade glycerin and 266.7 g (20% of total solids weight) of bamboo charcoal powder were slowly added. The mixture was stirred for 45 minutes. The slurry became viscous, and the bamboo charcoal dispersion was slightly uneven, with a small amount of agglomeration.

[0088] 4. Insole molding:

[0089] Similar to Example 1, the slurry has a higher viscosity and slightly poorer fluidity, resulting in a slightly uneven surface after molding.

[0090] 5. Drying and curing:

[0091] The drying curve is the same as in Example 1. After drying and curing, the moisture content of the insole stabilizes at 11%.

[0092] 6. Post-processing and inspection:

[0093] Remove the insoles and trim the edges. Perform performance testing on the finished insoles; the results are as follows:

[0094] Appearance: The surface is slightly rough with a few tiny cracks.

[0095] Size: Basically meets the design, but the thickness uniformity is slightly poor.

[0096] Shore A hardness: 45.

[0097] Bending fatigue cycles: Obvious cracks appear after approximately 30,000 cycles.

[0098] Tensile strength: 4.0 MPa.

[0099] Elongation at break: 110%.

[0100] Acetic acid adsorption rate: 65%.

[0101] Ammonia adsorption rate: 60%.

[0102] Breathability: 0.35L / (m 2 ·s)@100Pa.

[0103] Water vapor transmission rate: 950 g / (m 2•24h).

[0104] Performance Comparison Data Table

[0105] The table below compares the performance test results of Example 1 (the present invention) and Comparative Example 1 (conventional low-temperature gelatinization and low plasticizer content) to quantify the technical advantages of the present invention in several key indicators.

[0106]

[0107] The data comparison above shows that the cassava starch matrix prepared by the specific high-temperature and high-pressure steam treatment process proposed in this invention, combined with optimized plasticizer content and bamboo charcoal ratio, significantly improves the adsorption performance, structural stability, durability, softness, and breathability of the insole. The insole of Example 1 shows approximately 41% and 47% higher adsorption rates for acetic acid and ammonia, respectively, compared to Comparative Example 1, directly demonstrating the superior effect of the process of this invention in maximizing the adsorption activity of bamboo charcoal. Furthermore, its lower Shore A hardness (30 vs. 45) indicates better softness, while the higher flexural fatigue cycles (>150,000 vs. ~30,000) undeniably demonstrate its superior durability. The significant improvement in breathability and water vapor permeability further confirms the success of this invention in constructing a porous open structure and optimizing the foot microenvironment. These quantitative data fully demonstrate the innovation, practicality, and superiority of the activated carbon anti-odor insole of this invention in solving existing technical problems.

[0108] The activated carbon deodorizing insole disclosed in this invention has a structure that, macroscopically, conforms to the ergonomic curve of the foot, as shown in the attached figure. Figure 1 As shown, it typically includes an arch support area, a heel cup area, and a forefoot area. The entire insole material is integrally molded from a composite material of bamboo charcoal, tapioca starch matrix, and plasticizer. This integrally molded structure forms a uniformly distributed network of micropores and mesopores at the microscopic level, which not only gives the insole excellent odor-resistant properties but also ensures its structural stability and comfort under long-term wear and repeated stress. To further enhance the insole's abrasion resistance, the upper and lower surfaces of the insole can be pressed with fine textures to increase friction with the shoe insole and foot, preventing slippage. Simultaneously, the textured design also helps improve airflow. During the manufacturing process, the mold can be adjusted according to different shoe sizes to meet the needs of different consumers. The edges of the insole are precisely cut to form a rounded transition, avoiding abrasion to the foot or socks.

[0109] In summary, this invention, through systematic optimization of the component composition, proportions, and preparation process of activated carbon deodorizing insoles, successfully overcomes key technical challenges in existing technologies, such as micropore clogging of activated carbon, poor breathability, and insufficient comfort. The use of bio-based materials and an environmentally friendly preparation process also ensures that the product meets the modern demands of sustainable development and green manufacturing, providing a new, efficient, stable, comfortable, and environmentally friendly solution for the field of functional insoles. Those skilled in the art can make various modifications and variations to the above embodiments based on the detailed description above, without departing from the spirit and scope of this invention.

Claims

1. An activated carbon deodorizing insole, characterized in that, The insole body is composed of the following components: a. Bamboo charcoal, comprising 20% ​​of the total solid weight of the insole, wherein the bamboo charcoal is prepared by high-temperature pyrolysis of selected bamboo materials in an oxygen-free or low-oxygen environment at 600°C to 800°C, forming a carbonaceous material with a highly developed microporous and mesoporous structure, wherein the bamboo charcoal is used to efficiently remove volatile organic compounds from the feet through the principle of physical adsorption. b. Cassava starch, comprising 45% of the total solid weight of the insole, wherein the cassava starch, as a bio-based adhesive and matrix material for the insole, is derived from edible cassava tubers and has an amylose content of 15% to 25% and an amylopectin content of 75% to 85%; the cassava starch undergoes a specific gelatinization treatment, specifically: the cassava starch is mixed with purified water at a mass ratio of 1:3 to 1:5 to form a starch suspension, and then the starch suspension is heated in a closed high-pressure steam environment by introducing saturated steam at a temperature of 200 degrees Celsius (±5 degrees Celsius) for 5 to 15 minutes to promote complete gelatinization and partial hydrolysis of the cassava starch particles, forming an elastic gel network structure with porosity. This structure provides excellent mechanical strength and elasticity after curing, while minimizing clogging of the bamboo charcoal micropores; c. A plasticizer comprising 15% of the total solid weight of the insole, the plasticizer being used to adjust the flexibility and elasticity of the cassava starch matrix to improve the wearing comfort and fatigue resistance of the insole.

2. The activated carbon deodorizing insole according to claim 1, characterized in that: The preferred preparation process for the bamboo charcoal involves isothermal pyrolysis at 700 degrees Celsius for 2 to 4 hours to ensure the formation of a highly developed and uniformly distributed microporous and mesoporous structure within it; the BET specific surface area of ​​the bamboo charcoal is 800 m². 2 / g to 1500m 2 / g, preferably 1200m 2 / g; the total pore volume of the bamboo charcoal is 0.4cm³. 3 / g to 0.8cm 3 / g, wherein the micropore volume ratio is 60% to 80%, and the average pore size is 1.5nm to 3nm; the particle diameter of the bamboo charcoal is in the range of 5 micrometers to 50 micrometers, the median particle size (D50) is preferably 20 micrometers, and the cumulative distribution D90 value is not higher than 45 micrometers; the bamboo charcoal efficiently captures and fixes volatile organic compounds emitted from the feet through physical adsorption mechanisms such as van der Waals forces, hydrogen bonds, and π-π stacking, including but not limited to typical foot odor components such as acetic acid, isovaleric acid, propionic acid, butyric acid, hydrogen sulfide, and ammonia; in addition, the weakly alkaline surface of the bamboo charcoal (pH value between 7.5 and 9.0) has the effect of inhibiting the growth of bacteria and fungi. The preferred mass ratio of cassava starch to purified water is 1:

4. The preferred precise duration of the heat treatment is 10 minutes (±1 minute). The pressure in the closed high-pressure steam environment is automatically maintained between 1.5 MPa and 2.0 MPa, preferably 1.8 MPa. The extreme gelatinization conditions cause moderate shearing and rearrangement of the starch molecular chains, and the resulting gel network structure has a certain porosity after solidification, thereby maintaining the adsorption activity of bamboo charcoal and giving the insole material excellent mechanical strength and elasticity, ensuring the structural stability of the insole during long-term use. The plasticizer is preferably a biodegradable, non-toxic polyol compound with good compatibility with starch, specifically including at least one of glycerol, sorbitol, or polyethylene glycol with a molecular weight range of 200 to 600. The plasticizer inserts into the starch molecules by forming hydrogen bonds with the starch polymer chain, reducing the interaction force between starch molecules, increasing the free volume of the polymer chain, thereby lowering the glass transition temperature of the starch matrix, increasing the mobility of its chain segments, and giving the insole material excellent flexibility, extensibility, and elasticity. This effectively prevents the insole from cracking and breaking due to material embrittlement, and significantly improves the durability and wearing comfort of the insole.

3. A method for preparing activated carbon deodorizing insoles, characterized in that, Includes the following steps: a. Pretreatment of bamboo charcoal: The raw bamboo charcoal is dried at 105 degrees Celsius (±2 degrees Celsius) until its moisture content is less than 2%. Then it is ultra-finely ground by a vibratory mill or air jet mill to ensure that its particle size distribution is between 5 micrometers and 50 micrometers. The ground bamboo charcoal powder is stored in a sealed container. b. Preparation of cassava starch paste: Cassava starch and purified water are mixed at a mass ratio of 1:3 to 1:5 to form a uniform starch suspension, which is then added to a high-pressure mixing vessel. Saturated steam at 200°C (±5°C) is then injected into the mixing vessel through a high-pressure steam generator to maintain the pressure inside the vessel between 1.5 MPa and 2.0 MPa. This high-temperature, high-pressure steam treatment condition is maintained for 5 to 15 minutes to promote complete gelatinization and partial hydrolysis of the cassava starch granules, forming a viscous starch paste. After the treatment is completed, the pressure inside the vessel is slowly released through a pressure relief valve. c. Mixing of plasticizer: Transfer the starch paste prepared in step b to a cooling kettle with a stirring function. Under continuous stirring, slowly add the bamboo charcoal powder pretreated in step a and the pre-weighed plasticizer. The amount of bamboo charcoal powder added to the starch paste is 20% of the total weight of the insole solids, and the amount of plasticizer added is 15% of the total weight of the insole solids. Continue stirring for 30 to 60 minutes to ensure that all components are uniformly and fully mixed to form a composite slurry that is non-agglomerated and rheologically stable. d. Insole molding: The composite slurry prepared in step c is precisely delivered to the insole mold preheated to 60 degrees Celsius (±2 degrees Celsius) by a metering pump. Then, the surface of the slurry is smoothed by a scraper or calendering roller to ensure uniform thickness. e. Drying and Curing: The mold filled with slurry is placed in a drying chamber with precise temperature and humidity control. First, it is pre-dried at 50 degrees Celsius (±2 degrees Celsius) and 60% (±5%) relative humidity for 4 hours. Then, the temperature is gradually increased to 70 degrees Celsius (±2 degrees Celsius) and the relative humidity is reduced to 40% (±5%) for 12 hours. Finally, it is naturally air-dried at room temperature (25 degrees Celsius ±2 degrees Celsius) and 50% (±5%) relative humidity for 24 hours to completely remove residual moisture and bring the insole to a stable moisture content. f. Post-processing and inspection: After drying and curing, the insoles are removed from the mold, their edges are trimmed, and the finished insoles are subjected to quality tests on multiple indicators such as appearance, size, thickness, hardness, flexibility, tensile strength and adsorption performance.

4. The method for preparing activated carbon deodorizing insoles according to claim 3, characterized in that: In step a, the drying treatment of the bamboo charcoal raw material is preferably carried out for 4 to 8 hours until its moisture content is less than 0.5%; the ultrafine grinding is preferably carried out using an air jet mill system under nitrogen protection, and is monitored in real time by an online laser particle size analyzer to ensure that the median particle size (D50) of the bamboo charcoal is preferably 20 micrometers and the D90 value is not higher than 45 micrometers. In step b, the preferred mixing ratio of cassava starch to purified water is 1:4, the mixing speed is 150 rpm (±10 rpm), and the mixing time is 15 to 20 minutes. The pressure inside the high-pressure mixing vessel is preferably maintained at 1.8 MPa, and the high-temperature and high-pressure steam treatment conditions are preferably maintained for 10 minutes (±1 minute). After the treatment is completed, the pressure inside the vessel is slowly released at a rate of 0.2 MPa per minute through the pressure relief valve, and the starch paste is transferred to a cooling vessel when it cools to about 70 degrees Celsius. In step c, the stirring speed of the starch paste in the cooling kettle is preferably 80 rpm (±5 rpm), and the plasticizer is preferably food-grade glycerin with a purity higher than 99.5%. The addition of bamboo charcoal powder and plasticizer is preferably carried out under vacuum or inert gas protection to avoid air mixing. The temperature during the stirring process is controlled between 40 degrees Celsius and 50 degrees Celsius by the cooling jacket to maintain the appropriate viscosity of the slurry and prevent the starch paste from retrograding prematurely. In step e, the pre-drying stage lasts for 4 to 6 hours, with the air circulation speed controlled at 0.5 m / s to 1.0 m / s; the main drying stage lasts for 12 to 16 hours; and the natural air drying stage lasts for 24 to 48 hours to allow the insole to reach a stable moisture content of 8% to 12%. Throughout the drying and curing process, the degree of drying is precisely controlled by continuously monitoring the weight change of the insole. In step f, the quality inspection includes, but is not limited to: Shore A hardness (preferably 25 to 35), bending fatigue test (requiring no obvious cracks or structural damage after 100,000 bending cycles), tensile strength, elongation at break, adsorption rate of acetic acid (preferably higher than 80%), adsorption rate of ammonia (preferably higher than 80%), and air permeability (preferably higher than 0.5 L / (m³)). 2 •s)@100Pa) and water vapor transmission rate.

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