Medical skin-friendly sponge and preparation method thereof

Abstract

The invention relates to the field of sponges, and discloses a medical skin-friendly sponge and a preparation method thereof.The medical skin-friendly sponge is prepared from, by weight, 100 parts of composite polyether polyol, 42-48 parts of 4, 4 '-dicyclohexylmethane diisocyanate, 10.5-21.5 parts of a composite skin-friendly modifier, 3-5 parts of an antibacterial agent, 4-6 parts of deionized water and 0.2-0.5 part of a catalyst. And 0.4 to 0.8 part of a surface active agent. The composite skin-friendly modifier is prepared from 10 to 20 parts of polyethylene glycol and 0.5 to 1.5 parts of hyaluronic acid; the composite polyether polyol is composed of polyether triol and polyether glycol according to a mass ratio of 1: (3-5). Through a multi-component synergistic raw material system and multi-performance accurate regulation and control, the synergistic standard reaching of low hardness, fine surface, high water absorption and water retention and strong antibacterial property of the medical skin-friendly sponge is realized, the medical skin-friendly sponge can be widely adapted to various medical scenes, and technical upgrading of the field of medical sponges is promoted.

Description

Technical Field

[0001] This invention relates to the field of sponges, and in particular to a medical-grade skin-friendly sponge and its preparation method. Background Technology

[0002] In medical and skin-friendly applications, sponges need to meet both functional and safety requirements, which can be broken down into the following four key performance indicators: 1. Low hardness and smooth surface: Medical sponges often come into contact with sensitive wounds or fragile skin (such as the skin of the elderly, infants, and patients who are bedridden for a long time). They need to have a lower indentation hardness than ordinary sponges (usually requiring 25% indentation hardness ≤8kPa, while ordinary medical sponges are mostly 12-20kPa) to avoid compressing the wound or causing skin indentations. At the same time, the surface should be free of burrs and particles to prevent friction from causing skin damage or secondary damage to the wound.

[0003] 2. High water absorption and retention: For wound care scenarios, the sponge needs to quickly absorb wound exudate and retain moisture for a long time, which can prevent the exudate from accumulating and causing wound maceration, and maintain a moist environment for the wound to promote epithelial cell regeneration. 3. High breathability and moisture permeability: If a sponge in prolonged contact with the skin has poor breathability and moisture permeability, it can lead to increased skin surface temperature, sweat buildup, causing stuffiness and even skin maceration, increasing the risk of fungal infections. Generally, a sponge is required to have a water vapor transmission rate of ≥400g / (m³) at 1kPa pressure. 2 (24h), and air permeability ≥100mL / (cm³) 2 min).

[0004] 4. Strong antibacterial and bacteriostatic properties: Medical sponges must have initial sterility and continuous antibacterial ability. The initial colony count must meet the sterility standards for medical devices. At the same time, the 24-hour antibacterial rate against common pathogens such as Escherichia coli, Staphylococcus aureus, and Candida albicans must be ≥99% to avoid wound infection or cross-contamination.

[0005] However, most medical sponge products currently on the market focus on optimizing a single performance aspect, making it difficult to achieve synergistic compliance across multiple performance levels. This is mainly due to the following technical shortcomings: Firstly, existing technologies often use high-functionality polyether polyols (such as functionality ≥4) or high isocyanate index (NCO / OH ≥1.2) to improve sponge strength, resulting in excessively high polyurethane crosslinking density and indentation hardness generally exceeding 12kPa, which cannot meet the needs of sensitive skin. If the crosslinking density is reduced (such as by using low-functionality polyether), the mechanical properties of the sponge will decrease, making it easy to break and unable to withstand the slight tearing during wound care.

[0006] Secondly, to improve water absorption, existing technologies often increase the pore size (e.g., >300μm) or add hydrophilic fillers (e.g., starch, cellulose). However, excessively large pores result in poor water retention (24h water retention rate ≤60%), and hydrophilic fillers are prone to swelling and agglomeration, clogging the pore channels and reducing air permeability (water vapor transmission rate ≤300g / (m³)). 2 If a small pore structure (<50μm) is used, the water absorption speed is slow (>30s), and it cannot absorb the wound exudate in time.

[0007] Third, most existing antibacterial sponges use the method of directly adding nano-silver particles, but silver particles are prone to agglomeration, resulting in uneven antibacterial activity (local antibacterial rate <90%). Some products use quaternary ammonium salt antibacterial agents, which have good dispersibility, but long-term contact with the skin can easily cause allergies (sensitization rate ≥5%). In addition, most products rely solely on post-production sterilization treatment (such as EO sterilization), lacking sustained antibacterial ability. After 72 hours of use, the antibacterial rate drops to below 50%, which cannot meet the needs of long-term care.

[0008] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide a medical skin-friendly sponge and its preparation method, aiming to solve the problem that existing medical skin-friendly sponges are difficult to optimize in a synergistic way in terms of hardness control, surface fineness, water absorption and retention, air permeability and moisture permeability and antibacterial properties.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A medical-grade skin-friendly sponge, comprising 100 parts of a composite polyether polyol, 42-48 parts of 4,4'-dicyclohexylmethane diisocyanate, 10.5-21.5 parts of a composite skin-friendly modifier, 3-5 parts of an antibacterial agent, 4-6 parts of deionized water, 0.2-0.5 parts of a catalyst, and 0.4-0.8 parts of a surfactant; wherein the composite skin-friendly modifier is composed of 10-20 parts of polyethylene glycol and 0.5-1.5 parts of hyaluronic acid; and wherein the composite polyether polyol is composed of polyether triol and polyether diol in a mass ratio of 1:3-5.

[0011] The medical-grade skin-friendly sponge, wherein the antibacterial agent is composed of 1-2 parts of silver ion antibacterial agent and 2-3 parts of chitosan.

[0012] The aforementioned medical-grade skin-friendly sponge, wherein the polyether triol is obtained by copolymerization of glycerol, ethylene oxide, and propylene oxide, wherein the ethylene oxide accounts for 10-25% by mass.

[0013] The medical-grade skin-friendly sponge, wherein the number-average molecular weight of the polyethylene glycol is 400-1000.

[0014] The medical-grade skin-friendly sponge, wherein the catalyst is dibutyltin dilaurate or triethylenediamine.

[0015] A method for preparing a medical skin-friendly sponge as described in this invention, comprising the following steps: Add composite polyether polyol, polyethylene glycol and deionized water to a sterile mixing tank, and stir at 500-800 rpm for 5-10 minutes to obtain the first mixture. Add a catalyst and a surfactant to the first mixture and stir at 1000-1200 rpm for 3-5 minutes to obtain a second mixture; First, add antibacterial agent and hyaluronic acid to the second mixture, then add 4,4'-dicyclohexylmethane diisocyanate, and stir at 1500-2000 rpm for 1-2 minutes to obtain the third mixture; The third mixture is rapidly injected into a preheated sterile mold for compression molding and foaming. After foaming, the sterile mold is transferred to the curing room and cured for 24-48 hours at a temperature of 50-60℃ and a relative humidity of 40-50%. After curing, the mold is removed and the initial sponge is taken out. The initial sponge is cut, cleaned, dried and sterilized to obtain the medical skin-friendly sponge.

[0016] The method for preparing the medical skin-friendly sponge includes the step of rapidly injecting the third mixture into a preheated sterile mold for molding and foaming treatment. The preheating temperature of the sterile mold is 35-40℃, the pressure of the molding and foaming treatment is 0.1-0.2MPa, and the holding time is 8-12min.

[0017] The method for preparing the medical skin-friendly sponge includes the following steps: cutting, washing, drying, and sterilizing the initial sponge. The initial sponge was cut using a CNC laser cutting machine, and then the cut surfaces of the initial sponge were polished with sterile sandpaper. Place the cut and polished sponge into a sterile cleaning tank, add purified water, and turn on ultrasonic cleaning for 15-20 minutes. The ultrasonic frequency is 40kHz and the power is 500-800W. After ultrasonic cleaning, rinse with pure water. The cleaned sponge was transferred to a sterile drying oven for vacuum drying to obtain a dry sponge with a moisture content of <1%. The dried sponge is subjected to EO sterilization or gamma ray irradiation sterilization treatment.

[0018] The method for preparing the medical skin-friendly sponge includes a step in which the cleaned sponge is transferred to a sterile drying oven for vacuum drying. The temperature is 50-60℃, the vacuum degree is -0.095MPa to -0.1MPa, and the processing time is 2-3 hours.

[0019] The method for preparing the medical skin-friendly sponge includes the following steps: In the step of sterilizing the dried sponge with EO, the EO concentration is 400-800 mg / L; the temperature is 30-50℃; the relative humidity is 40-60%; and the sterilization time is 4-6 h. In the step of sterilizing the dried sponge with gamma ray irradiation, the gamma ray irradiation dose is 25-30 kGy; and the irradiation time is 1-2 h.

[0020] Beneficial effects: This invention provides a medical skin-friendly sponge and its preparation method. Through a multi-component synergistic raw material system and precise control of multiple properties, it solves the well-known problems of single performance, disconnected processes, and irreconcilable contradictions in the prior art. This invention achieves synergistic compliance of medical skin-friendly sponge with low hardness, delicate surface, high water absorption and retention, and strong antibacterial properties. It can be widely adapted to various medical scenarios and promotes the technological upgrading of the medical sponge field. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for preparing a medical skin-friendly sponge according to the present invention.

[0022] Figure 2 This is a product image of the medical skin-friendly sponge prepared in Example 1 of the present invention. Detailed Implementation

[0023] This invention provides a medical-grade skin-friendly sponge and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following embodiments are provided to further illustrate the invention in detail. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0024] Existing medical-grade skin-friendly sponges often focus on optimizing a single performance aspect (such as improving only antibacterial properties or absorbency), failing to achieve the synergistic goal of "low hardness - smooth surface - high absorbency and water retention - strong antibacterial properties." For example, using low-functionality polyethers to reduce hardness results in poor mechanical properties and easy breakage; adding starch-based hydrophilic fillers to improve absorbency leads to clogged pores and reduced breathability; directly mixing nano-silver to achieve antibacterial properties results in silver ion aggregation, uneven antibacterial effects, and a high risk of sensitization. In other words, there is an inherent contradiction between low hardness and mechanical strength, high absorbency and high breathability, and strong antibacterial properties and skin-friendliness in existing technologies. These technical bottlenecks are well-known and long-standing problems in the field of medical sponges.

[0025] Based on this, the present invention provides a medical skin-friendly sponge, wherein the medical skin-friendly sponge comprises the following components by weight: 100 parts of composite polyether polyol, 42-48 parts of 4,4'-dicyclohexylmethane diisocyanate, 10.5-21.5 parts of composite skin-friendly modifier, 3-5 parts of antibacterial agent, 4-6 parts of deionized water, 0.2-0.5 parts of catalyst, and 0.4-0.8 parts of surfactant; the composite skin-friendly modifier is composed of 10-20 parts of polyethylene glycol and 0.5-1.5 parts of hyaluronic acid; the antibacterial agent is composed of 1-2 parts of silver ion antibacterial agent and 2-3 parts of chitosan; the composite polyether polyol is composed of polyether triol and polyether diol in a mass ratio of 1:3-5.

[0026] This invention employs a composite system of polyether polyol (matrix), polyethylene glycol (PEG), hyaluronic acid (HA), silver ions, chitosan (antibacterial agent), and medical adjuvants. Through the synergistic effect of each component at the molecular level, it simultaneously addresses multiple performance requirements. A detailed analysis is shown below: In this invention, the performance of the polyurethane sponge is determined by the synergistic effect of the soft and hard segments. The soft segments, mainly composed of polyether polyols, determine the sponge's flexibility, skin-friendliness, and water absorption capacity. The hard segments, composed of urethane bonds formed by the reaction of isocyanate and polyol, determine the crosslinking density and mechanical properties (tear resistance and breakage resistance). The core challenge of medical skin-friendly sponges is balancing low hardness with sufficient mechanical properties. They must meet the requirement of 25% crimping hardness ≤ 8 kPa (to avoid pressure on sensitive skin) while also being able to withstand minor tearing during care (tear strength ≥ 0.3 N / mm). The drawback of existing technologies is that using high-functionality polyether polyols (e.g., functionality ≥ 4) leads to too many crosslinking points in the hard segments, resulting in excessively high sponge hardness; while using pure difunctional polyether diols (functionality = 2) results in excessively low crosslinking density, poor mechanical properties (tear strength < 0.1 N / mm), and easy breakage.

[0027] This invention achieves a performance balance by precisely controlling the crosslinking density through a compounding of polyether triol (functionality = 3) and polyether diol (functionality = 2). Specifically, polyether triol is a trifunctional polyol copolymerized with glycerol as an initiator and ethylene oxide (EO) and propylene oxide (PO). Its core function is to provide branched crosslinking points through three hydroxyl groups. When polyether triol reacts with isocyanate, each molecule can combine with three isocyanate groups (-NCO) to form nodes in the three-dimensional network, preventing the sponge from losing structural stability due to excessive softness. Experimental data shows that when polyether triol accounts for 16.7%-25% of the total composite polyether polyol (i.e., a 1:3-5 ratio), the tear strength of the sponge can be stabilized at 0.3-0.5 N / mm, meeting the tear resistance requirements in nursing operations. If the ratio is lower than 1:5 (polyether triol < 16.7%), the tear strength drops to below 0.2 N / mm, making it prone to damage during cleaning or use. Polyether triol contains 10-25% EO (hydrophilic groups), which can form hydrogen bonds with water molecules through the ether bonds -O- in the molecular chain, thereby increasing the initial water absorption speed of the sponge and solving the problem of slow water absorption caused by the hydrophobicity of pure PO polyether.

[0028] Polyether glycol is a linear polyol synthesized by copolymerizing diols (such as ethylene glycol) with EO and PO as initiators. Its core function is to reduce the density of crosslinking points by diluting the linear segments, thereby reducing the hardness of the sponge. Polyether glycol is difunctional and forms only linear links (without branches) when reacting with isocyanates, which can increase the proportion of soft segments (accounting for 70-80% of the total structure), making the molecular chains easier to slide, thus reducing the indentation hardness. Experiments show that when the proportion of polyether glycol is 75-83.3% (1:3-5 ratio), the hardness of 25% indentation can be controlled at 6-8 kPa, which meets the needs of sensitive skin. If the ratio is higher than 1:3 (polyether glycol > 83.3%), the proportion of soft segments is too high, and the sponge will lose its support due to excessive softness. If it cannot rebound after being compressed, it will fit too tightly to the skin, affecting breathability.

[0029] The linear polyether diol and polyether triol have excellent compatibility (both are polyether segments with similar solubility parameters), which can avoid local hard spots caused by poor compatibility. Hard spots can cause skin friction and irritation, thus ensuring the smoothness of the sponge surface.

[0030] Isocyanates are the core raw material for rigid segments of polyurethane, and their chemical structure directly affects the biocompatibility (non-irritating, non-sensitizing) and toxic residues of sponges. Medical-grade skin-friendly sponges must meet the requirements of cytotoxicity ≤1 and skin sensitization rate 0% (ISO10993 standard). However, traditional isocyanates have significant drawbacks: aromatic isocyanates (such as TDI and MDI) contain benzene ring structures in their molecules, and residual monomers (such as free TDI) are highly irritating; aliphatic isocyanates (such as HDI) have excessively high reactivity (the reaction rate with hydroxyl groups is 3 times that of HMDI), making it difficult to control the foaming process and easily leading to cell collapse or unevenness. This invention selects 4,4'-dicyclohexylmethane diisocyanate (HMDI) because its cyclohexyl structure has no aromatic ring toxicity and excellent chemical stability, making it the optimal choice for medical applications.

[0031] Furthermore, the -NCO group of HMDI has moderate reactivity, which can match the foaming-crosslinking rate with the hydroxyl group of the composite polyether polyol. Specifically, the foaming reaction (water reacts with -NCO to generate CO2) and the crosslinking reaction (-OH reacts with -NCO to form urethane bonds) need to be carried out simultaneously: if the reaction is too fast (such as using HDI), the CO2 generation rate will exceed the crosslinking rate, and the bubbles will merge into large pores (>300μm) because they cannot be fixed, resulting in a decrease in water retention; if the reaction is too slow (such as aromatic isocyanate derivatives), the crosslinking will be completed in advance, and the CO2 cannot expand sufficiently, the pores will be dense, and the water absorption rate will be slow (>30s).

[0032] The reaction induction period and gelation time of HMDI and the complex ether polyol are perfectly matched with the amount of catalyst (0.2-0.5 parts) in the formulation, which can form a cell structure with uniform size (50-200μm) and closed pore rate <10%. The open pores ensure air and moisture permeability, and the uniform size ensures water absorption and water retention balance.

[0033] Furthermore, the urethane hard segments (-O-CO-NH-) formed by the reaction of HMDI and polyether polyol have excellent hydrolysis resistance. The steric hindrance effect of the cyclohexyl group can protect the urethane bonds from water molecule attack (the hydrolysis rate is 1 / 5 of that of TDI hard segments), preventing the sponge from degrading in long-term moist environments (such as wound exudate) and solving the problem of fragment shedding caused by hydrolysis in traditional sponges.

[0034] The alicyclic structure of HMDI has a weak interaction (van der Waals force) with the ether bond (-O-) of polyether, which can reduce phase separation and avoid surface roughness caused by phase separation (the aggregate size of hard segments in traditional TDI sponge is >50nm, and the touch feels grainy), ensuring that the sponge surface is delicate and meets the requirements of being burr-free, non-irritating, and skin-friendly.

[0035] The amount of HMDI used (42-48 parts) needs to be matched with the total amount of hydroxyl groups in the composite polyether polyol. If the amount is less than 42 parts, the excessive hydroxyl groups will lead to insufficient cross-linking and a decrease in the mechanical properties of the sponge. If the amount is greater than 48 parts, the residual amount of free -NCO may exceed 0.1% (the limit of GB18445-2019 standard). The residual -NCO will react with skin moisture to generate amines, causing redness, swelling, and itching. An amount of 42-48 parts can ensure sufficient cross-linking while maintaining the optimal cross-linking density. This works synergistically with the soft segment structure of the composite polyether to ultimately achieve medical-grade performance with low hardness, high tear resistance, and high biocompatibility (0% sensitization rate).

[0036] The combination of the composite polyether (1:3-5) and HMDI in this invention is not a simple superposition, but a performance leap achieved through structural complementarity: the branching and crosslinking points of the polyether triol and the bis-NCO groups of HMDI form rigid nodes, and the linear segments of the polyether diol and the alicyclic structure of HMDI form flexible connections, jointly constructing a three-dimensional network with a balance between rigidity and flexibility, solving the industry problem that low hardness inevitably sacrifices mechanical strength. The hydrophilic groups (10-25%) of EO in polyether work synergistically with the weakly polar structure of HMDI hard segments to make the sponge surface both hydrophilic and non-swellable, thus resolving the contradiction that high water absorption must sacrifice structural stability. The combination of HMDI's low toxicity and the biocompatibility of polyether enabled the sponge to pass the full set of ISO10993 biocompatibility tests (cytotoxicity grade 0, skin irritation grade 0, sensitization rate 0%), meeting the requirements for long-term contact with sensitive wounds and skin.

[0037] The composite polyether polyol (1:3-5) achieves a balance between low hardness and high mechanical strength by precisely controlling the crosslinking density. HMDI ensures safety and structural stability through its excellent biocompatibility and controllable reaction. The synergy between the two enables the medical skin-friendly sponge to simultaneously meet the core indicators of low hardness, high water absorption and retention, high breathability, and strong antibacterial properties, completely solving the bottleneck of single performance optimization in existing technologies.

[0038] In existing technologies, PEG is only used as a softener (to reduce hardness), and HA is only used as a moisturizer in the cosmetics field; the two have never been synergistically introduced into medical sponges. This invention utilizes the linear flexible segments of PEG and the three-dimensional network structure of HA to form a synergistic effect for use in medical sponges. PEG is a linear water-soluble polyether polymerized from ethylene oxide. Its skin-friendly properties stem from the unique chemical properties of the numerous ether bonds (-O-) in its molecular chain: the oxygen atoms in the ether bonds have lone pairs of electrons, which can form stable hydrogen bonds with water molecules, giving PEG extremely strong hydrophilicity. When PEG is dispersed in the sponge matrix, it migrates to the sponge surface and forms a hydrophilic layer, significantly reducing the contact angle between the sponge and water, enabling rapid spreading and absorption of wound exudate, and solving the problems of slow water absorption and easy droplet accumulation in traditional medical sponges. The flexible nature of PEG's linear molecular chains allows it to form a lubricating film on the sponge surface. When the sponge comes into contact with skin / wounds, the PEG molecular chains slide under contact pressure, significantly reducing the surface friction coefficient and preventing skin damage or secondary injury caused by friction. This makes it particularly suitable for sensitive skin groups such as the elderly and infants. Furthermore, as an FDA-approved medical-grade material, PEG exhibits excellent biocompatibility.

[0039] Hyaluronic acid (HA) is a linear mucopolysaccharide formed by alternating links of D-glucuronic acid and N-acetyl-D-glucosamine. It is a natural component of human skin dermis, synovial fluid, and other tissues. Its skin-friendly advantage stems from its dual characteristics of structural homology and chemical hydrophilicity. HA is non-immunogenic to human tissues, with a sensitization rate of 0% in skin irritation tests. It is perfectly suited for extreme skin-friendly scenarios such as sensitive wounds and infant skin, solving the problem of easy sensitization from long-term contact with existing hydrophilic modifiers. Each repeating unit in the HA molecular chain contains a carboxyl group (-COOH) and a hydroxyl group (-OH). These polar functional groups can form hydrogen bonds with a large number of water molecules. 1g of HA can absorb more than 1000 times its own weight in water, and the hydrogel formed after water absorption has extremely strong water retention capacity, providing a continuously moist environment for wounds.

[0040] Clearly, unlike the basic function of PEG's rapid water absorption, HA's core role is long-lasting water retention, precisely complementing the function of PEG. The hydrogel network formed after HA absorbs water has water-locking capabilities. When the sponge absorbs wound exudate, the HA molecular chains form a three-dimensional hydrogel within the pores, preventing rapid evaporation or loss of water, thus increasing the sponge's 24-hour water retention rate from 72% for pure PEG-modified sponges to over 85%. This long-lasting water retention prevents the wound from drying out and forming scabs due to rapid water loss, reducing secondary damage to the wound when scabs fall off.

[0041] This invention chooses a combination of PEG and HA, rather than using a single component, because the core of this invention lies in the complementary functions and synergistic performance of the two, thus completely solving the performance defects of existing single modifiers. Although single PEG modified sponge absorbs water quickly, it has poor water retention (72% water retention rate in 24 hours). The hydrophilic layer formed by PEG has no water-locking ability, and water evaporates easily. Although single HA modified sponge has good water retention (88% water retention rate in 24 hours), it absorbs water slowly. The high viscosity of HA leads to high resistance to water penetration.

[0042] When combined, PEG acts as an absorption channel, rapidly reducing the surface tension of the sponge and allowing exudate to quickly penetrate into the sponge within 10 seconds; HA acts as a water-retaining core, forming a hydrogel within the pores to firmly lock in the infiltrated water; with the synergistic effect, the sponge achieves the dual advantages of fast water absorption and long-lasting water retention, perfectly matching the needs of timely absorption and continuous moisturization in wound care.

[0043] PEG's linear molecular chains provide physical lubrication, reducing mechanical friction irritation between the sponge and the skin; HA's human-derived structure provides low biological irritation, avoiding chemical irritation. Together, they make the sponge not only soft to the touch but also safe to use. Both PEG and HA are water-soluble polyethers / polysaccharides, with excellent compatibility with composite polyether polyols and HMDI, and will not undergo phase separation or aggregation, avoiding the problems of existing hydrophilic fillers (such as starch) clogging the pores and reducing mechanical properties.

[0044] In this invention, the amount of PEG used must be strictly controlled between 10-20 parts (based on 100 composite polyether polyol). The core reason is to avoid the destruction of the sponge's structural stability by excessive hydrophilicity. If the amount is less than 10 parts (e.g., 8 parts): the number of hydrophilic groups is insufficient, the surface hydrophilic layer is not completely covered, the contact angle is greater than 65°, the water absorption rate is greater than 18s, and it is unable to absorb wound exudate in time, which easily leads to exudate soaking the wound. If the amount is greater than 20 parts (e.g., 25 parts): excessive PEG will interfere with the polyurethane crosslinking reaction. The hydroxyl groups of the PEG molecular chain will compete with the -NCO groups of HMDI for reaction, resulting in a decrease in crosslinking density, which in turn leads to a sharp deterioration in the mechanical properties of the sponge. When the amount is 10-20 parts, PEG can provide sufficient hydrophilic groups without excessively interfering with the crosslinking reaction, achieving a balance between rapid hydrophilicity and structural stability.

[0045] In this invention, the amount of HA is controlled at 0.5-1.5 parts, which is based on a comprehensive consideration of water retention effect, foaming feasibility, and cost control. If the amount is <0.5 parts (e.g., 0.3 parts), the number of HA molecular chains is insufficient, and a continuous hydrogel network cannot be formed, resulting in an insignificant water retention effect. If the amount is >1.5 parts (e.g., 2 parts), HA has extremely high viscosity. Excessive HA will cause the viscosity of the foaming reaction system to increase sharply, making it difficult for CO2 bubbles to expand, resulting in problems such as cell collapse and uneven pore size. When the amount is 0.5-1.5 parts, HA can be uniformly dispersed in the reaction system, which does not affect the foaming process and can form an effective hydrogel network.

[0046] In existing technologies, antibacterial sponges only use silver ions (which are prone to aggregation and have uneven antibacterial activity) or chitosan (which has low antibacterial strength and poor durability), and have never used the two in combination at a ratio of 1-2 parts silver ions and 2-3 parts chitosan for medical skin-friendly sponges. This invention utilizes the cationic properties of chitosan to create a synergistic effect with the metallic ionic antibacterial properties of silver ions. Specifically, the amino groups of chitosan are protonated (-NH3) under neutral conditions. + Chitosan, being positively charged, can bind tightly to the negatively charged bacterial cell membrane, immobilizing bacteria and disrupting the membrane structure; furthermore, the cationic sites of chitosan can adsorb silver ions, forming a localized high concentration of Ag. + The area avoids silver ion aggregation, resulting in an antibacterial rate of ≥99.8% over 24 hours. Furthermore, the biocompatibility of chitosan can neutralize the potential sensitization of silver ions, resolving the contradiction between strong antibacterial properties and skin-friendliness.

[0047] This fixed bacteria, concentrated Ag + The three-stage antibacterial mechanism that reduces sensitization represents a breakthrough from existing single antibacterial technologies. The synergistic effect of cation adsorption and concentration enhancement discovered in this invention requires a deep understanding of the mechanism of action of microbial cell membranes and the charge characteristics of polymers.

[0048] In some embodiments, the number-average molecular weight of the polyethylene glycol is 400-1000. In this embodiment, polyethylene glycol is the core component of the composite skin-friendly modifier, and its molecular weight is limited to 400-1000, which is key to achieving the core properties of low hardness, high water absorption, and smooth surface of the medical skin-friendly sponge.

[0049] Specifically, the linear flexible segments of PEG (-CH2-CH2-O-) can react with isocyanates (MDI) via hydroxyl groups, integrating into the polyurethane backbone and diluting the density of rigid urethane bonds (-NH-CO-O-), thus lowering the glass transition temperature (Tg) of the polyurethane. PEG with a molecular weight of 400-1000 has a moderate chain length (approximately 9-23 repeating units), ensuring uniform dispersion of the flexible segments within the polyurethane backbone. This effectively reduces the Tg from 50°C in ordinary sponges to below 20°C, maintaining the sponge's high elasticity at room temperature and ultimately achieving a 25% indentation hardness ≤6 kPa (far lower than the 12-20 kPa of ordinary medical sponges). Simultaneously, PEG in this molecular weight range exhibits excellent compatibility with polyether polyols (molecular weight 2000-4000), showing no delamination or aggregation, ensuring uniform overall sponge hardness and preventing localized hard spots that irritate the skin.

[0050] Furthermore, PEG with a molecular weight of 400-1000 has a moderate hydroxyl density and a short molecular chain, which can be evenly distributed on the surface of the sponge pore wall, increasing the hydrophilic sites and making the sponge absorb water in less than 10 seconds with a water absorption rate of ≥280% (by mass), thus rapidly absorbing wound exudate. At the same time, PEG with this molecular weight can work synergistically with hyaluronic acid (HA) in the composite skin-friendly modifier: PEG adsorbs water molecules through hydroxyl groups, and HA encapsulates the water adsorbed by PEG through a three-dimensional network structure, forming a dual adsorption-water-locking mechanism to help improve the 24-hour water retention rate and prevent rapid water loss.

[0051] PEG molecules with a molecular weight <400 have excessively short chains (<9 repeating units), resulting in a greater polarity difference with polyether polyols. This leads to stratification during mixing, causing localized PEG enrichment and loss in the foamed sponge. The enriched areas have lower hardness (easily damaged), while the lost areas have higher hardness (skin irritation). Furthermore, the water absorption is uneven, with local water absorption rates <200%, failing to evenly absorb wound exudate and easily causing local maceration. The weak intermolecular forces of PEG molecules with a molecular weight <400 cause the formed surface hydration film to easily detach upon skin contact, increasing the skin friction coefficient to 0.2-0.25, resulting in a rough feel. It also fails to fill surface micropores, increasing the surface roughness Ra to 1.2-1.5 μm, potentially causing frictional irritation to the wound and secondary damage.

[0052] PEG molecules with a molecular weight >1000 have excessively long chains (>23 repeating units), which are prone to entanglement within the polyurethane backbone. This increases resistance to chain movement, leading to a smaller decrease in Tg, increased sponge hardness, and insufficient softness. Simultaneously, the excessively long chains can mask some hydroxyl groups, reducing the density of hydrophilic sites and slowing water absorption, lowering the water absorption rate to 250-270%, making it unable to quickly handle large amounts of exudate from wounds. Furthermore, PEG with a molecular weight >1000 has reduced water solubility, making it difficult to completely remove residues during subsequent ultrasonic cleaning, resulting in PEG accumulation within the sponge. Prolonged skin contact with residual high molecular weight PEG may cause local skin irritation (such as redness and itching), failing to meet the requirements of low allergenicity and high biocompatibility.

[0053] Therefore, this embodiment limits the number-average molecular weight of PEG to 400-1000. This is a precise design based on the four core requirements of reducing hardness, enhancing water absorption, optimizing surface, and ensuring safety. A molecular weight lower than 400 or higher than 1000 will cause the performance to deviate from the medical skin-friendly standard and will not be able to realize the clinical application value of the sponge.

[0054] In some embodiments, the catalyst is dibutyltin dilaurate, and the surfactant is medical-grade silicone oil, but not limited thereto. The medical-grade silicone oil can reduce surface tension, stabilize the cell structure, and prevent cell merging or collapse.

[0055] This invention also provides a method for preparing a medical-grade skin-friendly sponge, such as... Figure 1 As shown, it includes the following steps: S10. Add composite polyether polyol, polyethylene glycol and deionized water to a sterile mixing tank, and stir at 500-800 rpm for 5-10 minutes to obtain the first mixture; the speed is low at this stage to avoid generating too many bubbles and to ensure that the hydrophilic components are evenly dispersed. S20. Add catalyst and surfactant to the first mixture and stir at 1000-1200 rpm for 3-5 minutes to obtain the second mixture. At this stage, the stirring speed needs to be increased to ensure that the additives are completely dissolved in the hydrophilic system and to avoid local over-catalysis. S30. First, add the antibacterial agent and hyaluronic acid to the second mixture, then add 4,4'-dicyclohexylmethane diisocyanate. Stir at 1500-2000 rpm for 1-2 minutes to obtain the third mixture. This stage is the key reaction stage: MDI has high reactivity (reaction half-life of about 10 minutes at 25°C), so high-speed stirring is required to ensure instantaneous and uniform mixing with other components to avoid excessive local NCO concentration leading to gelation. The stirring time should be strictly controlled within 1-2 minutes to avoid over-stirring and premature gelation. S40. The third mixture is rapidly injected into a preheated sterile mold for molding and foaming treatment. After mixing, the third mixture is rapidly injected into the preheated sterile mold (35-40℃, preheated for 1 hour in advance) using a sterile pouring pump. The filling amount of the third mixture is 60-70% of the mold volume (leaving room for expansion). The pouring time is controlled within 30 seconds to avoid premature foaming of the liquid during the pouring process. S50. After foaming, the sterile mold is transferred to the curing chamber and cured for 24-48 hours at a temperature of 50-60℃ and a relative humidity of 40-50%. After curing, the mold is demolded and the initial sponge is removed. After foaming in this stage, the mold is transferred to the curing chamber and cured for 24-48 hours to allow the polyurethane segments to fully cross-link and improve the mechanical properties of the sponge. S60. After cutting, cleaning, drying and sterilizing the initial sponge, the medical skin-friendly sponge is obtained.

[0056] Specifically, the production environment preparation of this invention meets GMPD and GMPC standards. The cleanroom areas are divided as follows: General cleanroom (Class 100,000, GMPD): raw material storage, pretreatment, cleaning, and drying processes; environmental parameters: temperature 22-25℃, relative humidity 40-60%, ≥0.5μm particles <352,000 / m³, microbial colony count <10 CFU / m³; Critical cleanroom (Class 10,000, GMPC): foaming, molding, cutting, and sterilization processes; environmental parameters: temperature 23-24℃, relative humidity 45-55%, ≥0.5μm particles <35,200 / m³, microbial colony count <5 CFU / m³. Environmental disinfection: Turn on the air purification system (HEPA high-efficiency filter, filtration efficiency ≥99.97%) 12 hours in advance, and use ultraviolet irradiation (254nm, 1h) + hydrogen peroxide fumigation (concentration 10%, 2h) for dual disinfection; 30 minutes before production, test the concentration of microorganisms and particles in key clean areas, and if they do not meet the standards, disinfect again. Personnel and tool aseptic control: Operators: must change clothes (sterile underwear → sterile gown → sterile shoe covers → sterile gloves → sterile mask), undergo air shower (air speed ≥25m / s, time 30s), and hand disinfection (wiping with 75% medical alcohol) before entering the clean area, and be disinfected again every 2 hours; Tool sterilization: mixing tanks, molds, cutting equipment, etc. are sterilized by moist heat sterilization at 121℃ for 30min or EO sterilization (concentration 800mg / L, 50℃, 6h), and transferred to the clean area after sterilization, with a storage time not exceeding 4h; The inner wall of the mold is coated with medical-grade polytetrafluoroethylene release agent (VOC <5mg / kg), with the thickness controlled at 5-10μm to avoid release agent residue.

[0057] This invention solves the cascading problems of surface quality, sterility, and residue control by constructing a synergistic process that integrates aseptic pretreatment of raw materials, molding in a clean environment, precise cutting, ultrasonic residue removal, and on-demand sterilization.

[0058] In some embodiments, the preheating temperature of the sterile mold is 35-40℃, the pressure of the compression molding foaming process is 0.1-0.2MPa, and the holding time is 8-12min. The compression molding foaming method of this embodiment is suitable for high-precision products such as wound dressings. By controlling the pressure to 0.1-0.2MPa, this embodiment can control the pore size to 50-200μm, avoiding poor water retention due to excessively large pores (>200μm) or poor air permeability due to excessively small pores (<50μm). The holding time of 8-12min ensures that the foaming reaction and gelation reaction are complete, avoiding sponge shrinkage after demolding.

[0059] In existing technologies, a sponge with an indentation hardness ≤8kPa inevitably results in a tensile strength ≤0.3MPa (unable to withstand the slight tearing during wound care). This invention, through a combination of polyether with a molecular weight of 2000-4000 (moderate chain segment length), 10-20 parts of PEG (flexible chain insertion), and compression molding at 0.1-0.2MPa (uniform cell size), achieves an indentation hardness of 5.2kPa and a tensile strength of 0.6MPa. This satisfies the low hardness requirements of sensitive skin while ensuring mechanical stability during use. This synergy of low hardness and high mechanical strength is achieved through multi-dimensional control of polymer chain structure, cell morphology, and processing pressure—a feat that cannot be achieved by those skilled in the art through adjusting a single parameter.

[0060] In existing technologies, a sponge with a water absorption rate ≥200% inevitably results in a water vapor transmission rate ≤300g / (m²). 2 (24h) (the pores are blocked by moisture); This invention achieves a water absorption rate of 310% and a water vapor transmission rate of 520g / (m³) by combining PEG hydroxyl groups (hydrophilic sites) + HA three-dimensional network (water-locking) + open pores (diameter 50-200μm, open rate ≥90%). 2 (24h) It can quickly absorb wound exudate while avoiding skin suffocation and maceration. This synergy of high absorbency and high breathability is achieved through the coordinated regulation of hydrophilic group density, pore structure, and channel integrity, which cannot be achieved by those skilled in the art through simply increasing hydrophilic components or enlarging pores.

[0061] In some embodiments, the initial sponge is subjected to cutting, cleaning, drying, and sterilization, including the following steps: cutting the initial sponge using a CNC laser cutting machine, and then polishing the cut surfaces of the initial sponge with sterile sandpaper; placing the cut and polished sponge into a sterile cleaning tank, adding purified water, and performing ultrasonic cleaning for 15-20 minutes at an ultrasonic frequency of 40kHz and a power of 500-800W; rinsing with pure water after ultrasonic cleaning; transferring the cleaned sponge to a sterile drying oven for vacuum drying to obtain a dried sponge with a moisture content of <1%; and subjecting the dried sponge to EO sterilization or gamma-ray irradiation sterilization.

[0062] Specifically, existing technologies for cutting medical sponges only employ mechanical blade cutting (which easily produces burrs) or ordinary laser cutting (without subsequent polishing), failing to balance dimensional accuracy and surface smoothness. This embodiment combines CNC laser cutting with 1000-2000 grit sterile sandpaper polishing (pressure <5N). Laser cutting creates a smooth cut surface through thermal melting, avoiding fiber tearing caused by mechanical cutting. Sterile polishing only removes residual molten particles after laser cutting, without damaging the cell structure, ensuring a smooth, non-gritty surface without any stinging sensation. The entire process is conducted in a Class 1,000 cleanroom to avoid microbial contamination during polishing. This combined process of hot cutting, cold polishing, and sterile control represents a breakthrough from the isolated cutting and polishing steps of existing technologies. This embodiment recognizes the irritation risk of molten particles and requires process design that considers the material's melting characteristics and skin sensitivity needs, representing a non-obvious process integration.

[0063] In existing technologies, sponge cleaning only uses running water rinsing (which does not thoroughly remove residues), and drying uses high-temperature hot air drying (which damages skin-friendly components), easily leading to both excessive residues and performance degradation. In contrast, this embodiment utilizes the synergy of ultrasonic cavitation effect and low-temperature vacuum environment. Specifically, 40kHz ultrasonic cleaning (power 500-800W) generates local high pressure through the rupture of cavitation bubbles, penetrating deep into the sponge pores to remove MDI monomer and catalyst residues (MDI residue <5μg / g); 50-60℃ vacuum drying (-0.095MPa to -0.1MPa) accelerates moisture evaporation in a low-oxygen environment (moisture content <1%), avoiding HA degradation (molecular weight reduction of 50%) and PEG volatilization (loss rate >10%) caused by high temperature (>60℃), thus ensuring the activity of skin-friendly components. This synergistic process of deep residue removal and low-temperature activity preservation represents a breakthrough in existing cleaning and drying technologies. Those skilled in the art typically believe that ultrasonic cleaning damages the foam cells or that low-temperature drying is inefficient. However, this application solves the residue problem and protects performance by matching parameters of frequency, power, temperature, and vacuum, which is a non-obvious process optimization.

[0064] In existing technologies, medical sponges only employ a single sterilization method (such as EO sterilization) without considering the compatibility between sponge components and sterilization methods. This embodiment designs a scenario-based solution for EO sterilization and γ-irradiation based on the sponge components. For sponges containing HA / collagen (such as wound dressings): EO sterilization is used (EO concentration of 400-800 mg / L; temperature of 30-50℃; relative humidity of 40-60%; sterilization time of 4-6 h) to avoid protein denaturation caused by γ-irradiation; for pure polyether-PEG sponges (such as electrode pads): γ-irradiation is used (dose of 25-30 kGy, irradiation time of 1-2 h), eliminating the need for analysis and improving production efficiency.

[0065] To further illustrate the medical skin-friendly sponge and its preparation method provided by the present invention, the following embodiments are provided.

[0066] Example 1 A medical skin-friendly sponge for wound dressings comprises, by weight, the following components: 20 parts polyether triol, 80 parts polyether glycol, 45 parts 4,4'-dicyclohexylmethane diisocyanate, 16 parts composite skin-friendly modifier, 4 parts antibacterial agent, 5 parts deionized water, 0.3 parts catalyst, and 0.5 parts surfactant; the composite skin-friendly modifier is composed of 15 parts polyethylene glycol and 1 part hyaluronic acid; the antibacterial agent is composed of 1.5 parts silver ion antibacterial agent and 2.5 parts chitosan; the number average molecular weight of polyethylene glycol is 600, the catalyst is dibutyltin dilaurate, and the surfactant is medical silicone oil; its preparation method includes the following steps: Preliminary preparation (aseptic pretreatment) Environmental preparation: The production workshop is divided into Class 100,000 (pretreatment) and Class 10,000 (foaming / cutting). The HEPA system is turned on 12 hours in advance, followed by 1 hour of ultraviolet disinfection and 2 hours of 10% hydrogen peroxide fumigation. Operators wear sterile coveralls, N95 masks and sterile gloves and enter through an air shower (28m / s, 30s). The mold (stainless steel, with PTFE coating on the inner wall) is sterilized by moist heat at 121℃ for 30 minutes, and the inner wall is coated with 5μm medical release agent.

[0067] Core processes (molding and performance control) Precise ingredient mixing: First stage: Add 20 parts polyether triol and 80 parts polyether diol → PEG (15 parts) → deionized water (5 parts) to a 50L sterile mixing tank, stir at low speed (600 rpm) for 8 minutes, and the online viscometer displays 100 mPa. Second stage: Add catalyst (0.3 parts) → surfactant (0.5 parts), stir at medium speed (1100 rpm) for 4 min, FTIR detection shows no catalyst agglomeration peak; Third stage: Add antibacterial agent → hyaluronic acid → HMDI (45 parts), stir at high speed (1800 rpm) for 1.5 min, viscosity rises to 350 mPa. Stop at s, pH=7.0; Foaming and Molding: Casting: The liquid material is injected into the preheated mold (38℃) using a sterile casting pump (80mL / s), filling 65% of the mold volume, with a casting time of 25s; Compression Molding: The mold is closed, a pressure of 0.15MPa is applied, and the pressure is held for 10min. DSC detection shows that the exothermic peak of the reaction has disappeared (the reaction is complete); Curing: The mixture is transferred to a 55℃ curing chamber and cured for 36h. Samples are taken to test the tensile strength, which is 0.6MPa, and the elongation at break is 120%. Cutting and trimming: After demolding, remove the flash (0.8mm thick), and cut into 5cm×5cm×2mm dressings using a CNC laser cutting machine (1064nm, 80W) at a cutting speed of 15mm / s; lightly sand with 2000-grit sterile sandpaper (pressure 4N, 12s / side), and blow away dust with sterile compressed air.

[0068] Post-processing (sterilization and residue removal) Cleaning and Drying: Ultrasonic Cleaning: Place the sponge in a sterile tank and add purified water (18.5 MΩ). (cm), ultrasonic cleaning at 40kHz for 18 min, HPLC analysis showed MDI residue of 3.2 μg / g; rinsing: rinsed 3 times with fresh purified water (10 min each time), water resistivity after rinsing was 18.4 MΩ. cm; Drying: Vacuum drying at 55℃ (-0.096MPa) for 2.5h, Karl Fischer moisture content was 0.8%; Sterilization: Sterilization was performed using EO (concentration 600 mg / L, 40℃, RH 50%, 5 h), followed by analyzing for 36 h. Gas chromatography detected EO residue at 6.5 μg / g. Sealing: The sterile aluminum-plastic bag is sealed with nitrogen gas, with a sealing strength of 60 N / 15 mm, and stored in a sterile room at 23°C. The medical-grade skin-friendly sponge prepared in this embodiment is as follows: Figure 1 As shown.

[0069] Example 2 A medical skin-friendly sponge for wound dressings comprises the following components by weight: 25 parts polyether triol, 75 parts polyether glycol, 42 parts 4,4'-dicyclohexylmethane diisocyanate, 21 parts composite skin-friendly modifier, 3.2 parts antibacterial agent, 6 parts deionized water, 0.2 parts catalyst, and 0.6 parts surfactant; the composite skin-friendly modifier is composed of 20 parts polyethylene glycol and 1 part hyaluronic acid; the antibacterial agent is composed of 1.2 parts silver ion antibacterial agent and 2 parts chitosan; the number average molecular weight of polyethylene glycol is 1000, the catalyst is dibutyltin dilaurate, and the surfactant is medical silicone oil; the preparation method differs from that of Example 1 in that: Post-processing: ultrasonic cleaning for 20 min, followed by γ-ray irradiation sterilization (dose 28 kGy, 1.5 h), no analysis required; the steps are the same as in Example 1.

[0070] Example 3 A medical skin-friendly sponge for wound dressing comprises the following components by weight: 20 parts polyether triol, 80 parts polyether glycol, 48 parts 4,4'-dicyclohexylmethane diisocyanate, 12.5 parts composite skin-friendly modifier, 5 parts antibacterial agent, 4 parts deionized water, 0.5 parts catalyst, and 0.8 parts surfactant; the composite skin-friendly modifier is composed of 11 parts polyethylene glycol and 1.5 parts hyaluronic acid; the antibacterial agent is composed of 2 parts silver ion antibacterial agent and 3 parts chitosan; the number average molecular weight of polyethylene glycol is 400, the catalyst is dibutyltin dilaurate, and the surfactant is medical silicone oil; the preparation method is the same as in Example 1.

[0071] Comparative Example 1 (without hyaluronic acid) A medical skin-friendly sponge, the composition of which differs from that of Example 1 in that the skin-friendly modifier consists of only 16 parts of polyethylene glycol and does not contain hyaluronic acid; the composition of the remaining components is the same as that of Example 1, and the preparation steps are also the same as those of Example 1.

[0072] Comparative Example 2 (without chitosan) A medical skin-friendly sponge differs from Example 1 in that its antibacterial agent consists of only 4 parts of anionic antibacterial agent and does not contain chitosan; the remaining components are the same as in Example 1, and the preparation steps are also the same as in Example 1.

[0073] Comparative Example 3 A medical skin-friendly sponge, the only difference between its composition and that of Example 1 is the use of a single-component polyether polyol with a functionality of 4 and a number-average molecular weight of 6000. The composition of all other components is the same as that of Example 1, and the preparation steps are also the same as those of Example 1.

[0074] Comparative Example 4 A medical skin-friendly sponge, the only difference between its composition and that of Example 1 is that the number average molecular weight of polyethylene glycol is 1500, while the composition of other components is the same as that of Example 1, and the preparation steps are also the same as those of Example 1.

[0075] Comparative Example 5 A medical skin-friendly sponge, the composition of which differs from that of Example 1 is: the weight of 4,4'-dicyclohexylmethane diisocyanate is 60 parts, while the composition of the remaining components is the same as that of Example 1, and the preparation steps are also the same as those of Example 1.

[0076] The medical-grade skin-friendly sponges prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests. To ensure the objectivity of the performance comparison between the examples and the comparative examples, all performance indicators were tested according to the standards shown in Table 1. The testing environment was a Class 10,000 cleanroom (temperature 23±1℃, relative humidity 50±5%). Table 1 Testing Standards

[0077] Performance tests were conducted on Examples 1-3 and Comparative Examples 1-5 based on the testing standards in Table 1 above, and the results are shown in Table 2: Table 2 Performance Test Results

[0078] As can be seen from the data in Examples 1-3 in Table 2, the medical skin-friendly sponge benchmark formula provided by this invention meets all performance requirements for medical skin-friendliness. This proves that the technical solution of composite polyether polyol, composite skin-friendly modifier (PEG+HA), synergistic antibacterial agent (silver ions + chitosan), and precise process can achieve multiple performance synergistic standards of low hardness, delicate surface, high water absorption and retention, and strong antibacterial properties in the sponge, making it widely adaptable to various medical scenarios. Compared to Example 1, Example 2 achieved lower hardness and higher breathability by adjusting the composition ratio of composite polyether polyol and the amount of PEG, and verified the compatibility with gamma-ray sterilization, proving that the solution of this application can be adapted to wounds with different sensitivity levels by fine-tuning the raw material parameters. Compared to Example 1, Example 3 enhanced water absorption, retention, and antibacterial properties by increasing the amount of HA and antibacterial agent, proving that the solution of this application can be adapted to wound scenarios with a lot of exudate and high risk of infection by adjusting the amount of key components.

[0079] Compared to Example 1, the sponge in Comparative Example 1 showed a 1.6 kPa increase in 25% indentation hardness, indicating that HA can fill the gaps between polyurethane segments and reduce the frictional resistance of the foam walls. A lack of HA resulted in an increase in localized hard spots, exceeding the target of ≤6 kPa and compressing the wound. The surface roughness of the sponge in Comparative Example 1 increased by 1.2 μm, indicating that HA can form a hydration film to cover residual particles from laser cutting. A lack of HA exposed tiny pores on the surface, exceeding the <1 μm standard, causing frictional irritation to the wound. The water absorption rate of the sponge in Comparative Example 1 decreased by 90%, indicating that the carboxyl groups of HA can provide a large number of hydrophilic sites. A lack of HA resulted in insufficient hydrophilic sites, causing its water absorption rate to be lower than the target of ≥280%, making it unable to absorb large amounts of exudate. The 24-hour water retention rate of the sponge in Comparative Example 1 decreased by 23%, indicating that the three-dimensional network structure of HA can encapsulate water molecules. A lack of HA caused water molecules to evaporate easily, falling below the target of ≥82%, making it unable to maintain wound moisture. The data from Comparative Example 1 demonstrate that HA is the key component for achieving low hardness, smooth surface, and high water absorption and retention. PEG alone cannot replace its synergistic effect, confirming the necessity of the composite skin-friendly modifier design in this application.

[0080] Compared to Example 1, the 24-hour antibacterial rate of the sponge in Comparative Example 2 was significantly reduced. Specifically, the 24-hour antibacterial rate against Escherichia coli was only 91.5% (a decrease of 8.4%), the 24-hour antibacterial rate against Staphylococcus aureus was only 89.8%, and the 24-hour antibacterial rate against Candida albicans was only 85.2%. This indicates that chitosan can adsorb silver ions to form a localized high concentration of Ag. + In areas lacking chitosan, silver ions aggregate (particle size 200nm), causing the antibacterial rate to drop below the target of ≥99.8%, easily leading to infection. Furthermore, this invention also tested the skin sensitization rate of the sponge in Comparative Example 2, which reached 3.2%. This indicates that chitosan can neutralize the irritation of silver ions. The absence of chitosan causes free silver ions to exceed the threshold of 0.5μg / g, resulting in a sensitization rate exceeding the standard of <0.1%. Comparative Example 2 demonstrates that chitosan is a key component for achieving strong antibacterial activity, low sensitization, and long-lasting antibacterial properties. Single silver ions cannot balance antibacterial efficiency and safety, confirming the necessity of the synergistic antibacterial agent design in this application.

[0081] Compared to Example 1, the 25% indentation hardness of the sponge in Comparative Example 3 was 14.2 kPa, an increase of 9 kPa; its water absorption rate was 210%, a decrease of 100%; and its water vapor transmission rate decreased by 240 g / (m²). 2 (24h). This indicates that the crosslinking density of the polyether polyol with a functionality of 4 and a number-average molecular weight of 6000 used in Comparative Example 3 was too high, restricting chain segment movement and resulting in a hardness exceeding the ≤8kPa standard, thus compressing the wound. Furthermore, the high crosslinking density of the polyether polyol encapsulates hydrophilic groups, preventing the hydrophilic sites from being exposed, resulting in a water absorption rate lower than the target of ≥280%, failing to absorb exudate. The high crosslinking density also thickens the cell walls and narrows the channels, resulting in a water vapor permeability lower than ≥400g / (m³). 2 (24h) standard, skin is suffocated by heat. Comparative Example 3 proves that the use of a compound of polyether triol and polyether diol is the key to balancing hardness, water absorption and breathability. Deviating from these parameters will cause multiple performance failures, confirming the effectiveness of the composite polyether polyol raw material design of this application.

[0082] Compared to Example 1, the 25% indentation hardness of the sponge in Comparative Example 4 was 7.5 kPa, an increase of 2.3 kPa; its surface roughness was 2.1 μm, an increase of 1.5 μm. This indicates that the PEG molecular weight used in Comparative Example 4 was too high, with more than 23 repeating units in its chain segments. The main chain entanglement increased resistance, resulting in a hardness exceeding the target of ≤6 kPa, causing pressure on the skin. Furthermore, PEG1500 has poor fluidity at room temperature and cannot form a uniform film layer, resulting in the sponge exceeding the <1 μm standard, causing friction and irritation to the wound. Comparative Example 4 demonstrates that a PEG molecular weight of 400-1000 is key to achieving low hardness, a smooth surface, and low residue.

[0083] Compared to Example 1, the 25% indentation hardness of the sponge in Comparative Example 5 was 18.5 kPa, an increase of 13.3 kPa; its residual MDI content was 18.6 μg / g, an increase of 15.4 μg / g; and its water absorption rate was 180%, a decrease of 130%. Comparative Example 5 used 60 parts of 4,4'-dicyclohexylmethane diisocyanate, which resulted in an NCO / OH ratio of 1.35 (excessive HMDI), a sharp increase in cross-linking density, and thus a hardness exceeding the ≤8 kPa standard, severely compressing the wound. Excess MDI could not react completely, and ultrasonic cleaning only removed 60%, resulting in a residue exceeding the <10 μg / g standard, causing skin chemical irritation. High cross-linking density easily blocked hydrophilic groups, resulting in a water absorption rate lower than the "≥200%" basic standard, and inability to absorb exudate. Comparative Example 5 demonstrates that 42-48 parts of 4,4'-dicyclohexylmethane diisocyanate are key to balancing crosslinking density, residue, and moldability. Excessive amounts lead to the collapse of multiple properties and process stability, confirming the necessity of the 4,4'-dicyclohexylmethane diisocyanate dosage design in this application.

[0084] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A medical-grade skin-friendly sponge, characterized in that, The medical skin-friendly sponge comprises the following components by weight: 100 parts of composite polyether polyol, 42-48 parts of 4,4'-dicyclohexylmethane diisocyanate, 10.5-21.5 parts of composite skin-friendly modifier, 3-5 parts of antibacterial agent, 4-6 parts of deionized water, 0.2-0.5 parts of catalyst, and 0.4-0.8 parts of surfactant; the composite skin-friendly modifier is composed of 10-20 parts of polyethylene glycol and 0.5-1.5 parts of hyaluronic acid; the composite polyether polyol is composed of polyether triol and polyether diol in a mass ratio of 1:3-5.

2. The medical-grade skin-friendly sponge according to claim 1, characterized in that, The antibacterial agent consists of 1-2 parts of silver ion antibacterial agent and 2-3 parts of chitosan.

3. The medical-grade skin-friendly sponge according to claim 1, characterized in that, The polyether triol is obtained by copolymerization of glycerol, ethylene oxide, and propylene oxide, wherein the mass percentage of ethylene oxide is 10-25%.

4. The medical-grade skin-friendly sponge according to claim 1, characterized in that, The number average molecular weight of the polyethylene glycol is 400-1000.

5. The medical-grade skin-friendly sponge according to claim 4, characterized in that, The catalyst is dibutyltin dilaurate or triethylenediamine.

6. A method for preparing a medical skin-friendly sponge as described in any one of claims 1-5, characterized in that, Includes the following steps: Add composite polyether polyol, polyethylene glycol and deionized water to a sterile mixing tank, and stir at 500-800 rpm for 5-10 minutes to obtain the first mixture. Add a catalyst and a surfactant to the first mixture and stir at 1000-1200 rpm for 3-5 minutes to obtain a second mixture; First, add antibacterial agent and hyaluronic acid to the second mixture, then add 4,4'-dicyclohexylmethane diisocyanate, and stir at 1500-2000 rpm for 1-2 minutes to obtain the third mixture; The third mixture is rapidly injected into a preheated sterile mold for compression molding and foaming. After foaming, the sterile mold is transferred to the curing room and cured for 24-48 hours at a temperature of 50-60℃ and a relative humidity of 40-50%. After curing, the mold is removed and the initial sponge is taken out. The initial sponge is cut, cleaned, dried and sterilized to obtain the medical skin-friendly sponge.

7. The method for preparing the medical skin-friendly sponge according to claim 6, characterized in that, In the step of rapidly injecting the third mixture into a preheated sterile mold for compression molding and foaming, the preheating temperature of the sterile mold is 35-40℃, the pressure of the compression molding and foaming process is 0.1-0.2MPa, and the holding time is 8-12min.

8. The method for preparing the medical skin-friendly sponge according to claim 6, characterized in that, The initial sponge is cut, washed, dried, and sterilized, including the following steps: The initial sponge was cut using a CNC laser cutting machine, and then the cut surfaces of the initial sponge were polished with sterile sandpaper. Place the cut and polished sponge into a sterile cleaning tank, add purified water, and turn on ultrasonic cleaning for 15-20 minutes. The ultrasonic frequency is 40kHz and the power is 500-800W. After ultrasonic cleaning, rinse with pure water. The cleaned sponge was transferred to a sterile drying oven for vacuum drying to obtain a dry sponge with a moisture content of <1%. The dried sponge is subjected to EO sterilization or gamma ray irradiation sterilization treatment.

9. The method for preparing the medical skin-friendly sponge according to claim 7, characterized in that, In the step of transferring the cleaned sponge to a sterile drying oven for vacuum drying, the temperature is 50-60℃, the vacuum degree is -0.095MPa to -0.1MPa, and the processing time is 2-3 hours.

10. The method for preparing the medical skin-friendly sponge according to claim 7, characterized in that, In the step of sterilizing the dried sponge with EO, the EO concentration is 400-800 mg / L; the temperature is 30-50℃; the relative humidity is 40-60%; and the sterilization time is 4-6 h. In the step of sterilizing the dried sponge with gamma ray irradiation, the gamma ray irradiation dose is 25-30 kGy; and the irradiation time is 1-2 h.

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