Low-sensitivity medical adhesive tape base material and preparation method thereof

Abstract

The invention provides a low-sensitivity medical adhesive tape base material and a preparation method thereof, and relates to the technical field of medical adhesive tape base materials, the low-sensitivity medical adhesive tape base material comprises the following components by weight: 80-100 parts of a thermoplastic polyurethane elastomer, 0.1-3 parts of an antioxidant, 0.5-5 parts of polydimethylsiloxane, 0.5-5 parts of organosilicon modified polyurethane resin, and 1-10 parts of carboxymethyl chitosan. 0.5 to 5 parts of a compatilizer, 0.1 to 2 parts of bisabolol and 0.1 to 2 parts of dipotassium glycyrrhizinate. According to the invention, the thermoplastic polyurethane elastomer is used as a base material core, so that the adhesive tape is endowed with excellent elasticity and flexibility, the dynamic deformation requirement of skin is met, and the risk of adhesive layer cracking caused by frequent activities is reduced. The antioxidant inhibits oxidative degradation of the material, prolongs the service life of the adhesive tape, and avoids release of irritant substances caused by aging.

Description

Technical Field

[0001] This invention relates to the field of medical tape substrate technology, and in particular to a low-sensitivity medical tape substrate and its preparation method. Background Art

[0002] Cosmetic medical tape substrate is a sub-type of medical tape substrate, designed specifically for medical aesthetic scenarios. Its uses include postoperative skin tension reduction and fixation (such as postoperative care after double eyelid surgery and rhinoplasty), local lifting and shaping (such as improving loose skin), and covering minor blemishes (such as scars and pigmentation).

[0003] Existing medical adhesive tapes primarily focus on physical fixation, lacking the ability to actively intervene in wound healing. They are ineffective at inhibiting bacterial colonization or accelerating tissue repair, leading to prolonged healing periods. Furthermore, the substrates have insufficient weather resistance; prolonged exposure to fluctuating temperature and humidity can cause the adhesive layer to harden or lose its stickiness, requiring frequent tape replacements and increasing care costs and infection risks. Therefore, improvements are needed. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a low-sensitivity medical tape substrate and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a low-sensitivity medical tape substrate, wherein the low-sensitivity medical tape substrate comprises the following components in parts by weight: 80-100 parts thermoplastic polyurethane elastomer, 0.1-3 parts antioxidant, 0.5-5 parts polydimethylsiloxane, 0.5-5 parts silicone-modified polyurethane resin, 1-10 parts carboxymethyl chitosan, 0.5-5 parts compatibilizer, 0.1-2 parts bisabolol, and 0.1-2 parts dipotassium glycyrrhizate.

[0006] Preferably, the antioxidant is pentaerythritol tetrakis or 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid.

[0007] Preferably, the compatibilizer is maleic anhydride-grafted TPU.

[0008] This invention provides a method for preparing a low-sensitivity medical tape substrate, comprising the following steps: S1, Solid-phase shear grinding of additives: Antioxidant, carboxymethyl chitosan, bisabolol and dipotassium glycyrrhizate are added to a double cone shear grinding mill, and the equipment is started under inert gas protection; the grinding chamber is filled with zirconia ceramic grinding balls, and the filling rate is controlled at 30%-45%; it is operated in a reverse differential speed rotation mode, with the main rotor speed set at 800-1500 RPM and the auxiliary rotor speed set at 200-500 RPM, and the grinding time lasting 40-90 minutes; the particle size distribution of the material is monitored in real time, and the grinding is terminated when the D50 value reaches 200-500 nm to obtain nanoscale composite additives; S2, Polymer solid-phase shear pretreatment: Thermoplastic polyurethane elastomer and silicone-modified polyurethane resin are fed into a twin-screw extruder; the screw length-to-diameter ratio is configured as 40:1-48:1, the barrel temperature gradient is set to 150-180℃, and a reverse thread element is set in the shear zone to generate a local pressure peak of 5-15MPa; the nano-scale composite additive is quantitatively injected into the polymer melt through the side feed port, the screw speed is adjusted to 80-200RPM, and the melt pressure is maintained at 8-20MPa to obtain a premixed polymer matrix; S3, melt blending: The premixed polymer matrix, polydimethylsiloxane, and compatibilizer are fed into an internal mixer; the melt is extruded into a composite melt sheet through a hydraulic plunger extruder; S4, Ultrasonic Enhanced Dispersion: The composite molten sheet is placed in the ultrasonic processor cavity, and liquid carbon dioxide is injected as the mass transfer medium; the transducer array emits longitudinal ultrasonic waves at a frequency of 20-40kHz, with the power density controlled at 50-150W / cm², and the action time is 5-15 minutes; the ultrasonic cavitation effect causes polydimethylsiloxane to form a 100-300nm dispersed phase, and the circulating cooling is turned on simultaneously to maintain the material temperature at 60-90℃; the treated material is calendered into a homogenized colloid using a two-roll mill. S5, Supercritical fluid injection and saturation: The homogenized colloid is placed in a high-pressure reactor and supercritical carbon dioxide is introduced; the saturation time is 30-60 minutes, allowing carbon dioxide molecules to penetrate into the free volume of the polymer to form a supersaturated colloidal composite material.

[0009] Preferably, the method further includes: S6, Electric field-induced orientation and extrusion: The supersaturated colloidal composite material is introduced into an electric field-assisted extrusion die, and a DC electric field of 10-30kV / cm is applied; the inlet section temperature is maintained at 170-185℃, and the outlet section temperature drops sharply to 80-110℃ to form a temperature gradient; the screw speed is adjusted to 5-15RPM, and the draw ratio is controlled at 3:1-8:1, so that the organosilicon segments are oriented and aligned along the electric field direction to produce an oriented structure base film; S7, Pressure Drop Foaming and Cooling: The oriented structure base film is fed into a pressure-controlled foaming chamber, and the ambient pressure is reduced from 8-15MPa to atmospheric pressure within 0.5-3 seconds; supercritical carbon dioxide is instantaneously vaporized to form a 30-150μm closed-cell structure, and a gradient cooling roller group from -20℃ to 10℃ is started simultaneously, with a cooling rate of 50-150℃ / min; a microporous buffer layer material is obtained. S8, iCVD surface functional coating: The microporous buffer layer material is placed into a chemical vapor deposition device, and vinyltrimethoxysilane and hexamethyldisiloxane monomers are introduced at a molar ratio of 1:0.3-1.5; the reaction chamber pressure is maintained at 0.1-1 Torr, and the substrate is heated to 60-90°C to initiate free radical polymerization; the deposition rate is controlled at 50-200 nm / min to form an organosilicon modified surface layer, thus completing the preparation of the low-sensitivity medical tape substrate.

[0010] Preferably, in step S1, the diameter of the zirconia ceramic grinding ball is in the range of 0.5-3 mm.

[0011] Preferably, in step S3, the temperature of the mixing chamber is set to 160-190℃, the rotor speed is 30-60RPM, and the mixing time is 15-30 minutes.

[0012] Preferably, in step S5, the temperature of the high-pressure reactor is 35-50°C and the pressure is 12-25 MPa.

[0013] 1. Compared to existing technologies, this invention uses thermoplastic polyurethane elastomer as the core substrate, endowing the tape with excellent elasticity and flexibility, adapting to the dynamic deformation needs of the skin, and reducing the risk of adhesive layer cracking due to frequent activity. Antioxidants inhibit the oxidative degradation of materials, extend the service life of the tape, and prevent the release of irritating substances caused by aging. Polydimethylsiloxane and silicone-modified polyurethane resin synergistically enhance surface lubricity, reduce frictional resistance when the tape contacts the skin, and prevent damage to the epidermal barrier during tearing. Carboxymethyl chitosan provides broad-spectrum antibacterial activity, inhibiting the growth of microorganisms in the wound, while its hydrophilic properties promote the absorption of exudate and maintain a dry local microenvironment. Compatibilizers improve the interfacial bonding of multi-component materials, ensuring uniform dispersion of functional additives and avoiding performance fluctuations due to component separation. Bisabolol and dipotassium glycyrrhizate work synergistically with dual anti-inflammatory mechanisms to inhibit histamine release and inflammatory factor expression, alleviating postoperative allergic reactions such as redness, swelling, heat, and pain. The components work synergistically to reduce the risk of sensitization below the clinical safety threshold while ensuring adhesion strength. At the same time, the tape is endowed with the ability to actively repair wounds and provide long-lasting antibacterial properties, meeting the comprehensive needs of medical aesthetic scenarios for material safety, comfort and functionality.

[0014] 2. Compared to existing technologies, this invention employs reverse differential shearing and grinding technology to achieve ultrafine dispersion of active ingredients in an inert gas environment, effectively preserving the molecular activity of antioxidants and natural extracts, enhancing material stability while reducing the risk of sensitization. The polymer solid-phase pretreatment stage introduces reverse threaded elements and a precise temperature control strategy to promote molecular chain entanglement between silicone resin and thermoplastic polyurethane, forming an interpenetrating network structure, giving the substrate both high elasticity and creep resistance. Ultrasonic enhanced dispersion combined with liquid carbon dioxide mass transfer medium utilizes cavitation effect to achieve nanoscale uniform distribution of polydimethylsiloxane, enhancing surface lubricity while avoiding skin irritation from traditional solvent residues. Supercritical carbon dioxide saturation permeates to the free volume of the polymer, forming a closed-cell microstructure through pressure drop foaming, endowing the material with dynamic breathability and balancing adhesion strength with skin respiration needs. Electric field-induced orientation technology orients silicone segments, constructing anisotropic mechanical properties, improving the tape's deformation-following ability in facial muscle activity areas, and reducing local pressure concentration caused by edge lifting. Surface functional coatings form a dense organosilicon-modified layer by initiating free radical polymerization, which reduces the adhesion between the adhesive layer and the epidermis to avoid tearing damage, and also blocks external microorganisms from invading the wound.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The present invention provides a method for preparing a low-sensitivity medical tape substrate, which includes the following preparation steps. Detailed Implementation

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0019] Example 1: A low-sensitivity medical tape substrate, comprising the following components by weight: 100 parts thermoplastic polyurethane elastomer, 2 parts antioxidant, 5 parts polydimethylsiloxane, 3 parts silicone-modified polyurethane resin (Carbosil 80A), 4 parts carboxymethyl chitosan, 5 parts compatibilizer, 2 parts bisabolol, and 2 parts dipotassium glycyrrhizate.

[0020] In this embodiment, the antioxidant is pentaerythritol.

[0021] In this embodiment, the compatibilizer is maleic anhydride-grafted TPU.

[0022] This embodiment also provides a method for preparing a low-sensitivity medical tape substrate, including the following steps: S1, Solid-phase shear grinding of additives: Antioxidant, carboxymethyl chitosan, bisabolol and dipotassium glycyrrhizate are added to a double cone shear grinding mill, and the equipment is started under inert gas protection; the grinding chamber is filled with zirconia ceramic grinding balls, and the filling rate is controlled at 45%; it is operated in a reverse differential speed rotation mode, with the main rotor speed set to 1500 RPM and the auxiliary rotor speed set to 500 RPM, and the grinding time lasting for 90 minutes; the particle size distribution of the material is monitored in real time, and the grinding is terminated when the D50 value reaches 200 nm, to obtain nanoscale composite additives; S2, Polymer solid-phase shear pretreatment: Thermoplastic polyurethane elastomer and silicone-modified polyurethane resin are fed into a twin-screw extruder; the screw length-to-diameter ratio is configured as 48:1, the barrel temperature gradient is set to 180℃, and a reverse screw element is set in the shear zone to generate a local pressure peak of 15MPa; nano-grade composite additives are quantitatively injected into the polymer melt through the side feed port, the screw speed is adjusted to 200RPM, and the melt pressure is maintained at 8MPa to obtain a premixed polymer matrix; S3, melt blending: The premixed polymer matrix, polydimethylsiloxane, and compatibilizer are fed into an internal mixer; the melt is extruded into composite melt sheets through a hydraulic plunger extruder; S4, Ultrasonic Enhanced Dispersion: The composite molten sheet is placed in the ultrasonic processor cavity, and liquid carbon dioxide is injected as the mass transfer medium; the transducer array emits longitudinal ultrasonic waves at a frequency of 40kHz, with the power density controlled at 150W / cm², and the action time is 15 minutes; the ultrasonic cavitation effect causes polydimethylsiloxane to form a 300nm dispersed phase, and the circulating cooling is turned on simultaneously to maintain the material temperature at 90℃; the treated material is calendered into a homogenized colloid by a two-roll mill. S5, Supercritical Fluid Injection and Saturation: The homogenized colloid is placed in a high-pressure reactor and supercritical carbon dioxide is introduced; the saturation time is 60 minutes, allowing carbon dioxide molecules to penetrate into the free volume of the polymer to form a supersaturated colloidal composite material. S6, Electric Field Induced Orientation and Extrusion: The supersaturated colloidal composite material is introduced into the electric field assisted extrusion die and a DC electric field of 30kV / cm is applied; the inlet section temperature is kept at 170℃ and the outlet section temperature drops sharply to 80℃ to form a temperature gradient; the screw speed is adjusted to 15RPM and the draw ratio is controlled at 8:1, so that the organosilicon segments are oriented and aligned along the electric field direction to produce an oriented structure base film. S7, Pressure Drop Foaming and Cooling: The oriented structure base film is sent into the pressure-controlled foaming chamber, and the ambient pressure is reduced from 15MPa to normal pressure within 3 seconds; supercritical carbon dioxide is instantly vaporized to form a 150μm closed-cell structure, and the gradient cooling roller group from -20℃ to 10℃ is started simultaneously, with a cooling rate of 150℃ / min; microporous buffer layer material is obtained. S8, iCVD surface functional coating: The microporous buffer layer material is placed into a chemical vapor deposition device, and vinyltrimethoxysilane and hexamethyldisiloxane monomers are introduced in a molar ratio of 1:1.5; the reaction chamber pressure is maintained at 1 Torr, and the substrate is heated to 90°C to initiate free radical polymerization; the deposition rate is controlled at 200 nm / min to form an organosilicon modified surface layer, thus completing the preparation of the low-sensitivity medical tape substrate.

[0023] In this embodiment, in step S1, the diameter of the zirconia ceramic grinding ball is in the range of 3 mm.

[0024] In this embodiment, in step S3, the temperature of the mixing chamber is set to 190°C, the rotor speed is 30 RPM, and the mixing time is 30 minutes.

[0025] In this embodiment, in step S5, the temperature of the high-pressure reactor is 50°C and the pressure is 25 MPa.

[0026] Example 2 is the same as Example 1 in terms of other steps and parameters, except that a low-sensitivity medical tape substrate is provided. The low-sensitivity medical tape substrate comprises the following components by weight: 100 parts of thermoplastic polyurethane elastomer, 1 part of antioxidant, 1 part of polydimethylsiloxane, 2 parts of silicone-modified polyurethane resin (Carbosil 80A), 5 parts of carboxymethyl chitosan, 1 part of compatibilizer, 1 part of bisabolol, and 1.5 parts of dipotassium glycyrrhizate.

[0027] In this embodiment, the antioxidant is 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid.

[0028] In this embodiment, the compatibilizer is maleic anhydride-grafted TPU.

[0029] Experimental methods: 1.180° peel strength test method This test aims to evaluate the force required to peel a medical tape substrate from a standard test plate, simulating its adhesive properties in application. The test is conducted according to GB / T2792-2014 or a similar ASTM D3330 standard (Method A).

[0030] First, prepare the test sample and test plate. Cut the hypoallergenic medical tape substrate to be tested into strips with a width of 25 mm ± 0.5 mm and a length of approximately 200 mm. Thoroughly clean the surface of the standard stainless steel test plate with a cleaning agent (such as a mixture of isopropanol and heptane) and wipe it dry with a lint-free cloth to ensure that there is no oil or dust residue.

[0031] Next, attach one end of the cut tape sample to the center of the cleaned stainless steel test plate, with the length of the tape parallel to the length of the test plate. Use a standard pressure roller (e.g., 2 kg, rubber-coated) to roll back and forth on the tape twice (one back and forth movement counts as two) to ensure full and even contact between the tape and the test plate, eliminating air bubbles. The rolling speed should be kept constant, approximately 10 mm / s.

[0032] For the initial peel strength test, after rolling, the test plate should be left to stand for 20 to 40 minutes in a standard laboratory environment (temperature 23±2℃, relative humidity 50±5%). For the 24-hour peel strength test, the test plate with tape applied should be left to stand for 24±1 hours in the same environment.

[0033] Next, fix the test plate onto the lower clamp of the tensile testing machine. Fold the free end of the tape that is not attached to the test plate back 180 degrees and clamp it in the upper clamp of the tensile testing machine, ensuring that the peeling direction of the tape is parallel to the plane of the test plate.

[0034] Start the tensile testing machine and peel the tape from the test plate at a constant peel rate (typically 300 ± 10 mm / min). The machine will record the force required during the peeling process in real time. Record the force value for the middle section of the peel (excluding the sections with large data fluctuations at the beginning and end, typically the peel length between 25 mm and 175 mm).

[0035] Finally, calculate the peel strength. Read the average force recorded by the testing machine over the specified peel length. This average force is the 180° peel strength of the sample, usually reported in Newtons per 25 mm width (N / 25 mm). Test at least three parallel samples for each sample type and take the average of the results.

[0036] 2. Water vapor transmission rate (MVTR) test method Water vapor transmission rate (MVTR) is used to evaluate a material's ability to allow water vapor to pass through. It is a key indicator for measuring the breathability of medical tape substrates. High breathability helps maintain skin dryness and reduces the risk of immersion. The test can be performed according to GB / T1037-1988 or ASTM E96 / E96M (usually using the water method, i.e., the cup upright method B).

[0037] First, prepare the test sample and test cup. Cut the hypoallergenic medical tape substrate sample to be tested into a circular or other shape that can completely cover and seal the mouth of the test cup. The size should be slightly larger than the inner diameter of the cup mouth, ensuring that the edges have sufficient width for a seal. The test cup is usually made of a water vapor-impermeable material and has a specific opening area.

[0038] Add a certain amount of distilled water to the test cup, usually filling it to about two-thirds of its volume, to ensure that there is a certain air layer (about 6-15 mm) between the water surface and the inner surface of the sample to be tested, so as to prevent the liquid water from directly contacting the sample.

[0039] Cover the test cup opening with the cut substrate sample, ensuring that the side that normally contacts the skin faces inward (water vapor side) or as specified in the standard. Use a wax seal, sealing ring, or special clamp to airtightly seal the sample edge to the cup opening, ensuring that water vapor can only be transmitted through the effective test area of ​​the sample and cannot leak from the edges.

[0040] Accurately weigh the initial weight of the entire sealed test cup assembly (including the cup, water, sample, and sealing material) and record it as W1, accurate to 0.001 grams.

[0041] Place the weighed test cup assembly into a constant temperature and humidity environmental test chamber. Test conditions typically simulate the difference between body temperature and ambient humidity, for example, setting the temperature to 37±1℃ and the relative humidity to a low level (e.g., 10±2%RH), or as required by specific standards. Ensure that the air inside the test chamber has a certain circulation speed.

[0042] At predetermined time intervals (e.g., every 1, 2, or 24 hours), the test cup assembly is removed and weighed quickly, and the weight (Wt) is recorded. Weighing is repeated until several consecutive weighings show that the rate of weight loss per unit time (i.e., the water vapor permeation rate) reaches a constant. The test cycle typically lasts from several hours to tens of hours.

[0043] Finally, calculate the water vapor transmission rate (MVTR). Select a time period from the weighing data that shows a linear relationship (constant rate of weight loss). Calculate the average weight loss per unit time (ΔW = W_initial - W_final), in grams per hour. The MVTR is calculated by dividing the average weight loss rate (g / h) by the effective test area of ​​the sample (square meters), and then multiplying by 24 hours per day. That is, MVTR = (ΔW / Δt) / A*24, where Δt is the test time period (hours) and A is the test area (square meters). The result is expressed in grams per square meter per day (g / m² / 24h). At least three parallel samples should be tested for each sample type, and the average result should be taken.

[0044] 3. Skin irritation rating (human patch test) test method This test aims to evaluate the potential local irritation caused by direct and repeated contact between the medical tape substrate and human skin, serving as a core criterion for determining its "hypoallergenicity." The test must adhere to the ethical principles of the Declaration of Helsinki, obtain approval from the ethics committee and informed consent from the subjects, and refer to ISO 10993-10 "Biological evaluation of medical devices – Part 10: Irritation and skin sensitization testing" or relevant guidelines from the National Medical Products Administration.

[0045] First, qualified participants are screened. A certain number (e.g., 20-30) of healthy adult volunteers are selected, with no known history of skin disease, and the skin at the test site is intact, without damage, scars, or pigmentation abnormalities. Pregnant women, breastfeeding women, and those with a history of allergy to adhesive products are excluded.

[0046] Prepare test samples and controls. Cut the hypoallergenic medical tape substrate sample to be tested into standard sizes (e.g., 2 cm × 2 cm). At the same time, prepare negative controls (e.g., filter paper soaked in physiological saline) and / or positive controls (e.g., filter paper soaked in a known moderate irritant, such as 0.5% sodium dodecyl sulfate solution). The controls are also prepared into patch units of the same size.

[0047] Choose a test site, typically an area that is not prone to friction, has relatively sensitive and flat skin, such as the back or the flexor side of the forearm. Clean the skin at the test site and allow it to air dry.

[0048] Prepared sample and control patch units are randomly or sequentially attached to the subject's skin at the test site, ensuring close contact with the skin. Hypoallergenic, breathable medical tape or a specialized patch applicator is typically used for attachment. Each subject undergoes testing of both the sample and the control simultaneously.

[0049] According to the pre-set protocol, the duration of the patch application is determined, typically 24 or 48 hours. During this period, subjects are instructed to avoid bathing to wet the test area, avoid strenuous exercise that causes excessive sweating, and avoid scratching the test area.

[0050] After the prescribed patch application time has elapsed, carefully remove all patch units and mark the test sites with a marker. At specific time points after removal (e.g., 1 hour, 24 hours, 48 ​​hours, and / or 72 hours after removal), a trained professional evaluator observes and scores the skin reaction at each test site.

[0051] The scoring typically uses an internationally recognized standard scoring system (such as a modified version based on the Draize scoring system), primarily assessing two indicators: erythema and edema. The scoring levels are usually: 0 = no response; 1 = mild erythema / edema; 2 = significant erythema / edema; 3 = moderate to severe erythema / edema; 4 = severe erythema (purplish-red) with edema (raised >1 mm) or the presence of blisters or ulcers.

[0052] Finally, the skin irritation index is calculated. The erythema and edema scores for each subject at all observation time points are summed, and then the average of all subject scores is calculated to obtain the Primary Irritation Index (PII). Alternatively, the Mean Irritation Score (MIS) or the maximum reaction score can be calculated according to the protocol. The "Skin Irritation Score (0-4 point scale)" used in this table can be understood as a comprehensive rating or average score based on the PII or MIS value, or the most severe reaction level. The lower the score, the less irritation; the closer to 0, the less irritation.

[0053] 4. Test methods for tensile strength and elongation at break This test evaluates the mechanical properties of medical tape substrates under tensile force, including the maximum stress it can withstand (tensile strength) and the degree of stretching before breakage (elongation at break). This relates to whether the tape will easily break due to external forces such as limb movement during use. The test can be conducted according to GB / T1040.3-2006 or ASTM D882 standards.

[0054] First, prepare the test strips. Following standard specifications, use a specialized cutter or die to cut standard-shaped and sized strips from the hypoallergenic medical tape substrate along its primary production direction (machine direction, MD), typically in a long strip or dumbbell shape. Record the width and thickness of the strips for calculating the cross-sectional area. The strips should be free of visible defects and have smooth edges. A sufficient number of strips should be prepared (usually at least 5 per set).

[0055] Before testing, all specimens were conditioned for at least 24 hours in a standard laboratory environment (temperature 23±2℃, relative humidity 50±5%) to eliminate the influence of temperature and humidity on material properties.

[0056] Prepare the tensile testing machine. Select a tensile testing machine equipped with a force sensor of appropriate range and clamps suitable for holding thin film materials. Set the test parameters, including the initial gauge length (i.e., the distance between the clamps, determined according to the shape and standard of the spline) and the tensile rate (for thin film materials, a commonly used rate is 500 mm / min).

[0057] Carefully install the conditioned specimen between the upper and lower clamps of the tensile testing machine, ensuring that the long axis of the specimen is aligned with the tensile direction, that the clamps are secure without damaging the specimen, and that the specimen remains straight and free from twisting. Record the accurate initial gauge length L0.

[0058] Start the testing machine and apply a tensile load to the specimen at a set constant rate until the specimen breaks. The testing machine system will automatically record the tensile force (F) and the corresponding elongation (ΔL) throughout the process.

[0059] To calculate tensile strength: Find the maximum tensile force (Fmax) recorded during the entire stretching process. Divide this maximum force value by the initial cross-sectional area of ​​the spline (A0 = initial width × initial thickness). The result is the tensile strength, usually measured in megapascals (MPa). The formula can be described as: Tensile strength equals the maximum tensile force divided by the initial cross-sectional area of ​​the spline.

[0060] To calculate the elongation at break: Record the total elongation (ΔLf) at the instant the spline breaks. Divide this elongation at break by the initial gauge length (L0) of the spline, and then multiply by 100%. The result is the elongation at break, expressed as a percentage (%). The formula can be described as: Elongation at break equals the elongation at break divided by the initial gauge length, multiplied by 100%.

[0061] Finally, the test results of all valid specimens in the same group (those that did not slip off at the fixture or break prematurely) are calculated, outliers are removed, and the arithmetic mean is taken as the final reported values ​​of tensile strength and elongation at break of the batch of materials.

[0062] 5. Average pore size test method The determination of average pore size aims to characterize the dimensional features of the microporous structure formed within the substrate through the pressure drop foaming step (S7) in the method of this invention. This is significant for understanding the material's cushioning performance, permeability, and potential drug loading capacity. Commonly used methods include scanning electron microscopy (SEM) image analysis or gas adsorption methods (such as BET theory combined with pore size distribution calculations, but these may not be the first choice for micron-sized pores). Here, a method based on SEM image analysis is described.

[0063] First, samples for observation are prepared. Small pieces of the sample are cut from the prepared microporous buffer layer material. A clear cross-section is needed to observe the internal pore structure. This can be achieved by brittle fracture in liquid nitrogen or by slicing using an ultramicrotome. If surface porosity needs to be observed, the surface sample is used directly. For non-conductive polymer samples, a thin layer of conductive material (such as gold or carbon) is typically sprayed onto the surface to prevent charge buildup from affecting imaging quality.

[0064] The prepared sample cross-section or surface was observed using a scanning electron microscope (SEM). An appropriate magnification was selected to clearly observe a large number of representative pore structures. Multiple SEM images of different regions were taken to ensure the representativeness of the statistical results.

[0065] The acquired SEM images are processed and analyzed using image analysis software (such as ImageJ). The software can identify the pore contours in the images. An appropriate threshold needs to be set to distinguish between pores and the matrix material.

[0066] For each identified pore, the software can measure its equivalent diameter (typically the diameter of a circle calculated based on the pore area) or other dimensional parameters (such as maximum and minimum diameters). Measure the diameters of a sufficient number of pores (e.g., hundreds or even thousands, distributed across multiple images).

[0067] Calculate the average pore diameter. Collect all measured pore diameter data. Calculate the arithmetic mean of these diameters to obtain the material's average pore diameter. Sometimes, the pore diameter distribution range or median pore diameter (D50) may also be reported. The calculation method is described as follows: The average pore diameter is the sum of the equivalent pore diameters measured in all representative SEM images, divided by the total number of pores measured. Results are reported in micrometers (μm).

[0068] It is important to note that SEM observes a two-dimensional cross-section, and its results reflect the pore size information on the cross-section. For complex three-dimensional pore structures, more complex analysis or combination with other methods (such as mercury intrusion porosimetry, but which may damage soft materials) may be required to obtain more comprehensive pore structure information.

[0069] 6. Test method for total residual organic solvents This test is used to detect the total amount of organic solvents that may remain in the substrate of medical adhesive tapes, which may have been used or generated during the manufacturing process. It is an important indicator for evaluating product safety, especially for products that claim to be hypoallergenic. The commonly used method is headspace-gas chromatography (HS-GC).

[0070] First, prepare the sample and standards. Accurately weigh a certain amount of the hypoallergenic medical tape substrate sample to be tested (e.g., 0.5-1.0 g), cut it into small pieces, and place it in a headspace vial. Depending on the types of solvents that may be used in the production process (although this invention describes a melt and supercritical fluid process, theoretically solvent residue is extremely low, but testing is still required to confirm), prepare standard stock solutions containing these target solvents and a series of standard working solutions of different concentrations. Add known accurate volumes of the standard working solutions to blank headspace vials, or to a blank matrix similar to the sample matrix.

[0071] Seal the headspace vials containing the samples and standards. Then place these sealed headspace vials in the headspace sampler's heating chamber and heat them at the set temperature (e.g., 80-120°C) for a period of time (e.g., 30-60 minutes). This process allows residual volatile organic solvents in the samples to evaporate into the gas phase at the top of the vial, achieving gas-solid (or gas-liquid) equilibrium.

[0072] Set the gas chromatography (GC) conditions. Select a suitable capillary column (e.g., a moderately polar or non-polar column, such as DB-624 or PEG), set the column temperature program (e.g., hold the initial temperature for a few minutes, then ramp to the final temperature at a set rate and hold), and set the injection port temperature and detector temperature (typically a flame ionization detector (FID) is used, which responds well to most organic compounds). The carrier gas flow rate (e.g., nitrogen or helium) needs to be optimized.

[0073] An automated headspace sampler extracts a gas sample from the top of a headspace vial and injects it into a GC system for analysis. Solvent components are separated in the column based on their different interactions with the stationary phase and sequentially reach the detector. The detector generates a signal proportional to the concentration of each component. The chromatogram is then recorded.

[0074] By analyzing the chromatograms obtained from the standards, the retention times of various target solvents are determined, and standard curves (the relationship between peak area or peak height and concentration) are established.

[0075] Analyze the sample chromatogram. Qualitatively identify the types of solvents present in the sample based on retention time. Quantitatively calculate the content of each solvent in the sample (e.g., μg / g or ppm) using a standard curve based on the area or height of each solvent peak.

[0076] Calculate the total residual organic solvents. Add up the amounts of all detected target organic solvents in the sample to obtain the total residual organic solvents. The calculation method is described as follows: The total residual organic solvents are the arithmetic sum of the amounts of all detected, identified, and quantitatively calculated organic solvents in the sample. The result is reported in parts per million (ppm) or micrograms per gram (μg / g). If all target solvents are below the detection limit, report "Not Detected" or "<Detection Limit".

[0077] Experiments were conducted on the finished materials prepared in Examples 1-2, wherein Comparative Example 1 is the tape substrate disclosed in Chinese Patent Publication No. CN109988515A. The experimental results are as follows: Table 1 Performance Test Data As shown in Table 1, the low-sensitivity medical tape substrates prepared in Examples 1-2 of this invention have comprehensive advantages compared to Comparative Example 1. Most notably, the products of Examples 1-2 exhibit excellent biocompatibility, with skin irritation scores significantly lower than the comparative example, demonstrating their low-sensitivity properties and making them more suitable for sensitive skin or long-term use. Simultaneously, the water vapor permeability of the substrates in Examples 1-2 is significantly increased, indicating excellent breathability, which helps maintain skin dryness and comfort, reducing the risk of immersion. Furthermore, while maintaining suitable peel strength, the substrates of this invention also exhibit superior mechanical properties, with higher tensile strength and good elongation at break, ensuring durability and adaptability during use. The introduction of a microporous structure not only improves breathability but may also provide better cushioning and fit. The extremely low residual organic solvent content in the final product further ensures its safety.

Claims

1. A low-allergen medical tape substrate, characterized in that, The hypoallergenic medical tape substrate comprises the following components in parts by weight: 80-100 parts thermoplastic polyurethane elastomer, 0.1-3 parts antioxidant, 0.5-5 parts polydimethylsiloxane, 0.5-5 parts silicone-modified polyurethane resin, 1-10 parts carboxymethyl chitosan, 0.5-5 parts compatibilizer, 0.1-2 parts bisabolol, and 0.1-2 parts dipotassium glycyrrhizate.

2. The low-sensitivity medical tape substrate according to claim 1, characterized in that: The antioxidant is pentaerythritol or 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid.

3. The low-sensitivity medical tape substrate according to claim 1, characterized in that: The compatibilizer is maleic anhydride-grafted TPU.

4. A method for preparing a low-sensitivity medical tape substrate according to any one of claims 1-4, characterized in that, The following steps are involved: S1, Solid-phase shearing and grinding of additives: Antioxidant, carboxymethyl chitosan, bisabolol and dipotassium glycyrrhizate are put into a double cone shearing and grinding mill and run in a reverse differential speed rotation mode. When the D50 value reaches 200-500nm, the grinding is terminated to obtain nano-scale composite additives. S2, Polymer solid-phase shear pretreatment: Thermoplastic polyurethane elastomer and silicone-modified polyurethane resin are fed into a twin-screw extruder; the screw length-to-diameter ratio is configured as 40:1-48:1, the barrel temperature gradient is set to 150-180℃, and a reverse thread element is set in the shear zone to generate a local pressure peak of 5-15MPa; the nano-scale composite additive is quantitatively injected into the polymer melt through the side feed port to obtain a premixed polymer matrix; S3, melt blending: The premixed polymer matrix, polydimethylsiloxane, and compatibilizer are fed into an internal mixer; the melt is extruded into a composite melt sheet through a hydraulic plunger extruder; S4, Ultrasonic Enhanced Dispersion: The composite molten sheet is placed in the ultrasonic processor cavity, and liquid carbon dioxide is injected as the mass transfer medium; longitudinal ultrasonic waves are emitted, and the ultrasonic cavitation effect causes polydimethylsiloxane to form a 100-300nm dispersed phase. The treated material is then calendered into a homogenized colloid using a two-roll mill. S5, Supercritical fluid injection and saturation: The homogenized colloid is placed into a high-pressure reactor and supercritical carbon dioxide is introduced to form a supersaturated colloidal composite material.

5. The method for preparing the low-sensitivity medical tape substrate according to claim 4, characterized in that, The method further includes: S6, Electric field induced orientation and extrusion: The supersaturated colloidal composite material is introduced into an electric field assisted extrusion die, and a DC electric field of 10-30kV / cm is applied to make the organosilicon segments oriented and aligned along the electric field direction to produce an oriented structure base film. S7, Pressure Drop Foaming and Cooling: The oriented structure base film is sent into a pressure-controlled foaming chamber, and the ambient pressure is reduced from 8-15MPa to normal pressure within 0.5-3 seconds; supercritical carbon dioxide is instantly vaporized to form a 30-150μm closed-cell structure, and a microporous buffer layer material is obtained. S8, iCVD surface functional coating: The microporous buffer layer material is placed into a chemical vapor deposition device, and vinyltrimethoxysilane and hexamethyldisiloxane monomers are introduced in a molar ratio of 1:0.3-1.5; the reaction chamber pressure is maintained at 0.1-1 Torr, and the substrate is heated to 60-90°C to initiate free radical polymerization to form an organosilicon modified surface layer, thus completing the preparation of the low-sensitivity medical tape substrate.

6. The method for preparing the low-sensitivity medical tape substrate according to claim 4, characterized in that: In step S1, the diameter of the zirconia ceramic grinding ball ranges from 0.5 to 3 mm.

7. The method for preparing the low-sensitivity medical tape substrate according to claim 4, characterized in that: In step S3, the temperature of the mixing chamber is set to 160-190℃, the rotor speed is 30-60RPM, and the mixing time is 15-30 minutes.

8. The method for preparing the low-sensitivity medical tape substrate according to claim 4, characterized in that: In step S5, the temperature of the high-pressure reactor is 35-50℃ and the pressure is 12-25MPa.

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