Mosquito-repellent thermoplastic polyurethane composite fabric and preparation method thereof

Abstract

The invention belongs to the field of functional composite fabrics, and provides a mosquito-repellent thermoplastic polyurethane composite fabric and a preparation method thereof.According to the mosquito-repellent thermoplastic polyurethane composite fabric and the preparation method thereof, the design that mosquito-repellent microcapsules of a core-shell structure are dispersed in a thermoplastic polyurethane hot melt adhesive layer is adopted, a microcapsule core layer comprises mosquito-repellent active ingredients such as icaridin, deet or dimethyl phthalate, and the mosquito-repellent active ingredients are dispersed in a thermoplastic polyurethane hot melt adhesive layer; the shell layer is made of a polyurea material and is prepared through an interfacial polymerization method, high-load stable dispersion and controllable dot matrix film forming of the microcapsule in a hot melt adhesive system are achieved, the content of the microcapsule can reach 0.5-15 wt%, the particle size is controlled to be 0.1-2.0 m, the drug loading capacity reaches 10-60 wt%, the problem that the mosquito-repelling microcapsule is prone to damage and failure in the high-temperature melting mixing and hot-pressing compounding process is solved, and the mosquito-repelling microcapsule has good application prospects. The prepared composite fabric is high in mosquito repelling rate, still keeps an effective mosquito repelling function after being washed for multiple times, and has a wide application value.

Description

Technical Field

[0001] This invention relates to the field of functional textile composite materials, specifically to a mosquito-repellent thermoplastic polyurethane composite fabric and its preparation method. Background Technology

[0002] With the continuous growth in demand for outdoor sports, tourism and leisure, and children's health protection, textiles with mosquito-repellent functions have gradually become a research hotspot in the field of functional fabrics. These fabrics need to maintain wearing comfort while continuously releasing mosquito-repellent active ingredients to form an effective protective concentration on the skin surface, thereby reducing the risk of mosquito bites and reducing the spread of mosquito-borne diseases. In practical applications, the performance requirements of mosquito-repellent fabrics exhibit multi-dimensional characteristics. First, the mosquito-repellent efficiency must achieve a perceptible protective effect and maintain a stable release rate of active ingredients during wear. Second, the washability must meet the requirements of daily care to avoid rapid functional decay. At the same time, the release of mosquito-repellent active ingredients must be controlled within a low-odor, low-irritation range to ensure wearing comfort. In addition, the softness and breathability of the fabric should not be significantly reduced compared to the performance of conventional textiles due to functional treatment. The synergistic satisfaction of these performance requirements is of great significance for broadening the application scenarios of mosquito-repellent fabrics, increasing consumer acceptance, and promoting the development of functional textiles towards higher added value. In particular, the performance improvement of mosquito-repellent fabrics in the fields of children's clothing, sports equipment, and outdoor products will directly affect the market competitiveness of products and the health protection effect on users.

[0003] Regarding the current state of mosquito-repellent fabric development, mainstream technologies face several shortcomings. Firstly, there is a contradiction between the immobilization and controlled release of active mosquito-repellent ingredients. While traditional impregnation methods or finishing processes are simple to operate, the active ingredients are easily lost during washing, leading to a rapid decline in mosquito-repellent effectiveness. Typically, after 5-10 washes, the mosquito-repellent rate drops below 30%, failing to meet practical needs. This is because the active ingredients adhere to the fiber surface only through physical adsorption or surface coating, lacking an effective encapsulation and protective structure. Secondly, there are issues with the processing compatibility of microencapsulation technology in thermoplastic polymer systems. The problem is that although microcapsule technology can provide protection for active ingredients, the shell of the microcapsule is easily damaged by thermal stress and shear force during the high-temperature melting and mixing of thermoplastic polyurethane and other hot melt adhesive systems, which can lead to premature leakage or degradation of the active ingredients. For example, Chinese patent CN112281479A provides a moisture-wicking and quick-drying mosquito-repellent fabric and its preparation method. The fabric includes a surface fabric and an inner fabric. The finishing liquid of the inner fabric includes a moisture-wicking and quick-drying agent and a mosquito-repellent microcapsule finishing agent containing mosquito-repellent microcapsules. The mosquito-repellent agent contained in the mosquito-repellent microcapsules is a natural mosquito repellent. However, when this technology is applied to hot melt adhesive systems, the microcapsules have insufficient heat resistance and cannot withstand the processing temperature window of 110-160℃. Furthermore, there is a contradiction between the high filling capacity of microcapsules and the film quality. In order to improve the mosquito repellent effect, it is necessary to increase the content of microcapsules in the hot melt adhesive layer. However, a high filling capacity will lead to a significant increase in melt viscosity, affecting the uniformity and fineness of the lattice film formation, and easily causing defects such as missing glue dots, uneven thickness, or fluctuation in coverage. The fundamental reason is that microcapsules, as solid fillers, will destroy the rheological behavior of polymer melts, and the tendency of particle agglomeration will exacerbate the problem of uneven dispersion. Summary of the Invention

[0004] The purpose of this invention is to provide a mosquito-repellent thermoplastic polyurethane composite fabric and its preparation method, which solves the processing-structure contradiction in the prior art where mosquito-repellent microcapsules in thermoplastic polyurethane hot melt adhesive systems easily cause increased melt viscosity, narrowed processing window, and film-forming defects when achieving high filling and stable lattice film formation. It also addresses the mass transfer-durability contradiction where mosquito-repellent active ingredients need to continuously migrate and volatilize to form an effective repellent concentration, while simultaneously maintaining low odor, low irritation, and mosquito-repellent effect after multiple washes. Furthermore, it resolves the inherent conflict between insufficient mosquito-repellent efficiency due to limited release caused by improving the heat and shear stability of the microcapsule shell and the decrease in drug dosage caused by weakening the shell integrity to improve release efficiency, which cannot be simultaneously optimized by a single method.

[0005] This invention employs a synergistic design approach combining core-shell mosquito-repellent microcapsules with a thermoplastic polyurethane hot-melt adhesive layer. A highly heat-resistant polyurea shell is constructed using interfacial polymerization to encapsulate the mosquito-repellent active ingredient, forming a stable core-shell structure. This ensures the microcapsules maintain structural integrity during melt mixing and hot-pressing at 110-160℃, preventing premature leakage of the active ingredient. Simultaneously, by optimizing the shell thickness and microcapsule particle size, controlled and sustained release of the active ingredient is achieved. During wear, the microcapsule shell gradually releases the mosquito-repellent ingredient onto the skin surface under the influence of body temperature and friction, forming an effective protective concentration. Even after washing, the shell structure remains stable, maintaining a high level of mosquito-repellent effect after multiple washes. This synergistic design achieves a balance between processing stability and functional durability, overcoming the limitations of traditional technologies that struggle to simultaneously achieve both processing stability and active ingredient release.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A mosquito-repellent thermoplastic polyurethane composite fabric includes a base fabric and a thermoplastic polyurethane hot melt adhesive layer disposed on at least one side of the base fabric.

[0008] The thermoplastic polyurethane hot melt adhesive layer comprises thermoplastic polyurethane and mosquito-repellent microcapsules dispersed in the thermoplastic polyurethane hot melt adhesive layer; the mosquito-repellent microcapsules have a core-shell structure, and their core layer contains mosquito-repellent active ingredients, which are selected from one or more of picaridin, DEET, and ethyl butyl acetylaminopropionate (IR3535, also known as mosquito repellent ester).

[0009] The shell of the mosquito repellent microcapsule is a polyurea shell formed by the reaction of diisocyanate and diamine. The diisocyanate is selected from one or two of hexamethylene diisocyanate or isophorone diisocyanate, and the diamine is selected from one or two of ethylenediamine or 1,6-hexanediamine.

[0010] The mosquito-repellent microcapsules are present in the thermoplastic polyurethane hot melt adhesive layer at a content of 0.5–15 wt%, said content being based on the total mass of the thermoplastic polyurethane hot melt adhesive layer.

[0011] Furthermore, the preparation method of the mosquito-repellent microcapsules includes the following steps:

[0012] A1. Aqueous phase preparation: Polyvinyl alcohol is added to deionized water to prepare an aqueous phase with a polyvinyl alcohol mass fraction of 0.5–5.0 wt%. The aqueous phase is stirred at 200–800 r / min for 0.5–3.0 h at 60–95 °C, and the pH of the aqueous phase is adjusted to 8.5–10.5 with anhydrous sodium carbonate.

[0013] A2. Oil phase preparation: The mosquito-repellent active ingredient, diisocyanate, and optional organic solvent are mixed to form an oil phase, wherein the mosquito-repellent active ingredient accounts for 30–95 wt% of the oil phase mass, the diisocyanate accounts for 5–40 wt% of the oil phase mass, the organic solvent accounts for 0–50 wt% of the oil phase mass, and the sum of the mass fractions of the mosquito-repellent active ingredient and the diisocyanate is 50–100 wt%.

[0014] A3. Emulsification: The oil phase is added to the aqueous phase and emulsified to obtain an oil-water emulsion. The emulsification is carried out at 20–45°C and 3000–20000 r / min for 1–30 min by high-speed shear emulsification for 1–30 min at 3000–20000 r / min.

[0015] A4. Interfacial shell formation reaction: A diamine aqueous solution is added dropwise to an oil-water emulsion to make the molar ratio of NCO to NH2 in the system 0.95–1.10, and the reaction is carried out at 20–45℃ for 1.0–4.0 h to form core-shell microcapsules; wherein, the molar number of NCO groups is calculated based on the molar number of NCO groups provided by the diisocyanate in the oil phase, and the molar number of NH2 groups is calculated based on the molar number of NH2 groups provided by the diamine; the mass fraction of the diamine aqueous solution is 1–20 wt%, the dropwise addition time is 5–60 min, and the reaction is stirred at 200–800 r / min.

[0016] Furthermore, the endpoint criterion for the interfacial shell-forming reaction is that the reaction is terminated when the free NCO content in the system is ≤0.20 wt%, wherein the free NCO content is the proportion of the mass of NCO converted from unreacted isocyanate groups to the total mass of the reaction system, and is determined by dibutylamine back titration.

[0017] Furthermore, the mosquito-repellent microcapsules also include post-processing, specifically as follows: the obtained microcapsules are subjected to solid-liquid separation by centrifugation at 500–5000×g for 5–30 min at a centrifugation temperature of 15–35℃, and washed with deionized water until the pH of the supernatant is 6.5–8.0. The washing is performed by washing with deionized water 1–5 times, and centrifugation is repeated after each washing. The microcapsules are then dried at 40–70℃ for 6–24 h to obtain the mosquito-repellent microcapsules.

[0018] Furthermore, before adding the thermoplastic polyurethane hot melt adhesive layer, the mosquito-repellent microcapsules are first prepared as a thermoplastic polyurethane hot melt adhesive masterbatch containing microcapsules. The thermoplastic polyurethane hot melt adhesive masterbatch is prepared through the following steps:

[0019] B1. Raw materials: thermoplastic polyurethane and mosquito-repellent microcapsules;

[0020] B2. Formulation: The content of mosquito-repellent microcapsules in thermoplastic polyurethane hot melt adhesive masterbatch is 5–60 wt%;

[0021] B3. Melt mixing: Thermoplastic polyurethane and mosquito repellent microcapsules are melt-mixed at 110–160℃ for 0.5–5.0 min and then granulated to obtain thermoplastic polyurethane hot melt adhesive masterbatch.

[0022] Furthermore, the thermoplastic polyurethane hot melt adhesive layer is prepared by using a microcapsule-containing thermoplastic polyurethane hot melt adhesive material to form a dot matrix hot melt adhesive film, which is then laminated with release paper to form an intermediate before being hot-pressed onto the base fabric. The thermoplastic polyurethane hot melt adhesive layer has a dot matrix structure with a dot diameter of 0.2–1.5 mm, a center-to-center distance between adjacent dots of 0.5–3.0 mm, and a coverage of 20–70%.

[0023] Furthermore, the mosquito-repellent microcapsules have a particle size of 0.1–2.0 µm and a drug loading of 10–60 wt%, wherein the drug loading is the proportion of the mass of the mosquito-repellent active ingredient in the mosquito-repellent microcapsules to the total mass of the mosquito-repellent microcapsules; the average thickness of the thermoplastic polyurethane hot melt adhesive layer in the adhesive dot area is 5–40 µm; the base fabric is one of polyester, nylon, or polyester-spandex blended fabric; the melt index of the thermoplastic polyurethane is 1–25 g / 10 min, wherein the melt index is determined under conditions of 190°C and 2.16 kg load; and the Shore A hardness is 70–95.

[0024] As a concept of this invention, the design of combining core-shell structured mosquito-repellent microcapsules with a thermoplastic polyurethane hot melt adhesive layer is mainly used to enhance the functional durability and processing stability of mosquito-repellent fabrics. The polyurea shell layer forms a dense three-dimensional network through the rapid polymerization of diisocyanate and diamine at the oil-water interface. This structure has excellent heat resistance and mechanical strength, and can maintain its integrity during the melt mixing process at 110-160℃, avoiding shell layer damage and leakage of active ingredients. The selective use of hexamethylene diisocyanate and isophorone diisocyanate achieves a balance between rigidity and flexibility in the shell layer. The former provides high reactivity and a dense network, while the latter introduces an alicyclic structure to enhance weather resistance. Ethylenediamine and 1,6-hexanediamine serve as shell-forming agents, and their short-chain structures ensure rapid interfacial reactions, while the difference in carbon chain length regulates the crosslinking density and permeability of the shell layer. Icaridine, DEET, or IR3535, used as core layer materials, exhibit low water solubility and volatility. Microcapsule encapsulation significantly reduces the rate of aqueous phase migration during washing. The shell layer allows for controlled, sustained release of the active ingredients. During wear, body temperature and friction promote the diffusion of the active ingredients outward from the shell, establishing an effective concentration gradient on the skin surface for continuous mosquito repellency. Under static conditions, the release rate is lower. Under washing conditions, the polyurea shell layer blocks the migration of the mosquito-repellent active ingredients into the aqueous phase, significantly reducing its loss rate compared to unencapsulated systems, thus extending its functional lifespan. The thermoplastic polyurethane hot melt adhesive containing microcapsules is formed into regularly arranged adhesive dots through a dot matrix process. Precise control of the dot diameter and center distance ensures the fabric remains soft and breathable while achieving uniform distribution of the mosquito-repellent function. The 20-70% coverage design balances functionality and comfort.

[0025] This invention also discloses a method for preparing the mosquito-repellent thermoplastic polyurethane composite fabric, comprising the following steps:

[0026] S1. Provides mosquito repellent microcapsules;

[0027] S2. Thermoplastic polyurethane and mosquito-repellent microcapsules are melt-blended at 110–160℃ for 0.5–5.0 min to obtain a thermoplastic polyurethane hot melt adhesive material containing microcapsules, wherein the content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive material containing microcapsules is 0.5–15 wt%.

[0028] S3. The thermoplastic polyurethane hot melt adhesive material is bonded to the base fabric and hot-pressed at 110–140℃ to obtain a mosquito-repellent thermoplastic polyurethane composite fabric.

[0029] In step S2, thermoplastic polyurethane hot melt adhesive masterbatch is first prepared, and then the thermoplastic polyurethane hot melt adhesive masterbatch is mixed with thermoplastic polyurethane to form thermoplastic polyurethane hot melt adhesive material.

[0030] The preparation of the thermoplastic polyurethane hot melt adhesive masterbatch includes: melting and mixing thermoplastic polyurethane with mosquito repellent microcapsules at 110–160°C for 0.5–5.0 min and then granulating, wherein the content of mosquito repellent microcapsules in the thermoplastic polyurethane hot melt adhesive masterbatch is 5–60 wt%.

[0031] Furthermore, the thermoplastic polyurethane hot melt adhesive material is prepared into a dot matrix hot melt adhesive film, and after the release paper is laminated onto the dot matrix hot melt adhesive film, hot pressing is performed. The hot pressing pressure is 0.2–0.6 MPa, the hot pressing time is 3–30 s, and the hot pressing process also includes a cooling and shaping step, with a cooling and shaping temperature of 15–35℃.

[0032] Furthermore, the dot diameter of the dot matrix hot melt adhesive film is 0.2–1.5 mm, the center distance between adjacent dots is 0.5–3.0 mm, and the coverage is 20–70%.

[0033] Furthermore, the degree of alcoholysis of the polyvinyl alcohol is 85–99 mol%, and the viscosity of the 4 wt% aqueous solution of the polyvinyl alcohol at 20°C is 3–30 mPa·s.

[0034] Furthermore, the aqueous phase described in step A1 is adjusted to a pH of 8.5–10.5 and then cooled to 20–45°C before proceeding to step A3.

[0035] Furthermore, adjusting the pH of the aqueous phase to 8.5–10.5 with anhydrous sodium carbonate in step A1 includes adjusting the pH to 8.5–10.5 using an aqueous sodium carbonate solution with a mass fraction of 1–20 wt%.

[0036] Furthermore, the oil phase in step A2 further comprises an organic solvent selected from one or more of ethyl acetate, cyclohexane, and isododecane, and the organic solvent accounts for 0.1–50 wt% of the oil phase mass.

[0037] Furthermore, the mass ratio of the oil phase to the water phase in step A3 is 1:0.5–1:10.

[0038] Furthermore, the high-speed shear emulsification described in step A3 uses a stator-rotor shear head, and the temperature fluctuation during the emulsification process does not exceed ±3℃.

[0039] Furthermore, in step A4, the diamine aqueous solution is added at a rate of 0.1–10 mL / min.

[0040] Furthermore, in step A4, the pH of the system is maintained at 8.5–10.5 during the interfacial shell-forming reaction.

[0041] Furthermore, in step A5, the sample amount for the dibutylamine back titration method is 0.1–5.0 g, and the titration endpoint is determined using bromophenol blue indicator or potentiometric titration.

[0042] Furthermore, in step A6, the amount of deionized water used for washing is 1–20 times the mass of the microcapsule wet filter cake, and each washing is performed with stirring at 100–500 r / min for 1–10 min.

[0043] Furthermore, in step B3, the melt mixing is performed using a twin-screw extruder with a screw speed of 50–500 r / min and a barrel temperature zone of 110–160℃.

[0044] Furthermore, in step S3, the hot-pressing pressure is 0.2–0.6 MPa, the hot-pressing time is 3–30 s, and after hot-pressing, the product is cooled and shaped at 15–35℃ for 10–300 s.

[0045] Furthermore, the particle size of the mosquito-repellent microcapsules was determined by dynamic light scattering at a test temperature of 25°C. The dispersion medium was deionized water. The sample was diluted to a solid content of 0.01–0.10 wt%, and ultrasonically dispersed at 20–40 kHz and 50–300 W for 1–10 min while controlling the temperature of the dispersion at 20–30°C before testing.

[0046] Furthermore, the drug loading was obtained by solvent extraction of the mosquito-repellent active ingredient and determination by gas chromatography or high performance liquid chromatography. The solvent was selected from one or more of acetonitrile, methanol, and ethyl acetate. The extraction conditions were a mass-to-volume ratio of microcapsules to solvent of 1 g: 5–100 mL. After shaking or stirring at 20–40℃ for 30–240 min, the supernatant was taken for quantitative analysis. The external standard method was used to establish a calibration curve for quantification.

[0047] Furthermore, the mosquito-repellent effect of the mosquito-repellent thermoplastic polyurethane composite fabric is evaluated according to the mosquito repellency test specified in GB / T 30126 or the standardized mosquito repellency test based on the equivalent principle, and the mosquito repellency rate is still not less than 50% after 5–50 washes. The washing is carried out at 40°C, the single washing time is 30 min, and the detergent concentration is 2 g / L.

[0048] Furthermore, the mosquito repellent microcapsules retain no less than 70% of their drug loading after being melt-mixed at 110–160℃ for 0.5–5.0 min.

[0049] As another aspect of this invention, the method of preparing mosquito-repellent microcapsules using interfacial polymerization combined with masterbatch dilution and lattice hot-pressing composite process is mainly used to enhance the dispersion uniformity and processing adaptability of microcapsules in thermoplastic polyurethane systems. In the aqueous phase preparation, polyvinyl alcohol (PVA) acts as a protective colloid, forming a stable adsorption layer on the surface of oil droplets. Its concentration of 0.5-5.0 wt% and the alkaline environment with a pH of 8.5-10.5 jointly reduce the interfacial tension between oil and water and inhibit droplet aggregation. Heating and stirring at 60-95℃ promotes the full dissolution of PVA and enhances interfacial stability. In the oil phase preparation, the mass ratio of mosquito-repellent active ingredient to diisocyanate is 30-95:5-40 to achieve a balance between high drug loading and sufficient shell material concentration. High-speed shear emulsification at 3000-20000 r / min and 20-45℃ disperses the oil phase into tiny droplets with a particle size of 0.1-2.0 µm. The rotation speed and temperature are controlled in a coordinated manner to ensure emulsification efficiency and avoid high-temperature pre-reaction. In the interfacial shell-forming reaction, the dropwise addition of diamine aqueous solution initiates rapid polymerization at the oil-water interface. Precise control of the NCO / NH2 molar ratio (0.95-1.10) ensures the reaction approaches stoichiometry, avoiding excess monomer residue. A reaction temperature of 20-45℃ and a time of 1.0-4.0 h allow the polyurea shell to gradually thicken and solidify. The melt-blending process involves first preparing a high-concentration masterbatch (5-60 wt% microcapsule content) and then diluting it to 0.5-15 wt%, a two-step method that significantly improves dispersion uniformity. During masterbatch preparation, the high-concentration microcapsules are briefly blended with polyurethane at 110-160℃, wetting and coating the microcapsule surface to form a pre-dispersed structure, which reduces the tendency for agglomeration in subsequent dilution. The lattice hot-pressing lamination process, controlled at 0.2-0.6 MPa and 3-30 s, ensures a strong bond between the adhesive layer and the base fabric while avoiding excessive pressure that could damage the microcapsules. Cooling and setting at 15-35℃ allows the hot melt adhesive to solidify rapidly, maintaining the integrity of the lattice structure.

[0050] The polyurea shell and thermoplastic polyurethane matrix exhibit a significant synergistic effect in the system of this invention. The polyurea shell primarily focuses on the immobilization and controlled release of the mosquito-repellent active ingredients. Through rapid interfacial polymerization of diisocyanate and diamine, it forms a dense three-dimensional network, providing high heat resistance and mechanical strength. During melt processing at 110-160℃, it resists thermal stress and shear force, preventing shell damage and leakage of active ingredients. The microporous structure and certain permeability of the shell allow for controlled and slow release of the active ingredients onto the skin surface during wear, forming an effective mosquito-repellent concentration. During washing, the shell's barrier effect on the aqueous phase significantly reduces the rate of active ingredient loss, improving wash resistance. The thermoplastic polyurethane matrix primarily focuses on providing soft and comfortable wearability and good film-forming properties. Its low melt viscosity and excellent rheological properties allow the microcapsule-containing melt to successfully form a lattice film. A melt index of 1-25 g / 10 min and a Shore A hardness of 70-95 match, ensuring the hot melt adhesive layer maintains a certain strength without affecting the fabric's softness and breathability. The synergistic effect of the two is reflected in the fact that the polyurea shell protects the microcapsules from damage during the thermoplastic polyurethane melt processing, while the thermoplastic polyurethane matrix provides the microcapsules with a dispersion carrier and film-forming matrix. Through the two-step masterbatch method, the surface of the microcapsules is fully wetted and coated by polyurethane, reducing the tendency of agglomeration and achieving uniform dispersion. Finally, in the lattice hot pressing composite, the polyurethane matrix and the base fabric fibers form mechanical interlocking and molecular diffusion bonding, while the polyurea microcapsules are stably dispersed in the adhesive layer and continuously release mosquito-repellent ingredients. This synergistic mechanism also improves the processing stability, functional durability and wearing comfort of the fabric.

[0051] Beneficial technical effects

[0052] 1. Significantly improves the durability and washability of mosquito repellent function: Through the dense encapsulation of mosquito repellent active ingredients by polyurea shell, the protective effect of microcapsules on active ingredients is significantly enhanced during water washing. The barrier effect of the shell on water phase penetration greatly reduces the rate of loss of active ingredients. Experiments show that after 5-50 standard washes (40℃, 30 min, 2 g / L detergent), the mosquito repellent rate can still be maintained at more than 50%. Compared with the traditional immersion method or finishing process (the mosquito repellent rate drops to below 30% after 5-10 washes), the washability is improved by more than 3 times. This fundamentally solves the problem of rapid decline in the function of mosquito repellent fabrics, extends the service life of the product, and reduces the cost of use for consumers.

[0053] 2. Effectively solves the processing stability problem of microcapsules in thermoplastic polyurethane systems: The dense three-dimensional network structure formed by interfacial polymerization of polyurea shell has excellent heat resistance and mechanical strength, and can maintain structural integrity during melt mixing and hot pressing at 110-160℃. After high-temperature melt mixing, the drug loading retention rate of microcapsules is not less than 70%, avoiding the problem of large-scale leakage and degradation of active ingredients caused by shell damage during the heat processing of traditional microcapsules. This significantly broadens the application window of microcapsules in thermoplastic polymer systems and provides technical support for the large-scale application of mosquito repellent function in the field of hot melt adhesive composite fabrics.

[0054] 3. Achieving synergy between high microcapsule filling and excellent lattice film quality: A two-step dispersion strategy using masterbatch is adopted. First, a high-concentration masterbatch with a microcapsule content of 5-60 wt% is prepared so that the surface of the microcapsules is fully wetted and coated by thermoplastic polyurethane to form a pre-dispersed structure. Then, it is diluted to a final content of 0.5-15 wt%. This process significantly improves the dispersion uniformity of microcapsules in the polyurethane matrix and reduces the tendency to agglomerate. This allows for the achievement of a fine lattice structure with a dot diameter of 0.2-1.5 mm, a center distance of 0.5-3.0 mm, and a coverage of 20-70% even with a high microcapsule filling amount. This avoids problems such as increased melt viscosity and film defects (missing glue dots, uneven thickness) caused by high filling. While ensuring the mosquito repellent effect, the softness and breathability of the fabric are maintained.

[0055] 4. Balancing controlled release of mosquito-repellent active ingredients with low odor and low irritation: The microporous structure and permeability of the polyurea shell enable the mosquito-repellent active ingredients to exhibit controlled and sustained release during wear. Under body temperature (approximately 36-37℃) and friction, the active ingredients migrate outward from the shell through a diffusion mechanism, establishing an effective mosquito-repellent concentration gradient on the skin surface. The moderate release rate ensures a continuous mosquito-repellent effect while avoiding the strong odor and skin irritation caused by instantaneous large-scale volatilization. Compared to direct coating or impregnation processes, microencapsulation technology enables the release of active ingredients to exhibit sustained and controlled release characteristics, improving wearing comfort and consumer acceptance. It is particularly suitable for children's clothing and skin-friendly textiles.

[0056] 5. Offers flexible product design and application expansion space: The dot matrix hot melt adhesive film structure can achieve product designs with different functional levels and comfort levels by combining and adjusting the dot diameter, center distance and coverage. High coverage (60-70%) is suitable for scenarios with high mosquito repellency requirements, such as outdoor sports equipment and camping products, while low coverage (20-30%) is suitable for everyday casual wear and children's underwear, which have high requirements for softness and breathability. The choice of polyester, nylon or polyester-spandex blended fabrics for the base fabric further broadens the application range. This technical route has good process flexibility and market adaptability, providing technical support for the differentiated development of functional textiles. Attached Figure Description

[0057] Figure 1 This is a superimposed FTIR infrared spectrum of the polyurea shell of the core-shell microcapsule.

[0058] Figure 2 This is a particle size and volume distribution diagram of DLS in core-shell microcapsules.

[0059] Figure 3 This is a cumulative particle size distribution diagram of DLS in core-shell microcapsules.

[0060] Figure 4 This is a superimposed TGA thermogravimetric curve of the core-shell microcapsules.

[0061] Figure 5 This is a superimposed graph of the DTG weight loss rate curves of core-shell microcapsules.

[0062] Figure 6 This is a superimposed DSC differential scanning calorimetry curve of the core-shell microcapsule. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0064] Example 1

[0065] This embodiment provides a mosquito-repellent thermoplastic polyurethane composite fabric, including a polyester base fabric and a thermoplastic polyurethane hot melt adhesive layer disposed on one side of the polyester base fabric.

[0066] The thermoplastic polyurethane hot melt adhesive layer of this embodiment comprises thermoplastic polyurethane and mosquito-repellent microcapsules dispersed in the thermoplastic polyurethane hot melt adhesive layer, with the content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive layer being 8 wt%. The mosquito-repellent microcapsules of this embodiment have a core-shell structure, with the core layer containing DEET as the mosquito-repellent active ingredient, and the shell layer being a polyurea shell layer formed by the reaction of hexamethylene diisocyanate and 1,6-hexanediamine.

[0067] The mosquito-repellent microcapsules of this embodiment are prepared according to the following method:

[0068] Step A1: Aqueous phase preparation: Polyvinyl alcohol (PVA) was added to deionized water to prepare an aqueous phase with a PVA mass fraction of 2.5 wt%. In this example, the degree of alcoholysis of PVA used was 92 mol%, and the viscosity of a 4 wt% aqueous solution at 20°C was 15 mPa·s. The aqueous phase was stirred at 500 r / min for 1.5 h at 75°C. The pH of the aqueous phase was adjusted to 9.5 using a 10 wt% sodium carbonate aqueous solution. After adjusting the pH, the aqueous phase was cooled to 30°C.

[0069] Step A2: Oil phase preparation: DEET, hexamethylene diisocyanate and ethyl acetate are mixed to form an oil phase, wherein DEET accounts for 60 wt% of the oil phase mass, hexamethylene diisocyanate accounts for 25 wt% of the oil phase mass, ethyl acetate as an organic solvent accounts for 15 wt% of the oil phase mass, and the sum of the mass fractions of the mosquito repellent active ingredient and diisocyanate is 85 wt%.

[0070] Step A3 Emulsification: The oil phase is added to the aqueous phase for emulsification to obtain an oil-water emulsion. In this embodiment, the mass ratio of the oil phase to the aqueous phase is 1:3. The emulsification operation is performed at 30°C using a stator-rotor shear head at 10,000 r / min for 10 minutes. Temperature fluctuations during the emulsification process are controlled within ±3°C.

[0071] Step A4: Interface shell formation reaction: 1,6-hexamethylenediamine aqueous solution was added dropwise to the oil-water emulsion at a rate of 2 mL / min for 30 min, so that the molar ratio of NCO to NH2 in the system was 1.02. The molar number of NCO groups was calculated based on the number of NCO groups provided by hexamethylene diisocyanate in the oil phase, and the molar number of NH2 groups was calculated based on the number of NH2 groups provided by 1,6-hexamethylenediamine. In this example, the mass fraction of the 1,6-hexamethylenediamine aqueous solution was 10 wt%. The reaction was carried out at 30°C for 2.5 h with stirring at 500 r / min to form core-shell microcapsules. The pH of the system was maintained at 9.5 during the reaction.

[0072] Step A5 Endpoint Determination: The reaction is terminated when the free NCO content in the system is ≤0.20 wt%. In this example, the free NCO content is determined by dibutylamine back titration, with a sample size of 1.0 g. The titration endpoint is determined using bromophenol blue indicator. The free NCO content is the proportion of the mass of NCO converted from unreacted isocyanate groups to the total mass of the reaction system, and the determined result is 0.15 wt%.

[0073] Post-processing in step A6: The obtained microcapsules were centrifuged at 2500×g for 15 min at 25℃, and washed with deionized water until the pH of the supernatant reached 7.2. The amount of deionized water used for washing was 10 times the mass of the wet filter cake of the microcapsules. Each wash was performed with stirring at 300 r / min for 5 min, followed by repeated centrifugation, for a total of 3 washes. After washing, the microcapsules were dried at 55℃ for 12 h to obtain mosquito-repellent microcapsules.

[0074] The mosquito-repellent microcapsules prepared in this embodiment have a particle size of 1.0 µm. Dynamic light scattering was used for particle size determination at a test temperature of 25℃. Deionized water was used as the dispersion medium. The sample was diluted to a solid content of 0.05 wt%, and ultrasonically dispersed at 30 kHz and 150 W for 5 min, with the dispersion temperature controlled at 25℃ before testing. The drug loading of the mosquito-repellent microcapsules was 35 wt%, obtained by extracting the active mosquito-repellent ingredient with ethyl acetate and determining it by gas chromatography. The extraction conditions were a mass-to-volume ratio of microcapsules to ethyl acetate of 1 g: 50 mL. After stirring at 30℃ for 120 min, the supernatant was collected for quantitative analysis, and an external standard method was used to establish a calibration curve for quantification. The drug loading retention rate of the mosquito-repellent microcapsules in this embodiment was 82% after melt mixing at 110-160℃ for 2.5 min, meeting the requirement of not less than 70%.

[0075] In this embodiment, a thermoplastic polyurethane hot melt adhesive masterbatch containing microcapsules was first prepared: thermoplastic polyurethane and mosquito-repellent microcapsules were melt-blended at 135°C using a twin-screw extruder for 2.5 min, followed by granulation to obtain the thermoplastic polyurethane hot melt adhesive masterbatch. The content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive masterbatch was 30 wt%. The screw speed of the twin-screw extruder was 250 r / min, and the barrel temperature zone was 135°C. The thermoplastic polyurethane used in this embodiment had a melt index of 12 g / 10min and a Shore A hardness of 82, measured at 190°C and a load of 2.16 kg.

[0076] In this embodiment, thermoplastic polyurethane hot melt adhesive masterbatch and pure thermoplastic polyurethane were melt-blended at 135°C for 2.5 min to obtain a thermoplastic polyurethane hot melt adhesive material containing microcapsules. The mosquito-repellent microcapsules accounted for 8 wt% of the content in the microcapsule-containing thermoplastic polyurethane hot melt adhesive material. The thermoplastic polyurethane hot melt adhesive material was then prepared into a dot matrix hot melt adhesive film using a hot melt adhesive dotting method while molten at 135°C. The dot diameter was 0.8 mm, the center-to-center distance between adjacent dots was 1.6 mm, the coverage was 45%, and the thickness of the dot matrix hot melt adhesive film was 20 µm. Release paper was then laminated onto the dot matrix hot melt adhesive film to form an intermediate.

[0077] The intermediate and polyester base fabric were hot-pressed together at 125°C with a pressure of 0.4 MPa for 15 seconds to obtain a mosquito-repellent thermoplastic polyurethane composite fabric. After hot-pressing, the fabric was cooled and set at 25°C for 150 seconds.

[0078] The mosquito-repellent effect of the mosquito-repellent thermoplastic polyurethane composite fabric prepared in this embodiment was evaluated according to the mosquito repellency test specified in GB / T 30126. After 25 washes, the mosquito repellency rate was 68%, meeting the requirement of not less than 50%. The washing conditions were 40℃, with a single washing time of 30 min and a detergent concentration of 2 g / L.

[0079] Features of Example 1: This example uses moderate process parameters: polyvinyl alcohol concentration of 2.5 wt%, DEET content in the oil phase of 60 wt%, and microcapsule content in the hot melt adhesive layer of 8 wt%. The reaction temperature and time are moderate, resulting in good process stability and high reproducibility. The microcapsule particle size is 1.0 µm, the drug loading is 35 wt%, the hot melt adhesive layer thickness is 20 µm, and the dot matrix coverage is 45%. With balanced parameters, it is suitable for the production of everyday protective outdoor clothing, sportswear, and home textiles, maintaining good hand feel and breathability while ensuring mosquito repellency.

[0080] Example 2

[0081] This embodiment provides a mosquito-repellent thermoplastic polyurethane composite fabric, including a nylon base fabric and a thermoplastic polyurethane hot melt adhesive layer disposed on one side of the nylon base fabric.

[0082] The thermoplastic polyurethane hot melt adhesive layer of this embodiment comprises thermoplastic polyurethane and mosquito-repellent microcapsules dispersed in the thermoplastic polyurethane hot melt adhesive layer, with the content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive layer being 12 wt%. The mosquito-repellent microcapsules of this embodiment have a core-shell structure, with the core layer containing a mixture of icolinergic acid and IR3535 as the mosquito-repellent active ingredient, wherein icolinergic acid accounts for 70 wt% of the total amount of mosquito-repellent active ingredient and IR3535 accounts for 30 wt%, and the shell layer is a polyurea shell layer formed by the reaction of isophorone diisocyanate and ethylenediamine.

[0083] The mosquito-repellent microcapsules of this embodiment are prepared according to the following method:

[0084] Step A1: Aqueous phase preparation: Polyvinyl alcohol (PVA) was added to deionized water to prepare an aqueous phase with a PVA mass fraction of 3.5 wt%. In this example, the degree of alcoholysis of PVA used was 95 mol%, and the viscosity of a 4 wt% aqueous solution at 20°C was 22 mPa·s. The aqueous phase was stirred at 85°C and 650 r / min for 2.2 h. The pH of the aqueous phase was adjusted to 10.0 using a 15 wt% sodium carbonate aqueous solution. After adjusting the pH, the aqueous phase was cooled to 38°C.

[0085] Step A2: Oil phase preparation: Icaridine, DEET, isophorone diisocyanate and cyclohexane are mixed to form an oil phase, wherein the mosquito-repellent active ingredient (70% icaridine + 30% DEET) accounts for 85 wt% of the oil phase mass, isophorone diisocyanate accounts for 10 wt% of the oil phase mass, and cyclohexane as an organic solvent accounts for 5 wt% of the oil phase mass. The sum of the mass fractions of the mosquito-repellent active ingredient and diisocyanate is 95 wt%.

[0086] Step A3 Emulsification: The oil phase is added to the aqueous phase for emulsification to obtain an oil-water emulsion. In this embodiment, the mass ratio of the oil phase to the aqueous phase is 1:6. The emulsification operation is carried out at 38°C using a stator-rotor shear head at 15000 r / min for 20 minutes. The temperature fluctuation during the emulsification process is controlled within ±3°C.

[0087] Step A4: Interface shell formation reaction: An aqueous ethylenediamine solution was added dropwise to the oil-water emulsion at a rate of 4 mL / min over a period of 45 min, resulting in a NCO to NH2 molar ratio of 1.05. The molar number of NCO groups was calculated based on the number of NCO groups provided by isophorone diisocyanate in the oil phase, and the molar number of NH2 groups was calculated based on the number of NH2 groups provided by ethylenediamine. In this example, the mass fraction of the aqueous ethylenediamine solution was 15 wt%. The reaction was carried out at 38°C for 3.0 h with stirring at 650 r / min to form core-shell microcapsules. The pH of the system was maintained at 10.0 during the reaction.

[0088] Step A5 Endpoint Determination: The reaction is terminated when the free NCO content in the system is ≤0.20 wt%. In this example, the free NCO content is determined by dibutylamine back titration, with a sample size of 1.5 g. The titration endpoint is determined by potentiometric titration. The free NCO content is the proportion of the mass of NCO converted from unreacted isocyanate groups to the total mass of the reaction system, and the result is 0.12 wt%.

[0089] Post-processing in step A6: The obtained microcapsules were centrifuged at 3500×g for 20 min at 30℃, and washed with deionized water until the pH of the supernatant reached 7.5. The amount of deionized water used for washing was 15 times the mass of the wet filter cake of the microcapsules. Each wash was performed with stirring at 400 r / min for 6 min, followed by repeated centrifugation, for a total of 4 washes. After washing, the microcapsules were dried at 62℃ for 16 h to obtain mosquito-repellent microcapsules.

[0090] The mosquito-repellent microcapsules prepared in this embodiment have a particle size of 1.5 µm. Dynamic light scattering was used for particle size determination at a test temperature of 25°C. Deionized water was used as the dispersion medium. The sample was diluted to a solid content of 0.08 wt%, and ultrasonically dispersed at 35 kHz and 200 W for 6 min, with the dispersion temperature controlled at 25°C before testing. The drug loading of the mosquito-repellent microcapsules was 50 wt%, obtained by methanol extraction of the active mosquito-repellent ingredient and determination by high-performance liquid chromatography (HPLC). The extraction conditions were a mass-to-volume ratio of microcapsules to methanol of 1 g:80 mL. After shaking at 35°C for 180 min, the supernatant was collected for quantitative analysis, and an external standard method was used to establish a calibration curve for quantification. The drug loading retention rate of the mosquito-repellent microcapsules in this embodiment was 76% after melt mixing at 110-160°C for 3.5 min, meeting the requirement of not less than 70%.

[0091] In this embodiment, a thermoplastic polyurethane hot melt adhesive masterbatch containing microcapsules was first prepared: thermoplastic polyurethane and mosquito-repellent microcapsules were melt-blended at 145°C using a twin-screw extruder for 3.5 min, followed by granulation to obtain the thermoplastic polyurethane hot melt adhesive masterbatch. The content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive masterbatch was 45 wt%. The screw speed of the twin-screw extruder was 350 r / min, and the barrel temperature zone was 145°C. The thermoplastic polyurethane used in this embodiment had a melt index of 18 g / 10min and a Shore A hardness of 88, measured at 190°C and a load of 2.16 kg.

[0092] In this embodiment, thermoplastic polyurethane hot melt adhesive masterbatch and pure thermoplastic polyurethane were melt-blended at 145°C for 3.5 min to obtain a microcapsule-containing thermoplastic polyurethane hot melt adhesive material. The mosquito-repellent microcapsules accounted for 12 wt% of the content in the microcapsule-containing thermoplastic polyurethane hot melt adhesive material. The thermoplastic polyurethane hot melt adhesive material was then prepared into a dot matrix hot melt adhesive film using a hot melt adhesive dotting method while molten at 145°C. The dot diameter was 1.2 mm, the center-to-center distance between adjacent dots was 2.4 mm, the coverage was 60%, and the thickness of the dot matrix hot melt adhesive film was 30 µm. Release paper was then laminated onto the dot matrix hot melt adhesive film to form an intermediate.

[0093] The intermediate and nylon base fabric were hot-pressed together at 135℃ with a pressure of 0.5 MPa for 25 s to obtain a mosquito-repellent thermoplastic polyurethane composite fabric. After hot-pressing, the fabric was cooled and set at 30℃ for 200 s.

[0094] The mosquito-repellent effect of the mosquito-repellent thermoplastic polyurethane composite fabric prepared in this embodiment was evaluated according to the mosquito repellency test specified in GB / T 30126. After 35 washes, the mosquito repellency rate was 75%, meeting the requirement of not less than 50%. The washing conditions were 40℃, with a single washing time of 30 min and a detergent concentration of 2 g / L.

[0095] Features of Example 2: This example utilizes a high concentration of mosquito-repellent active ingredients. The oil phase contains 85 wt% of the active mosquito-repellent ingredient (a combination of picaridin and IR3535), the microcapsule loading is as high as 50 wt%, the microcapsule content in the hot melt adhesive layer is 12 wt%, the hot melt adhesive layer thickness is 30 µm, the dot matrix coverage is 60%, and the mosquito-repellent effect is long-lasting. Isophorone diisocyanate and ethylenediamine are used to form the shell layer. The high reaction temperature (85℃ aqueous phase preparation, 38℃ emulsification and shell formation) and long reaction time (3.0 h) are beneficial for forming a dense polyurea shell layer. It is suitable for long-lasting protective outdoor adventure clothing, field work protective clothing, and functional textiles requiring high-strength mosquito repellency, providing excellent mosquito-repellent durability and washability.

[0096] Example 3

[0097] This embodiment provides a mosquito-repellent thermoplastic polyurethane composite fabric, including a polyester-spandex blended base fabric and a thermoplastic polyurethane hot melt adhesive layer disposed on one side of the polyester-spandex blended base fabric.

[0098] The thermoplastic polyurethane hot melt adhesive layer of this embodiment comprises thermoplastic polyurethane and mosquito-repellent microcapsules dispersed in the thermoplastic polyurethane hot melt adhesive layer, with the content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive layer being 3 wt%. The mosquito-repellent microcapsules of this embodiment have a core-shell structure, with the core layer containing DEET as the mosquito-repellent active ingredient, and the shell layer being a polyurea shell layer formed by reacting a mixture of hexamethylene diisocyanate and isophorone diisocyanate (mass ratio 6:4) with 1,6-hexanediamine.

[0099] The mosquito-repellent microcapsules of this embodiment are prepared according to the following method:

[0100] Step A1: Aqueous phase preparation: Polyvinyl alcohol (PVA) was added to deionized water to prepare an aqueous phase with a PVA mass fraction of 1.2 wt%. In this example, the degree of alcoholysis of PVA used was 88 mol%, and the viscosity of a 4 wt% aqueous solution at 20°C was 8 mPa·s. The aqueous phase was stirred at 350 r / min for 1.0 h at 68°C. The pH of the aqueous phase was adjusted to 9.0 using a 5 wt% sodium carbonate aqueous solution. After adjusting the pH, the aqueous phase was cooled to 25°C.

[0101] Step A2: Oil phase preparation: DEET is mixed with hexamethylene diisocyanate, isophorone diisocyanate and isododecane to form an oil phase, wherein DEET accounts for 40 wt% of the oil phase mass, the diisocyanate mixture (60% hexamethylene diisocyanate + 40% isophorone diisocyanate) accounts for 30 wt% of the oil phase mass, and isododecane, as an organic solvent, accounts for 30 wt% of the oil phase mass. The sum of the mass fractions of the mosquito-repellent active ingredient and the diisocyanates is 70 wt%.

[0102] Step A3 Emulsification: The oil phase is added to the aqueous phase for emulsification to obtain an oil-water emulsion. In this embodiment, the mass ratio of the oil phase to the aqueous phase is 1:8. The emulsification operation is carried out at 25°C using a stator-rotor shear head at 6000 r / min for 5 min, and the temperature fluctuation during the emulsification process is controlled within ±3°C.

[0103] Step A4: Interface shell formation reaction: 1,6-hexanediamine aqueous solution was added dropwise to the oil-water emulsion at a rate of 1 mL / min for 15 min, so that the molar ratio of NCO to NH2 in the system was 0.98. The molar number of NCO groups was calculated based on the number of NCO groups provided by the diisocyanate mixture in the oil phase, and the molar number of NH2 groups was calculated based on the number of NH2 groups provided by 1,6-hexanediamine. In this example, the mass fraction of the 1,6-hexanediamine aqueous solution was 5 wt%. The reaction was carried out at 25°C for 1.5 h with stirring at 350 r / min to form core-shell microcapsules. The pH of the system was maintained at 9.0 during the reaction.

[0104] Step A5 Endpoint Determination: The reaction is terminated when the free NCO content in the system is ≤0.20 wt%. In this example, the free NCO content is determined by dibutylamine back titration, with a sample size of 0.5 g. The titration endpoint is determined using bromophenol blue indicator. The free NCO content is the proportion of the mass of NCO converted from unreacted isocyanate groups to the total mass of the reaction system, and the measured result is 0.18 wt%.

[0105] Post-processing in step A6: The obtained microcapsules were centrifuged at 1200×g for 10 min at 20℃, and washed with deionized water until the pH of the supernatant reached 7.0. The amount of deionized water used for washing was 5 times the mass of the wet filter cake of the microcapsules. Each wash was performed with stirring at 200 r / min for 3 min, followed by repeated centrifugation, for a total of 2 washes. After washing, the microcapsules were dried at 48℃ for 8 h to obtain mosquito-repellent microcapsules.

[0106] The mosquito-repellent microcapsules prepared in this embodiment have a particle size of 0.4 µm. Dynamic light scattering was used for particle size determination at a test temperature of 25°C. Deionized water was used as the dispersion medium. The sample was diluted to a solid content of 0.02 wt%, and ultrasonically dispersed at 25 kHz and 100 W for 3 min, with the dispersion temperature controlled at 25°C before testing. The drug loading of the mosquito-repellent microcapsules was 18 wt%, obtained by extracting the active mosquito-repellent ingredient with ethyl acetate and determining it by gas chromatography. The extraction conditions were a mass-to-volume ratio of microcapsules to ethyl acetate of 1 g: 20 mL. After stirring at 25°C for 60 min, the supernatant was collected for quantitative analysis, and an external standard method was used to establish a calibration curve for quantification. The drug loading retention rate of the mosquito-repellent microcapsules in this embodiment was 78% after melt mixing at 110-160°C for 1.2 min, meeting the requirement of not less than 70%.

[0107] In this embodiment, a thermoplastic polyurethane hot melt adhesive masterbatch containing microcapsules was first prepared: thermoplastic polyurethane and mosquito-repellent microcapsules were melt-blended at 122°C using a twin-screw extruder for 1.2 min, followed by granulation to obtain the thermoplastic polyurethane hot melt adhesive masterbatch. The content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive masterbatch was 15 wt%. The screw speed of the twin-screw extruder was 150 r / min, and the barrel temperature zone was 122°C. The thermoplastic polyurethane used in this embodiment had a melt index of 5 g / 10min and a Shore A hardness of 75, measured at 190°C and a load of 2.16 kg.

[0108] In this embodiment, thermoplastic polyurethane hot melt adhesive masterbatch and pure thermoplastic polyurethane were melt-blended at 122°C for 1.2 min to obtain a thermoplastic polyurethane hot melt adhesive material containing microcapsules. The mosquito-repellent microcapsules accounted for 3 wt% of the content in the microcapsule-containing thermoplastic polyurethane hot melt adhesive material. The thermoplastic polyurethane hot melt adhesive material was then prepared into a dot matrix hot melt adhesive film using a hot melt adhesive dotting method while molten at 122°C. The dot diameter was 0.4 mm, the center-to-center distance between adjacent dots was 0.8 mm, the coverage was 30%, and the thickness of the dot matrix hot melt adhesive film was 12 µm. Release paper was then laminated onto the dot matrix hot melt adhesive film to form an intermediate.

[0109] The intermediate was hot-pressed with a polyester-spandex blended base fabric at 118℃, with a hot-pressing pressure of 0.28 MPa and a hot-pressing time of 8 s, to obtain a mosquito-repellent thermoplastic polyurethane composite fabric. After hot-pressing, the fabric was cooled and set at 20℃ for 80 s.

[0110] The mosquito-repellent effect of the mosquito-repellent thermoplastic polyurethane composite fabric prepared in this embodiment was evaluated according to the mosquito repellency test specified in GB / T 30126. After 15 washes, the mosquito repellency rate was 58%, meeting the requirement of not less than 50%. The washing conditions were 40℃, with a single washing time of 30 min and a detergent concentration of 2 g / L.

[0111] Features of Example 3: This example uses relatively low process parameters: polyvinyl alcohol concentration is 1.2 wt%, DEET content in the oil phase is 40 wt%, diisocyanate content is relatively high (30 wt%), microcapsule content in the hot melt adhesive layer is 3 wt%, reaction temperature is low (25℃ for emulsification and shell formation), reaction time is short (1.5 h), and the process is fast and efficient. The microcapsule particle size is small (0.4 µm), drug loading is 18 wt%, hot melt adhesive layer thickness is thin (12 µm), the lattice is dense but the dot diameter is small (0.4 mm), the coverage is moderate (30%), and the feel is soft and thin. Two types of diisocyanates are used in combination, and the shell properties are adjustable. It is suitable for lightweight close-fitting clothing, yoga wear, sports compression clothing, and elastic functional textiles with high requirements for softness and breathability, providing basic mosquito repellent protection while maintaining excellent wearing comfort.

[0112] Example 4

[0113] This embodiment provides a mosquito-repellent thermoplastic polyurethane composite fabric, including a nylon base fabric and a thermoplastic polyurethane hot melt adhesive layer disposed on one side of the nylon base fabric.

[0114] The thermoplastic polyurethane hot melt adhesive layer of this embodiment comprises thermoplastic polyurethane and mosquito-repellent microcapsules dispersed in the thermoplastic polyurethane hot melt adhesive layer, with the content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive layer being 1.0 wt%. The mosquito-repellent microcapsules of this embodiment have a core-shell structure, with the core layer containing icosaredin as the mosquito-repellent active ingredient, and the shell layer being a polyurea shell layer formed by reacting a mixture of hexamethylene diisocyanate, ethylenediamine, and 1,6-hexanediamine (mass ratio 7:3).

[0115] The mosquito-repellent microcapsules of this embodiment are prepared according to the following method:

[0116] Step A1: Aqueous phase preparation: Polyvinyl alcohol (PVA) was added to deionized water to prepare an aqueous phase with a PVA mass fraction of 4.2 wt%. In this example, the degree of alcoholysis of PVA used was 97 mol%, and the viscosity of the 4 wt% aqueous solution at 20°C was 26 mPa·s. The aqueous phase was stirred at 88°C and 680 r / min for 2.5 h. The pH of the aqueous phase was adjusted to 10.2 using an 18 wt% sodium carbonate aqueous solution. After adjusting the pH, the aqueous phase was cooled to 35°C.

[0117] Step A2: Oil phase preparation: Icaridin, hexamethylene diisocyanate and ethyl acetate are mixed to form an oil phase, wherein iccaridin accounts for 88 wt% of the oil phase mass, hexamethylene diisocyanate accounts for 7 wt% of the oil phase mass, ethyl acetate as an organic solvent accounts for 5 wt% of the oil phase mass, and the sum of the mass fractions of the mosquito repellent active ingredient and diisocyanate is 95 wt%.

[0118] Step A3 Emulsification: The oil phase is added to the aqueous phase for emulsification to obtain an oil-water emulsion. In this embodiment, the mass ratio of the oil phase to the aqueous phase is 1:9. The emulsification operation is carried out at 35°C using a stator-rotor shear head at 16000 r / min for 22 min, and the temperature fluctuation during the emulsification process is controlled within ±3°C.

[0119] Step A4: Interfacial shell formation reaction: An aqueous solution of a diamine mixture was added dropwise to the oil-water emulsion at a rate of 6 mL / min over a period of 50 min, resulting in a NCO to NH2 molar ratio of 1.07. The molar number of NCO groups was calculated based on the number of NCO groups provided by hexamethylene diisocyanate in the oil phase, and the molar number of NH2 groups was calculated based on the number of NH2 groups provided by the diamine mixture (70% ethylenediamine + 30% 1,6-hexanediamine). In this example, the aqueous solution of the diamine mixture had a mass fraction of 16 wt%. The reaction was carried out at 35°C for 3.2 h with stirring at 600 r / min to form core-shell microcapsules. The pH of the system was maintained at 10.2 during the reaction.

[0120] Step A5 Endpoint Determination: The reaction is terminated when the free NCO content in the system is ≤0.20 wt%. In this example, the free NCO content is determined by dibutylamine back titration, with a sample size of 2.0 g. The titration endpoint is determined by potentiometric titration. The free NCO content is the proportion of the mass of NCO converted from unreacted isocyanate groups to the total mass of the reaction system, and the result is 0.10 wt%.

[0121] Post-processing in step A6: The obtained microcapsules were centrifuged at 4200×g for 22 min at 30℃, and washed with deionized water until the pH of the supernatant reached 7.3. The amount of deionized water used for washing was 18 times the mass of the wet filter cake of the microcapsules. Each wash was performed with stirring at 450 r / min for 8 min, followed by repeated centrifugation, for a total of 4 washes. After washing, the microcapsules were dried at 63℃ for 18 h to obtain mosquito-repellent microcapsules.

[0122] The mosquito-repellent microcapsules prepared in this embodiment have a particle size of 1.7 µm. Dynamic light scattering was used for particle size determination at a test temperature of 25°C. Deionized water was used as the dispersion medium. The sample was diluted to a solid content of 0.09 wt%, and ultrasonically dispersed at 38 kHz and 250 W for 8 min, with the dispersion temperature controlled at 25°C before testing. The drug loading of the mosquito-repellent microcapsules was 54 wt%, obtained by acetonitrile extraction of the active mosquito-repellent ingredient and determination by high-performance liquid chromatography (HPLC). The extraction conditions were a mass-to-volume ratio of microcapsules to acetonitrile of 1 g:90 mL. After shaking at 38°C for 200 min, the supernatant was collected for quantitative analysis, and an external standard method was used to establish a calibration curve for quantification. The drug loading retention rate of the mosquito-repellent microcapsules in this embodiment was 74% after melt mixing at 110-160°C for 4.2 min, meeting the requirement of not less than 70%.

[0123] In this embodiment, a thermoplastic polyurethane hot melt adhesive masterbatch containing microcapsules was first prepared: thermoplastic polyurethane and mosquito-repellent microcapsules were melt-blended at 152°C using a twin-screw extruder for 4.2 min, followed by granulation to obtain the thermoplastic polyurethane hot melt adhesive masterbatch. The content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive masterbatch was 52 wt%. The screw speed of the twin-screw extruder was 420 r / min, and the barrel temperature zone was 152°C. The thermoplastic polyurethane used in this embodiment had a melt index of 21 g / 10min and a Shore A hardness of 90, measured at 190°C and a load of 2.16 kg.

[0124] In this embodiment, thermoplastic polyurethane hot melt adhesive masterbatch and pure thermoplastic polyurethane were melt-blended at 152°C for 4.2 min to obtain a thermoplastic polyurethane hot melt adhesive material containing microcapsules. The content of mosquito-repellent microcapsules in the thermoplastic polyurethane hot melt adhesive material containing microcapsules was 1.0 wt%. The thermoplastic polyurethane hot melt adhesive material was then prepared into a dot matrix hot melt adhesive film by hot melt adhesive dotting in the molten state at 152°C. The dot diameter was 0.3 mm, the center-to-center distance between adjacent dots was 0.6 mm, the coverage was 25%, and the thickness of the dot matrix hot melt adhesive film was 8 µm. Release paper was then laminated onto the dot matrix hot melt adhesive film to form an intermediate.

[0125] The intermediate and nylon base fabric were hot-pressed together at 136℃ with a pressure of 0.52 MPa for 26 s to obtain a mosquito-repellent thermoplastic polyurethane composite fabric. After hot-pressing, the fabric was cooled and set at 28℃ for 180 s.

[0126] The mosquito-repellent effect of the mosquito-repellent thermoplastic polyurethane composite fabric prepared in this embodiment was evaluated according to the mosquito repellency test specified in GB / T 30126. After 20 washes, the mosquito repellency rate was 62%, meeting the requirement of not less than 50%. The washing conditions were 40℃, with a single washing time of 30 min and a detergent concentration of 2 g / L.

[0127] Features of Example 4: This example employs a special configuration with a high mosquito-repellent active ingredient content (88 wt%) and a low microcapsule addition amount (1.0 wt%). The microcapsule drug loading is as high as 54 wt%, with a relatively large particle size of 1.7 µm. The hot melt adhesive layer is ultra-thin (8 µm), with a fine dot matrix (dot diameter 0.3 mm, center distance 0.6 mm), resulting in a low coverage (25%). The fabric is lightweight and breathable, with minimal impact on the performance of the base fabric. A high preparation temperature (88℃ aqueous phase preparation, 152℃ mixing, 136℃ hot pressing) and a long processing time (2.5 h aqueous phase stirring, 3.2 h reaction, 4.2 min mixing, 18 h drying) ensure thorough process execution, resulting in a microcapsule content of up to 52 wt% in the masterbatch, which is diluted to obtain a final low concentration. Two diamines are mixed to form the shell, improving shell performance. Suitable for ultra-lightweight high-end fashion fabrics, premium underwear, and functional fashion textiles with extremely high requirements for feel, it imparts mosquito-repellent function with almost no impact on the original style of the fabric, meeting the dual needs of lightweight and functionality.

[0128] Comparative Example 1: Basically the same as Example 1, except that the content of mosquito repellent microcapsules in the thermoplastic polyurethane hot melt adhesive layer is 0.3 wt%, while the amount of other components and preparation conditions remain unchanged.

[0129] Comparative Example 2: It is basically the same as Example 1, except that the content of mosquito repellent microcapsules in the thermoplastic polyurethane hot melt adhesive layer is 18 wt%, while the amount of other components and preparation conditions remain unchanged.

[0130] Comparative Example 3: It is basically the same as Example 1, except that the particle size of the mosquito repellent microcapsules is 0.08 µm. Specifically, it is achieved by increasing the high-speed shear emulsification speed in step A3 to 25000 r / min and extending the emulsification time to 35 min. Other preparation conditions remain unchanged.

[0131] Comparative Example 4: Basically the same as Example 1, except that the particle size of the mosquito repellent microcapsules is 2.5 µm. Specifically, this is achieved by reducing the high-speed shear emulsification speed in step A3 to 2500 r / min and shortening the emulsification time to 3 min. Other preparation conditions remain unchanged.

[0132] Comparative Example 5: It is basically the same as Example 1, except that the drug loading of the mosquito repellent microcapsule is 6 wt%. Specifically, it is achieved by adjusting the proportion of DEET in the oil phase to 15 wt% and the proportion of hexamethylene diisocyanate in the oil phase to 45 wt% in step A2. Other preparation conditions remain unchanged.

[0133] Comparative Example 6: It is basically the same as Example 1, except that the drug loading of the mosquito repellent microcapsule is 68 wt%. Specifically, it is achieved by adjusting the proportion of DEET in the oil phase to 92 wt% and the proportion of hexamethylene diisocyanate in the oil phase to 3 wt% in step A2. Other preparation conditions remain unchanged.

[0134] Comparative Example 7: It is basically the same as Example 1, except that the thickness of the thermoplastic polyurethane hot melt adhesive layer is 3 µm. Specifically, it is achieved by adjusting the coating amount of the dot matrix hot melt adhesive film and making the dot diameter 0.25 mm, the center distance between adjacent dots 0.55 mm, and the coverage 42%. Other preparation conditions remain unchanged.

[0135] Comparative Example 8: It is basically the same as Example 1, except that the thickness of the thermoplastic polyurethane hot melt adhesive layer is 48 µm. Specifically, it is achieved by adjusting the coating amount of the dot matrix hot melt adhesive film and making the dot diameter 1.8 mm, the center distance between adjacent dots 3.5 mm, and the coverage 48%. Other preparation conditions remain unchanged.

[0136] Performance testing:

[0137] Mosquito repellency effect evaluation experiment. Test subject: Mosquito-repellent thermoplastic polyurethane composite fabric sample of the present invention. Test purpose: To evaluate the repellency effect of the composite fabric on mosquitoes and verify the effectiveness of the release of mosquito-repellent active ingredients. Test principle: Based on the mosquito repellency behavior response of mosquitoes to mosquito-repellent active ingredients, the mosquito repellency rate is quantitatively determined through a standardized mosquito repellency test. Experimental method: The test is conducted according to the mosquito repellency test method specified in GB / T 30126. The fabric sample is cut into 10 cm × 10 cm pieces and placed in the test chamber under standard laboratory conditions (temperature 27±2℃, relative humidity 70±10%). A specified number of female Aedes albopictus mosquitoes (20-30 mosquitoes) are released. The number of times and the time of mosquitoes staying on the sample within 30 minutes are observed and recorded. An untreated blank fabric is used as a control. The mosquito repellency rate is calculated. Standard basis: GB / T 30126 "Test and evaluation of mosquito repellency performance of textiles". Key parameters: Test temperature 27±2℃, relative humidity 70±10%, mosquito species: female Aedes albopictus, observation time 30 min, sample size 10 cm×10 cm. Data processing: mosquito repellency rate = (number of stays in control group - number of stays in sample group) / number of stays in control group × 100%, each sample was tested in triplicate, and the mean ± standard deviation was taken.

[0138] Washability test; Test subject: Sample of the mosquito-repellent thermoplastic polyurethane composite fabric of this invention after multiple washes. Test objective: To evaluate the ability of the composite fabric to retain its mosquito-repellent effect after multiple washes and to verify the durability of the mosquito-repellent function. Test principle: Simulating the washing process in actual use, the change in mosquito repellency rate was measured after treatment with a standard washing program to evaluate the protective effect of microcapsule encapsulation and hot melt adhesive layer on the mosquito-repellent active ingredients. Experimental method: A standard washing machine was used according to the washing program specified in GB / T 8629, with a washing temperature of 40℃, a single washing time of 30 min, and a detergent concentration of 2 g / L (using a standard anionic surfactant). After each wash, the product was rinsed 3 times with clean water and air-dried at room temperature. The mosquito repellency rate was measured according to the method in Experiment 1 after 5, 10, 15, 20, and 25 washes. Key parameters: Washing temperature 40℃, washing time 30 min / wash, detergent concentration 2 g / L, rinsing 3 times / washing cycle, test points are after 5, 10, 15, 20, and 25 washes. Data processing: Plot the mosquito repellency rate as a function of the number of washes. Perform three parallel tests at each washing node and take the mean ± standard deviation. Calculate the mosquito repellency retention rate after 25 washes.

[0139] Drug loading determination experiment; Test subject: mosquito-repellent microcapsule samples prepared in this invention. Test objective: To quantitatively determine the content of mosquito-repellent active ingredients in mosquito-repellent microcapsules and evaluate the microcapsule encapsulation efficiency. Test principle: Solvent extraction is used to break the microcapsule shell and release the mosquito-repellent active ingredients. The content of mosquito-repellent active ingredients is quantitatively analyzed by gas chromatography or high performance liquid chromatography. Experimental method: Weigh 0.1-0.5 g of microcapsule sample into a 50 mL volumetric flask, add ethyl acetate or acetonitrile solvent (microcapsule to solvent mass-volume ratio of 1 g: 50-80 mL), and magnetically stir or ultrasonically vibrate at 30℃ for 120 min to fully extract the mosquito-repellent active ingredients. Filter the supernatant through a 0.45 µm filter membrane and perform chromatographic analysis. Chromatographic conditions: Gas chromatography was used for DEET with a DB-5 capillary column (30 m × 0.25 mm × 0.25 µm) and an FID detector; high-performance liquid chromatography (HPLC) was used for picaridin and IR3535 with a C18 column (250 mm × 4.6 mm, 5 µm) and a detection wavelength of 210 nm. An external standard method was used to establish a calibration curve for quantification. Key parameters: Ethyl acetate or acetonitrile was used as the extraction solvent; the extraction temperature was 30℃; the extraction time was 120 min; chromatographic conditions were as described above; and the linear range of the calibration curve covered the sample concentration. Data processing: Drug loading (wt%) = mass of mosquito-repellent active ingredient in the extract / mass of microcapsule sample × 100%. Each sample was tested in triplicate, and the mean ± standard deviation was used.

[0140] Microcapsule Particle Size and Distribution Determination Experiment. Test Subject: Mosquito-repellent microcapsule dispersion prepared in this invention. Test Objective: To determine the particle size and distribution of microcapsules and evaluate the controllability and uniformity of the microcapsule preparation process. Test Principle: Based on the principle of dynamic light scattering, the hydrodynamic diameter and particle size distribution of the particles are calculated by measuring the intensity fluctuation of scattered light caused by the Brownian motion of the microcapsule particles. Experimental Method: The microcapsule samples were dispersed in deionized water to prepare a dispersion with a solid content of 0.01-0.10 wt%. Ultrasonic dispersion (20-40 kHz, power 50-300 W) was used for 1-10 min to fully deagglomerate the particles, ensuring the dispersion temperature was controlled at 20-30℃. A dynamic light scattering particle size analyzer was used for testing at 25℃ and a scattering angle of 90°. Each sample was measured 10 times consecutively, and the average value was taken. Key parameters: The dispersion medium was deionized water with a solid content of 0.01-0.10 wt%. The ultrasonic dispersion parameters were 20-40 kHz, 50-300 W, and 1-10 min. The test temperature was 25℃, and the scattering angle was 90°. The measurement was repeated 10 times. Data processing: The average particle size (Z-average), particle size distribution width (PDI, polydispersity index), and D10 / D50 / D90 values ​​are given. The volume-weighted average is used, and at least 3 parallel samples are required for each sample. The mean ± standard deviation is taken.

[0141] Thermal processing stability evaluation experiment; Test object: mosquito repellent microcapsules of the present invention before and after hot melt mixing. Test purpose: To evaluate the stability of mosquito repellent microcapsules during the melt mixing process of thermoplastic polyurethane and to determine the drug loading retention rate. Test principle: By comparing the change in drug loading of microcapsules before and after hot melt mixing, the tolerance of the microcapsule shell to high temperature and shear force is evaluated, and the stability of the encapsulation structure is verified. Experimental method: A certain amount of mosquito repellent microcapsule sample was weighed, and the initial drug loading (denoted as M0) was determined according to the method in Experiment 3. The microcapsules and thermoplastic polyurethane were melt-mixed at a set temperature (110-160℃) using a twin-screw extruder or internal mixer for 0.5-5.0 min, with a screw speed of 50-500 r / min. After mixing, the composite material was cooled and pulverized, and the mosquito repellent active ingredients were separated by solvent extraction. The drug loading after mixing (denoted as M1) was determined according to the method in Experiment 3. Key parameters: mixing temperature 110-160℃, mixing time 0.5-5.0 min, screw speed 50-500 r / min, drug loading determination method is the same as in Experiment 3, and extraction conditions are kept consistent to ensure comparability. Data processing: Drug loading retention rate (%) = M1 / M0 × 100%, each temperature and time condition was tested in parallel 3 times, and the mean ± standard deviation was taken to plot the drug loading retention rate as a function of mixing temperature and time.

[0142] The quality evaluation experiment of the dot matrix hot melt adhesive film, test object: the microcapsule-containing dot matrix hot melt adhesive film prepared in this invention and the composite fabric after being laminated with the base fabric. Test purpose: to evaluate the film-forming quality, dot matrix structure uniformity, and lamination strength of the dot matrix hot melt adhesive film, and to verify the stability of the processing technology. Test principle: the geometric parameters such as dot diameter, center distance, and coverage are determined by microscopic observation and image analysis, and the bonding strength between the hot melt adhesive layer and the base fabric is evaluated by peel strength test. Experimental method: the dot matrix hot melt adhesive film is observed under an optical microscope or stereomicroscope at a magnification of 50-200x, and at least 10 fields of view are photographed. The diameter of each adhesive dot and the center distance between adjacent dots are measured using image analysis software (such as ImageJ). The average value and standard deviation of at least 100 adhesive dots are calculated, and the coverage (adhesive dot area / total area × 100%) is calculated. Peel strength testing was conducted according to GB / T 2792 "Adhesives - Test Method for Peel Strength". The composite fabric was cut into 25 mm × 150 mm specimens and subjected to a 180° peel test at a rate of 300 mm / min on a tensile testing machine. The peel force was recorded. Key parameters: microscope magnification 50-200x, statistical sample size ≥100 adhesive dots, peel rate 300 mm / min, specimen size 25 mm × 150 mm, peel angle 180°. Data processing: The mean ± standard deviation of dot diameter, center distance, and coverage is given. Peel strength is expressed as N / 25 mm. For each sample group, 5-10 parallel samples were tested, and the mean ± standard deviation was taken.

[0143] Figure 1 The image shows a superimposed FTIR infrared spectrum of the polyurea shell of the core-shell microcapsule. The parameters were fixed under the same test conditions and data processing flow without smoothing. The sample types were Example 1, Comparative Example 5, and Comparative Example 6. The characterization method was Fourier transform infrared spectroscopy. Example 1 and Comparative Example 5 showed stable polyurea-related signals in the characteristic absorption regions of amide I and amide II, while Comparative Example 6 still showed a residual signal trend in the NCO-related absorption region. This indicates that the shell reaction in Example 1 was more complete and the structure more stable, thus supporting the technical route of achieving effective encapsulation and stability through shell construction at the chemical structure level.

[0144] Figure 2The DLS particle size distribution map of the core-shell microcapsules is shown. The parameters were fixed with identical dispersion and testing conditions; the particle size abscissa was logarithmic; and the distribution curves were the output of the instrument software without artificial smoothing. The variable parameters were the sample types: Example 1, Comparative Example 3, and Comparative Example 4. The characterization method was dynamic light scattering particle size measurement. The volume distribution peak of Example 1 is located in the nano-to-micron scale transition range corresponding to the micron scale and is concentrated. Comparative Example 3 is biased towards a smaller particle size range, while Comparative Example 4's distribution shifts towards a larger particle size. This indicates that this method can control the particle size within a range more conducive to fabric adhesion and uniform coverage, thus providing a basis for subsequent lattice stabilization and performance consistency.

[0145] Figure 3 The DLS cumulative particle size distribution map of the core-shell microcapsules is shown. The parameters were fixed under the same test conditions and logarithmic particle size coordinates. The cumulative distribution curve is the output of the instrument software without artificial smoothing. The variable parameters were the sample types: Example 1, Comparative Example 3, and Comparative Example 4. The characterization method was dynamic light scattering particle size measurement. Example 1 shows a more concentrated D10, D50, and D90 quantile interval, indicating a narrower particle size distribution and better batch consistency. Comparative Examples 3 and 4 show a larger quantile span, suggesting that the dispersion system is more prone to end-to-end particle size expansion. This demonstrates that this method is more conducive to obtaining a stable particle size distribution and reducing performance dispersion caused by particle size fluctuations in terms of dispersion and nucleation growth control.

[0146] Figure 4 The image shows a superimposed TGA thermogravimetric curve of the core-shell microcapsules. The parameters were fixed as a nitrogen atmosphere and a constant heating rate. The curves are the output of the instrument software without any artificial smoothing. The varying parameters were the sample types: Example 1, Comparative Example 5, and Comparative Example 6. The characterization method was thermogravimetric analysis. Example 1 showed more stable mass in the medium-low temperature range, with the main weight loss occurring in the higher temperature range. In contrast, Comparative Example 6 showed significant weight loss earlier, indicating that the encapsulation system of Example 1 has better thermal shielding and retention effects for the active components. This verifies the rationality of this scheme in achieving effective drug loading and stable release carrier through shell and structural regulation from a thermal stability perspective.

[0147] Figure 5This is a superimposed graph of DTG weight loss rate curves for core-shell microcapsules. The parameters were fixed with the same atmosphere and temperature program as TGA, and the DTG curves were the output of the instrument software without artificial smoothing. The variable parameters were the sample types: Example 1, Comparative Example 5, and Comparative Example 6. The characterization method was derivative thermogravimetric data processing from thermogravimetric analysis. In Example 1, the main weight loss rate peak is more concentrated and positioned further up in the high-temperature region, indicating that the decomposition process is more constrained by the shell structure and exhibits more controllable thermal decomposition behavior. In contrast, Comparative Example 6 shows a more significant rate contribution in the low-temperature region, suggesting insufficient structural stability. This demonstrates that the core-shell structure constructed in this scheme can provide clearer and more repeatable decomposition characteristics under thermal action and reduce the risk of early failure.

[0148] Figure 6 This is a superimposed DSC differential scanning calorimetry (DSC) curve of the core-shell microcapsules. The parameters were fixed at a nitrogen atmosphere and a constant heating rate, and the curves are the output of the instrument software without artificial smoothing. The varying parameters were the sample types: Example 1, Comparative Example 5, and Comparative Example 6. The characterization method was differential scanning calorimetry. Example 1 showed a more stable baseline and more consistent thermal response in the temperature range corresponding to the glass transition and endothermic / exothermic events. The comparative sample showed greater differences in the location and intensity of the thermal events, indicating that the phase-state and shell-related thermal behavior of the Example 1 system was more stable. This further supports the correctness of this scheme in terms of structure construction and component compatibility control from a thermal analysis perspective.

[0149] As can be seen from the performance of the embodiments and comparative examples in Table 1, the present invention achieves the best balance between mosquito repellent effect, washability, and processing stability by controlling the mosquito repellent microcapsule content within the range of 0.5-15 wt%, the microcapsule particle size within the range of 0.1-2.0 µm, and the drug loading within the range of 10-60 wt%. Comparative Example 1, due to its low microcapsule content (0.3 wt%), resulted in insufficient total amount of mosquito repellent active ingredients, leading to a mosquito repellency rate of only 42%, far lower than the 82-92% level of the embodiments. Although Comparative Example 2 had a microcapsule content as high as 18 wt%, exceeding the scope of the claims, the excessively high filling amount caused a sharp increase in melt viscosity, a narrowing of the processing window, and a decrease in the quality of lattice film formation. Simultaneously, the microcapsules were unevenly dispersed in the matrix, resulting in a drug loading retention rate of only 58% under thermal history and a significant decrease in washability. Comparative Examples 3 and 4 had particle sizes below and above the claims, respectively. While excessively small particle sizes (0.08 µm) facilitated dispersion, the large surface area resulted in decreased shell encapsulation efficiency, with a drug retention rate of only 62%. Excessively large particle sizes (2.5 µm) easily caused localized defects during lattice film formation, leading to decreased mosquito-repellent efficacy and washability. Comparative Examples 5 and 6 verified the boundaries of the lower and upper limits of drug loading, respectively. When the drug loading was too low (6 wt%), the amount of mosquito-repellent active ingredient carried by each microcapsule was insufficient, requiring a significant increase in microcapsule addition to achieve a mosquito-repellent effect, resulting in a mosquito-repellent rate of only 35%. When the drug loading was too high (68 wt%), the shell thickness became relatively thin. Although the initial mosquito-repellent effect was acceptable, the microcapsule breakage rate increased during thermal processing, the drug retention rate dropped to 52%, and the mosquito-repellent rate was only 45% after 25 washes. Comparative Examples 7 and 8 verified the boundary effect of hot melt adhesive layer thickness. Although the thinner adhesive layer (3 µm) could maintain the light and thin feel of the fabric, the microcapsule encapsulation was insufficient, the peel strength was insufficient (6.2 N / 25 mm), and the mosquito repellency was poor. Although the thicker adhesive layer (48 µm) could improve the peel strength to 15.8 N / 25 mm, the fabric felt stiffer and the breathability decreased. Moreover, the thicker adhesive layer did not significantly improve the mosquito repellency effect. On the contrary, the mosquito repellency rate dropped to 68% due to the increased mass transfer resistance. A comprehensive comparison shows that by precisely controlling key parameters such as the content, particle size, drug loading, and hot melt adhesive layer thickness of the microcapsules within the scope defined in the claims, this invention can simultaneously achieve excellent mosquito repellent effect (mosquito repellency rate of 82-92%), good wash resistance and durability (mosquito repellency rate of 58-75% after 25 washes), and excellent processing stability (drug loading retention rate of 74-82%), while also taking into account the fabric feel, peel strength, and other performance characteristics, thus proving the scientific nature and superiority of the technical solution of this invention.

[0150] Table 1 Performance comparison data between the examples and comparative examples

[0151]

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A mosquito repellent thermoplastic polyurethane composite fabric, characterized by, The base cloth and the thermoplastic polyurethane hot melt adhesive layer arranged on at least one side of the base cloth; The thermoplastic polyurethane hot melt adhesive layer comprises thermoplastic polyurethane and mosquito-repelling microcapsules dispersed in the thermoplastic polyurethane hot melt adhesive layer; the mosquito-repelling microcapsules are of a core-shell structure, the core layer of the mosquito-repelling microcapsules comprises mosquito-repelling active ingredients selected from one or more of icaridin, diethyltoluamide and p-methane 3,8-diol; The shell layer of the mosquito-repelling microcapsules is a polyurea shell layer formed by the reaction of diisocyanate and diamine, the diisocyanate is selected from one or both of hexamethylene diisocyanate and isophorone diisocyanate, and the diamine is selected from one or both of ethylenediamine and 1,6-hexanediamine; The content of the mosquito-repelling microcapsules in the thermoplastic polyurethane hot melt adhesive layer is 0.5-15 wt%, based on the total mass of the thermoplastic polyurethane hot melt adhesive layer.

2. The mosquito repellent thermoplastic polyurethane composite fabric of claim 1, wherein, The preparation method of the mosquito-repelling microcapsules comprises the following steps: A1. Water phase preparation: polyvinyl alcohol is added to deionized water to prepare a water phase with a polyvinyl alcohol mass fraction of 0.5-5.0 wt%, stirring at 200-800 r / min at 60-95 ℃ for 0.5-3.0 h, and adjusting the pH value of the water phase to 8.5-10.5 with anhydrous sodium carbonate; A2. Oil phase preparation: mosquito-repelling active ingredients, diisocyanate and optional organic solvents are mixed to form an oil phase, wherein the mosquito-repelling active ingredients account for 30-95 wt% of the mass of the oil phase, the diisocyanate accounts for 5-40 wt% of the mass of the oil phase, the organic solvent accounts for 0-50 wt% of the mass of the oil phase, and the mass fraction of the mosquito-repelling active ingredients and the diisocyanate is 50-100 wt%; A3. Emulsification: the oil phase is added to the water phase to form an oil-water emulsion, and the emulsification is carried out at 3000-20000 r / min at 20-45 ℃ for 1-30 min; A4. Interfacial shell formation reaction: a diamine aqueous solution is added dropwise to the oil-water emulsion to make the molar ratio of NCO to NH2 in the system 0.95-1.10, and the reaction is carried out at 20-45 ℃ for 1.0-4.0 h to form core-shell microcapsules; wherein the number of moles of NCO is calculated based on the number of moles of NCO groups provided by the diisocyanate in the oil phase, and the number of moles of NH2 is calculated based on the number of moles of NH2 groups provided by the diamine; the mass fraction of the diamine aqueous solution is 1-20 wt%, the dropwise addition time is 5-60 min, and the stirring speed is 200-800 r / min during the reaction.

3. The mosquito repellent thermoplastic polyurethane composite fabric of claim 1, wherein, The end point criterion of the interfacial shell formation reaction is to terminate the reaction when the free NCO content in the system is ≤0.20 wt%, wherein the free NCO content is the proportion of the NCO mass calculated from the unreacted isocyanate groups in the total mass of the reaction system, and the dibutylamine back titration method is used for determination.

4. The mosquito repellent thermoplastic polyurethane composite fabric of claim 2, wherein, The mosquito-repelling microcapsules also include post-processing, the specific process being: performing solid-liquid separation on the obtained microcapsules, the solid-liquid separation being centrifugation at 500-5000xg for 5-30 min, the centrifugation temperature being 15-35℃, and washing with deionized water until the pH value of the supernatant is 6.5-8.0, the washing being washing with deionized water for 1-5 times and repeating the centrifugal separation after each washing, and then drying at 40-70℃ for 6-24 h to obtain the mosquito-repelling microcapsules.

5. The mosquito repellent thermoplastic polyurethane composite fabric of claim 1, wherein, The mosquito-repelling microcapsules are prepared into a thermoplastic polyurethane hot melt adhesive master batch containing microcapsules before being added to the thermoplastic polyurethane hot melt adhesive layer, and the thermoplastic polyurethane hot melt adhesive master batch is prepared by the following steps: B1. Raw materials: thermoplastic polyurethane and mosquito-repelling microcapsules; B2. Proportioning: the content of mosquito-repelling microcapsules in the thermoplastic polyurethane hot melt adhesive master batch is 5-60 wt%; B3. Melt mixing: granulating after melt mixing the thermoplastic polyurethane and mosquito-repelling microcapsules at 110-160℃ for 0.5-5.0 min to obtain the thermoplastic polyurethane hot melt adhesive master batch.

6. A mosquito repellent thermoplastic polyurethane composite fabric as claimed in claim 1, wherein, The thermoplastic polyurethane hot melt adhesive layer is prepared into a dot array hot melt adhesive film from the thermoplastic polyurethane hot melt adhesive material containing microcapsules, and then the intermediate is formed by laminating release paper, and then the thermoplastic polyurethane hot melt adhesive layer is hot-pressed and compounded with the base cloth, the thermoplastic polyurethane hot melt adhesive layer is a dot array structure, the dot diameter is 0.2-1.5 mm, the center distance between adjacent dots is 0.5-3.0 mm, and the coverage rate is 20-70%.

7. A mosquito repellent thermoplastic polyurethane composite fabric as claimed in claim 1, wherein, The particle size of the mosquito-repelling microcapsules is 0.1-2.0 µm, the drug loading of the mosquito-repelling microcapsules is 10-60 wt%, the drug loading is the proportion of the mass of the mosquito-repelling active ingredient in the mosquito-repelling microcapsules to the total mass of the mosquito-repelling microcapsules, the average thickness of the thermoplastic polyurethane hot melt adhesive layer in the glue dot area is 5-40 µm, the base cloth is one of polyester, nylon or polyester-spandex blended fabric, the melt index of the thermoplastic polyurethane is 1-25 g / 10 min, the melt index is measured at 190℃ under a load of 2.16 kg, and the Shore hardness is Shore A 70-95.

8. A process for the preparation of the mosquito repellent thermoplastic polyurethane composite fabric as claimed in any one of claims 1 to 7, wherein, The method comprises the following steps: S1. Obtaining mosquito-repelling microcapsules; S2. Melt mixing the thermoplastic polyurethane and mosquito-repelling microcapsules at 110-160℃ for 0.5-5.0 min to obtain a thermoplastic polyurethane hot melt adhesive material containing microcapsules, and the content of mosquito-repelling microcapsules in the thermoplastic polyurethane hot melt adhesive material containing microcapsules is 0.5-15 wt%; S3. Laminating the thermoplastic polyurethane hot melt adhesive material with the base cloth, and hot-pressing and compounding at 110-140℃ to obtain a mosquito-repelling thermoplastic polyurethane composite fabric; In step S2, a thermoplastic polyurethane hot melt adhesive master batch is first prepared, and then the thermoplastic polyurethane hot melt adhesive master batch is mixed with the thermoplastic polyurethane to form the thermoplastic polyurethane hot melt adhesive material; The preparation of the thermoplastic polyurethane hot melt adhesive master batch comprises: melt mixing the thermoplastic polyurethane and mosquito-repelling microcapsules at 110-160℃ for 0.5-5.0 min, and the content of mosquito-repelling microcapsules in the thermoplastic polyurethane hot melt adhesive master batch is 5-60 wt%.

9. The production method according to claim 8, wherein The thermoplastic polyurethane hot melt adhesive material is prepared as a dot array hot melt adhesive film, and after a release paper is attached to the dot array hot melt adhesive film, hot press compounding is performed, the pressure of the hot press compounding is 0.2-0.6 MPa, the hot press time is 3-30 s, and after the hot press compounding, a cooling and setting step is further included, and the cooling and setting temperature is 15-35℃.

10. The production method according to claim 8, wherein The dot diameter of the dot array hot melt adhesive film is 0.2-1.5 mm, the center distance between adjacent dots is 0.5-3.0 mm, and the coverage rate is 20-70%.

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