A temperature-sensitive controlled-release plant source mosquito-repelling fiber, a preparation method thereof, and a textile

Abstract

The application belongs to the technical field of textiles, and specifically discloses a temperature-sensitive controlled-release plant source mosquito-repelling fiber, a preparation method thereof and a textile. The temperature-sensitive controlled-release plant source mosquito-repelling fiber comprises a cellulose matrix, the cellulose matrix has a gradient microporous slow-release channel inside, and a dense temperature-sensitive protective film on a surface layer; double-layer temperature-sensitive microcapsules are loaded in the cellulose matrix; the double-layer temperature-sensitive microcapsules comprise a core material, and an inner-layer temperature-sensitive wall material and an outer-layer protective wall material which are coated on the core material from inside to outside; the core material comprises a plant source mosquito-repelling essence liquid; the inner-layer temperature-sensitive wall material comprises an N-isopropyl acrylamide-acrylic acid copolymer; and the outer-layer protective wall material comprises a chitosan-beta-cyclodextrin composite crosslinker. The application improves the activity retention rate and temperature-sensitive controlled-release precision of mosquito-repelling components, and improves the mechanical properties and long-acting water washing resistance of the fiber.

Description

Technical Field

[0001] This application relates to the field of textile technology, and in particular to a thermosensitive controlled-release plant-derived mosquito repellent fiber, its preparation method, and textiles. Background Technology

[0002] With the improvement of people's living standards and the enhancement of health awareness, functional textiles with mosquito-repellent functions are increasingly favored by consumers. Traditional mosquito-repellent textiles are mostly prepared using chemically synthesized mosquito repellents through post-treatment coatings, which not only pose a risk of skin sensitization but also have poor washability and a stiff, rough feel. In contrast, green, safe, and skin-friendly plant-derived mosquito-repellent cellulose fibers prepared using natural plant essential oils and other plant-derived mosquito-repellent materials have become a research hotspot in the field of functional textiles. To achieve stable loading and slow release of plant-derived mosquito-repellent components in the fiber, microencapsulation technology is usually used to encapsulate heat-sensitive plant essential oils, which are then blended with cellulose spinning solution for wet spinning. However, in the actual preparation and application process, many bottlenecks still exist in related technologies.

[0003] To address the issues of essential oil volatility, poor washability, and decreased mechanical properties in the preparation and application of plant-derived mosquito-repellent cellulose fibers, a commonly used method is a multifunctional plant-based regenerated cellulose fiber preparation method disclosed in a related technology. This method involves adding sweet basil extract and compounded plant essential oil microcapsules to a conventional viscose preparation process to obtain fibers with antibacterial and mosquito-repellent functions. However, in this approach, the microcapsules utilize a simple silica aerogel monolayer coating structure, resulting in microscopic pore defects in the wall material and extremely low mechanical strength. During the high-shear, high-pressure extrusion and stretching processes of wet spinning, wall material tearing and core breakage leading to leakage are highly likely, causing significant loss of essential oils during the spinning stage. Furthermore, this method lacks an intelligent response controlled-release mechanism, allowing the essential oils to continuously evaporate during room temperature storage and idle periods, resulting in a very short mosquito-repellent effectiveness period and failing to meet the requirements for long-term service.

[0004] To introduce a thermosensitive controlled-release mechanism, another related technology discloses a method for preparing long-lasting aromatic lyocell fibers with bio-enzyme-immobilized thermosensitive microcapsules. This method employs a coaxial spinning process, using N-isopropylacrylamide (PNIPAM) thermosensitive hydrogel as the intermediate layer of the microcapsules to achieve temperature-responsive release. However, in this approach, the coaxial spinning process is extremely complex, requiring stringent flow rate matching between the inner and outer spinning solutions, making large-scale, continuous, and stable industrial production extremely difficult. More critically, the minimum eutectic critical temperature (LCST) of the single PNIPAM wall material used in this method is relatively low (typically below 31°C), significantly lower than human body surface temperature. This causes the thermosensitive "switch" to prematurely activate during room temperature storage or idle conditions, resulting in slow and ineffective evaporation of the essential oil, thus losing the core advantage of "low-temperature lock-in," and failing to achieve precise temperature-responsive incremental drug release during periods of high mosquito activity (greater than or equal to 33°C).

[0005] In addition, another related technology discloses a method for preparing mosquito-repellent fibers. This method involves mixing mosquito-repellent microcapsules (a complex coagulated system of gelatin and gum arabic) with a modified cellulose spinning solution and then spinning in a coagulation bath. However, in this method, because the microcapsules are only a single-layer complex coagulated structure, their mechanical strength and solvent resistance are poor, making them prone to swelling and breakage in strongly alkaline, high-viscosity spinning solvent systems such as N-methylmorpholine-N-oxide (NMMO). Furthermore, this preparation process uses traditional single-stage instantaneous high-stretching, subjecting the nascent fibers to severe tensile stress in the soft state of the incompletely solidified hydrogel, directly leading to large-area breakage of the microcapsules, premature leakage of essential oils, and oxidation failure. Moreover, the fiber's internal structure is dense, lacking interconnected microporous slow-release channels, making it difficult for the mosquito-repellent active ingredients released from the microcapsules to diffuse outwards, failing to achieve a synergistic balance between fiber mechanical properties and mosquito-repellent function. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a thermosensitive controlled-release plant-derived mosquito repellent fiber, its preparation method, and textiles, so as to improve the thermosensitive controlled-release performance, long-lasting mosquito repellent effect, and physical and mechanical properties of the plant-derived mosquito repellent fiber.

[0007] To achieve the above and other related objectives, this application provides a method for preparing thermosensitive controlled-release plant-derived mosquito repellent fibers, comprising the following steps: S1. A plant-derived mosquito repellent essence is extracted from at least one plant material; S2. Preparation of bilayer temperature-sensitive microcapsules: Using the plant-derived mosquito repellent essence as the core material and N-isopropylacrylamide-acrylic acid (PNIPAM-AA) copolymer as the inner temperature-sensitive wall material, a single-layer temperature-sensitive microcapsule was prepared by in-situ polymerization. On the outside of the single-layer temperature-sensitive microcapsule, a chitosan-β-cyclodextrin composite cross-linking system is used to carry out a cross-linking reaction to construct an outer protective wall material, thereby obtaining the double-layer temperature-sensitive microcapsule. S3. Gradient phase separation wet spinning preparation of thermosensitive controlled-release plant-derived mosquito repellent fibers: A phase separation regulator is added to the cellulose spinning solution, followed by the addition of the bilayer thermosensitive microcapsules to obtain a mixed spinning solution. The mixed spinning solution is extruded through a porous spinneret and then placed in a coagulation bath for phase separation and solidification, thereby constructing nascent fibers with internal gradient microporous slow-release channels and a dense thermosensitive protective film on the surface in situ. The nascent fibers undergo multi-stage wet stretching and shaping and post-treatment to obtain thermosensitive controlled-release plant-derived mosquito repellent fibers.

[0008] Optionally, in step S1, the extraction method is supercritical CO2 extraction.

[0009] Optionally, in step S1, the plant material is at least one of the following: magnolia, geranium, Murraya paniculata, night-blooming jasmine, marigold, verbena, carnation, snapdragon, calla lily, ageratum, pyrethrum, impatiens, jasmine, catnip, blue plumbago, lemongrass, pitcher plant, mugwort, mint, artemisia, rosemary, star anise, patchouli, velvet tea, basil, and lavender.

[0010] Optionally, in step S1, a plant-derived mosquito repellent essence is extracted from at least one plant material by supercritical CO2 extraction, and carried out in accordance with at least one of requirements (11) to (14): (11) Before extraction, the plant material is crushed, freeze-dried and sieved to obtain plant material powder; (12) The extraction temperature is 35℃~45℃; (13) The extraction pressure is 5~50MPa; (14) Extraction time is 15 to 180 minutes.

[0011] Optionally, in step S2, the process of preparing the bilayer temperature-sensitive microcapsules includes: The N-isopropylacrylamide-acrylic acid copolymer was added to water and heated to dissolve it, forming an aqueous phase system. The plant-derived mosquito repellent essence was added to the aqueous system and subjected to shear emulsification to form an oil-in-water emulsion system. The oil-in-water emulsion system is heated to carry out a polymerization reaction; After the polymerization reaction was completed, a chitosan-β-cyclodextrin composite crosslinking system was added to the system, and the mixture was heated to carry out the crosslinking reaction. After the cross-linking reaction was completed, centrifugation, washing and purification, and drying were performed to obtain the bilayer temperature-sensitive microcapsules.

[0012] Optionally, in step S2, the process of preparing the bilayer thermosensitive microcapsules is carried out in accordance with at least one of the following requirements (21) to (27): (21) The mass fraction of the N-isopropylacrylamide-acrylic acid copolymer in the aqueous system is 3%~5%; (22) The mass ratio of the N-isopropylacrylamide-acrylic acid copolymer to the plant-derived mosquito repellent essence is 1~2:1; (23) The chitosan-β-cyclodextrin composite cross-linking system includes chitosan and β-cyclodextrin, and the mass ratio of the sum of the mass of chitosan and β-cyclodextrin in the chitosan-β-cyclodextrin composite cross-linking system to the mass of the plant-derived mosquito repellent essence is 1~2:1; (24) The chitosan-β-cyclodextrin composite crosslinking system includes chitosan, β-cyclodextrin and a crosslinking agent, wherein the crosslinking agent includes citric acid; (25) During shear emulsification, the rate is 6000~10000 r / min and the duration is 10~20 minutes; (26) The polymerization reaction temperature is 55~65℃; (27) The cross-linking reaction temperature is 40~50℃.

[0013] Optionally, in step S3, the wet spinning is performed according to at least one of the following requirements (31) to (36): (31) The solid content of the cellulose spinning solution is controlled at 8%~18%; (32) The phase separation regulator is selected from at least one of polyethylene glycol, glycerin, and sorbitol, and its dosage is 0.1% to 0.3% of the mass of the cellulose spinning solution; (33) The flow rate of the mixed spinning solution extruded through the porous spinneret is controlled at 6~12 mL / min, the orifice diameter of the porous spinneret is 0.10~0.18 mm, and the extrusion speed is controlled at 15~25 m / min; (34) The coagulation bath is a constant temperature gradient coagulation bath, the temperature of which is controlled at 18~22℃, and the coagulation bath liquid is a mixed solution of water and N-methylmorpholine-N-oxide; (35) The multi-stage wet drawing is a three-stage gradient wet drawing process, with the total drawing ratio controlled at 2.8 to 3.5 times, of which the first-stage pre-drawing ratio is controlled at 1.1 to 1.3 times, the second-stage regularization drawing ratio is controlled at 1.5 to 2.0 times, and the third-stage shaping drawing ratio is controlled at 2.8 to 3.5 times; (36) The post-processing includes multi-stage countercurrent washing and drying.

[0014] Optionally, in step S3, an antioxidant stabilizer is also added to the cellulose spinning solution, wherein the antioxidant stabilizer is selected from at least one of L-ascorbic acid, sodium isoascorbate, and water-soluble tea polyphenols.

[0015] This application also provides a thermosensitive controlled-release plant-derived mosquito repellent fiber, comprising: A cellulose matrix, wherein the interior of the cellulose matrix has gradient microporous slow-release channels and the surface has a dense temperature-sensitive protective film; A double-layered thermosensitive microcapsule is loaded in the cellulose matrix; the double-layered thermosensitive microcapsule includes a core material, and an inner thermosensitive wall material and an outer protective wall material that encapsulate the core material from the inside out. The core material includes a plant-derived mosquito repellent essence, the inner thermosensitive wall material includes an N-isopropylacrylamide-acrylic acid copolymer, and the outer protective wall material includes a chitosan-β-cyclodextrin composite crosslinker.

[0016] Optionally, the average particle size of the bilayer temperature-sensitive microcapsules is 20 nm to 80 nm.

[0017] Optionally, the average diameter of the temperature-sensitive controlled-release plant-derived mosquito repellent fiber is 0.10~0.18mm.

[0018] This application also provides a textile containing thermosensitive controlled-release plant-derived mosquito-repellent fibers prepared according to the method described above and / or thermosensitive controlled-release plant-derived mosquito-repellent fibers as described above.

[0019] The technical solution provided in this application has at least the following beneficial effects: First, this application modifies N-isopropylacrylamide (NIPAM) molecular chains by introducing hydrophilic acrylic acid (AA) monomers into the copolymer. The abundant hydrophilic carboxyl groups in the acrylic acid macromolecular chains enhance the hydrophilic hydrogen bonding of the polymer chains, thereby precisely adjusting the LCST of the copolymer material to 33°C, thus constructing an intelligent temperature-responsive switch that matches the human body surface temperature. At room temperature below 33°C, the thermosensitive copolymer macromolecular chains exhibit a hydrophilic, extended state, while the inner thermosensitive wall material has a dense, closed structure, firmly locking the plant-derived mosquito-repellent essence inside the microcapsules, achieving excellent low-temperature retention. When a person wears this fiber fabric and their body surface temperature reaches or exceeds 33°C, or in environments with high mosquito prevalence above 33°C, the thermosensitive copolymer macromolecular chains rapidly undergo a hydrophobic phase transition and contract, creating microscopic conductive channels in the inner thermosensitive wall material. This allows the plant-derived mosquito-repellent essence to be released smoothly and efficiently, achieving precise high-temperature drug release and significantly extending the effective service life of the mosquito-repellent fiber.

[0020] Secondly, this application ingeniously utilizes the unique amphiphilic topology of the PNIPAM-AA binary copolymer macromolecular chain. This copolymer molecular chain simultaneously possesses strongly hydrophilic carboxyl groups and strongly hydrophobic isopropyl groups, spatially interspersed, endowing the copolymer with excellent self-emulsifying properties. During high-speed shear emulsification, without the addition of any small-molecule emulsifiers, the copolymer macromolecules can autonomously and rapidly accumulate at the interface between the plant-derived mosquito repellent essence (oil phase) and deionized water (aqueous phase), significantly reducing the oil-water interfacial tension and forming a water-in-oil emulsion with uniform particle size and extremely stable system. This self-emulsification mechanism not only ensures the smooth progress of subsequent in-situ polymerization reactions but also avoids problems such as spinning instability, microcapsule breakage, and increased fiber micro-defects caused by small-molecule auxiliary agent residues, guaranteeing the purity of the spinning system and the mechanical stability of the finished fiber.

[0021] Third, this application introduces a chitosan-β-cyclodextrin composite crosslinking system into the outer layer, using citric acid as a crosslinking agent. Through the efficient esterification and crosslinking reaction between the polycarboxyl structure of citric acid and the amino and hydroxyl groups on the chitosan macromolecular chain, as well as the hydroxyl groups on the β-cyclodextrin macromolecular chain, and multiple hydrogen bonds, a dense and high-strength three-dimensional network protective layer is constructed in situ on the outside of the inner temperature-sensitive wall material. This outer protective wall material not only effectively seals the microscopic leakage defects that may occur during the phase transition of the inner temperature-sensitive wall material, significantly improving the overall mechanical strength of the microcapsules and the storage stability of the essential oils, but also, because the surfaces of chitosan and β-cyclodextrin are rich in polar groups, they can form good hydrogen bond bonds with the cellulose macromolecular chain, greatly optimizing the interfacial compatibility between the microcapsules and the cellulose matrix. This allows the microcapsules to be firmly embedded inside the fiber, remaining intact even after multiple washes, mechanical friction, and complex wearing environments, giving the finished fiber excellent wash resistance and a long service life for mosquito repellency.

[0022] Fourth, in the wet spinning process, this application adds a phase separation regulator to the cellulose spinning solution. This regulator distributes between the cellulose polymer chains and the aqueous phase interface, acting as an interfacial buffer. This moderately reduces the coagulation driving force, delays the instantaneous solidification of the surface layer, and induces the formation of continuous, gradient-distributed nanoscale gradient microporous slow-release channels within the fiber. It also buffers the enormous interfacial shrinkage stress generated by phase separation, protecting the double-layer microcapsule structure from tearing. Combined with a three-stage gradient wet drawing process, the gradual application of tension throughout the process avoids instantaneous stress impacts. This not only protects the double-layer temperature-sensitive microcapsule structure from damage but also gradually induces the ordered orientation of the polymer chains, significantly improving the fiber's breaking strength and achieving a synergistic improvement in both fiber mechanical properties and mosquito-repellent function. Detailed Implementation

[0023] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0024] In this application, unless otherwise stated, the term "multiple" means two or more.

[0025] The character "" indicates that the objects before and after it are in an "OR" relationship. For example, A / B means: A or B.

[0026] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0027] Traditional plant-derived mosquito-repellent fiber preparation technologies suffer from the following drawbacks: First, traditional surface finishing modification methods can only load mosquito-repellent active components onto the fiber surface, resulting in low loading, uneven distribution, and weak bonding between the functional layer and the matrix. These components are prone to detachment and failure during washing and friction, leading to short-lasting and unstable mosquito-repellent effects. Second, conventional wet spinning and simple blending methods lack intelligent response structure design, possessing only passive constant-release characteristics. This results in significant issues such as ineffective volatilization at room temperature, insufficient release dosage during periods of high mosquito activity, and rapid activity decay during long-term storage. Third, conventional microcapsule doping modification easily leads to poor compatibility and stress concentration at the cellulose matrix interface. Furthermore, traditional single-stage instantaneous high-stretching processes can cause fiber micropore collapse and disordered molecular chain orientation, ultimately resulting in reduced fiber strength, high fiber breakage rate, and poor molding regularity.

[0028] To address the aforementioned deficiencies, one embodiment of this application provides a thermosensitive controlled-release plant-derived mosquito-repellent fiber, comprising: A cellulose matrix, wherein the interior of the cellulose matrix has gradient microporous slow-release channels and the surface has a dense temperature-sensitive protective film; A double-layered thermosensitive microcapsule is loaded in the cellulose matrix; the double-layered thermosensitive microcapsule includes a core material, and an inner thermosensitive wall material and an outer protective wall material that encapsulate the core material from the inside out. The core material includes a plant-derived mosquito repellent essence (also known as a plant-based mosquito repellent essential oil), the inner thermosensitive wall material includes an N-isopropylacrylamide-acrylic acid copolymer, and the outer protective wall material includes a chitosan-β-cyclodextrin composite crosslinker.

[0029] The working principle and structural synergistic effect of this thermosensitive controlled-release plant-derived mosquito repellent fiber are as follows: The cellulose matrix has a fiber structure that is dense on the outside and loose on the inside, consisting of "internal through-gradient microporous sustained-release channels + dense release membrane on the surface". It achieves structural intelligent switch-controlled release at the fiber structure level, solving the pain points of traditional dense and non-porous fibers, uncontrolled drug release, and serious waste at room temperature.

[0030] The dual-layer thermosensitive microcapsule adopts a dual-layer encapsulation structure of "inner layer thermosensitive response + outer layer high-strength locking protection," overcoming the shortcomings of traditional single-layer microcapsules such as poor controlled release precision and easy leakage. The inner layer uses PNIPAM-AA binary thermosensitive copolymer to precisely lock the critical phase transition temperature of 33℃ for human and mosquito activity, achieving low-temperature dense drug locking and high-temperature phase transition open-pore drug release. The outer layer uses a chitosan-β-cyclodextrin-citric acid cross-linked composite system, utilizing the three-dimensional cross-linked network of polysaccharides to seal the micropores of the thermosensitive layer, preventing ineffective volatilization at room temperature. At the same time, it uses cyclodextrin cavities to anchor essential oils, providing antioxidant protection and maintaining activity, and is homologous and compatible with the cellulose matrix, solving the problems of microcapsule aggregation, interface detachment, and spinning damage. The polysaccharide structure of the outer layer of the dual-layer thermosensitive microcapsule is molecularly compatible with the cellulose matrix, with no interface delamination or detachment defects, significantly improving the fiber's wash resistance, abrasion resistance, and long-term stability.

[0031] In some embodiments of this application, the average particle size of the bilayer thermosensitive microcapsules is 20nm~80nm, and the average diameter of the thermosensitive controlled-release plant-derived mosquito repellent fiber is 0.10~0.18mm.

[0032] In wet spinning, the size matching between the functional filler particle size and the fiber diameter is crucial to the mechanical properties and functionality of the fiber. If the particle size of the bilayer temperature-sensitive microcapsules is greater than 500 nm, obvious physical protrusions or nodules are easily formed inside the ultrafine nanofibers. Under external tensile force, these nodules will generate severe stress concentration, leading to a sharp decrease in the fiber's breaking strength, and the microcapsules are easily peeled off from the fiber surface. At the same time, large-diameter microcapsules are prone to clogging the spinneret's micropores (the spinneret orifice diameter is usually 0.10~0.18 mm), causing a sharp increase in spinning pressure, uneven fiber output, and even frequent fiber breakage, seriously affecting the stability of continuous production. If the microcapsule particle size is less than 200 nm, the microcapsule wall material is too thin, making it difficult to form an effective bilayer coating structure, and the drug loading of essential oils will be significantly reduced.

[0033] In another embodiment, this application provides a method for preparing the thermosensitive controlled-release plant-derived mosquito-repellent fiber as described above, comprising the following steps: S1. A plant-derived mosquito repellent essence is extracted from at least one plant material; S2. Preparation of bilayer temperature-sensitive microcapsules: Using the plant-derived mosquito repellent essence as the core material and PNIPAM-AA copolymer as the inner temperature-sensitive wall material, a single-layer temperature-sensitive microcapsule was prepared by in-situ polymerization. On the outside of the single-layer temperature-sensitive microcapsule, a chitosan-β-cyclodextrin composite cross-linking system is used to carry out a cross-linking reaction to construct an outer protective wall material, thereby obtaining the double-layer temperature-sensitive microcapsule. For example, in step S2, the process of preparing the bilayer temperature-sensitive microcapsules includes: adding the N-isopropylacrylamide-acrylic acid copolymer to water and heating it to dissolve it, forming an aqueous phase system; adding the plant-derived mosquito repellent essence to the aqueous phase system and performing shear emulsification treatment to form an oil-in-water emulsion system; heating the oil-in-water emulsion system to carry out a polymerization reaction; after the polymerization reaction is completed, adding a chitosan-β-cyclodextrin composite crosslinking system to the system and heating it to carry out a crosslinking reaction; after the crosslinking reaction is completed, centrifuging, washing and purifying, and drying are performed to obtain the bilayer temperature-sensitive microcapsules.

[0034] Traditional microencapsulation emulsification processes rely heavily on low molecular weight surfactants such as Tween, Span, and sodium dodecyl sulfate (SDS). These small molecule auxiliaries are very likely to remain on the surface of the microcapsules and inside the fibers after the reaction. In the subsequent wet spinning process, they will significantly reduce the interfacial tension and viscoelasticity of the spinning solution, resulting in unstable spinning jets, microcapsule breakage, temperature shift of the thermosensitive phase transition, and forming defects such as beading and breakage in the finished fibers.

[0035] Specifically, the binary thermosensitive copolymer PNIPAM-AA is fully dispersed in deionized water to prepare a solution with a mass fraction of 3%~5%. The solution is continuously heated to 50℃ and stirred until completely dissolved, forming a transparent and homogeneous thermosensitive polymer aqueous system. The plant-derived mosquito repellent essence core material from step S1 is slowly added dropwise to this aqueous system at a weight ratio of 1~2:1 (i.e., the mass ratio of N-isopropylacrylamide-acrylic acid copolymer to plant-derived mosquito repellent essence is 1~2:1). High-speed shear emulsification is performed at 6000~10000 r / min for 10~20 min, utilizing strong shearing to uniformly disperse the oil phase into nano-sized droplets, forming a water-in-oil emulsion with uniform particle size and a stable system. The obtained emulsion was placed under a nitrogen inert atmosphere and heated to 55-65℃ for low-temperature in-situ polymerization. The reaction was carried out at a constant temperature for 1-3 hours, allowing the thermosensitive polymer molecules to polymerize and solidify in situ on the surface of the essential oil droplets, uniformly encapsulating the core material of the plant-derived mosquito repellent essence, forming a dense inner thermosensitive wall material with stable thermosensitive response performance, thus completing the initial molding of the single-layer thermosensitive microcapsule.

[0036] This application ingeniously utilizes the unique amphiphilic topology of the PNIPAM-AA binary copolymer macromolecular chain. The copolymer molecular chain simultaneously possesses strongly hydrophilic carboxyl groups (from acrylic acid monomers) and strongly hydrophobic isopropyl groups (from N-isopropylacrylamide monomers), spatially interspersed, thus endowing the copolymer with excellent self-emulsifying properties. During high-speed shear emulsification, without the addition of any small-molecule emulsifiers, the PNIPAM-AA copolymer macromolecules can autonomously and rapidly accumulate at the interface between the plant-derived mosquito repellent essence core material (oil phase) and deionized water (aqueous phase). Its hydrophobic ends face the essential oil droplets, and its hydrophilic ends face the aqueous phase, significantly reducing the oil-water interfacial tension and forming a water-in-oil emulsion with uniform particle size and extremely stable system. This self-emulsification mechanism not only ensures the smooth progress of subsequent in-situ polymerization reactions but also avoids problems such as spinning instability, microcapsule breakage, and increased fiber micro-defects caused by small-molecule auxiliary agent residues, guaranteeing the purity of the spinning system and the mechanical stability of the finished fiber.

[0037] After the in-situ polymerization reaction, a pre-prepared chitosan-β-cyclodextrin composite crosslinking system was slowly added to the system (the weight ratio of the outer protective wall material to the plant-derived mosquito repellent essence core material was 1~2:1, specifically referring to the ratio of the sum of the masses of chitosan and β-cyclodextrin in the chitosan-β-cyclodextrin composite crosslinking system to the mass of the plant-derived mosquito repellent essence). The system temperature was adjusted to 40~50℃ for a constant temperature crosslinking reaction for 1~2 hours, allowing the chitosan and β-cyclodextrin to crosslink and solidify on the outer surface of the microcapsules, constructing a high-strength, highly compatible outer protective wall material, forming a double-layer encapsulation structure with a precisely temperature-sensitive inner layer and a high-strength outer layer. After the reaction, the mixture was centrifuged and purified by multiple deionized water washings to remove unreacted monomers, free polymers, and residual additives. Finally, it was subjected to low-temperature vacuum drying to obtain double-layer temperature-sensitive microcapsules with a controllable particle size of 200~500nm, high sphericity, excellent monodispersity, and no agglomeration defects. The entire microcapsule preparation process is carried out at a mild temperature not exceeding 60°C, which basically avoids the heat-induced volatilization and deterioration of the essential oils.

[0038] S3. Gradient phase separation wet spinning preparation of thermosensitive controlled-release plant-derived mosquito repellent fibers: A phase separation regulator is added to the cellulose spinning solution, followed by the addition of the bilayer thermosensitive microcapsules to obtain a mixed spinning solution. The mixed spinning solution is extruded through a porous spinneret and then placed in a coagulation bath for phase separation and solidification, thereby constructing nascent fibers with internal gradient microporous slow-release channels and a dense thermosensitive protective film on the surface in situ. The nascent fibers undergo multi-stage wet stretching and shaping and post-treatment to obtain thermosensitive controlled-release plant-derived mosquito repellent fibers.

[0039] For example, in step S3, the process of preparing thermosensitive controlled-release plant-derived mosquito-repellent fibers by gradient phase separation wet spinning includes: First, an NMMO solution of cellulose pulp with a solid content of 8%–18% is prepared as the cellulose spinning solution. A phase separation regulator is added to this solution, and the mixture is stirred at low speed until homogeneous. Subsequently, the bilayer temperature-sensitive microcapsules prepared in step S2 are added in batches, ultrasonically dispersed until homogeneous, and allowed to stand for degassing for 15–24 hours for later use. The phase separation regulator is selected from one or more combinations of polyethylene glycol (such as PEG-400, PEG-600, etc.), glycerol, and sorbitol, and its dosage is 0.1%–0.3% of the mass of the cellulose spinning solution.

[0040] Next, using a low-temperature wet spinning machine, the deaerated spinning solution is pumped through a metering pump to a porous spinneret with an aperture of 0.10~0.18mm. The solution is extruded at a uniform flow rate of 6~12mL / min and an extrusion speed of 15~25m / min to form a fine stream, which directly enters a constant-temperature gradient coagulation bath. The coagulation bath temperature is controlled at 18~22℃, and the coagulation bath solution is a mixed solution of water and NMMO (water to NMMO mass ratio of 80~90:10~20). Utilizing the solvent-non-solvent microphase separation effect between the coagulation bath and the spinning solution, a continuous, interconnected, dense-outer-and-loose-inner nanogradient microporous slow-release channel and a dense temperature-sensitive protective film on the surface are constructed in situ. The extruded nascent fibers are then continuously stretched and shaped under wet conditions through a three-stage gradient wet stretching process, with the total draw ratio controlled at 2.8~3.5 times. Among them, the first-stage pre-drawing ratio is controlled at 1.1 to 1.3 times, the second-stage regularization draw ratio is controlled at 1.5 to 2.0 times, and the third-stage shaping draw ratio is controlled at 2.8 to 3.5 times.

[0041] Finally, the shaped fibers are subjected to multi-stage countercurrent water washing to remove residual solvents and free additives, and then dried with low-temperature hot air at 35~45℃ and wound up under constant tension to obtain the finished temperature-sensitive controlled-release plant-derived mosquito repellent fiber.

[0042] This application utilizes a fully low-temperature green processing and homogeneous integrated wet spinning process to construct a temperature-sensitive controlled-release plant-derived mosquito-repellent fiber with a gradient porous structure of "dense on the outside and loose on the inside". The entire process is carried out at low temperatures without high-temperature heat damage, comprehensively inhibiting the oxidative degradation of the thermosensitive unsaturated components of plant extracts. It abandons traditional finishing and secondary modification processes, achieving integrated completion of microcapsule homogeneous doping, fiber forming, structural construction, and functional solidification. The process is simple and suitable for industrial mass production.

[0043] In contrast, in conventional NMMO wet spinning systems without phase separation modifiers, the spinning solution undergoes instantaneous and intense solvent / non-solvent displacement upon contact with the water-based coagulation bath. The excessively rapid phase separation causes the fiber surface to solidify and form a skin instantly, preventing timely diffusion of the internal solvent. This results in defective fibers with an excessively thick surface layer, collapsed internal pores, irregular pore sizes, and an unevenly dense structure. Simultaneously, the enormous interfacial shrinkage stress generated by this instantaneous phase separation directly tears the outer chitosan-β-cyclodextrin cross-linked film, causing microcapsule rupture, essential oil leakage, and loss of temperature-sensitive functionality. The phase separation regulator added in this application can be distributed in the interstitial space between cellulose polymer chains and the aqueous phase interface layer, playing multiple roles such as interface buffering, delaying phase separation, uniform water conduction, and regularizing pore formation: First, it moderately reduces the coagulation driving force, delays the instantaneous solidification of the surface layer, and allows the solvent and water molecules to diffuse slowly and uniformly in both directions; second, it induces the formation of continuous, interconnected, and gradient-distributed nano-slow-release microporous channels inside; third, it buffers phase separation stress, protects the integrity of the double-layer microcapsule structure, and avoids wall material cracking and essential oil leakage during high shear and phase shrinkage in spinning; fourth, it improves the interfacial wettability between the microcapsule and the cellulose matrix, and eliminates spinning defects such as dopant agglomeration, local blanks, and stress concentration.

[0044] In contrast, freshly extruded nascent fibers are in a soft, incompletely cured hydrogel state. The internal cellulose molecular chains are loose and disordered, the solvent has not fully precipitated, the microporous structure is not yet fixed, and the overall mechanical strength is extremely low, making it unable to withstand a single high-ratio strong stretching. If traditional single-stage instantaneous stretching is used, it is very easy to cause tearing of the microcapsule wall material, leakage of essential oils, collapse of micropores, stress cracking of fibers, and fiber breakage and scrapping. The three-stage gradient wet drawing process adopted in this application has the following technical advantages: First, it applies tension gradually throughout the process, avoiding instantaneous stress impact and completely protecting the double-layer temperature-sensitive microcapsule structure from damage. This ensures that the microcapsules are spherically intact, without cracking or deformation, and without essential oil leakage, thus maximizing the preservation of the temperature-sensitive phase change function and essential oil activity. Second, it regularizes the overall microstructure and surface dense structure of the fiber, further strengthening the surface release barrier, eliminating the ineffective volatilization of essential oils at room temperature, and extending the storage life. Third, it induces the ordered orientation of polymer chains step by step, improving the fiber entanglement tightness and structural regularity, significantly improving the fiber breaking strength and dimensional stability, and solving the common industry problem of "functional improvement but mechanical decline" in traditional functional fibers. Fourth, it uniformly releases the internal stress of the fiber, reducing defects such as fiber breakage, uneven thickness, and local collapse, improving the spinning yield and batch stability, and making it suitable for continuous industrial production.

[0045] In some embodiments of this application, in step S3, an antioxidant stabilizer is also added to the cellulose spinning solution. The antioxidant stabilizer is selected from at least one of L-ascorbic acid, sodium isoascorbate, and water-soluble tea polyphenols. The antioxidant stabilizer is added to the solution at an amount of 1% to 5% of the solution weight and stirred thoroughly to prevent thermo-oxidative degradation of the polymer macromolecular chains during spinning and subsequent setting processes.

[0046] In some embodiments of this application, in step S1, the extraction method is supercritical CO2 extraction. Specifically, before extraction, the plant material is pulverized, freeze-dried, and sieved to obtain plant material powder. Specifically, the plant material is placed in a low-temperature cold trap... 20℃~ Vacuum freeze-drying was performed at 70℃ for 18-72 hours. This low-temperature freeze-drying allows for direct sublimation of water within the plant tissue, largely avoiding the loss of volatile essential oils and oxidative deterioration of heat-sensitive active components caused by conventional high-temperature drying. The dried residue was then ultra-finely pulverized in a cryo-mill under liquid nitrogen protection, passing through a 150-250 mesh sieve to obtain a freeze-dried powder with uniform particle size distribution and a large specific surface area. Ultra-fine pulverization effectively breaks down plant cell walls, fully exposing intracellular active ingredients and significantly reducing mass transfer resistance during supercritical extraction.

[0047] The freeze-dried powder was placed in a supercritical CO2 extraction vessel, and carbon dioxide gas was introduced at a flow rate of 15-30 L / h. The extraction vessel was pressurized by a high-pressure pump. The extraction pressure was controlled at 5-50 MPa (preferably 15-30 MPa), and the extraction temperature was 35℃-45℃. The extraction was continuously circulated for 15-180 min (preferably 60-120 min). Supercritical CO2 combines the low viscosity and high diffusivity of a gas with the low density and high solubility of a liquid, enabling it to efficiently dissolve and extract non-polar and moderately polar mosquito-repellent active components from plant tissues at extremely mild temperatures. As the extract flows through a separation vessel, the CO2 is rapidly vaporized and recycled through a gradient depressurization process, resulting in a pure, solvent-free, and highly active plant-derived mosquito-repellent essence collected at the bottom of the separation vessel. This gentle extraction process ensures the integrity of the heat-sensitive mosquito-repellent components in the essential oil, providing a broad-spectrum and highly effective mosquito-repellent activity guarantee for the finished fiber.

[0048] In some embodiments of this application, in step S1, the plant material is at least one of the following: magnolia, geranium, Murraya paniculata, night-blooming jasmine, marigold, verbena, carnation, snapdragon, calla lily, ageratum, pyrethrum, impatiens, jasmine, catnip, plumbago, lemongrass, pitcher plant, mugwort, mint, artemisia, rosemary, star anise, patchouli, velvet tea, basil, and lavender.

[0049] The above-mentioned plant materials can be compounded in equal mass ratios. Different plant materials are rich in natural mosquito-repellent active ingredients with different molecular structures. For example, pyrethrum is rich in pyrethrin, which has a strong contact killing and mosquito-repelling effect; artemisia and rosemary are rich in volatile terpenoids such as artemisia essential oil, eucalyptol, and camphor, which have a long-lasting airborne repellent effect; peppermint is rich in menthol, which can provide a cooling sensation and interfere with the olfactory localization system of mosquitoes. By compounding the above-mentioned plant materials, the core material of the plant-derived mosquito-repellent essence obtained by supercritical CO2 extraction and other technologies contains multiple active ingredients such as pyrethrin, menthol, and eucalyptol. These components produce a synergistic effect after evaporation in space, which can not only achieve broad-spectrum and high-efficiency repellency against a variety of common mosquitoes such as Aedes albopictus and Culex, but also avoid the shortcomings of single essential oil components, such as narrow mosquito repellent spectrum and easy adaptation. Meanwhile, these natural plant extracts are free of chemically synthesized mosquito repellents such as DEET, and have extremely high biocompatibility and skin-friendliness, making them suitable for applications in close-fitting textiles and high-end outdoor protection.

[0050] In some embodiments of this application, in step S2, the chitosan-β-cyclodextrin composite crosslinking system uses citric acid as a crosslinking agent. Through the esterification and crosslinking reaction between citric acid and chitosan and β-cyclodextrin, a three-dimensional network protective layer is constructed in situ on the outside of the monolayer thermosensitive microcapsule.

[0051] When a single-layer temperature-sensitive wall material undergoes a temperature-response phase change shrinkage, its micropores expand rapidly. Without an outer protective layer, this can easily lead to excessive instantaneous loss of essential oils or minute leakage at room temperature. This application addresses this issue by introducing a chitosan-β-cyclodextrin composite crosslinking system into the outer layer. Utilizing the multi-carboxyl structure of citric acid, under isothermal conditions, the carboxyl groups of citric acid undergo efficient esterification crosslinking reactions and multiple hydrogen bond synergistic bonding with the amino and hydroxyl groups on the chitosan macromolecular chain and the hydroxyl groups on the β-cyclodextrin macromolecular chain.

[0052] This chemical cross-linking process constructs a dense, high-strength three-dimensional mesh protective layer, the outer protective layer, in situ on the outside of the inner temperature-sensitive wall material. This outer protective layer not only effectively seals the microscopic leakage defects that may occur during the phase transition of the inner temperature-sensitive wall material, significantly improving the overall mechanical strength and essential oil storage stability of the double-layer temperature-sensitive controlled-release mosquito repellent microcapsules, but also optimizes the interfacial compatibility between the double-layer temperature-sensitive controlled-release mosquito repellent microcapsules and the cellulose matrix because the chitosan and β-cyclodextrin surfaces are rich in a large number of active polar groups such as hydroxyl and amino groups. These groups can form good hydrogen bonds with the cellulose macromolecular chains, thereby optimizing the interfacial compatibility between the double-layer temperature-sensitive controlled-release mosquito repellent microcapsules and the cellulose matrix. This allows the microcapsules to be firmly embedded in the fiber, remaining intact even after repeated washing, mechanical friction, and complex wearing environments, giving the finished fiber excellent wash resistance and a long service life for mosquito repellency.

[0053] In some embodiments of this application, in step S2, the mass ratio of chitosan to β-cyclodextrin in the chitosan-β-cyclodextrin composite crosslinking system is controlled at 1:1. Chitosan provides high-strength skeletal support, while β-cyclodextrin utilizes its unique hydrophobic cavity structure to form a secondary inclusion of essential oil molecules. The equal mass combination of the two can produce the best synergistic locking effect. In addition, the amount of crosslinking agent citric acid is controlled to be 5%~10% of the total mass of the chitosan-β-cyclodextrin composite crosslinking system. The amount of citric acid directly determines the crosslinking density of the outer protective wall material: if the amount is less than 5%, the crosslinking network is too loose and cannot effectively seal the microscopic leakage defects of the inner layer; if the amount is more than 10%, excessive crosslinking will lead to an overly rigid and brittle outer shell, and will easily consume too many polar hydroxyl groups, reducing the interfacial compatibility between the microcapsule and the cellulose matrix. Through the above precise ratio design, the average particle size of the finally prepared bilayer thermosensitive microcapsules is stable at about 300nm, with good monodispersity and structural stability.

[0054] Another embodiment of this application provides a textile containing the thermosensitive controlled-release plant-based mosquito-repellent fiber described above and / or the thermosensitive controlled-release plant-based mosquito-repellent fiber prepared according to the method described above. Specifically, the thermosensitive controlled-release plant-based mosquito-repellent fiber can be woven into fabric alone, or blended with other fibers (such as cotton fiber, polyester fiber, modal fiber, lyocell fiber, etc.) to form fabric, and then applied to the fields of high-end outdoor protection, close-fitting textiles, infant skin-friendly mosquito-repellent fabrics, and special operation protective textiles, playing multiple roles such as precise and long-lasting mosquito repellency, mechanical stability, breathability, and comfort.

[0055] The following specific embodiments are provided to illustrate this application in detail. It should also be understood that the following embodiments are only for specific illustration of this application and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of this application are within the scope of protection of this application. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not limited to the specific values ​​in the examples below.

[0056] Example 1 This embodiment provides a thermosensitive controlled-release plant-derived mosquito repellent fiber, the preparation method of which includes the following steps: S1, Plant-derived mosquito repellent essence extract: Plant materials, including peppermint, artemisia, rosemary, and pyrethrum, were selected and blended in equal mass ratios. These were placed in a low-temperature cold trap and freeze-dried at -40°C for 36 hours. After drying, the mixture was pulverized using a cryogenic grinder under liquid nitrogen protection and passed through a 200-mesh sieve to obtain freeze-dried powder. The powder was then placed in a supercritical CO2 extraction vessel, and carbon dioxide gas was introduced (flow rate controlled at 20 L / h). The extraction vessel was pressurized using a high-pressure pump, and continuous extraction was performed at an extraction pressure of 20 MPa and an extraction temperature of 40°C for 90 minutes. The resulting plant-derived mosquito repellent essence was collected.

[0057] S2. Preparation of double-layer temperature-sensitive mosquito repellent microcapsules: A 4% (w / w) PNIPAM-AA aqueous solution was prepared and dissolved at a constant temperature of 50°C. The plant-derived mosquito repellent essence obtained in step S1 was slowly added dropwise to the aqueous solution at a weight ratio of 1.5:1 (inner layer temperature-sensitive wall material to core material). High-speed shear emulsification was performed at 8000 r / min for 15 min to form a stable oil-in-water emulsion. The resulting emulsion was placed under a nitrogen inert atmosphere and heated to 60°C for low-temperature initiation of in-situ polymerization. The reaction was maintained at this temperature for 2 h, allowing the temperature-sensitive polymer molecules to polymerize and solidify in situ on the surface of the essential oil droplets, forming a single-layer temperature-sensitive microcapsule.

[0058] After the reaction was completed, a pre-prepared chitosan-β-cyclodextrin composite cross-linking system (prepared by adding the outer protective wall material to the mosquito repellent essence core material at a weight ratio of 1.5:1, wherein the mass ratio of chitosan to β-cyclodextrin was 1:1, and 8% citric acid was added as a cross-linking agent) was added to the system. The system temperature was adjusted to 45℃ and the cross-linking reaction was carried out at a constant temperature for 1.5 hours. After the reaction was completed, the mixture was centrifuged, repeatedly washed and purified with deionized water, and finally dried under low temperature vacuum to obtain bilayer temperature-sensitive microcapsules with an average particle size of approximately 300 nm.

[0059] S3. Gradient phase separation wet spinning preparation of thermosensitive controlled-release plant-derived mosquito repellent fibers: A NMMO solution of cellulose pulp with a solid content of 20% was prepared as the cellulose spinning solution. 0.2 wt% PEG-400 as a phase separation regulator and 0.3 wt% as ascorbic acid as an antioxidant stabilizer were added to the solution, and the mixture was stirred at low speed until homogeneous. Subsequently, the bilayer temperature-sensitive microcapsules prepared in step S2 were added in batches, ultrasonically dispersed for 15 min, and allowed to stand for degassing for 20 h for later use.

[0060] A low-temperature wet spinning process is employed. The deaerated spinning solution is pumped to a multi-hole spinneret (0.15mm orifice) via a high-precision metering pump, and extruded at a uniform flow rate of 8mL / min and an extrusion speed of 20m / min to form a fine stream of the solution, which directly enters a constant-temperature gradient coagulation bath. The coagulation bath temperature is precisely controlled at 20℃, and the coagulation bath solution is a mixture of water and NMMO (water to NMMO mass ratio of 85:15). Utilizing the solvent-non-solvent microphase separation effect between the coagulation bath and the spinning solution, a continuous, interconnected, dense-outer-and-loose nano-gradient microporous slow-release channel and a dense temperature-sensitive protective film on the surface are constructed in situ within the fiber. The extruded nascent fiber undergoes a three-stage gradient wet drawing process in a wet state for continuous stretching and shaping, with the total draw ratio controlled at 3.2 times. Specifically, the first-stage pre-draw ratio is controlled at 1.2 times, the second-stage regularization draw ratio at 1.7 times, and the third-stage shaping draw ratio at 3.2 times.

[0061] Finally, the shaped fibers are subjected to multi-stage countercurrent water washing to remove residual solvents and free additives, and then dried with low-temperature hot air at 40℃ and wound up under constant tension to obtain the finished temperature-sensitive controlled-release plant-derived mosquito repellent fiber.

[0062] Example 2 The only difference between the method for preparing the thermosensitive controlled-release plant-derived mosquito-repellent fiber in this embodiment and that in Example 1 is: In step S2, the mass fraction of PNIPAM-AA aqueous solution is 5%, the wall-to-core ratio of the two wall materials is 1:1, and the amount of citric acid crosslinking agent added is 10%.

[0063] In step S3, glycerol is selected as the phase separation regulator, with an addition amount of 0.3 wt%, and water-soluble tea polyphenols are selected as the stabilizer, with an addition amount of 0.5 wt%. The total spinning draw ratio is controlled at 3.5 times.

[0064] Example 3 The only difference between the method for preparing the thermosensitive controlled-release plant-derived mosquito-repellent fiber in this embodiment and that in Example 1 is: In step S2, the mass fraction of PNIPAM-AA aqueous solution is 3%, the wall-to-core ratio of the two wall materials is 2:1, and the amount of citric acid crosslinking agent added is 5%.

[0065] In step S3, sorbitol is selected as the phase separation regulator, with an addition amount of 0.1 wt%, sodium isoascorbate is selected as the stabilizer, with an addition amount of 0.2 wt%, and the total spinning draw ratio is controlled at 2.8 times.

[0066] Comparative Example 1 The fiber preparation method in this comparative example differs from that in Example 1 only in that: Step S2 prepares a single-layer microcapsule. This microcapsule uses a chitosan-β-cyclodextrin composite crosslinker as the outer protective wall material and has no inner temperature-sensitive wall material, PNIPAM-AA copolymer.

[0067] Comparative Example 2 The fiber preparation method in this comparative example differs from that in Example 1 only in that: Step S2 prepares a single-layer temperature-sensitive microcapsule. This microcapsule uses pure PNIPAM homopolymer instead of PNIPAM-AA copolymer as the wall material and has no outer chitosan-β-cyclodextrin crosslinking protection.

[0068] Comparative Example 3 The fiber preparation method in this comparative example differs from that in Example 1 only in that: In step S3, no phase separation regulator is added to the spinning solution, the nascent fibers are not subjected to three-stage gradient wet drawing, and a single-stage instantaneous drawing process is adopted, with the drawing ratio controlled at 3.2 times.

[0069] Comparative Example 4 The fiber preparation method in this comparative example differs from that in Example 1 only in that: Antioxidant stabilizers are added directly to the cellulose spinning solution to create a wet spinning solution, which is then used to produce pure viscose filament fibers.

[0070] The fibers in the above embodiments and comparative examples were tested for performance using the following methods, and the test results are shown in Table 1.

[0071] 1. Fiber breaking strength: The breaking strength of the fiber was determined by a tensile strength tester in accordance with GB / T 14344 "Test Method for Tensile Properties of Chemical Fiber Filaments".

[0072] 2. Mosquito repellency performance of textiles: In accordance with GB / T 30126-2013 "Test and evaluation of mosquito repellency performance of textiles", the repellency method was adopted, and the test insect was Aedes albopictus. The instantaneous repellency rate was tested in a normal temperature environment of 25℃ and a high temperature environment of 34℃ to evaluate the accuracy of temperature-sensitive controlled release.

[0073] 3. Plant extract retention rate test: Quantitative testing was performed using gas chromatography (GC) with external standard method. The extract was purified by ultrasonic extraction with organic solvent and centrifugation, followed by chromatographic detection. The retention rate was calculated by comparing the initial extract content with the chromatographic results.

[0074] 4. Water resistance test: The plant-derived mosquito repellent essence was tested by using a water resistance tester and following the standard washing procedure to determine the retention rate of the product after 20 washes.

[0075] 5. Long-term stability: After storing all samples at room temperature (25℃) in the dark for 180 days, their mosquito repellency rate at 34℃ was tested again to verify the long-term stability of the product.

[0076] Table 1

[0077] Based on the above test data, the test results of each embodiment and comparative example are analyzed in depth: Comparative Example 4 uses conventional unmodified viscose fiber, which lacks mosquito-repellent components. Its room-temperature mosquito-repellent rate, high-temperature mosquito-repellent rate, and long-lasting mosquito-repellent rate are all extremely low, indicating no effective mosquito-repellent effect. This data demonstrates that the superior mosquito-repellent performance of the fiber in this application is not inherent to the matrix fiber but is entirely achieved through the synergistic process of the double-layer temperature-sensitive microcapsules and gradient microporous structure of this application, providing a benchmark for the effectiveness of the functional modification in this application.

[0078] The fiber in Comparative Example 1 completely eliminates the PNIPAM-AA inner temperature-sensitive wall material, relying solely on chitosan-β-cyclodextrin as a single wall material to encapsulate the plant essence. Lacking a temperature-responsive regulation mechanism, its drug release relies entirely on natural diffusion and lacks intelligent switching characteristics. This structure lacks a temperature-sensitive closed-cell locking effect, allowing the plant essence to evaporate freely and continuously at room temperature, resulting in a room-temperature mosquito repellency rate as high as 68.5%, but with extremely severe ineffective evaporation losses. Although its short-term room-temperature mosquito repellency is outstanding, the lack of a stable locking structure results in a 90-day room-temperature essence retention rate of only 74.6%, and a retention rate of only 78.2% after 20 washes, indicating extremely poor washability and long-term storage stability. Furthermore, this structure cannot actively expand pores to improve drug release efficiency at high temperatures, resulting in a high-temperature mosquito repellency rate of only 71.5%, significantly weaker than the fibers in Examples 1-3. This fully demonstrates that the PNIPAM-AA temperature-sensitive inner layer added in this application can accurately achieve intelligent regulation functions such as room temperature closed-cell storage, significantly reducing ineffective volatilization, high temperature open-cell drug release, and enhanced mosquito repellent effect. It solves the core defects of non-temperature-sensitive systems, such as "rapid dissipation at room temperature, poor long-term effect, and limited improvement in high temperature drug release", and verifies the indispensability of the inner layer temperature-sensitive wall material.

[0079] Comparative Example 2 uses a single-layer PNIPAM-AA thermosensitive microcapsule structure, retaining the core 33°C precise thermosensitive response system of this application, with only the outer chitosan-β-cyclodextrin high-strength protective layer removed, to verify the synergistic gain effect of the bilayer composite structure. This single-layer thermosensitive structure possesses basic temperature-controlled release capability. Compared to Comparative Example 1 without a thermosensitive layer, ineffective volatilization at room temperature is somewhat suppressed, the room temperature mosquito repellency rate is reduced to 34.5%, ineffective loss is reduced, and the high-temperature mosquito repellency rate is increased to 77.5%, with significantly improved drug release controllability. However, due to the lack of an outer three-dimensional cross-linked protective network, the wall material has microscopic pore defects, resulting in insufficient antioxidant, water-washable, and anti-volatile properties. Its 90-day essence retention rate, water-washable retention rate, and 180-day long-lasting mosquito repellency performance are all significantly lower than those of the fibers in Examples 1-3. This demonstrates that the inner temperature-sensitive structure is responsible for precise controlled release, while the outer chitosan-β-cyclodextrin cross-linked structure is responsible for high-strength protection, erosion resistance, and oxidation resistance. The two form a synergistic system with complementary functions, which is the key to achieving both intelligent drug release and long-term stability in this application.

[0080] Comparative Example 3 fibers were prepared using a conventional uncontrolled spinning process. No phase separation modifier was added to the spinning solution, and the three-stage gradient wet drawing process was replaced with traditional single-stage instantaneous drawing. The poor mosquito-repellent effect of this fiber was due to the instantaneous and violent solvent-non-solvent exchange that occurred after the spinning solution entered the coagulation bath without the addition of a phase separation modifier. This explosive phase separation led to excessively rapid skinning on the fiber surface and internal solvent retention, preventing normal diffusion. Ultimately, this resulted in a defective structure with an excessively thick and dense surface, large-area collapse of internal pores, chaotic and blocked channels, and no gradient distribution. It failed to form functional slow-release channels that were dense on the outside and loose on the inside, resulting in extremely poor structural uniformity. Furthermore, severe microcapsule rupture and leakage occurred, and the instantaneous and violent phase separation created a large interface. Shrinkage stress, combined with the impact stress of single-stage instantaneous strong stretching, directly tears the double-layer microcapsule wall material, causing premature leakage and oxidation of a large amount of essential oil, resulting in the loss of the precise temperature-sensitive controlled release function at 33℃, severe ineffective volatilization at room temperature, and disordered drug release at high temperatures. Simultaneously, the fiber's mechanical strength is only 2.03 cN / tex, with a significant decrease in mechanical properties. Single-stage stretching stress concentration is obvious, the polymer chains lack ordered orientation and are randomly arranged, resulting in numerous internal defects and microcracks, poor fiber flexibility, and easy breakage. This leads to a high fiber breakage rate and poor mass production stability during spinning. In summary, conventional uncontrolled spinning processes suffer from multiple problems, including structural defects, functional failure, weak mechanical properties, and poor mass production stability.

[0081] Data from 180 days of long-lasting mosquito repellency showed that the mosquito repellency performance of all comparative examples decreased significantly and approached failure. However, Examples 1-3 still maintained a high-temperature mosquito repellency rate of over 75%, with Example 1 reaching 82.5%. This demonstrates that the double-layer locking structure and gradient slow-release system can resist the oxidation and natural volatilization of components for a long time, effectively extending the product's shelf life and service life. Simultaneously, this application, through a three-stage gradient wet drawing process, regulates the molecular chain structure and preserves the intact morphology of the microcapsules. The modified fiber's breaking strength is significantly better than that of ordinary single-layer modified systems and unoptimized process systems, and also surpasses the benchmark strength of conventional viscose fibers. This addresses the technical shortcomings of traditional functional modified fibers, such as decreased mechanical strength, susceptibility to breakage, and poor weaving resistance, achieving synergistic optimization of functional improvement and structural performance.

[0082] In summary, this application effectively addresses the core technical challenges of existing plant-derived mosquito repellent fibers, such as lack of intelligent controlled release, severe volatilization at room temperature, poor long-lasting effect, weak washability, and contradiction between function and mechanical properties, through precise plant essence extraction technology, 33℃ temperature-adapted thermosensitive copolymerization modification, double-layer microcapsule locking structure, gradient microporous phase separation molding, and three-stage gradient wet stretching integrated process. Multiple sets of comparative experiments have verified that the mosquito repellent fiber prepared in this application possesses comprehensive advantages including precise temperature control, on-demand drug release, stable storage, washability, long-lasting service life, and excellent mechanical properties, demonstrating extremely high industrial application value.

[0083] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A method for preparing a thermosensitive controlled-release plant-derived mosquito-repellent fiber, characterized in that, Includes the following steps: S1. A plant-derived mosquito repellent essence is extracted from at least one plant material; S2. Preparation of bilayer temperature-sensitive microcapsules: Using the plant-derived mosquito repellent essence as the core material and N-isopropylacrylamide-acrylic acid copolymer as the inner temperature-sensitive wall material, a single-layer temperature-sensitive microcapsule was prepared by in-situ polymerization. On the outside of the single-layer temperature-sensitive microcapsule, a chitosan-β-cyclodextrin composite cross-linking system is used to carry out a cross-linking reaction to construct an outer protective wall material, thereby obtaining the double-layer temperature-sensitive microcapsule. S3. Gradient phase separation wet spinning preparation of thermosensitive controlled-release plant-derived mosquito repellent fibers: A phase separation regulator is added to the cellulose spinning solution, followed by the addition of the bilayer thermosensitive microcapsules to obtain a mixed spinning solution. The mixed spinning solution is extruded through a porous spinneret and then placed in a coagulation bath for phase separation and solidification, thereby constructing nascent fibers with internal gradient microporous slow-release channels and a dense thermosensitive protective film on the surface in situ. The nascent fibers undergo multi-stage wet stretching and shaping and post-treatment to obtain thermosensitive controlled-release plant-derived mosquito repellent fibers.

2. The method for preparing thermosensitive controlled-release plant-derived mosquito-repellent fiber according to claim 1, characterized in that: In step S1, the extraction method is supercritical CO2 extraction. And / or, the plant material is at least one of the following: magnolia, geranium, Murraya paniculata, night-blooming jasmine, marigold, verbena, carnation, snapdragon, calla lily, ageratum, pyrethrum, impatiens, jasmine, catnip, blue plumbago, lemongrass, pitcher plant, mugwort, mint, artemisia, rosemary, star anise, patchouli, velvet tea, basil, and lavender.

3. The method for preparing thermosensitive controlled-release plant-derived mosquito-repellent fiber according to claim 2, characterized in that: In step S1, a plant-derived mosquito repellent essence is extracted from at least one plant material using supercritical CO2 extraction, and is carried out in accordance with at least one of requirements (11) to (14): (11) Before extraction, the plant material is crushed, freeze-dried and sieved to obtain plant material powder; (12) The extraction temperature is 35℃~45℃; (13) The extraction pressure is 5~50MPa; (14) Extraction time is 15 to 180 minutes.

4. The method for preparing thermosensitive controlled-release plant-derived mosquito-repellent fiber according to claim 1, characterized in that: In step S2, the process of preparing the bilayer temperature-sensitive microcapsules includes: The N-isopropylacrylamide-acrylic acid copolymer was added to water and heated to dissolve it, forming an aqueous phase system. The plant-derived mosquito repellent essence was added to the aqueous system and subjected to shear emulsification to form an oil-in-water emulsion system. The oil-in-water emulsion system is heated to carry out a polymerization reaction; After the polymerization reaction was completed, a chitosan-β-cyclodextrin composite crosslinking system was added to the system, and the mixture was heated to carry out the crosslinking reaction. After the cross-linking reaction was completed, centrifugation, washing and purification, and drying were performed to obtain the bilayer temperature-sensitive microcapsules.

5. The method for preparing thermosensitive controlled-release plant-derived mosquito-repellent fiber according to claim 4, characterized in that: In step S2, the process of preparing the bilayer temperature-sensitive microcapsules shall be carried out in accordance with at least one of the following requirements (21) to (27): (21) The mass fraction of the N-isopropylacrylamide-acrylic acid copolymer in the aqueous system is 3%~5%; (22) The mass ratio of the N-isopropylacrylamide-acrylic acid copolymer to the plant-derived mosquito repellent essence is 1~2:1; (23) The chitosan-β-cyclodextrin composite cross-linking system includes chitosan and β-cyclodextrin, and the mass ratio of the sum of the mass of chitosan and β-cyclodextrin in the chitosan-β-cyclodextrin composite cross-linking system to the mass of the plant-derived mosquito repellent essence is 1~2:1; (24) The chitosan-β-cyclodextrin composite crosslinking system includes chitosan, β-cyclodextrin and a crosslinking agent, wherein the crosslinking agent includes citric acid; (25) During shear emulsification, the rate is 6000~10000 r / min and the duration is 10~20 minutes; (26) The polymerization reaction temperature is 55~65℃; (27) The cross-linking reaction temperature is 40~50℃.

6. The method for preparing thermosensitive controlled-release plant-derived mosquito-repellent fiber according to claim 1, characterized in that: In step S3, the wet spinning is performed according to at least one of the following requirements (31) to (36): (31) The solid content of the cellulose spinning solution is controlled at 8%~18%; (32) The phase separation regulator is selected from at least one of polyethylene glycol, glycerin, and sorbitol, and its dosage is 0.1% to 0.3% of the mass of the cellulose spinning solution; (33) The flow rate of the mixed spinning solution extruded through the porous spinneret is controlled at 6~12 mL / min, the orifice diameter of the porous spinneret is 0.10~0.18 mm, and the extrusion speed is controlled at 15~25 m / min; (34) The coagulation bath is a constant temperature gradient coagulation bath, the temperature of which is controlled at 18~22℃, and the coagulation bath liquid is a mixed solution of water and N-methylmorpholine-N-oxide; (35) The multi-stage wet drawing is a three-stage gradient wet drawing process, with the total drawing ratio controlled at 2.8 to 3.5 times, of which the first-stage pre-drawing ratio is controlled at 1.1 to 1.3 times, the second-stage regularization drawing ratio is controlled at 1.5 to 2.0 times, and the third-stage shaping drawing ratio is controlled at 2.8 to 3.5 times; (36) The post-processing includes multi-stage countercurrent washing and drying.

7. The method for preparing thermosensitive controlled-release plant-derived mosquito-repellent fiber according to any one of claims 1 to 6, characterized in that: In step S3, an antioxidant stabilizer is also added to the cellulose spinning solution. The antioxidant stabilizer is selected from at least one of L-ascorbic acid, sodium isoascorbate, and water-soluble tea polyphenols.

8. A temperature-sensitive controlled-release plant-derived mosquito-repellent fiber, characterized in that, include: A cellulose matrix, wherein the interior of the cellulose matrix has gradient microporous slow-release channels and the surface has a dense temperature-sensitive protective film; A double-layered thermosensitive microcapsule is loaded in the cellulose matrix; the double-layered thermosensitive microcapsule includes a core material, and an inner thermosensitive wall material and an outer protective wall material that encapsulate the core material from the inside out. The core material includes a plant-derived mosquito repellent essence, the inner thermosensitive wall material includes an N-isopropylacrylamide-acrylic acid copolymer, and the outer protective wall material includes a chitosan-β-cyclodextrin composite crosslinker.

9. The thermosensitive controlled-release plant-derived mosquito-repellent fiber according to claim 8, characterized in that: The average particle size of the bilayer temperature-sensitive microcapsules is 20nm~80nm; And / or, the average diameter of the temperature-sensitive controlled-release plant-derived mosquito repellent fiber is 0.10~0.18mm.

10. A textile product, characterized in that: The textile contains thermosensitive controlled-release plant-derived mosquito-repellent fibers prepared according to any one of claims 1 to 7 and / or thermosensitive controlled-release plant-derived mosquito-repellent fibers according to any one of claims 8 to 9.

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