A red light-enhanced, temperature-controlled nonwoven fabric and its preparation method

Abstract

This invention relates to the field of intelligent functional textile materials technology, and discloses a red light-enhanced temperature-controlled nonwoven fabric and its preparation method. The preparation method of the red light-enhanced temperature-controlled nonwoven fabric includes the following steps: pretreating a polyester-based nonwoven fabric substrate to obtain a pretreated substrate; mixing reversible thermochromic microcapsules with an aqueous polyurethane emulsion to obtain a thermochromic polyurethane mixed emulsion; coating the thermochromic polyurethane mixed emulsion onto the pretreated substrate to form a thermochromic layer; mixing a surface-modified red luminescent material with an aqueous polyurethane emulsion to obtain a red luminescent polyurethane mixed emulsion; coating the red luminescent polyurethane mixed emulsion onto the thermochromic layer to form a red luminescent layer; cooling and winding to obtain the red light-enhanced temperature-controlled nonwoven fabric; the red light-enhanced temperature-controlled nonwoven fabric has a multi-layer composite structure, realizing the dual functions of temperature-controlled color change and red light enhancement.

Description

Technical Field

[0001] This invention relates to the field of intelligent functional textile materials technology, specifically to a red light-enhanced temperature-controlled nonwoven fabric and its preparation method. Background Technology

[0002] With the intelligent upgrading of the safety protection industry and the rapid development of intelligent monitoring technology, the market demand for multifunctional materials that combine environmental responsiveness and active warning functions is becoming increasingly urgent. In scenarios such as nighttime construction, cold chain transportation, and outdoor emergency response, traditional warning materials mostly rely on single reflective strips or fixed color markings, which have significant technical shortcomings: on the one hand, the color recognition of traditional markings decreases significantly under different temperature environments, making it impossible to effectively reflect temperature changes; on the other hand, they lack active light emission capabilities in nighttime or low-light environments, and relying solely on passive reflection makes it difficult to achieve long-distance warnings, which can easily lead to safety hazards.

[0003] Currently, existing composite products of thermochromic and luminescent materials have many technical defects: First, the compatibility between thermochromic microcapsules and luminescent materials in polymer matrices is poor, and they are prone to aggregation, resulting in insufficient functional stability; Second, when using solvent-based adhesives to prepare functional layers, there are volatile organic compound (VOC) emissions, which fail to meet environmental protection standards; Third, traditional coating processes make it difficult to accurately control the thickness of functional layers, and the adhesion between functional layers and substrates is not firm, which cannot meet the needs of long-term use; In addition, some products only achieve single-function superposition and do not form a synergistic effect of "temperature monitoring-visual warning", making it difficult to adapt to complex application scenarios.

[0004] Therefore, developing a composite nonwoven fabric that combines temperature-controlled color-changing response, high-efficiency red light enhancement, structural stability, durability, and environmental friendliness to solve the technical pain points of traditional warning materials such as "low low-temperature visibility, lack of active warning at night, poor performance stability, and insufficient environmental friendliness" has become an urgent problem to be solved in the field of functional textile materials. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a red light-enhanced, temperature-controlled nonwoven fabric, comprising the following steps: Step 1: Substrate pretreatment: The polyester staple fiber spunlace nonwoven fabric is subjected to surface dust removal and leveling treatment to obtain the pretreated substrate; Step 2: Preparation of thermochromic polyurethane mixed emulsion: Disperse reversible thermochromic microcapsules in an aqueous polyurethane emulsion and stir to obtain a thermochromic polyurethane mixed emulsion; wherein, the reversible thermochromic microcapsules include a polyurethane wall material and a reversible thermochromic color-developing system core material; the reversible thermochromic color-developing system core material includes a color-developing agent, a color-developing agent, and a solvent, and the color-developing agent includes crystal violet lactone; Step 3, Thermochromic layer coating and drying: The thermochromic polyurethane mixed emulsion is coated onto the pretreated substrate surface and dried to form a thermochromic layer; Step 4: Preparation of Red Luminescent Polyurethane Mixed Emulsion: The surface-modified red luminescent material is dispersed in an aqueous polyurethane emulsion and ultrasonically dispersed to obtain a red luminescent polyurethane mixed emulsion; the surface-modified red luminescent material is obtained by modifying red luminescent materials with a silane coupling agent; the red luminescent material includes Y2O2S:Eu 3+ Mg 2+ Ti 4+ ; Step 5: Coating and drying the red luminescent layer: Coat the surface of the thermochromic layer with the red luminescent polyurethane mixed emulsion, dry it to form a red luminescent layer, and cool it to obtain the red light-enhanced temperature-controlled nonwoven fabric.

[0006] Preferably, in step one, the basis weight of the polyester staple fiber spunlace nonwoven fabric is 50-100 g / m², and the tensile strength is ≥15 N / 5 cm.

[0007] This invention uses polyester short fiber spunlace nonwoven fabric as the substrate. The fibers have a three-dimensional fully interwoven structure, forming an irregular "hook and lock" pore network at the microscale. This structure has a good physical anchoring effect. After coating with waterborne polyurethane emulsion, it partially penetrates into the fiber gaps under the action of capillary force. After drying and curing, it forms mechanically interlocking anchor points, which significantly improves the interfacial bonding strength between the functional layer and the substrate. The structure also has controllable penetration depth. The pores of its fully interwoven structure are evenly distributed and have moderate connectivity. Combined with the moderate wettability of waterborne polyurethane, it can form an ideal interface structure of "surface film formation - shallow anchoring", avoiding excessive penetration leading to glue penetration or hardening of the feel, while avoiding coating peeling due to insufficient penetration.

[0008] Preferably, in step one, the flatness deviation of the pretreated substrate is ≤0.5mm / m.

[0009] Preferably, the solid content of the waterborne polyurethane emulsion in steps two and four is 30-35 wt%.

[0010] Preferably, in step two, the content of reversible thermochromic microcapsules in the thermochromic polyurethane mixed emulsion is 0.05-0.50 wt%.

[0011] Preferably, in step two, the reversible thermochromic microcapsules have a particle size of 1-10 μm and a thermochromic temperature range of 20-60℃.

[0012] Preferably, in step two, in the reversible thermochromic color-developing system, the color developer includes bisphenol A, and the solvent includes a long-chain alcohol with 12-16 carbon atoms.

[0013] The reversible thermochromic microcapsules in the thermochromic layer of this invention have polyurethane wall materials that are homologous to the aqueous polyurethane emulsion film-forming matrix. Homologous wall materials and the matrix have similar chemical structures and surface properties, resulting in excellent interfacial compatibility. This avoids problems such as phase separation and interfacial defects that may occur with heterogeneous wall materials. Therefore, the reversible thermochromic microcapsules of this invention can be uniformly and stably dispersed in the aqueous polyurethane emulsion without sedimentation or demulsification, ensuring uniform coating performance. During the drying and film-forming process, the wall material of the reversible thermochromic microcapsules and the polyurethane matrix can form a continuous, defect-free thin film structure, improving the coating performance. The mechanical integrity and durability are excellent; at the same time, the core material of the reversible thermochromic color-developing system of the present invention uses crystal violet lactone as the color-developing agent, which turns red after ring opening, forming a color synergy with the red light emission of the lower red light-emitting layer of the present invention, enhancing the overall visual effect; using C12-C16 long-chain alcohols as solvents, the color-changing temperature can be precisely customized in a wide temperature range by selecting the carbon chain length or adjusting the mixing ratio, adapting to different application scenarios. The three components of color-developing agent, color developer, and solvent work together to ensure rapid color-changing response, excellent reversibility, and long cycle life, meeting the practical requirements of functional textiles.

[0014] Preferably, in step two, the stirring time is 3-15 minutes.

[0015] Preferably, in step three, the thickness of the thermochromic layer is 10-25 μm.

[0016] Preferably, in step three, the coating process of the thermochromic polyurethane mixed emulsion includes a doctor blade coating process; the doctor blade coating process conditions are: doctor blade gap of 0.02-0.05mm and coating speed of 1-3m / min.

[0017] Preferably, in step three, the drying conditions are: drying temperature of 60-80℃ and drying time of 5-10 minutes.

[0018] Preferably, in step four, the surface-modified red luminescent material is prepared by the following method: Ethanol and water were mixed at a volume ratio of 9:1 to obtain an ethanol-water mixed solvent. A vinyl silane coupling agent was dissolved in the ethanol-water mixed solvent to prepare a silane solution with a mass fraction of 1.0-2.5%. Glacial acetic acid was added to the silane solution to adjust the pH to 4.0-5.0, and the solution was hydrolyzed at 15-30℃ for 10-60 min. Then, a red luminescent material was added at a solid-liquid ratio of 1:(5-10) g / mL, and the mixture was stirred at 60-80℃ for 2-4 h. After the reaction, the product was purified, ground, and sieved to obtain a surface-modified red luminescent material. The mass ratio of the vinyl silane coupling agent to the red luminescent material was (0.5-3.0):100. The vinyl silane coupling agent included any one of vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane.

[0019] This invention uses Y2O2S:Eu 3+ Mg 2+ Ti 4+ As a single red light-emitting material, and with surface modification using a vinyl silane coupling agent, it exhibits excellent compatibility with waterborne polyurethane emulsions. Under 320nm ultraviolet excitation, this material emits characteristic red light with high color purity, meeting the identification requirements of "standard red" in the field of safety warnings. Compared with other red light-emitting materials (such as sulfide systems), this material has good chemical stability and strong weather resistance, making it suitable for long-term outdoor use. This invention uses this material as the sole light source for an independent functional layer, ensuring stable and pure red light emission under any temperature conditions.

[0020] Preferably, in step four, the content of the surface-modified red luminescent material in the red luminescent polyurethane mixed emulsion is 0.30-1.00 wt%.

[0021] Preferably, in step four, the ultrasonic dispersion time is 20-30 minutes.

[0022] Preferably, in step five, the thickness of the red luminescent layer is 10-25 μm.

[0023] Preferably, in step five, the coating process of the red luminescent polyurethane mixed emulsion includes a doctor blade coating process; the doctor blade coating process conditions are: doctor blade gap of 0.02-0.05mm and coating speed of 1-3m / min.

[0024] Preferably, in step five, the drying conditions are: drying temperature of 80-100℃ and drying time of 5-10 minutes.

[0025] Preferably, the red light enhanced temperature-controlled nonwoven fabric can also undergo a secondary shaping process, with a shaping temperature of 100-110℃ and a shaping time of 1-2 minutes.

[0026] A red light-enhanced, temperature-controlled nonwoven fabric was prepared using the aforementioned method.

[0027] Furthermore, the multi-layer composite structure of red light enhancement-temperature-controllable nonwoven fabric as substrate-thermochromic layer-red luminescent layer has a total functional layer thickness of 20-50μm, a thermochromic response time ≤1min, and the emission peak of the red luminescent material under 320nm ultraviolet excitation is located at 667nm.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The red light-enhanced temperature-controlled nonwoven fabric of the present invention adopts a three-layer composite structure of "substrate - thermochromic layer - red luminescent layer". This structure is not a simple double coating. The thermochromic functional material and the luminescent functional material are placed in two independent coatings. In practical applications, the double coating structure can form the following synergistic working mode: under bright conditions, its color changes reversibly according to different temperatures; at night or in low light, under ultraviolet light excitation, the upper red luminescent layer emits stable red light; if the lower thermochromic layer is in a colorless state, red light is clearly transmitted; if the thermochromic layer is in a colored state, it selectively absorbs other visible light besides red light, significantly enhancing the red light purity of the nonwoven fabric.

[0029] 2. The reversible thermochromic microcapsules in the thermochromic layer of the present invention have the advantages of rapid color change response, excellent reversibility and long cycle life. Moreover, they can be uniformly and stably dispersed in aqueous polyurethane emulsion without settling or demulsification, ensuring that the thermochromic layer can form a continuous and defect-free film structure, thereby improving the mechanical integrity and durability of the coating and meeting the practical requirements of functional textiles.

[0030] 3. The red light-enhanced temperature-controlled nonwoven fabric of the present invention has adjustable performance and can be flexibly adjusted according to the application scenario: if the color-changing effect is to be enhanced, the thermochromic layer can be thickened; if the light-emitting effect is to be enhanced, the red light-emitting layer can be thickened, and the air permeability can be maintained by controlling the lower limit of the total thickness of the functional coating.

[0031] 4. The red light-enhanced temperature-controlled nonwoven fabric of the present invention solves the technical pain points of traditional warning materials such as "low low temperature recognition, no active warning at night, poor performance stability, and insufficient environmental protection" through multi-layer composite structure design and environmentally friendly continuous preparation process. It realizes the dual function of temperature-controlled color change and red light enhancement, and at the same time has excellent structural stability and environmental protection, effectively filling the technical gap of existing products. Attached Figure Description

[0032] Figure 1 The infrared spectrum of the red light-enhanced, temperature-controlled nonwoven fabric prepared in Example 1; Figure 2A scanning electron microscope image of the red light-enhanced temperature-controlled nonwoven fabric prepared in Example 1; Figure 3 Emission spectra of the red light-enhanced temperature-controlled nonwoven fabrics prepared in Example 1(a) and Comparative Example 2(b); Figure 4 CIE diagram of the red luminescent nonwoven fabric prepared in Comparative Example 1; Figure 5 CIE diagrams of the red light-enhanced temperature-controlled nonwoven fabrics prepared in Example 1(b) and Comparative Example 2(a). Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Example 1 This embodiment discloses a method for preparing a red light-enhanced, temperature-controlled nonwoven fabric, including the following steps: Step 1: Substrate pretreatment: The polyester staple fiber spunlace nonwoven fabric is subjected to surface dust removal and leveling treatment to obtain a pretreated substrate, ensuring that the substrate surface is free of impurities and the flatness deviation is 0.3mm / m; wherein, the basis weight of the polyester staple fiber spunlace nonwoven fabric is 70g / m². Step 2: Preparation of thermochromic polyurethane mixed emulsion: Disperse reversible thermochromic microcapsules in an aqueous polyurethane emulsion and stir for 6 minutes to obtain a thermochromic polyurethane mixed emulsion; wherein, the content of reversible thermochromic microcapsules in the thermochromic polyurethane mixed emulsion is 0.20 wt%; the particle size of the reversible thermochromic microcapsules is 4 μm, and the thermochromic temperature range is 30℃; the reversible thermochromic microcapsules include a polyurethane wall material and a reversible thermochromic color-developing system core material; the reversible thermochromic color-developing system includes a color-developing agent, a color-developing agent, and a solvent, wherein the color-developing agent includes crystal violet lactone, the color-developing agent includes bisphenol A, and the solvent is tetradecyl alcohol; the aqueous polyurethane emulsion is an aqueous polyurethane emulsion with a solid content of 35 wt% and a volatile organic compound (VOC) content ≤10 g / L; Step 3, Thermochromic layer coating and drying: Using a doctor blade coating process, the doctor blade gap is adjusted to 0.03 mm and the coating speed is 2 m / min. The thermochromic polyurethane mixed emulsion is uniformly coated on the pretreated substrate surface, and then dried at 80℃ for 3 min to form a thermochromic layer with a thickness of 15 μm. Step 4: Preparation of red luminescent polyurethane mixed emulsion: Vinyltrimethoxysilane, at a mass ratio of 1.5% (based on the red luminescent material), was dissolved in an ethanol-water mixture (volume ratio 9:1) to prepare a 2.0% (w / w) solution. The pH was adjusted to 4.5 with glacial acetic acid, and the solution was hydrolyzed at 25°C for 30 min. Y₂O₂S:Eu was then added. 3+ Mg 2+ Ti 4+ As a red luminescent material, the solid-liquid ratio was 1:8 g / mL, and the reaction was stirred at 70℃ for 3 h. After the reaction was completed, the solid product was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80℃ for 2 h. The product was then ground through a 200-mesh sieve to obtain the surface-modified red luminescent material. A surface-modified red luminescent material was dispersed in an aqueous polyurethane emulsion and ultrasonically dispersed for 25 min to obtain a red luminescent polyurethane mixed emulsion; wherein the content of the surface-modified red luminescent material in the red luminescent polyurethane mixed emulsion was 0.60 wt%; the solid content of the aqueous polyurethane emulsion was 35 wt%, and the volatile organic compound (VOC) content was ≤10 g / L. Step 5, Red luminescent layer coating and drying: Using a doctor blade coating process, the doctor blade gap is adjusted to 0.03 mm and the coating speed is 2 m / min. The red luminescent polyurethane mixed emulsion is uniformly coated on the surface of the thermochromic layer. Then, it is dried at 90℃ for 5 min to form a red luminescent layer with a thickness of 15 μm. After cooling and winding, the red light-enhanced temperature-controlled nonwoven fabric is obtained.

[0035] Comparative Example 1 This comparative example discloses a method for preparing a red luminescent nonwoven fabric, comprising the following steps: Step 1: Substrate pretreatment: The polyester staple fiber spunlace nonwoven fabric is subjected to surface dust removal and leveling treatment to obtain a pretreated substrate, ensuring that the substrate surface is free of impurities and the flatness deviation is 0.3mm / m; wherein, the basis weight of the polyester staple fiber spunlace nonwoven fabric is 70g / m². Step 2: Preparation of red luminescent polyurethane mixed emulsion: Vinyltrimethoxysilane, at a mass ratio of 1.5% (based on the red luminescent material), was dissolved in an ethanol-water mixture (volume ratio 9:1) to prepare a 2.0% (w / w) solution. The pH was adjusted to 4.5 with glacial acetic acid, and the solution was hydrolyzed at 25°C for 30 min. Y₂O₂S:Eu was then added. 3+ Mg 2+ Ti 4+ As a red luminescent material, the solid-liquid ratio was 1:8 g / mL, and the reaction was stirred at 70℃ for 3 h. After the reaction was completed, the solid product was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80℃ for 2 h. The product was then ground through a 200-mesh sieve to obtain the surface-modified red luminescent material. A surface-modified red luminescent material was dispersed in an aqueous polyurethane emulsion and ultrasonically dispersed for 25 min to obtain a red luminescent polyurethane mixed emulsion. The content of the surface-modified red luminescent material in the red luminescent polyurethane mixed emulsion was 0.60 wt%, and the solid content of the aqueous polyurethane emulsion was 35 wt%. The volatile organic compound (VOC) content was ≤10 g / L. Step 3, Coating and Drying of Red Emissive Layer: Using a doctor blade coating process, the doctor blade gap is adjusted to 0.03 mm and the coating speed is 2 m / min. The red luminescent polyurethane mixed emulsion is uniformly coated on the pretreated substrate surface, and then dried at 90℃ for 5 min to form a red luminescent layer with a thickness of 15 μm. After cooling and winding, the red luminescent nonwoven fabric is obtained.

[0036] Comparative Example 2 This comparative example discloses a method for preparing a red light-enhanced, temperature-controlled nonwoven fabric, comprising the following steps: Step 1: Substrate pretreatment: The polyester staple fiber spunlace nonwoven fabric is subjected to surface dust removal and leveling treatment to obtain a pretreated substrate, ensuring that the substrate surface is free of impurities and the flatness deviation is 0.3mm / m; wherein, the basis weight of the polyester staple fiber spunlace nonwoven fabric is 70g / m². Step 2: Preparation of polyurethane composite emulsion: Vinyltrimethoxysilane, at a mass ratio of 1.5% (based on the red luminescent material), was dissolved in an ethanol-water mixture (volume ratio 9:1) to prepare a 2.0% (w / w) solution. The pH was adjusted to 4.5 with glacial acetic acid, and the solution was hydrolyzed at 25°C for 30 min. Y₂O₂S:Eu was then added. 3+ Mg 2+ Ti 4+ As a red luminescent material, the solid-liquid ratio was 1:8 g / mL, and the reaction was stirred at 70℃ for 3 h. After the reaction was completed, the solid product was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80℃ for 2 h. The product was then ground through a 200-mesh sieve to obtain the surface-modified red luminescent material. A surface-modified red luminescent material and reversible thermochromic microcapsules were simultaneously dispersed in an aqueous polyurethane emulsion and ultrasonically dispersed for 25 min to obtain a polyurethane composite emulsion. The polyurethane composite emulsion contained 0.60 wt% surface-modified red luminescent material and 0.20 wt% reversible thermochromic microcapsules. The reversible thermochromic microcapsules had a particle size of 4 μm and a thermochromic temperature range of 30°C. The reversible thermochromic microcapsules comprised a polyurethane wall material and a reversible thermochromic color-developing system core material. The reversible thermochromic color-developing system comprised a color-developing agent, a color-developing agent, and a solvent. The color-developing agent included crystal violet lactone, the color-developing agent included bisphenol A, and the solvent was tetradecyl alcohol. The aqueous polyurethane emulsion was an aqueous polyurethane emulsion with a solid content of 35 wt% and a volatile organic compound (VOC) content ≤10 g / L. Step 3, Composite Coating and Drying: Using a doctor blade coating process, the doctor blade gap is adjusted to 0.03 mm and the coating speed is 2 m / min. The polyurethane composite emulsion is uniformly coated onto the pretreated substrate surface. After drying at 80℃ for 3 min, it is then dried at 90℃ for 5 min to form a composite coating with a thickness of 30 μm. After cooling and winding, the red light enhanced temperature-controlled nonwoven fabric is obtained.

[0037] Experimental Example The performance of the red light-enhanced temperature-controlled nonwoven fabric prepared in Example 1, the red light-emitting nonwoven fabric prepared in Comparative Example 1, and the red light-enhanced temperature-controlled nonwoven fabric prepared in Comparative Example 2 were tested: Test results are as follows Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown: Figure 1 The infrared spectrum of the red light-enhanced, temperature-controlled nonwoven fabric prepared in Example 1; by Figure 1 It can be seen that the infrared spectrum of the red light enhanced-temperature controllable nonwoven fabric sample of Example 1 is an effective superposition of the characteristic peaks of all original components. Its spectrum simultaneously retains the C=O peak of the polyester base fabric and the peak of the thermochromic pigment.

[0038] Figure 2 The image shows a scanning electron microscope (SEM) image of the red light-enhanced, temperature-controlled nonwoven fabric prepared in Example 1. The results show that the reversible thermochromic microcapsules were successfully added into and attached to the surface of the base fabric, which ensured its thermochromic effect.

[0039] Figure 3 The emission spectra of the red-enhanced, temperature-controlled nonwoven fabrics prepared in Example 1(a) and Comparative Example 2(b) are shown. The results show that both exhibit a characteristic red emission peak at 667 nm under high temperature conditions (30 °C, the thermochromic layer is colorless), corresponding to Y2O2S:Eu3+ Mg 2+ Ti 4+ Eu 3+ Ionic 5 D0→ 7 The F2 electric dipole transition was observed, but the emission intensity of Example 1 was significantly higher than that of Comparative Example 2. This is because the red luminescent material in the layered structure is completely dispersed in an independent coating, without being affected by the mixing interference of the thermochromic microcapsules. The crystal field around the luminescent ions is highly uniform, resulting in a low fluorescence quenching effect. In contrast, in Comparative Example 2, the coating luminescent material and microcapsules coexist in the same coating, leading to greater absorption and scattering losses of the excitation and emission light by the organic components. Furthermore, local aggregation exacerbates non-radiative energy transfer, resulting in a decrease in luminescence efficiency. Under low-temperature conditions (15°C, the thermochromic layer is red), the emission intensity of Example 1 only decreased slightly, and the emission peak position (667 nm) remained essentially unchanged. The absence of red or blue shift indicates that temperature changes primarily affect the optical transmittance of the upper thermochromic layer without altering the energy level structure of rare earth ions. However, the emission intensity decrease in Comparative Example 2 is significantly greater than that in Example 1, and the peak shape exhibits slight asymmetric broadening. This is because the increased dipole moment of crystal violet lactone in the reversible thermochromic microcapsule core material after ring-opening at low temperatures causes slight disturbances to the local dielectric environment of the closely contacting luminescent ions. Simultaneously, the volume change accompanying the melting-crystallization phase transition of the long-chain alcohol solvent creates additional stress on the luminescent particles, exacerbating non-radiative energy transfer. This not only leads to a sharp decrease in luminescence intensity but also reduces the red color purity due to the broadening of the emission peak shape, which is detrimental to security identification. Therefore, by comparing Example 1 and Comparative Example 2, it can be clearly seen that Example 1 of the present invention places the thermochromic functional material and the luminescent functional material in two independent coatings. The layered structure is significantly better than the single-layer coating structure that directly mixes the thermochromic functional material and the luminescent functional material in terms of luminous efficiency and spectral stability. This proves that the structural design of placing the thermochromic functional material and the luminescent functional material in two independent coatings has clear technical advantages.

[0040] Figure 4 The CIE diagram of the red luminescent nonwoven fabric prepared in Comparative Example 1 is shown. Figure 5 CIE diagrams of the red light-enhanced temperature-controlled nonwoven fabrics prepared in Example 1(b) and Comparative Example 2(a); The results showed that Comparative Example 1, a nonwoven fabric with a single red luminescent layer and no thermochromic layer, maintained a constant CIE color coordinate at different temperatures, and the purity of the red light was limited by the Y2O2S:Eu ratio. 3+ Mg 2+ Ti 4+ The emission spectrum characteristics of the material itself cannot be actively adjusted with temperature changes; The red light-enhanced temperature-controlled nonwoven fabric of Example 1 exhibits a red color due to the ring-opening of crystal violet lactone in the upper thermochromic layer under low-temperature conditions. This red state layer has selective spectral transmittance characteristics for the red light emitted by the lower red luminescent layer, that is, it maintains high transmittance for red light with wavelengths around 667nm, while effectively absorbing stray emission peaks outside the red light region. This spectral narrowing effect causes the CIE color coordinates to shift significantly towards the standard red region, greatly improving the red light purity and realizing the "temperature-responsive color purity enhancement" function that Comparative Example 1 does not possess. Compared with the hybrid monolayer structure of Comparative Example 2, the layered structure of Example 1 also has the advantage of color purity: In Comparative Example 2, the red luminescent material and the thermochromic microcapsule are in close contact within the same coating. At low temperature, the absorption spectrum of the chromatic body and the emission spectrum of the luminescent particles overlap excessively, resulting in non-selective overall attenuation. At the same time, the multiple scattering effect broadens the red spectral line and limits the drift of the color coordinates. However, Example 1, by spatially decoupling the thermochromic and luminescent functions, can obtain the color purity gain brought by the synergy of filtering, and avoid the energy crosstalk and spectral line broadening caused by microscopic contact in the hybrid system. The CIE color coordinates shift more towards the pure red region, which fully demonstrates that the layered structure has unique and significant technical advantages in color purity control.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a red light-enhanced, temperature-controlled nonwoven fabric, characterized in that, Includes the following steps: Step 1: Substrate pretreatment: The polyester staple fiber spunlace nonwoven fabric is subjected to surface dust removal and leveling treatment to obtain the pretreated substrate; Step 2: Preparation of thermochromic polyurethane mixed emulsion: Add reversible thermochromic microcapsules to an aqueous polyurethane emulsion and stir to obtain a thermochromic polyurethane mixed emulsion; wherein, the reversible thermochromic microcapsules include a polyurethane wall material and a reversible thermochromic color-developing system core material; the reversible thermochromic color-developing system core material includes a color-developing agent, a color-developing agent, and a solvent, and the color-developing agent includes crystal violet lactone; Step 3, Thermochromic layer coating and drying: The thermochromic polyurethane mixed emulsion is coated onto the pretreated substrate surface and dried to form a thermochromic layer; Step 4: Preparation of red luminescent polyurethane mixed emulsion: Add the surface-modified red luminescent material to the aqueous polyurethane emulsion and disperse it ultrasonically to obtain the red luminescent polyurethane mixed emulsion. The surface-modified red luminescent material is obtained by modifying the red luminescent material with a silane coupling agent, and the specific method includes: A vinyl silane coupling agent was dissolved in an ethanol-water mixture to prepare a silane solution with a mass fraction of 1.0-2.5%. Acetic acid was added to the silane solution to adjust the pH to 4.0-5.0, and the solution was hydrolyzed at 15-30℃ for 10-60 min. Then, a red luminescent material was added at a solid-liquid ratio of 1:(5-10) g / mL, and the reaction was stirred at 60-80℃ for 2-4 h. After the reaction, the product was purified, ground, and sieved to obtain a surface-modified red luminescent material. The mass ratio of the vinyl silane coupling agent to the red luminescent material was (0.5-3.0):

100. The vinyl silane coupling agent included any one of vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane, and the red luminescent material included Y₂O₂S:Eu 3+ Mg 2+ Ti 4+ ; Step 5: Coating and drying the red luminescent layer: Coat the surface of the thermochromic layer with the red luminescent polyurethane mixed emulsion, dry it to form a red luminescent layer, and cool it to obtain the red light-enhanced temperature-controlled nonwoven fabric.

2. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, The solid content of the waterborne polyurethane emulsion in steps two and four is 30-35 wt%.

3. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, In step two, the content of reversible thermochromic microcapsules in the thermochromic polyurethane mixed emulsion is 0.05-0.50 wt%.

4. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, In step two, the reversible thermochromic microcapsules have a particle size of 1-10 μm and a thermochromic temperature range of 20-60℃.

5. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, In step two, the reversible thermochromic color-developing system includes bisphenol A as the color developer and long-chain alcohols with 12-16 carbon atoms as the solvent.

6. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, In step three, the thickness of the thermochromic layer is 10-25 μm.

7. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, In step four, the content of the surface-modified red luminescent material in the red luminescent polyurethane mixed emulsion is 0.30-1.00 wt%.

8. The method for preparing red light-enhanced temperature-controlled nonwoven fabric according to claim 1, characterized in that, In step five, the thickness of the red luminescent layer is 10-25 μm.

9. A red light-enhanced temperature-controlled nonwoven fabric prepared by the method for preparing red light-enhanced temperature-controlled nonwoven fabric as described in any one of claims 1-8.

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