A reversible thermochromic smart advertising sign material and its preparation method

Abstract

This invention relates to the field of advertising signage technology, and discloses a reversible thermochromic smart advertising signage material and its preparation method, comprising the following components in parts by weight: PVC resin: 100 parts, microencapsulated reversible thermochromic pigment: 5-15 parts, calcium-zinc composite stabilizer: 4-6 parts, polymeric dispersant: 1-3 parts, epoxidized soybean oil: 5-8 parts, weather-resistant additive: 1-2 parts, processing aid: 1-2 parts, titanium dioxide: 2-4 parts. By microencapsulation, the sensitive thermochromic system is completely isolated from harsh external environments such as ultraviolet light, moisture, chemicals, and plasticizers in the PVC substrate, greatly improving the lightfastness, weather resistance, and service life of the thermochromic material.

Description

Technical Field

[0001] This invention relates to the field of advertising signage technology, specifically to a reversible thermochromic smart advertising signage material and its preparation method. Background Technology

[0002] Traditional advertising signage materials primarily rely on static media such as printed cloth, metal plates, and acrylic, whose function is limited to conveying fixed text or image information. This static display method is ill-suited to the increasingly dynamic and interactive demands of information dissemination, particularly in attracting public attention, enabling human-computer interaction, and providing real-time content updates. While some commercial settings have experimented with using electronic media such as LED displays to achieve dynamic advertising effects, these solutions generally face challenges such as high manufacturing costs, high energy consumption, complex installation and maintenance, and fixed display formats, significantly limiting their application flexibility and sustainability.

[0003] To overcome the limitations of traditional static signage and electronic displays, intelligent responsive materials are gaining increasing attention. Among them, thermochromic materials, with their ability to reversibly change color according to temperature variations, show potential application value. These materials, through their microstructure or chemical composition responding to thermal stimuli, can achieve dynamic visual effects without an external power source, providing a new approach for developing low-energy, flexible advertising signage. However, existing thermochromic systems, especially organic thermochromic pigments, suffer from serious deficiencies in terms of long-term environmental stability required for outdoor advertising signage. Their weather resistance and UV resistance are generally poor, easily fading and deteriorating under continuous sunlight exposure and temperature and humidity cycles; their heat resistance range is narrow, easily leading to irreversible color failure in high-temperature summer environments; insufficient compatibility and anti-migration properties between pigments and substrates easily cause coating chalking, bleeding, or decreased adhesion, greatly limiting their practical application in the field of outdoor signage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a reversible thermochromic smart advertising sign material and its preparation method, solving the problem that traditional thermochromic pigments have extremely poor lightfastness, heat resistance, and migration resistance, and quickly fail under outdoor ultraviolet radiation and temperature changes.

[0005] To achieve the above objectives, the present invention provides a reversible thermochromic intelligent advertising sign material through the following technical solution, comprising the following components in parts by weight: PVC resin: 100 parts, microencapsulated reversible thermochromic pigment: 5-15 parts, calcium-zinc composite stabilizer: 4-6 parts, polymeric dispersant: 1-3 parts, epoxidized soybean oil: 5-8 parts, weather-resistant additive: 1-2 parts, processing aid: 1-2 parts, titanium dioxide: 2-4 parts.

[0006] The above solution utilizes PVC resin as the base material, typically SG-5, which provides stable structural support for advertising signage materials, meeting the requirements of subsequent extrusion molding and other processing techniques. Microencapsulated reversible thermochromic pigments are the core functional component. A calcium-zinc composite stabilizer, usually hydrotalcite-based, inhibits the thermal degradation of PVC resin during processing, improves the material's thermal stability, and prevents material performance deterioration due to PVC molecular chain breakage at processing temperatures. Hyperdispersant-16300 is typically used as a polymeric dispersant to improve the dispersion uniformity of the microencapsulated reversible thermochromic pigments in the PVC base material, prevent pigment agglomeration, and ensure consistent color-changing effects. Epoxidized soybean oil, as a plasticizer, improves the flexibility and processing fluidity of PVC resin, lowers the glass transition temperature, making the material easier to mold during processing, and enhances the low-temperature resistance of the finished material, preventing brittleness at low temperatures. Weather-resistant additives typically use UV-326 + hindered amine 770 to improve the weather resistance of materials, resisting aging damage caused by factors such as ultraviolet rays, oxygen, and moisture in the outdoor environment, extending the service life of advertising signage materials, and ensuring that color change performance and appearance quality do not significantly deteriorate during long-term use. Processing aids typically use ACR-401, which can improve the processing performance of materials, such as increasing melt strength, promoting plasticization, and reducing melt fracture during processing, ensuring the smooth progress of extrusion molding, and improving the surface finish and molding precision of the finished material. Titanium dioxide, as a white pigment and opacifier, can improve the hiding power of materials, making the colors of advertising signs more vibrant and eye-catching. At the same time, titanium dioxide also has a certain anti-aging effect, which can work synergistically with weather-resistant additives to improve the weather resistance of materials.

[0007] Preferably, the core of the microencapsulated reversible thermochromic pigment is a ternary system comprising a leuco dye, a color developer, and a solvent, wherein the leuco dye acts as an electron donor, the color developer acts as an electron acceptor, and the capsule wall of the microencapsulated reversible thermochromic pigment is melamine-formaldehyde resin or urea-formaldehyde resin.

[0008] The above-described scheme utilizes a core-shell structure for the microencapsulated reversible thermochromic pigment. The core is a ternary system containing a leuco dye, a color developer, and a solvent. This ternary system achieves reversible thermochromic functionality through synergistic action. The leuco dye acts as an electron donor, undergoing an electron transfer reaction under specific temperature conditions, thus changing color. The color developer, acting as an electron acceptor, interacts with the leuco dye, facilitating the appearance and disappearance of color. This synergistic effect is the core mechanism for reversible color change. The solvent provides the reaction medium for the leuco dye and color developer, regulating the color-changing temperature range to ensure the pigment's color-changing temperature matches the ambient temperature range of advertising signage materials, guaranteeing a stable color-changing effect during daily temperature changes. The capsule wall material is made of melamine-formaldehyde resin or urea-formaldehyde resin. These resins possess excellent film-forming properties, sealing properties, and chemical corrosion resistance, effectively encapsulating the ternary system of the core to form a stable microcapsule structure. This prevents leakage or volatilization of the core components. Simultaneously, these capsule wall materials exhibit good processing temperature resistance, able to withstand the temperature conditions during PVC resin processing without cracking, ensuring the stability of the pigment during material processing and use. Furthermore, melamine-formaldehyde resin and urea-formaldehyde resin also possess good mechanical properties, ensuring good compatibility with PVC substrates and not affecting the overall performance of the finished material.

[0009] Preferably, the leuco dye, color developer, and solvent are present in the following weight proportions: 2.0-3.0 parts: 5.0-7.0 parts: 85-95 parts.

[0010] A method for preparing a reversible thermochromic smart advertising sign material includes the following steps: S1. Pigment activation pretreatment: Microencapsulated reversible thermochromic pigment and polymeric dispersant are added to a premixer equipped with an ultrasonic device and dispersed at a speed of 300-500 rpm for 5-10 minutes to allow the polymeric dispersant to form a dense and complete coating layer on the pigment surface, thus obtaining activated pigment. S2. Multi-step sequential temperature-controlled mixing: First, add PVC resin, calcium-zinc composite stabilizer and vacuum-degassed epoxidized soybean oil to a high-speed mixer for mixing; then cool to 70-80℃, add processing aids and some titanium dioxide and mix; finally, precisely control the material temperature at 55-65℃, add the activated pigment, weather-resistant additive premix and the remaining titanium dioxide obtained in step S1, and mix at medium-low speed for 5-8 minutes to obtain a uniform dry-mixed powder. S3, Zoned Pressure Control and Dynamic Exhaust Extrusion: The dry-mixed powder from step S2 is fed into a twin-screw extruder, which is divided into a melting zone, a mixing and homogenizing zone, and a pressure-reducing and exhausting zone along the machine body direction; wherein, the temperature of the melting zone is set to 115-125℃, the temperature of the mixing and homogenizing zone is set to 125-135℃, and the pressure-reducing and exhausting zone is provided with two vacuum exhaust ports. S4. Stress-relieving molding and gradient shaping: The molten material extruded in step S3 is extruded into a sheet through a coat hanger-type flat die head and immediately fed into a calendering roller group with a three-level temperature gradient. The roller temperatures are set sequentially to 125-135℃, 95-105℃, and 60-70℃. Subsequently, the sheet undergoes segmented gradient cooling in a 50-60℃ warm water bath, a 25-30℃ cooling air curtain, and a 15-20℃ cold water bath. The total cooling time is 2-3 minutes. Finally, the sheet is trimmed and rolled up to obtain the intelligent advertising sign material.

[0011] The above scheme employs the following steps: The first step is pigment activation pretreatment. The core purpose of this step is to improve the dispersion performance of microencapsulated reversible thermochromic pigments and prevent pigment agglomeration during subsequent processing. High-frequency vibration through ultrasonic dispersion breaks down the initial agglomeration of the pigments and promotes the uniform adsorption of polymeric dispersants onto the pigment surface. The resulting coating layer reduces the interaction forces between pigment particles, improving their compatibility and dispersion uniformity in the PVC substrate, thus laying the foundation for a uniform color-changing effect. The second step is multi-step sequential temperature-controlled mixing. This is because the heat resistance of each component differs, especially since microencapsulated reversible thermochromic pigments are highly sensitive to temperature. High temperatures can easily degrade their color-changing performance. Therefore, the heat-resistant PVC resin, stabilizer, and epoxidized soybean oil are mixed first, then other components are added gradually at a lower temperature. Finally, the activated pigment is added at a lower temperature. This effectively protects the color-changing performance of the pigments while ensuring thorough and uniform mixing of all components, avoiding excessively high or low concentrations of certain components that could affect material performance. The third step is zoned pressure control and dynamic exhaust extrusion. The zoned temperature control design is determined based on the melting characteristics of PVC resin and the mixing requirements of each component. The temperature of the melting zone ensures that the PVC resin can be fully melted, and the temperature of the mixing and homogenization zone is slightly higher than that of the melting zone, which can promote further uniform mixing of the molten material and each component and improve the uniformity of the material. The pressure reduction and exhaust zone with two vacuum exhaust ports can effectively remove moisture, volatiles and low molecular weight compounds generated during processing from the material, avoiding the formation of bubbles or defects in the finished material and ensuring the density and mechanical properties of the material. The fourth step is stress-relieving molding and gradient shaping. The coat hanger-type flat die head ensures uniform extrusion of molten material, guaranteeing the uniformity of sheet thickness. The three-stage temperature gradient calendering roller group can gradually cool and calender the extruded sheet, which not only improves the surface smoothness of the sheet but also effectively releases the internal stress generated by the material during the melt extrusion process. The segmented gradient cooling design is to avoid stress concentration, warping, and other problems caused by excessive internal and external temperature differences due to rapid cooling of the sheet. By gradually reducing the temperature, the sheet is slowly cooled and shaped, improving the dimensional stability and mechanical properties of the finished material and ensuring that the advertising signage material will not deform due to temperature changes during subsequent use.

[0012] Preferably, the microencapsulated reversible thermochromic pigment is prepared by the following steps: P1. Oil phase pre-dispersion and stabilization: The contents of the leuco dye, bisphenol A color developer and long-chain alkane solvent are heated to 60-70℃ to completely melt and mix evenly. Then, 0.5%-1.5% of hydrophobic fumed silica is added according to the total weight of the core, and stirred to form a stable and uniform oil phase dispersion. P2, In-situ Prepolymerization and Interface Deposition: The oil-phase dispersion obtained in step P1 is added to an aqueous solution containing emulsifier and pH adjuster, and emulsified in a high-speed shear emulsifier to form a stable O / W type emulsion with a particle size of 1-3 μm; a prepolymerization solution of melamine and formaldehyde is slowly added dropwise, and the pH value of the reaction system is controlled between 4.0 and 4.5, so that the resin formed by condensation is deposited at the interface of the oil-phase droplets; P3. Gradient curing and surface modification: After the interface deposition is completed, the system temperature is slowly raised to 75-80℃ and the reaction is continued at this temperature to complete the final curing of the capsule wall; then the reaction system is cooled to below 40℃, and 2%-5% of the dry weight of the microcapsule is added, and the surface of the microcapsule is grafted and modified by gentle stirring. P4. Washing and Low-Temperature Drying: After filtering and washing the reaction product with deionized water until neutral, place it in a vacuum drying oven and dry it to constant weight at 40-45℃ and a vacuum degree of not less than -0.095MPa to obtain a microencapsulated reversible thermochromic pigment with a modified surface and good flowability.

[0013] The above scheme employs the following steps: First, oil phase pre-dispersion and stabilization. The addition of hydrophobic fumed silica utilizes its hydrophobicity and dispersion stability to adsorb onto the surface of oil droplets, preventing aggregation during subsequent emulsification and improving the stability of the oil dispersion. Second, in-situ prepolymerization and interfacial deposition. High-speed shear emulsification breaks the oil dispersion into uniformly sized microdroplets. The particle size is controlled at 1-3 μm because microcapsules within this range can disperse well in the PVC substrate while ensuring good color-changing effects. Third, gradient curing and surface modification. Gradient temperature curing allows for full cross-linking and curing of the capsule wall resin, improving the density and mechanical strength of the capsule wall and preventing leakage of the core components. After cooling to below 40°C, a silane coupling agent is added for surface modification to improve the compatibility of the microcapsule surface, enabling better bonding between the microcapsules and the PVC substrate and reducing interfacial defects during subsequent processing. The fourth step is washing and low-temperature drying. The purpose of filtration and washing is to remove impurities such as residual emulsifiers, pH adjusters, and unreacted monomers from the reaction process, so as to avoid these impurities affecting the color-changing properties of the microcapsules and their compatibility with the PVC substrate. Vacuum low-temperature drying can prevent the microcapsule core components from volatilizing or deteriorating in color-changing properties due to high temperatures, while ensuring the drying effect of the microcapsules, so that they have good flowability and are easy to mix with other components in subsequent processing.

[0014] Preferably, in step S1, the ultrasonic dispersion process is carried out under inert gas protection, and the polymeric dispersant is added in two parts. The first part is 60-70% of the total amount added and premixed with the pigment. The second part is added and then the ultrasonic process is started to achieve complete dispersion.

[0015] Through the above scheme: In step S1, the ultrasonic dispersion process is carried out under the protection of an inert gas. The inert gas can be a chemically stable gas such as nitrogen or argon. Its function is to isolate the pigment from air, preventing the microencapsulated reversible thermochromic pigment from reacting with oxygen in the air during ultrasonic dispersion, which would lead to pigment oxidation and deterioration, thus affecting its reversible thermochromic properties. In particular, it avoids a decrease in the pigment's color-changing sensitivity and reversibility, ensuring the functional stability of the pigment. Simultaneously, the polymeric dispersant is added in two stages. The first stage involves adding 60-70% of the total amount and pre-mixing it with the pigment. The second stage involves adding the remaining portion before ultrasonic dispersion is initiated. By adding the dispersant in two stages, the uniformity of its adsorption on the pigment surface can be improved. The first stage involves adding most of the dispersant for premixing, which allows the dispersant to be initially adsorbed onto the pigment particle surface, forming a preliminary coating layer. This prevents excessive aggregation or uneven distribution of the dispersant during subsequent ultrasonic dispersion. The second stage involves adding the remaining dispersant and then starting the ultrasonic process. The high-frequency vibration of the ultrasound promotes further uniform adsorption and diffusion of the dispersant onto the pigment surface, forming a dense and complete coating layer. This allows the dispersant to play a better role, prevents pigment agglomeration during subsequent processing, and ensures the uniformity of the material's color-changing effect.

[0016] Preferably, in step S2, the weather-resistant additive premix is ​​prepared by ball milling and blending ultraviolet absorber UV-326, light stabilizer hindered amine 770, and nano-sized titanium dioxide in a weight ratio of 1:1:0.5.

[0017] The above scheme involves ball milling and blending UV absorber UV-326, light stabilizer hindered amine 770, and nano-sized titanium dioxide in a weight ratio of 1:1:0.5. UV absorber UV-326 selectively absorbs harmful ultraviolet rays, converting the energy into heat and dissipating it, thus preventing UV damage to the PVC molecular chains and the structure of microencapsulated reversible thermochromic pigments. Hindered amine 770 captures free radicals generated during material aging, inhibiting free radical chain reactions and delaying material degradation. Nano-sized titanium dioxide has a large specific surface area and good light scattering properties, reflecting and scattering ultraviolet rays while also enhancing the material's mechanical properties. Working synergistically with the UV absorber and light stabilizer, it further improves the material's weather resistance. During the ball milling process, the impact and grinding action of the balls can fully mix the three components evenly, while breaking up any agglomerated particles. This disperses the components into tiny particles, improving the uniformity of weather-resistant additive premix in the PVC substrate, avoiding excessively high or low concentrations of weather-resistant additives in certain areas, and ensuring that the material as a whole has good weather resistance.

[0018] Preferably, in step S3, the second vacuum exhaust port of the depressurization exhaust zone is connected to a condenser trap to collect and separate the volatiles extracted during the extrusion process, preventing them from flowing back into the contaminated material.

[0019] Through the above scheme: In step S3, the second vacuum exhaust port of the depressurization exhaust zone is connected to a condenser to collect and separate the volatiles extracted during extrusion, preventing them from flowing back and contaminating the material. During the twin-screw extruder processing, moisture, a small amount of volatiles from epoxidized soybean oil, and low-molecular-weight volatiles generated during PVC resin processing are released in the high-temperature molten state. The first vacuum exhaust port is mainly used to discharge most of the volatiles, while the design of the second vacuum exhaust port connected to the condenser can further extract the residual volatiles. At the same time, through the cooling effect of the condenser, the volatiles are condensed into liquid or solid states and collected, preventing the volatiles from flowing back into the extruder under the action of the vacuum system and contaminating the molten material. If the volatiles flow back, it will cause impurities to be mixed into the material, affecting the uniformity of the material, and thus causing defects such as bubbles and pinholes in the finished material. It may also damage the structure of the microencapsulated reversible thermochromic pigment, affecting the color-changing performance of the material.

[0020] Preferably, in step S4, the surface of the first-stage roller of the calendering roller group is plated with a high-gloss hard chrome layer, and the distance between it and the die lip exit is adjustable to precisely control the initial forming thickness and surface gloss of the sheet.

[0021] Through the above scheme: In step S4, the surface of the first-stage roller of the calendering roller group is plated with a high-gloss hard chrome layer. The hard chrome layer has good hardness, wear resistance, and smoothness, which can improve the wear resistance of the roller surface and extend the service life of the roller. At the same time, the high-gloss surface can give the extruded sheet a smooth and flat surface, improving the appearance and texture of the advertising sign material. In addition, the hard chrome layer also has good corrosion resistance, which can resist the erosion of trace corrosive substances that may be generated by the material during processing, ensuring the stability of the roller surface quality. Meanwhile, the distance between the first-stage roller and the die lip exit is adjustable. The distance adjustment function can precisely control the initial forming thickness of the sheet according to the thickness requirements of the advertising sign material, adapting to the usage needs of advertising signs in different scenarios.

[0022] Preferably, in the warm water bath cooling stage of step S4, the cooling water is a deionized aqueous solution containing 0.1-0.3 wt% nonionic surfactant.

[0023] According to the above scheme: In the warm water bath cooling stage of step S4, the cooling water is a deionized aqueous solution containing 0.1-0.3 wt% nonionic surfactant. Deionized water is chosen as the base for the cooling water because it does not contain metal ions such as calcium and magnesium, or other impurities. This prevents these impurities from adhering to the sheet surface, forming scale or stains, which would affect the surface smoothness and appearance quality of the sheet. It also prevents impurities from adversely affecting the material's properties. The addition of 0.1-0.3 wt% nonionic surfactant reduces the surface tension of the cooling water, improves its wetting properties on the sheet surface, and ensures that the cooling water evenly covers the sheet surface, preventing uneven cooling and thus reducing internal stress and surface defects such as watermarks and wrinkles caused by uneven cooling. Nonionic surfactants have good compatibility and stability, will not chemically react with the sheet, and will not leave harmful residues on the sheet surface, meeting the safety requirements for advertising signage materials.

[0024] This invention provides a reversible thermochromic smart advertising signage material and its preparation method. It has the following beneficial effects: 1. This invention completely isolates the sensitive color-changing system from harsh external environments such as ultraviolet rays, water vapor, chemicals, and plasticizers in PVC substrates through microencapsulation, which greatly improves the light resistance, weather resistance and service life of the color-changing material.

[0025] 2. The microcapsules of this invention ensure the purity and independence of the color-changing system, making its color-changing response more sensitive, the color more vivid, the contrast higher, and less prone to migration and precipitation, thus maintaining long-term stable color-changing performance.

[0026] 3. This invention endows traditional static advertisements with dynamic interactive functions, enabling them to respond to changes in ambient temperature, such as hand touch, sunlight, and day-night temperature differences, greatly enhancing the interest and visual impact of the advertisements.

[0027] 4. This invention perfectly solves the industry problem of thermochromic materials being unable to withstand high-temperature processing through a unique low-temperature premixing-low-temperature blending-low-temperature low-shear molding process route, making it compatible with PVC standard processing technology. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the preparation process of the intelligent advertising signage material of the present invention; Figure 2 This is a schematic diagram of the preparation process of the microencapsulated reversible thermochromic pigment of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see the appendix Figure 1 - Appendix Figure 2 The present invention provides the following embodiments and comparative examples: I. Preparation Example Preparation of microencapsulated reversible thermochromic pigments and raw material ratios: Leuco dye: 2.5 parts; Bisphenol A-type color developer: 6.0 parts; Long-chain alkane solvent: 91.5 parts; Hydrophobic fumed silica as core modification: 1.0% of the total core weight; Emulsifier: 0.8% of the total aqueous solution weight; pH adjuster: Citric acid-sodium citrate buffer solution; Melamine-formaldehyde precondensation solution as the capsule wall; Silane coupling agent KH550: 3.5% of the dry weight of the microcapsules.

[0031] The preparation steps are as follows: P1. Oil Phase Predispersion and Stabilization: A leuco dye, bisphenol A-type color developer, and long-chain alkane solvent are mixed, heated to 65°C until completely melted and stirred uniformly. Hydrophobic fumed silica (1.0% of the total weight of the core) is added, and the mixture is stirred at 300 rpm for 15 minutes to form a stable and homogeneous oil phase dispersion. P2. In-situ Prepolymerization and Interface Deposition: The oil phase dispersion is added to an aqueous solution containing an emulsifier and a pH adjuster. The mixture is emulsified at 8000 rpm for 10 minutes using a high-speed shear emulsifier to form a stable O / W type emulsion with a particle size of 2 μm. A prepolymerization solution of melamine and formaldehyde is slowly added dropwise. The pH of the reaction system is stabilized at 4.2 using a pH adjuster, allowing the condensed resin to settle at the oil phase droplet interface. Interface deposition; P3, gradient curing and surface modification: After interface deposition, the system temperature was slowly increased to 78℃ at 2℃ / min, and the reaction was kept at a constant temperature for 2h to complete the capsule wall curing; cooled to 38℃, silane coupling agent KH550 accounting for 3.5% of the dry weight of microcapsules was added, and the mixture was gently stirred at 200rpm for 30min to complete the grafting modification of the microcapsule surface; P4, washing and low-temperature drying: After the reaction product was filtered, it was washed with deionized water until the pH of the filtrate was 7, and placed in a vacuum drying oven and dried to constant weight at 42℃ and a vacuum degree of -0.096MPa to obtain a surface-modified, free-flowing microencapsulated reversible thermochromic pigment, which is blue at room temperature and turns white when heated to >33℃, showing excellent reversibility.

[0032] II. Examples 1-3 were all prepared according to the following steps: S1. Pigment activation pretreatment: Microencapsulated reversible thermochromic pigment and polymeric dispersant are added to a premixer equipped with an ultrasonic device and dispersed at a speed of 300-500 rpm for 5-10 minutes to allow the polymeric dispersant to form a dense and complete coating layer on the pigment surface, thus obtaining activated pigment. S2. Multi-step sequential temperature-controlled mixing: First, add PVC resin, calcium-zinc composite stabilizer and vacuum-degassed epoxidized soybean oil to a high-speed mixer for mixing; then cool to 70-80℃, add processing aids and some titanium dioxide and mix; finally, precisely control the material temperature at 55-65℃, add the activated pigment, weather-resistant additive premix and the remaining titanium dioxide obtained in step S1, and mix at medium-low speed for 5-8 minutes to obtain a uniform dry-mixed powder. S3, Zoned Pressure Control and Dynamic Exhaust Extrusion: The dry-mixed powder from step S2 is fed into a twin-screw extruder. The extruder is divided into a melting zone, a mixing and homogenizing zone, and a pressure-reducing and exhausting zone along the machine body. The temperature of the melting zone is set to 115-125℃, the temperature of the mixing and homogenizing zone is set to 125-135℃, and the pressure-reducing and exhausting zone is equipped with two vacuum exhaust ports. S4. Stress-relieving molding and gradient shaping: The molten material extruded in step S3 is extruded into a sheet through a coat hanger-type flat die head and immediately fed into a calendering roller group with a three-level temperature gradient. The roller temperatures are set sequentially to 125-135℃, 95-105℃, and 60-70℃. Subsequently, the sheet undergoes segmented gradient cooling in a 50-60℃ warm water bath, a 25-30℃ cooling air curtain, and a 15-20℃ cold water bath. The total cooling time is 2-3 minutes. Finally, after edge trimming and winding, the intelligent advertising sign material is obtained.

[0033] In step S1, the ultrasonic dispersion process is carried out under inert gas protection, and the polymeric dispersant is added in two parts. The first part is 60-70% of the total amount added and premixed with the pigment. The second part is added and then the ultrasonic process is started to achieve complete dispersion.

[0034] In step S2, the weather-resistant additive premix is ​​prepared by ball milling and blending ultraviolet absorber UV-326, light stabilizer hindered amine 770 and nano-sized titanium dioxide in a weight ratio of 1:1:0.5.

[0035] In step S3, the second vacuum exhaust port of the depressurization exhaust zone is connected to a condenser trap to collect and separate the volatiles extracted during the extrusion process, preventing them from flowing back into the contaminated material.

[0036] In step S4, the surface of the first-stage roller of the calendering roller group is plated with a high-gloss hard chrome layer, and the distance between it and the die lip exit is adjustable to precisely control the initial forming thickness and surface gloss of the sheet.

[0037] In the warm water bath cooling stage of step S4, the cooling water is a deionized aqueous solution containing 0.1-0.3 wt% nonionic surfactant.

[0038] Ultraviolet absorber UV-326: light stabilizer hindered amine 770: nano-sized titanium dioxide = 1:1:0.5 ball-milled and blended in weight ratio; All preparation processes in all embodiments follow the complete steps S1 to S4, with the following unified process parameters: S1 ultrasonic dispersion speed 400 rpm, time 8 min; S2 temperature control sequentially high speed mixing → 75℃ → 60℃, medium and low speed mixing 6 min; S3 twin-screw extruder melting zone 120℃, mixing and homogenization zone 130℃, dual vacuum exhaust ports; S4 three-stage calender roller temperature 130℃ → 100℃ → 65℃, gradient cooling 55℃ warm water bath → 28℃ cold air curtain → 18℃ cold water bath, total cooling time 2.5 min. Example

[0039] PVC resin: 100 parts; microencapsulated reversible thermochromic pigment: 5 parts; calcium-zinc composite stabilizer: 4 parts; polymeric dispersant: 1 part; epoxidized soybean oil: 5 parts; weather-resistant agent: 1 part; processing aid: 1 part; titanium dioxide: 2 parts. Example

[0040] PVC resin: 100 parts; microencapsulated reversible thermochromic pigment: 10 parts; calcium-zinc composite stabilizer: 5 parts; polymeric dispersant: 2 parts; epoxidized soybean oil: 6.5 parts; weather-resistant agent: 1.5 parts; processing aid: 1.5 parts; titanium dioxide: 3 parts. Example

[0041] PVC resin: 100 parts; microencapsulated reversible thermochromic pigment: 15 parts; calcium-zinc composite stabilizer: 6 parts; polymeric dispersant: 3 parts; epoxidized soybean oil: 8 parts; weather-resistant agent: 2 parts; processing aid: 2 parts; titanium dioxide: 4 parts.

[0042] III. Comparative Examples 1-6: Reversible thermochromic smart advertising signage materials, with only component adjustments and no process changes. The preparation processes for all comparative examples are completely consistent with those for the examples, with only the types and proportions of raw material components adjusted.

[0043] Comparative Example 1: No microcapsule coating, just an equal amount of unmicrocapsulated ternary thermochromic pigment was added directly, and the remaining components were completely the same as in Example 2; Comparative Example 2: The amount of microencapsulated reversible thermochromic pigment added was insufficient, only 3 parts were added, and the remaining components were completely consistent with those in Example 2; Comparative Example 3: No polymeric dispersant; all other components are completely identical to those in Example 2. Comparative Example 4: No weather-resistant additives were added; all other components were identical to those in Example 2. Comparative Example 5: The microcapsule wall was replaced with ordinary acrylic resin (not melamine-formaldehyde resin), and the remaining components were completely consistent with those in Example 2; Comparative Example 6: The calcium-zinc composite stabilizer was replaced with a traditional lead salt stabilizer, and the remaining components were completely identical to those in Example 2.

[0044] IV. Performance Testing Experiment The test items and methods are as follows: This test was conducted on all finished sheets of intelligent advertising signage materials from Examples 1-3 and Comparative Examples 1-6. The test items fully matched the core beneficial effects of this invention and the key performance defined in the claims. The test methods were industry-standard. Color-changing performance: Observe the initial color at room temperature, touch it with your hand / heat it in a constant temperature oven at 35℃ to observe the color-changing effect, cool it to 25℃ to observe the recovery effect, and record the response sensitivity, reversibility, color brightness, and contrast. Judgment criteria: The following are acceptable: sensitive response, color change ≤2s, recovery ≤3s, good reversibility, no decay after repeated color changes ≥1000 times, bright blue / pure white, and high contrast.

[0045] Weather resistance: The QUV-A accelerated aging test was conducted at a wavelength of 340nm, an irradiance of 0.71W / (m²・nm), and a temperature of 60℃. The retention rate of color change performance was tested after 50h, 100h, and 200h respectively. The retention rate of color change performance = reversibility of color change after aging / reversibility of initial color change × 100%.

[0046] Migration resistance: According to industry standards, the sample film is tightly bonded to a white ABS board and placed in a 60℃ oven at a pressure of 0.05MPa for 72 hours. After removal, observe whether there are traces of blue pigment migration on the surface of the ABS board. Judgment standard: No color migration is acceptable.

[0047] Processing compatibility: Record whether pigment agglomeration, peeling / pitting on the sheet surface, or discoloration occurs during the extrusion molding process. Judgment criteria: The sheet surface is smooth, without agglomeration, and without discoloration is considered qualified. The embodiments 1-3 of this invention stand in stark contrast to the comparative examples, and the core conclusions are as follows: Microencapsulated thermochromic pigments completely isolate the sensitive ternary color-changing system from external environments such as ultraviolet light, moisture, and plasticizers in PVC substrates. The color-changing performance retention rate of the example is still ≥80% after 200h of ultraviolet aging; while the comparative example fails after 150h, and the performance of the comparative example 4 drops sharply after aging, proving that the combination of microencapsulation and weather-resistant additives is the core key to improving durability.

[0048] The formulation of this invention, combined with a low-temperature premixing-low-temperature blending-low-temperature low-shear molding process, is suitable for PVC standard processing. All embodiments showed no pigment agglomeration or discoloration failure, solving the industry problem of thermochromic materials being unable to withstand high-temperature processing. Comparative Example 3 showed pigment agglomeration due to the absence of a polymeric dispersant, further demonstrating the necessity of the dispersant.

[0049] The microcapsule encapsulation ensures the purity and independence of the color-changing system. The color-changing response of the embodiment is more sensitive, the color is more vivid, the contrast is higher, and there is no migration or precipitation. The unencapsulated pigment in Comparative Example 1 is prone to react with PVC substrate, which not only has dull color but also serious migration and a significant decrease in reversibility.

[0050] The finished material in the embodiment can accurately respond to the ambient temperature to achieve a reversible color change from blue to white, with a significant dynamic interactive effect; in contrast, due to insufficient pigment addition, the color change effect in Comparative Example 2 is dull, and the visual impact is greatly reduced.

[0051] 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 reversible thermochromic smart advertising signage material, characterized in that, The product contains the following components in parts by weight: PVC resin: 100 parts, microencapsulated reversible thermochromic pigment: 5-15 parts, calcium-zinc composite stabilizer: 4-6 parts, polymeric dispersant: 1-3 parts, epoxidized soybean oil: 5-8 parts, weather-resistant additive: 1-2 parts, processing aid: 1-2 parts, titanium dioxide: 2-4 parts.

2. The reversible thermochromic smart advertising signage material according to claim 1, wherein, The core of the microencapsulated reversible thermochromic pigment is a ternary system containing a leuco dye, a color developer, and a solvent. The leuco dye acts as an electron donor, the color developer acts as an electron acceptor, and the capsule wall of the microencapsulated reversible thermochromic pigment is melamine-formaldehyde resin or urea-formaldehyde resin.

3. The reversible thermochromic smart advertising signage material according to claim 2, characterized in that, The leuco dye, color developer, and solvent are present in the following weight proportions: 2.0-3.0 parts: 5.0-7.0 parts: 85-95 parts.

4. A method for preparing a reversible thermochromic smart advertising sign material, characterized in that, The method for using a reversible thermochromic smart advertising signage material according to any one of claims 1-3 includes the following steps: S1. Pigment activation pretreatment: Microencapsulated reversible thermochromic pigment and polymeric dispersant are added to a premixer equipped with an ultrasonic device and dispersed for 5-10 minutes to allow the polymeric dispersant to form a dense and complete coating layer on the pigment surface, thus obtaining activated pigment. S2. Multi-step sequential temperature-controlled mixing: First, add PVC resin, calcium-zinc composite stabilizer and vacuum-degassed epoxidized soybean oil to a high-speed mixer for mixing; then cool to 70-80℃, add processing aids and some titanium dioxide and mix; finally, precisely control the material temperature at 55-65℃, add the activated pigment, weather-resistant additive premix and the remaining titanium dioxide obtained in step S1, and mix at medium-low speed for 5-8 minutes to obtain a uniform dry-mixed powder. S3, Zoned Pressure Control and Dynamic Exhaust Extrusion: The dry-mixed powder from step S2 is fed into a twin-screw extruder, which is divided into a melting zone, a mixing and homogenizing zone, and a pressure-reducing and exhausting zone along the machine body direction; wherein, the temperature of the melting zone is set to 115-125℃, the temperature of the mixing and homogenizing zone is set to 125-135℃, and the pressure-reducing and exhausting zone is provided with two vacuum exhaust ports. S4. Stress-relieving molding and gradient shaping: The molten material extruded in step S3 is extruded into a sheet through a coat hanger-type flat die head and immediately fed into a calendering roller group with a three-level temperature gradient. The roller temperatures are set sequentially to 125-135℃, 95-105℃, and 60-70℃. Subsequently, the sheet undergoes segmented gradient cooling in a 50-60℃ warm water bath, a 25-30℃ cooling air curtain, and a 15-20℃ cold water bath. Finally, after edge trimming and winding, the intelligent advertising sign material is obtained.

5. The method for preparing a reversible thermochromic smart advertising sign material according to claim 4, characterized in that, The microencapsulated reversible thermochromic pigment is prepared by the following steps: P1. Oil phase pre-dispersion and stabilization: The contents of the leuco dye, bisphenol A color developer and long-chain alkane solvent are heated to 60-70℃ to completely melt and mix evenly. Then, 0.5%-1.5% of hydrophobic fumed silica is added according to the total weight of the core, and stirred to form a stable and uniform oil phase dispersion. P2, In-situ Prepolymerization and Interface Deposition: The oil-phase dispersion obtained in step P1 is added to an aqueous solution containing emulsifier and pH adjuster, and emulsified in a high-speed shear emulsifier to form a stable O / W type emulsion with a particle size of 1-3 μm; a prepolymerization solution of melamine and formaldehyde is slowly added dropwise, and the pH value of the reaction system is controlled between 4.0 and 4.5, so that the resin formed by condensation is deposited at the interface of the oil-phase droplets; P3. Gradient curing and surface modification: After the interface deposition is completed, the system temperature is slowly raised to 75-80℃ and the reaction is continued at this temperature to complete the final curing of the capsule wall; then the reaction system is cooled to below 40℃, and 2%-5% of the dry weight of the microcapsule is added, and the surface of the microcapsule is grafted and modified by gentle stirring. P4. Washing and low-temperature drying: After filtering and washing with deionized water until neutral, the reaction product is placed in a vacuum drying oven and dried to constant weight to obtain a microencapsulated reversible thermochromic pigment with a modified surface and good flowability.

6. The method for preparing a reversible thermochromic smart advertising sign material according to claim 4, characterized in that, In step S1, the ultrasonic dispersion process is carried out under inert gas protection, and the polymeric dispersant is added in two parts. The first part is 60-70% of the total amount added and premixed with the pigment. The second part is added and then the ultrasonic process is turned on to achieve complete dispersion.

7. The method for preparing a reversible thermochromic smart advertising sign material according to claim 4, characterized in that, In step S2, the weather-resistant additive premix is ​​prepared by ball milling and blending ultraviolet absorber UV-326, light stabilizer hindered amine 770 and nano-sized titanium dioxide in a weight ratio of 1:1:0.

5.

8. The method for preparing a reversible thermochromic smart advertising sign material according to claim 4, characterized in that, In step S3, the second vacuum exhaust port of the depressurization exhaust zone is connected to a condenser trap to collect and separate the volatiles extracted during the extrusion process, preventing them from flowing back into the contaminated material.

9. The method for preparing a reversible thermochromic smart advertising sign material according to claim 4, characterized in that, In step S4, the surface of the first-stage roller of the calendering roller group is plated with a high-gloss hard chrome layer, and the distance between it and the die lip exit is adjustable to precisely control the initial forming thickness and surface gloss of the sheet.

10. The method for preparing a reversible thermochromic smart advertising sign material according to claim 4, characterized in that, In the warm water bath cooling stage of step S4, the cooling water is a deionized aqueous solution containing 0.1-0.3 wt% nonionic surfactant.

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