Composite phase change microcapsule as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of glove thermal insulation materials, and particularly relates to a composite phase change microcapsule and a preparation method and application thereof.The composite phase change microcapsule is prepared from, by mass, 50%-60% of phase change material microcapsules, 8%-12% of photo-thermal conversion nanometer or micron particles and the balance auxiliary additives, the nano or micron particles are chemically bonded with the surface of the phase-change material microcapsule through in-situ polymerization reaction of a shell material of the phase-change material microcapsule, and the outer layer of the shell material is coated with the nano or micron particles through directional deposition in the polymerization process of the shell material to form the modified phase-change microcapsule. The invention provides the composite microcapsule which can absorb light energy and convert the light energy into heat energy, and can store and release heat through a phase change process, so that protective articles such as gloves and the like can be rapidly heated under an illumination condition, and after the illumination is weakened or disappears, the temperature is maintained through the heat storage and release functions of the phase change material; therefore, a more durable and stable warm-keeping effect is provided.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation materials for gloves, and in particular relates to a composite phase-change microcapsule and a preparation method and application thereof. Background Art

[0002] In cold environments, keeping hands warm is crucial for maintaining normal physiological functions and operational flexibility. Traditional gloves primarily reduce heat loss by increasing material thickness or using materials with better thermal insulation. However, this approach often results in insufficient glove flexibility, restricting hand movement while wearing, reducing comfort and flexibility. Furthermore, traditional thermal insulation gloves lack active heating and can only passively reduce heat transfer, failing to provide continuous warmth in extremely cold environments.

[0003] To overcome the limitations of traditional thermally insulating protective gloves, phase change materials (PCMs) are currently being researched and are attracting widespread attention due to their ability to absorb and release large amounts of latent heat within a specific temperature range. PCMs store and release heat through phase transitions, offering the potential for active temperature regulation in protective equipment such as gloves. However, the direct application of PCMs to gloves presents numerous challenges, including their stability, thermal conductivity, and bonding strength with the glove substrate.

[0004] Prior art research addresses the issues with the application of phase change materials in gloves, such as patent application CN105297473A, "A Temperature-Regulating Glove Leather and Its Preparation Method," which achieves automatic temperature regulation in gloves by distributing phase change material microcapsules within a double-sided napped base fabric. However, this method primarily relies on the passive temperature regulation of the phase change material and lacks active heating capabilities. Furthermore, the flexibility and comfort of the gloves still need to be improved. Another example is CN110387750A - A method for preparing a composite phase-change coated fabric for cold-proof gloves. While this method improves the cold-proof performance of the gloves by adding polyacrylate-coated paraffin phase-change microcapsules, it also lacks active heating, and the temperature adjustment range and flexibility of the gloves are still limited. Another example is CN117845625A - a one-step preparation method for temperature-regulating fabrics and its application. It realizes the temperature-regulating function of the fabric by preparing self-adhesive phase change microcapsules and arranging them on the fabric. Although this method has made progress in the preparation of temperature-regulating fabrics, it is mainly used in textiles such as clothing and bed sheets. The application effect on specific protective products such as gloves has not yet been clarified, and it also does not involve active heating function.

[0005] In summary, existing methods using phase-change microcapsules to achieve thermoregulation primarily focus on temperature regulation, lacking photothermal conversion capabilities. They are unable to actively absorb light energy from the external environment and convert it into heat energy, resulting in limitations in active heating and continuous heating. This limits their application scope and performance, making them difficult to meet the demands of use in a variety of complex environments. Therefore, a new technical solution is needed to address these technical issues. Summary of the Invention

[0006] The purpose of the present invention is to provide a composite phase change microcapsule and its preparation method and application, so as to solve the problems proposed in the above background technology that the current method of using phase change microcapsules to achieve temperature regulation function mainly focuses on temperature regulation, lacks photothermal conversion function, cannot actively absorb light energy from the external environment and convert it into heat energy, and has limitations in active heating and continuous heat supply, thereby limiting its application scope and performance, and making it difficult to meet the use requirements in various complex environments.

[0007] To achieve the above object, the present invention provides the following technical solution: a composite phase change microcapsule, wherein the composite phase change microcapsule comprises 50-60% phase change material microcapsules, 8-12% photothermal conversion nano- or micron-sized particles, and the remainder is auxiliary additives according to the mass percentage of the components, wherein the nano- or micron-sized particles are chemically bonded to the surface of the phase change material microcapsule through the in-situ polymerization reaction of the shell material of the phase change material microcapsule and are coated on the outer layer of the shell material through directional deposition during the polymerization process of the shell material to form a modified phase change microcapsule, wherein the phase change material The core material of the microcapsule is made of a paraffin-based phase change material, the phase change melting point of the paraffin-based phase change material is 17-18°C or 36-37°C, the shell material of the phase change material microcapsule is selected from one of chitosan, polymethyl methacrylate, gelatin-gum arabic, polyurethane PU, ethyl cellulose, and amino resin, the nano- or micron-sized particles are selected from one of nano-silicon carbide, copper sulfide, nano-carbon tubes, graphene, and metallic silver nanoparticles, and the auxiliary additives are selected from one of a dispersant, a thickener, and a stabilizer, or a mixture of several of them.

[0008] First, the above-mentioned nano- or micron-sized particles are chemically bonded to the surface of the phase change material microcapsule through an in-situ polymerization reaction of the shell material of the phase change material microcapsule, and then coated on the outer layer of the shell material through directional deposition during the polymerization process of the shell material to form a modified phase change microcapsule. The preparation steps of the modified phase change microcapsule powder are as follows: S1. Preparation of emulsion: Nano- or micron-sized particles are mixed with anhydrous ethanol and ultrasonically dispersed into a nanoparticle dispersion, which is then mixed with a paraffin-based phase change material, a 9% protective colloid solution, and deionized water. The mixture is stirred and emulsified in a water bath at 30-50°C at a stirring speed of 10,000-14,000 rpm using a homogenizer for 8-12 minutes to obtain an O / W emulsion, wherein the protective colloid solution is a polyvinyl alcohol aqueous solution. S2. Preparation of phase change microcapsules: The O / W emulsion obtained in S1 and the MF prepolymer solution are stirred and mixed at 65-95°C at a stirring speed of 1000-1400 rpm for 2-4 hours. During the stirring process, the pH value is continuously lowered to 4.5 by adding hydrochloric acid dropwise, and then the pH value is adjusted to neutral by adding 10% sodium hydroxide solution. After precipitation, filtration, washing and drying, modified phase change microcapsule powder, i.e., composite phase change microcapsules, is obtained.

[0009] Then, 30-40% of the modified phase change microcapsule powder prepared above is added into 60-70% of waterborne polyurethane or silica gel polymer emulsion to prepare a coating mixed glue.

[0010] Finally, the coating mixture prepared above is applied to the surface of the glove liner through a dispensing or continuous coating process, with an application amount of 20-30% of the mass of the glove liner. After curing at 50-80°C for 1-3 hours, a photothermal insulation layer is formed on the surface of the glove.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention introduces photothermal conversion nano- or micron-sized particles on the surface of phase change material microcapsules, which not only provides photothermal conversion function, but also significantly improves the thermal conductivity of the microcapsules, allowing heat to be transferred to the interior of the phase change material more quickly, accelerating the phase change heat storage and heat release process and suppressing supercooling, effectively improving the thermal response speed of protective equipment such as gloves, allowing users to feel warm more quickly in cold environments, and also improving the adaptability to temperature changes. The photothermal conversion nano- or micron-sized particles are integrated into the shell material of the phase change material microcapsule by chemical bonding and directional deposition, forming a composite microcapsule that can absorb light energy and convert it into heat energy, and can store and release heat through the phase change process, effectively improving the energy utilization efficiency of the material, so that protective equipment such as gloves can quickly heat up under light conditions, and after the light weakens or disappears, the temperature is maintained by the heat storage and heat release function of the phase change material, thereby providing a more lasting and stable warming effect. On this basis, the chemical bonding method is more durable than traditional methods such as physical adsorption, and can resist wear and tear during long-term use. The invention prevents the gloves from shedding, thereby extending the service life of protective equipment such as gloves, reducing the frequency of replacement due to material shedding or performance degradation, and lowering the cost of use. By precisely controlling the proportions of the various components, the material achieves an optimal balance between heating efficiency, comfort, and durability, meeting the user's usage needs in different environments. The two functions of photothermal conversion and phase change energy storage are integrated into the same microcapsule. As the insulation filling material of the gloves, it not only meets the warmth requirement, but also enables the gloves to work effectively under different energy inputs (human body heat, light energy), effectively broadening the scope of application of the gloves and enabling them to perform excellently in a variety of complex environments. The composite material can also be applied to other fields requiring temperature regulation, such as outdoor clothing, medical hot compress products, etc., effectively improving the market competitiveness of the product and providing users with more diverse choices. In addition, the phase change material and photothermal conversion nanomaterial used in the present invention are both environmentally friendly materials, and the preparation process focuses on energy conservation, emission reduction, and resource recycling, which meets the current social requirements for environmental protection and sustainable development, and helps promote the development of green manufacturing and circular economy. 2. This invention forms modified phase-change microcapsules with active heating capabilities by uniformly depositing photothermal conversion nano- or micron-sized particles (such as nano-silicon carbide, copper sulfide, carbon nanotubes, graphene, and metallic silver nanoparticles) on the surface of phase-change material microcapsules. This also imparts to the glove's surface a photothermal barrier the ability to absorb radiation within the wavelength range of 0.4 to 14 μm (including visible and near-infrared light) and actively absorb light energy and convert it into heat energy under illumination. This allows the glove to actively generate heat under illumination, overcoming the limitation of traditional thermal insulation gloves that can only passively reduce heat transfer and providing a continuous and stable source of heat for the hands. Furthermore, the photothermal barrier not only relies on the heat storage and release functions of the phase-change material but also incorporates the active heating properties of the photothermal conversion material, enabling the glove to operate effectively over a wide temperature range. Whether in extreme cold or warm environments, the glove can regulate hand temperature by absorbing light energy or human thermal radiation, thereby improving its adaptability and practicality. 3. The present invention adopts a preparation process of emulsion first and powder later, which reduces the complexity and energy consumption in the production process, improves production efficiency, realizes the directional deposition of photothermal conversion nano- or micron-sized particles on the surface of microcapsules, can accurately control the distribution of particles and the thickness of the coating layer, optimizes the performance of the material, effectively improves the photothermal conversion efficiency, and enables protective products such as gloves to more effectively absorb light energy and convert it into heat energy under light conditions, while maintaining the lightness and flexibility of the material. By optimizing the emulsion conditions, the stability of the nanoparticle dispersion and the formation of the O / W emulsion are ensured, providing a good foundation for the subsequent formation of modified phase change microcapsules, effectively improving the preparation efficiency and product quality of the modified phase change microcapsules, reducing the uncertainty and defective rate in the production process, and reducing production costs. Furthermore, by accurately controlling the adjustment of the pH value, the integrity of the shell material and the uniform distribution of the particles are ensured, thereby improving the thermal stability and photothermal conversion efficiency of the modified phase change microcapsules, thereby improving the overall performance of protective products such as gloves; 4. By optimizing the coating mixture ratio, this invention ensures good fluidity and coating properties while maintaining sufficient photothermal heating and phase change energy storage capacity. This effectively improves the performance stability and service life of the glove barrier and reduces the risk of decreased temperature control performance or glove damage due to unstable material properties. 5. By optimizing the preparation process of modified phase-change microcapsules and the design of the interlayer structure, the present invention allows the selection of lighter and thinner outer and inner layer materials while ensuring thermal insulation and heating functions. This improves the flexibility and comfort of the gloves, allowing the wearer to maintain hand dexterity and comfort during long-term use, reducing the operational inconvenience and fatigue caused by heavy gloves, and improving work efficiency and user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a SEM image of the phase change microcapsule of the present invention; Figure 2 This is a macroscopic morphology diagram of the phase change microcapsule of the present invention; Figure 3 A macroscopic morphology of the nano- or micron-sized particles of the present invention; Figure 4 is a bar graph of thermal conductivity and growth rate of the present invention; Figure 5 is a bar graph of the water contact angle of the present invention; Figure 6 is a SEM image of the waterborne polyurethane film and the composite material thereof of the present invention; Figure 7 Schematic diagram of heat transfer of the composite material of the present invention; Figure 8 is a light-to-heat conversion curve diagram of the waterborne polyurethane film and the composite material thereof of the present invention; Figure 9 This is a thermal regulation performance curve of the waterborne polyurethane film and its composite material of the present invention. DETAILED DESCRIPTION

[0013] The following examples are used to further illustrate the present invention but are not intended to limit its application. Example 1:

[0014] See also Figure 1-Figure 5 This embodiment provides a composite phase-change microcapsule, and the specific preparation steps are as follows: First, amino resin was selected as the shell material of phase change material microcapsules, and metallic silver nanoparticles (the macroscopic morphology of which is shown in FIG. Figure 3 Ag NPs (as shown in the figure) are used as nano- or micron-sized particles for photothermal conversion. The metallic silver nanoparticles are chemically bonded to the surface of the phase change material microcapsule through the in-situ polymerization reaction of the amino resin shell material and are coated on the outer layer of the amino resin shell material through directional deposition during the polymerization process of the amino resin shell material to form a modified thermal conductive-photothermal conversion dual-function phase change microgel; Next, 0.5 g of metallic silver nanoparticles were weighed, anhydrous ethanol was added until the metallic silver nanoparticles were completely immersed, and ultrasonic dispersion was performed for 5 minutes to prepare a nanoparticle dispersion. Then, 10 g of molten phase change material microcapsules were weighed, mixed with a 9% polyvinyl alcohol aqueous solution and a certain amount of deionized water, and emulsified in a 30-50°C water bath at a stirring speed of 10,000-14,000 rpm using a homogenizer for 8-12 minutes to obtain an O / W emulsion (oil-in-water emulsion). Secondly, the O / W emulsion is first poured into a three-necked flask, and then the MF prepolymer solution (melamine-formaldehyde prepolymer solution) is slowly added dropwise to the O / W emulsion, and the temperature is slowly raised to 65-95°C, and then mechanically stirred at a stirring speed of 1000-1400 rpm for 3 hours. During this process, hydrochloric acid needs to be continuously added to lower the reaction pH to 4.5. After the reaction is completed, the pH value is adjusted to neutral with 10% sodium hydroxide solution, cooled to room temperature, and precipitated for 24 hours. Finally, the obtained product is filtered, washed repeatedly, and dried in an oven at 60°C to obtain modified phase change microcapsule powder M1, i.e., composite phase change microcapsules, whose SEM image (scanning electron microscope image) is shown as follows. Figure 1 As shown in Figure b, the macroscopic morphology is as follows Figure 2 As shown in Figure M1, the thermal conductivity and growth rate are as follows Figure 4 As shown in the M1 box, the water contact angle is Figure 5 As shown in the middle M1 box; Then, 30-40% of the modified phase change microcapsule powder M1 prepared above is added to 60-70% of waterborne polyurethane or silicone polymer emulsion to prepare a coating mixed glue; Finally, the prepared coating mixed glue is applied to the surface of the glove liner through a dispensing or continuous coating process, with an application amount of 20-30% of the mass of the glove liner. After curing at 50-80°C for 1-3 hours, a photothermal insulation layer is formed on the glove surface.

[0015] The following is the situation when the gloves with the photothermal insulation layer are worn and when not worn: When the gloves are not worn and the ambient temperature is 2-3°C higher than the melting point of the phase change material, the glove liner will spontaneously complete the phase change and store external heat; When the gloves are worn, the phase change material in the glove liner absorbs the heat radiation emitted by the human body, completes the phase change, and stores the heat. When the external temperature is 5-9°C lower than the phase change melting point, the phase change material will spontaneously crystallize and release heat, slowing down the rate of temperature drop in the glove liner and playing a role in thermal buffering and heat preservation. When the gloves are not worn and the outside temperature is low, as long as there is a certain intensity of light radiation (the weak light intensity of the incandescent lamp is 0.025W / cm 2 ), the nano- or micron-sized particles of photothermal conversion in the photothermal insulation on the surface of the glove liner will spontaneously absorb external light energy and infrared radiation spontaneously released by the human body, causing the insulation temperature to rise to near the phase change melting point, thereby completing the phase change energy storage process. Example 2:

[0016] See also Figure 1-Figure 5The preparation process of the composite phase change microcapsules of this embodiment is consistent with that of Example 1, except that the nanometer or micrometer-sized particles used for photothermal conversion are different, namely, amino resin is selected as the shell material of the phase change material microcapsules, and nano silicon carbide (its macroscopic morphology is shown in FIG. Figure 3 SiC NPs (as shown in the figure) are used as nano- or micron-sized particles for photothermal conversion. Nano-silicon carbide is chemically bonded to the surface of the phase change material microcapsule through the in-situ polymerization reaction of the amino resin shell material and coated on the outer layer of the amino resin shell material through directional deposition during the polymerization process of the amino resin shell material to form a modified thermal conductive-photothermal conversion dual-functional phase change microgel. The modified phase change microcapsule powder M2 is obtained through the emulsion and powder preparation process, and its SEM image is shown as follows: Figure 1 As shown in Figure c, the macroscopic morphology is as follows Figure 2 As shown in Figure M2, the thermal conductivity and growth rate are as follows Figure 4 As shown in the M2 box, the water contact angle is Figure 5 Shown in the M2 box.

[0017] Similarly, the process of applying the modified phase change microcapsule powder M2 in this embodiment to the coating mixture and applying the coating mixture containing the modified phase change microcapsule powder M2 to the gloves to form a photoheating insulation layer is the same as that in Example 1. Example 3:

[0018] See also Figures 1-9 The preparation process of the composite phase change microcapsules of this embodiment is consistent with that of embodiment 1, except that the nanometer or micrometer-sized particles used for photothermal conversion are different, that is, amino resin is selected as the shell material of the phase change material microcapsules, and nano-carbon tubes (whose macroscopic morphology is shown in FIG. Figure 3 As shown in the figure of CNTs in the middle, nano- or micron-sized particles for photothermal conversion are used. The carbon nanotubes are chemically bonded to the surface of the phase change material microcapsule through the in-situ polymerization reaction of the amino resin shell material. During the polymerization process of the amino resin shell material, the modified heat-conducting and photothermal conversion dual-functional phase change microgel is coated on the outer layer of the amino resin shell material through directional deposition. The modified phase change microcapsule powder M3 is obtained through the preparation process of emulsion and powder. Its SEM image is shown as follows Figure 1 As shown in Figure d, the macroscopic morphology is as follows Figure 2 As shown in Figure M3, the thermal conductivity and growth rate are as follows Figure 4 As shown in the M3 box, the water contact angle is Figure 5 As shown in the M3 box.

[0019] Similarly, the process of applying the modified phase change microcapsule powder M3 in this embodiment to the coating mixture and applying the coating mixture containing the modified phase change microcapsule powder M3 to the gloves to form the photoheating insulation layer is the same as that in Example 1.

[0020] Comparative Example 1: See also Figure 1-Figure 2 and Figure 4-Figure 9 The SEM image of the original phase change microcapsule M0 used in this comparative example, which is not modified by the nano- or micron-sized particles of the photothermal conversion, is as follows: Figure 1 As shown in Figure a, the macroscopic morphology is as follows Figure 2 As shown in the M0 figure, the thermal conductivity and growth rate are as follows Figure 4 As shown in the M0 box, the water contact angle is as follows Figure 5 Shown in the M0 box.

[0021] Figure 6 The following are SEM images of waterborne polyurethane film (WPU), composite materials M0 / WPU and M3 / WPU formed by waterborne polyurethane film (WPU) and M0 and M3 respectively, where a is a front view and b is a cross-sectional view. The thermal performance data of the glove liner of M0 / WPU and M3 / WPU tested by differential scanning calorimetry (DSC) are shown as follows: ; Where Tm is the melting point, which refers to the critical temperature at which a substance changes from solid to liquid; ΔHm is the melting enthalpy, which refers to the amount of heat absorbed by a unit mass of a substance when it changes from solid to liquid during the melting process; Tc,1 and Tc,2 are the first crystallization temperature and the second crystallization temperature, respectively. The crystallization temperature refers to the temperature at which a substance changes from liquid to solid; ΔHc,1 and ΔHc,2 are the first crystallization enthalpy and the second crystallization enthalpy, respectively. It can be seen from the above table that M3 / WPU is superior to M0 / WPU in melting point, melting enthalpy, crystallization temperature and crystallization enthalpy.

[0022] Figure 7 The heat transfer schematics of M0 / WPU, M3 / WPU, and M0 / WPU / CNTs are shown in Figures a, b, and c, respectively.

[0023] Figure 8 The light-to-heat conversion curves of WPU, M0 / WPU, and M3 / WPU are shown in Figure a, where the value is 0.180 W / cm 2 Xenon lamp irradiation, Figure b is 0.025 W / cm 2 Incandescent lamp illumination.

[0024] Figure 9 Figure 2 is the thermal regulation performance curve of WPU, M0 / WPU, and M3 / WPU, where Figure a is the heating process and Figure b is the cooling process.

Claims

1. A composite phase change microcapsule, characterized in that: The composite phase change microcapsules are composed of 50-60% phase change material microcapsules, 8-12% nano- or micron-sized particles for photothermal conversion, and the remainder as auxiliary additives, according to the mass percentage of the components. The nano- or micron-sized particles are chemically bonded to the surface of the phase change material microcapsules through the in-situ polymerization reaction of the shell material of the phase change material microcapsules, and are coated on the outer layer of the shell material through directional deposition during the polymerization process of the shell material to form modified phase change microcapsules.

2. A composite phase-change microcapsule according to claim 1, characterized in that: The core material of the phase change material microcapsule is made of a paraffin-based phase change material, and the phase change melting point of the paraffin-based phase change material is 17-18°C or 36-37°C.

3. The composite phase-change microcapsule according to claim 1, characterized in that: The shell material of the phase change material microcapsule is selected from one of chitosan, polymethyl methacrylate, gelatin-arabic gum, polyurethane PU, ethyl cellulose and amino resin.

4. The composite phase-change microcapsule according to claim 1, characterized in that: The nano- or micron-sized particles are selected from one of nano-silicon carbide, copper sulfide, nano-carbon tubes, graphene, and metallic silver nanoparticles.

5. The composite phase-change microcapsule according to claim 1, characterized in that: The auxiliary additive is selected from one or a mixture of dispersants, thickeners and stabilizers.

6. The method for preparing a composite phase-change microcapsule according to any one of claims 1 to 5, characterized in that: The specific steps are as follows: S1. Preparation of emulsion: Nano- or micron-sized particles are mixed with anhydrous ethanol and dispersed by ultrasonication to form a nanoparticle dispersion, which is then mixed with a paraffin-based phase change material, a 9% protective colloid solution, and deionized water. The mixture is stirred and emulsified in a water bath at 30-50°C using a homogenizer to obtain an O / W emulsion. S2. Preparation of phase change microcapsules: The O / W emulsion obtained in S1 was stirred and mixed with the MF prepolymer solution, and the pH value was adjusted with 10% sodium hydroxide solution. After precipitation, filtration, washing and drying, modified phase change microcapsule powder, i.e., composite phase change microcapsules, was obtained.

7. The method for preparing a composite phase-change microcapsule according to claim 6, characterized in that: In S1, the protective colloid solution is a polyvinyl alcohol aqueous solution, the stirring speed of the homogenizer is 10000-14000 rpm, and the stirring and emulsification time of the homogenizer is 8-12 minutes.

8. The method for preparing a composite phase-change microcapsule according to claim 6, characterized in that: In S2, the stirring temperature is 65-95°C, the stirring speed is 1000-1400 rpm, and the stirring time is 2-4 hours. During the stirring process, the pH value needs to be continuously lowered to 4.5 by adding hydrochloric acid dropwise and then adjusted to neutral by using 10% sodium hydroxide solution.

9. A coating mixed adhesive, characterized in that: The coating mixed glue comprises 30-40% modified phase change microcapsule powder and 60-70% aqueous polyurethane or silicone polymer emulsion in terms of component mass percentage, wherein the modified phase change microcapsule powder is prepared by the preparation method according to any one of claims 6-8.

10. A temperature regulating glove, characterized in that: The coating mixed adhesive according to claim 9 is applied to the surface of the glove liner by a dispensing or continuous coating process, with an application amount of 20 to 30% of the mass of the glove liner. After curing at 50 to 80° C. for 1 to 3 hours, a photothermal insulation layer is formed on the surface of the glove.

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