A nano-inorganic cool-feeling composite material and a coating containing the same and its application

Abstract

The invention discloses a nano-inorganic cooling composite material and a coating containing the material and applications thereof. The cooling composite material comprises, by weight, 30-40 parts of aqueous optically active UV-curable polyurethane, 15-20 parts of a double-bond grafted cooling inorganic substance, 1-5 parts of flaky metal pigments, 5-10 parts of mint essential oil polyurethane microcapsules, and 5-10 parts of a defoaming agent. The nano-inorganic cooling composite material is composited with a double-bond grafted inorganic cooling substance and a water-soluble photocurable polyurethane, thereby solving the problem of easy agglomeration of the nano-cooling inorganic substance. The flaky metal pigment and the mint essential oil microcapsules are introduced and connected together, thereby improving the thermal conductivity and cooling properties of the composite material. The coating is applied to fabric, and the coating is firmly bonded to the fabric through the photocuring properties of the polyurethane, thereby achieving cooling modification of the fabric. The photocurable polyurethane is a green and economical material, which can reduce the amount of adhesive used in the production process and meets the requirements of green chemistry.

Description

Technical Field

[0001] The invention relates to a cooling material, in particular to a nano-inorganic cooling composite material and a coating containing the material and applications thereof. Background Art

[0002] Energy consumption and climate change are two major challenges facing humanity in the 21st century. The increased use of heating and cooling systems in buildings is leading to significant energy consumption and greenhouse gas emissions, exacerbating global climate change. Extreme heat events caused by global climate change not only impact daily life, social production, and economic development, but can also pose life-threatening risks. However, a common risk associated with outdoor activities is exposure to excessive heat stress. According to Am J Prev Med, heat stress is the leading cause of death from natural disasters in the United States. The physiological and psychological impacts on humans can reduce industrial productivity and supply, ultimately impacting the overall economy, particularly in developing countries. In the context of global warming, the threat of outdoor heat stress to health and the economy will become more severe and frequent. A recent analysis by the Climate Vulnerable Forum estimates that the annual cost of heat-related problems will reach $2.4 trillion by 2030. Radiant cooling coatings are functional coatings with high solar reflectivity and infrared emissivity. They effectively reflect sunlight while efficiently emitting heat as infrared radiation, thereby achieving radiant cooling and reducing energy consumption. Using radiant cooling coatings for heat dissipation requires no structural changes to the equipment, making them simple and effective. They offer advantages such as cost-effectiveness, excellent results, and a wide range of applications. The development of cooling coatings with high transmittance of human thermal radiation and their application to textiles, such as clothing, is of great significance for improving human comfort.

[0003] Compared with other cooling substances, nano zinc oxide particles and boron nitride nanosheets have cooling properties such as excellent thermal conductivity and high ultraviolet reflectivity. However, due to the limitations of their nanostructure, these substances spontaneously aggregate, and their cooling performance is limited. Summary of the Invention

[0004] Purpose of the invention: The first purpose of the present invention is to provide a nano-inorganic cooling composite material to solve the problem of easy agglomeration of nano-cooling materials and improve thermal conductivity and cooling properties; the second purpose of the present invention is to provide a coating containing the cooling material; the third purpose of the present invention is to provide the application of the coating in the cooling modification of fabrics.

[0005] Technical solution: The nano-inorganic cooling composite material of the present invention comprises, by weight, 30 to 40 parts of aqueous optically active UV-curable polyurethane, 15 to 20 parts of double-bond grafted cooling inorganic matter, 1 to 5 parts of flaky metal pigments, 5 to 10 parts of peppermint essential oil polyurethane microcapsules and 5 to 10 parts of defoaming agent.

[0006] The double-bond grafted cooling inorganic substance is combined with the light-cured optically active UV polyurethane to form a composite cooling material, which can effectively solve the problem of spontaneous agglomeration of nano-cooling substances, and can also reduce the amount of adhesive used to achieve green production.

[0007] Preferably, the flaky metallic pigment is a flaky aluminum powder pigment. Adding the flaky aluminum powder metallic pigment allows numerous flaky aluminum powder pigments to interconnect, with large and small particles filling each other to form a continuous metallic film. Together with the peppermint essential oil microcapsules, the flaky metallic pigments penetrate the coating, improving its thermal conductivity. The flaky metallic pigments also reflect light outside the coating, improving the coating's cooling properties, a property not found in conventional powdered cooling substances. Using the peppermint essential oil microcapsules as a connecting material between the layers of the metallic aluminum film allows for sustained, sustained release of the peppermint essential oil, which has cooling properties, improving the coating's cooling properties. Furthermore, compared to directly using substances such as menthol and peppermint essential oil, the microcapsule coating can effectively reduce the volatilization of the peppermint essential oil, improving its stability.

[0008] Preferably, the cool inorganic substance in the double-bond grafted cool inorganic substance is one or more of nano zinc oxide, boron nitride, nano titanium oxide, and nano silicon dioxide.

[0009] Preferably, the defoamer is defoamer BYK-011 or BYK-028.

[0010] Lotus essential oil polyurethane microcapsules, BYK-011, and BYK-028 were purchased from Shanghai Buding Chemical Co., Ltd.

[0011] Preferably, the preparation method of the water-based optically active UV-curable polyurethane in the raw materials is:

[0012] (1) synthesizing a polyurethane prepolymer by taking diisocyanate and diol oligomer under the action of a catalyst;

[0013] (2) adding a hydrophilic chain extender, polytetrahydrofuran, to react, and then adding a left-handed reagent dropwise to react. After the chain extension is completed, end-capping, neutralization, and solvent removal are performed to obtain a water-based optically active UV-curable polyurethane.

[0014] Preferably, in step (1), the polyurethane prepolymer solvent is acetone, and acetone is added to maintain the viscosity of the system at 4 to 6 Pa·s.

[0015] Preferably, in step (2), a hydrophilic chain extender is added for reaction, and a left-handed reagent is continuously added dropwise for reaction. After the chain extension is completed, a capping agent and a small amount of hydroquinone are dissolved in acetone and added dropwise to the system, and triethylamine is added for neutralization. Then, distilled water is added and stirred thoroughly, and the acetone is removed by vacuum distillation to obtain a water-based optically active UV-curable polyurethane.

[0016] Preferably, the polytetrahydrofuran is 1.0 to 1.5. The hydrophilic chain extender uses polytetrahydrofuran to improve the flexibility and hydrophilicity of the polyurethane.

[0017] Preferably, the left-handed reagent is S-binaphthol. On the one hand, binaphthol can maintain a stable chiral conformation during the polymerization process, ultimately imparting optical activity to the polyurethane; on the other hand, the introduction of an aromatic structure can greatly improve the stability of the polymer.

[0018] Preferably, the diisocyanate is isophorone diisocyanate.

[0019] Preferably, the diol oligomer is any one of polyethylene glycol 1000, polyethylene glycol 1500, and polypropylene glycol 2000.

[0020] Preferably, the molar ratio of the diisocyanate to the diol oligomer is 4-5:2-3.

[0021] Preferably, the catalyst is dibutyltin dilaurate.

[0022] Preferably, the capping agent is pentaerythritol triacrylate.

[0023] The preparation method of the double-bond grafted cooling inorganic substance is as follows:

[0024] (1) treating the cooling inorganic substance under alkaline conditions to perform hydroxylation; when the cooling inorganic substance is a metal oxide, hydroxylation treatment is not required;

[0025] (2) Vinyltrimethoxysilane is added to a mixture of methanol and deionized water, stirred evenly, and then a cooling inorganic substance is added, soaked, and finally rinsed and dried to obtain a cooling inorganic substance grafted with double bonds.

[0026] The preparation method of the nano-inorganic cooling composite material comprises the following steps: mixing all raw materials, performing vacuum treatment, and initiating double bond free radical polymerization between the cooling substance and polyurethane under a UV light curing apparatus to obtain the cooling composite material.

[0027] Adding a defoaming agent during the preparation of the coating and subjecting the raw materials to vacuum treatment to remove stagnant air in the raw materials can enhance the thermal conductivity of the cooling material.

[0028] The invention discloses a coating layer containing the nano inorganic cool feeling composite material.

[0029] The method for preparing the coating of the present invention comprises the following steps: mixing the composite cooling material with water, adding a thickener, and preparing a cooling coating.

[0030] Preferably, the thickener is thickener PU-202, purchased from Guantao County TEDA Chemical Co., Ltd.

[0031] Preferably, the ratio of the composite cooling material to water is 3-4:5-6.

[0032] Preferably, the ratio of the composite cooling material to the thickener is 6 to 7:1.

[0033] Application of the coating described in claim 8 in modifying the cool feel of fabrics.

[0034] The application method involves screen-printing the coating onto a fabric surface, then placing the fabric under a UV curing device to initiate a cross-linking reaction between the coating and the fabric surface. This process primarily involves the generation of active free radicals by the photoinitiator under UV light, which in turn initiates polymerization, resulting in the modification of the composite cooling fabric. The cooling fabric's thermal insulation and UV resistance are monitored during the heating process and UV light exposure.

[0035] Preferably, the temperature of the heating process is set to 35-36° C. in a flat-plate thermostat.

[0036] Preferably, the ultraviolet light source is any one of a xenon arc lamp, a tritium lamp and a sunlight simulator, or a combination of at least two of them.

[0037] Invention Mechanism: The present invention performs surface double bond grafting modification on cooling inorganic substances such as nano-boron nitride and nano-zinc oxide, and then combines them with light-cured optically active polyurethane, effectively solving the problem of spontaneous agglomeration of nano-cooling substances, and can also reduce the amount of adhesive used, thereby achieving green production.

[0038] By adding nano-aluminum flake pigments to the inorganic cooling material, the numerous flakes interconnect, with large and small particles filling each other to form a continuous metal film. This interpenetrating metal film, along with the peppermint essential oil microcapsules, improves thermal conductivity. The flakes also reflect light outside the coating, enhancing its cooling properties. The peppermint essential oil microcapsules, acting as a connecting material between the layers of the metallic aluminum film, continuously release the cooling peppermint essential oil, enhancing the coating's cooling properties. Furthermore, compared to directly applying substances like menthol and peppermint essential oil, the microcapsule coating effectively reduces the volatilization of the peppermint essential oil, improving its stability.

[0039] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The nano-inorganic cooling composite material solves the problem of easy agglomeration of nano-cooling inorganic substances by selecting inorganic cooling substances with grafted double bonds and compounding them with water-soluble photocurable polyurethane; (2) The nano-inorganic cooling composite material introduces flaky metal pigments and mint essential oil microcapsules, which are interconnected, thereby improving the thermal conductivity and cooling properties of the composite material; (3) The coating is applied to fabrics, and the coating is firmly bonded to the fabric through the photocuring properties of polyurethane, thereby achieving cooling modification of the fabric. At the same time, photocurable polyurethane is a green and economical material, which can reduce the amount of adhesive used in the production process and meet the requirements of green chemistry. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0041] Example 1

[0042] (1) Preparation of UV-resistant composite cool-feeling material:

[0043] Step 1: Synthesis of waterborne optically active polyurethane

[0044] Pour 5.57g of isophorone diisocyanate and 15g of polyethylene glycol 1000 into a three-necked flask equipped with a stirrer and a reflux condenser, heat to 80°C in an oil bath, adjust the speed and add 0.06g of dibutyltin dilaurate dropwise. After reflux for 2h, weigh 1.322g of polytetrahydrofuran 250 and dissolve it in the three-necked flask for chain extension reaction. The reaction lasts for 2h. The left-handed reagent S-binaphthol dissolved in anhydrous tetrahydrofuran is placed in the dropping funnel, the dropping funnel switch is turned on, and the pressure is pressed. The solution was added dropwise to the system at a rate of one drop per second, and then reacted for 1.5 hours. Acetone was continuously added during the process to maintain a certain viscosity of the system. After the chain extension was completed, the oil bath temperature was cooled to 70°C, and 1.39g of pentaerythritol triacrylate and a small amount of hydroquinone were dissolved in acetone and added dropwise to the system. The reaction was continued at 70°C for 4 hours. After the end-capping was completed, the temperature was lowered to 50°C, and 0.503g of triethylamine was added for neutralization for 0.5 hours. 77.3g of distilled water was added and stirred continuously for 30 minutes. Finally, the acetone was removed by rotary evaporation under reduced pressure for 30 minutes to obtain a uniform light-cured waterborne polyurethane.

[0045] Step 2: Preparation of surface double bond grafted boron nitride

[0046] Disperse 20g of boron nitride nanosheets in 5mol / L sodium hydroxide solution (2.5L), transfer to a hydrothermal autoclave and treat at 128℃ for 24h; after the reaction is completed, cool to room temperature, centrifuge (5000r / min, 7min), collect the precipitate, and wash with deionized water until neutral. The obtained solid is vacuum dried at 80℃ for 12h to obtain hydroxylated boron nitride and store in a desiccator. Weigh 25g of vinyltrimethoxysilane, 250g of methanol, and 125g of deionized water in a beaker, place a rotor, and stir on a magnetic stirrer for 30min to obtain a treatment solution. Add hydroxylated boron nitride to the treatment solution and soak for 24h, then take it out, rinse the surface 3 times with water, then rinse the surface 3 times with ethanol, and bake it in an oven at 60℃ for 30min to obtain double-bond modified boron nitride;

[0047] Step 3: Preparation of Boron Nitride-Polyurethane Composite Cooling Material

[0048] Take 40g of the waterborne polyurethane obtained in step 1 into a beaker, add 20g of the double-bond modified boron nitride nanosheets obtained in step 2, add 5g of flaky aluminum pigment (average particle size 15μm), 10g of defoamer BYK-011, and 10g of mint essential oil polyurethane microcapsules, continue stirring for 30min to fully mix, then place in a vacuum reactor for vacuum treatment for 30min, and treat under a UV light curing instrument for 30min to induce double bond free radical polymerization between the cooling substance and the polyurethane to obtain a composite cooling material;

[0049] (2) Preparation of nano-inorganic light-cured cool coating:

[0050] The prepared boron nitride-polyurethane composite cooling material was blended with water and a thickener in a beaker at a mass ratio of 20:30:3, and stirred at room temperature for 30 minutes to ensure complete mixing.

[0051] Example 2

[0052] (1) Preparation of UV-resistant composite cool-feeling material:

[0053] Step 1: Synthesis of waterborne optically active polyurethane

[0054] 5.57 g of isophorone diisocyanate and 15 g of polyethylene glycol 1000 were poured into a three-necked flask equipped with a stirrer and a reflux condenser. The temperature was raised to 80 ° C in an oil bath. After adjusting the speed, 0.06 g of dibutyltin dilaurate was added dropwise. After reflux for 2 h, 1.322 g of polytetrahydrofuran 250 was weighed and dissolved and added to the three-necked flask for chain extension reaction. The reaction lasted for 2 h. The left-handed reagent S-binaphthol dissolved in anhydrous tetrahydrofuran was placed in a dropping funnel. The dropping funnel switch was turned on and the solution was dripped into the system at a rate of 1 drop per second. After that, the reaction was continued. The reaction was continued for 1.5 hours, with acetone continuously added during the process to maintain a certain viscosity of the system. After the chain extension was completed, the oil bath temperature was cooled to 70°C, and 1.39g of pentaerythritol triacrylate and a small amount of hydroquinone were dissolved in acetone and added dropwise to the system for reaction at 70°C for 4 hours. After the end-capping was completed, the temperature was cooled to 50°C, and 0.503g of triethylamine was added for neutralization for 0.5 hour. 77.3g of distilled water was added and stirred continuously for 30 minutes. Finally, the acetone was removed by rotary evaporation under reduced pressure for 30 minutes to obtain a uniform light-cured waterborne polyurethane.

[0055] Step 2: Preparation of surface double bond grafted nano zinc oxide

[0056] Weigh 25 g of vinyltrimethoxysilane, 250 g of methanol, and 125 g of deionized water into a beaker, place a rotor in it, and stir on a magnetic stirrer for 30 min to obtain a treatment solution. Add nano-zinc oxide to the treatment solution and soak it for 24 h, then take it out and rinse the surface three times with water and then with ethanol. Bake it in an oven at 60°C for 30 min to obtain double-bond modified nano-zinc oxide.

[0057] Step 3: Preparation of nano zinc oxide-polyurethane composite cooling material

[0058] Take 30g of the waterborne polyurethane obtained in step 1 in a beaker, add 15g of the double-bond modified nano zinc oxide obtained in step 2, add 1g of flaky aluminum pigment (average particle size 15μm), 5g of defoamer BYK-011, and 5g of mint essential oil polyurethane microcapsules, continue stirring for 30min to fully mix, place the prepared coating in a vacuum reactor for vacuum treatment for 30min, and treat it under a UV light curing instrument for 30min to induce double bond free radical polymerization between the cooling substance and the polyurethane to obtain a composite cooling material;

[0059] (2) Preparation of nano-inorganic light-cured cool coating:

[0060] The prepared boron nitride-polyurethane composite cooling material was blended with water and a thickener in a beaker at a mass ratio of 20:30:3, and stirred at room temperature for 30 minutes to ensure complete mixing.

[0061] Example 3

[0062] (1) Preparation of UV-resistant composite cool-feeling material:

[0063] Step 1: Synthesis of waterborne optically active polyurethane

[0064] 5.57 g of isophorone diisocyanate and 15 g of polyethylene glycol 1000 were poured into a three-necked flask equipped with a stirrer and a reflux condenser. The temperature was raised to 80 ° C in an oil bath. After adjusting the speed, 0.06 g of dibutyltin dilaurate was added dropwise. After reflux for 2 h, 1.322 g of polytetrahydrofuran 250 was weighed and dissolved and added to the three-necked flask for chain extension reaction. The reaction lasted for 2 h. The left-handed reagent S-binaphthol dissolved in anhydrous tetrahydrofuran was placed in a dropping funnel. The dropping funnel switch was turned on and the solution was dripped into the system at a rate of 1 drop per second. After that, the reaction was continued. The reaction was continued for 1.5 hours, with acetone continuously added during the process to maintain a certain viscosity of the system. After the chain extension was completed, the oil bath temperature was cooled to 70°C, and 1.39g of pentaerythritol triacrylate and a small amount of hydroquinone were dissolved in acetone and added dropwise to the system for reaction at 70°C for 4 hours. After the end-capping was completed, the temperature was cooled to 50°C, and 0.503g of triethylamine was added for neutralization for 0.5 hour. 77.3g of distilled water was added and stirred continuously for 30 minutes. Finally, the acetone was removed by rotary evaporation under reduced pressure for 30 minutes to obtain a uniform light-cured waterborne polyurethane.

[0065] Step 2: Preparation of surface double bond grafted boron nitride

[0066] Disperse 10g of boron nitride nanosheets in 2.5mol / L sodium hydroxide solution (2.5L), move to a hydrothermal autoclave and treat at 128°C for 24h. After the reaction is completed, cool to room temperature, centrifuge (5000r / min, 7min), collect the precipitate, and wash with deionized water until neutral. The obtained solid is vacuum dried at 80°C for 12h to obtain hydroxylated boron nitride and store it in a desiccator. Weigh 12.5g of vinyltrimethoxysilane, 125g of methanol, and 65g of deionized water in a beaker, put a rotor in it, and stir on a magnetic stirrer for 30min to obtain a treatment solution. Add hydroxylated boron nitride to the treatment solution and soak it for 24h, then take it out, rinse the surface 3 times with water, then rinse the surface 3 times with ethanol, and bake it in an oven at 60°C for 30min to obtain double-bond modified boron nitride.

[0067] Step 3: Preparation of Boron Nitride-Polyurethane Composite Cooling Material

[0068] Take 35g of the waterborne polyurethane obtained in step 1 in a beaker, add 17.5g of the double-bond modified boron nitride nanosheets obtained in step 2, add 3g of flaky aluminum powder (average particle size 15μm), 6.5g of defoamer BYK-011, and 7g of mint essential oil polyurethane microcapsules, and continue stirring for 30min to fully mix. The prepared coating is placed in a vacuum reactor for vacuum treatment for 30min, and treated under a UV light curing instrument for 30min to induce double bond free radical polymerization between the cooling substance and the polyurethane to obtain a composite cooling material;

[0069] (2) Preparation of nano-inorganic light-cured cool coating:

[0070] The prepared boron nitride-polyurethane composite cooling material was blended with water and a thickener in a beaker at a mass ratio of 20:30:3, and stirred at room temperature for 30 minutes to ensure complete mixing.

[0071] Comparative Example 1

[0072] On the basis of Example 1, boron nitride nanosheets were used instead of double-bond grafted boron nitride, and other conditions remained unchanged.

[0073] Comparative Example 2

[0074] On the basis of Example 2, the water-based optically active UV-curing polyurethane was not added, and the other conditions remained unchanged.

[0075] Comparative Example 3

[0076] On the basis of Example 1, water-based light-curing polyurethane was used instead of water-based optically active UV-curing polyurethane, and other conditions remained unchanged.

[0077] Synthesis of water-based optically active polyurethane:

[0078] 5.57 g of isophorone diisocyanate and 15 g of polyethylene glycol 1000 were poured into a three-necked flask equipped with a stirrer and a reflux condenser, and the temperature was raised to 80 ° C in an oil bath. After adjusting the speed, 0.06 g of dibutyltin dilaurate was added dropwise. After reflux for 2 hours, 1.322 g of polytetrahydrofuran 250 was weighed and dissolved and added to the three-necked flask for chain extension reaction. Acetone was continuously added during the process to maintain a certain viscosity of the system. After the chain extension was completed, the temperature of the oil bath was cooled to 70 ° C, and 1.39 g of pentaerythritol triacrylate and a small amount of hydroquinone were dissolved in acetone and added dropwise to the system. The reaction was carried out at 70 ° C for 4 hours. After the end-capping was completed, the temperature was cooled to 50 ° C, and 0.503 g of triethylamine was added for neutralization for 0.5 hours. 77.3 g of distilled water was added and stirred for 30 minutes. Finally, the acetone was removed by rotary evaporation for 30 min using reduced pressure distillation to obtain uniform light-cured waterborne polyurethane.

[0079] Comparative Example 4

[0080] On the basis of Example 1, no defoaming agent was added in step 3, no vacuum treatment was performed, and other conditions remained unchanged.

[0081] Comparative Example 5

[0082] On the basis of Example 1, alumina powder was used instead of the flaky aluminum powder pigment, and the other conditions remained unchanged.

[0083] Comparative Example 6

[0084] On the basis of Example 1, peppermint essential oil was used instead of peppermint essential oil polyurethane microcapsules, and other conditions remained unchanged.

[0085] Comparative Example 7

[0086] On the basis of Example 1, no flaky nano-aluminum powder was added, and other conditions remained unchanged.

[0087] Comparative Example 8

[0088] On the basis of Example 1, mint essential oil polyurethane microcapsules were not added, and other conditions remained unchanged.

[0089] Performance Testing

[0090] The coating materials synthesized in Examples 1 to 3 and Comparative Examples 1 to 8 are first applied to the surface of the fabric by screen printing, and then scraped back and forth with a scraper until the coating is uniform. The coated cotton fabric is fixed on a polytetrafluoroethylene plate on a UV light curing machine. Under the irradiation of UV light, the photoinitiator produces active free radicals, which then initiates polymerization, thereby initiating a cross-linking reaction between the coating and the fabric surface, thereby achieving the modification of the composite cool fabric. The UV-cured coated fabric is cured with a lamp power of 2kW, a lamp height of 9.5cm, and a curing time of 15 seconds. The outdoor heating process and ultraviolet light irradiation conditions are simulated in a flat-plate thermal insulation instrument and an anti-ultraviolet performance tester, and the heat preservation rate, Crowe value and anti-ultraviolet performance of the cool fabric are monitored.

[0091] The thermal insulation rate and Crowe value were tested using a YG606D flat plate thermal insulation instrument.

[0092] The UV protection factor was tested using a YG(B)912 UV protection performance tester.

[0093] The test results are shown in Table 1.

[0094] Table 1 Comparison of cooling performance of various samples

[0095]

[0096] The lower the thermal insulation rate, the better the thermal conductivity. In this experiment, the thermal insulation rate of the untreated cotton fabric was 33.25%. The lower the Kroger value, the better the thermal conductivity. In this experiment, the Kroger value of the untreated cotton fabric was 0.46. The UV protection factor was greater than 40, indicating good UV protection. As shown in Table 1, the cooling coatings synthesized in Examples 1 to 3 had thermal insulation rates ranging from 5.37 to 19.61%, Kroger values ​​ranging from 0.04 to 0.17, and UV protection factors greater than 40, indicating that the coating materials synthesized in Examples 1 to 3 had good cooling properties and UV protection.

[0097] As can be seen from Table 1, the thermal conductivity of the cool coating finished fabric synthesized in Example 1 is 13.14%, the ultraviolet protection factor is 54.89, and the Crowe value is 0.13. The thermal conductivity in Comparative Example 1 is 23.12%, the ultraviolet protection factor is 20.44, and the Crowe value is 0.27. The cooling performance of the modified fabric in Comparative Example 1 is significantly weaker than that in Example 1. This is because the degree of dispersion of boron nitride in the composite cooling material in the nano-inorganic cooling coating significantly affects the cooling performance of the cooling coating. After the surface double bond grafting modification of nano-boron nitride, the longer carbon chain on the surface prevents it from spontaneously agglomerating and combining with polyurethane to form a composite system, which can effectively solve the problem of spontaneous agglomeration of nano-cooling materials and can better exert its cooling performance. Boron nitride without grafted double bonds will spontaneously agglomerate due to its larger surface energy during the composite process, affecting its cooling performance.

[0098] As shown in Table 1, the thermal insulation rate of the nano-inorganic cool feeling coating with UV light-cured optically active polyurethane as the carrier synthesized in Example 2 is 5.37%, the ultraviolet protection factor is 31.03, and the Crowe value is 0.04. The thermal insulation rate in Comparative Example 2 is 23.76%, the ultraviolet protection factor is 29.23, and the Crowe value is 0.28. The thermal conductivity and anti-ultraviolet performance of the modified fabric in Comparative Example 2 are significantly weaker than those in Example 2. This is because the polyurethane in the composite cool feeling material in the nano-inorganic cool feeling coating with UV light-cured optically active polyurethane as the carrier significantly affects the cool feeling performance of the cool feeling coating, and the resulting coating in Comparative Example 2 does not add water-based optically active polyurethane. This change in component ratio will cause the material composition and the dispersion degree of nano-zinc oxide in the composite material to change, thereby affecting the cool feeling performance. The reduction in the polyurethane component ratio will reduce the dispersion degree of nano-zinc oxide in the composite material, cause agglomeration, affect its cool feeling performance, and then cause the thermal conductivity efficiency and anti-ultraviolet performance of the cool feeling coating to weaken. Compared with Comparative Example 2, the nano zinc oxide cooling material in Example 2 is first compounded with polyurethane to form a composite cooling material. On the one hand, the particle size of the nanoparticles is small, resulting in a significant increase in its specific surface area and a higher surface energy, which makes it very easy for the nanoparticles to unite into a ball after generation, forming agglomerates, thereby greatly reducing its cooling performance. Dispersing in polyurethane to form a composite cooling material can avoid the agglomeration of nano zinc oxide, thereby improving the cooling performance. On the other hand, the optically active polyurethane effectively realizes diffuse emission, refraction and reflection in the thermal infrared band (8-14 μm), which has a certain improvement on the thermal insulation performance of the coating.

[0099] Taking Example 2 as a reference, the self-crosslinking fastness of the coating obtained in Comparative Example 2 on the fabric is lower than that in Example 2. Compared with Comparative Example 2, Example 2 adds UV light-curable polyurethane during the coating preparation process. Under the UV light curing instrument, the photoinitiator generates active free radicals, which in turn initiate polymerization and cross-linking reaction with the fabric surface, thereby modifying the composite cooling fabric and improving the self-crosslinking fastness of the coating and fabric. At the same time, light-curable polyurethane is an economical, green and environmentally friendly material. Combining light-curable polyurethane with a cooling material to form a composite cooling material can reduce the amount of adhesive used in the subsequent coating preparation process, meet the requirements of green chemistry, and achieve green production.

[0100] Fabrics treated with the cooling coating materials of Example 1 and Comparative Example 3 were tested for infrared emissivity. Testing method: Infrared emissivity was measured using an infrared emissivity meter. After calibration, the instrument was preheated for approximately 20 minutes, maintaining the test temperature at 40°C. The infrared emissivity of the sample was measured at 0-20 μm. The test results are shown in Table 2.

[0101] Table 2 Comparison of UV emissivity of samples

[0102]

[0103] As can be seen from Table 2, the infrared emissivity of the fabric treated with the cool coating material of Example 1 is 0.896, and the infrared emissivity of the fabric treated with the coating material of Comparative Example 3 is 0.691. The infrared emissivity of the fabric treated with the coating material of Comparative Example 3 is significantly lower than that of the fabric treated with the coating material of Example 1. This is because Comparative Example 3 uses water-based polyurethane and modified boron nitride to prepare a cool composite material, while Example 1 adds a left-handed reagent S-binaphthol during the preparation of polyurethane to prepare a water-based optically active polyurethane and a double-bond modified boron nitride to prepare a cool composite material for the preparation of cool coatings. Because the binaphthol group has a non-coplanar, torsional special rigid structure that hinders the vibration of the polymer chain, the more ordered secondary structure produces a large amount of intermolecular interactions and greatly reduces the unsaturation of the molecule, making it possible to effectively achieve diffuse emission, refraction and reflection in the thermal infrared band. On the other hand, the various durable fastnesses of the coating prepared in Example 1 are all better than Comparative Example 3 to a certain extent. This is because the unique aromatic structure of S-binaphthol can greatly improve polymer stability when introduced into the polymer chain.

[0104] As can be seen from Table 1, using Example 1 as a reference, the thermal insulation rate of the fabric treated with the cooling material in Comparative Example 4 increased from 13.14% to 21.01%. Compared to Example 1, Comparative Example 4 did not add a defoamer during the coating preparation process, and the prepared coating material was not vacuum-treated. The thermal conductivity of the prepared nano-inorganic cooling coating based on UV-curable optically active polyurethane was reduced. From the perspective of thermal conductivity, since the thermal conductivity of still air is the lowest, the more still air trapped in the coating material when air is not flowing, the worse the thermal conductivity. Vacuuming the prepared coating material can remove excess still air in the coating material, improving the thermal conductivity of the cooling coating. At the same time, the defoamer can accelerate the foam drainage rate by reducing the surface tension of the foam generated during the coating material preparation process and reducing the viscosity of the foam liquid film, thereby eliminating the foam breakage and releasing the air generated during the coating stirring process, thereby improving the thermal conductivity of the coating material. Therefore, removing the air contained in the coating material as much as possible is crucial to the thermal conductivity of the cooling coating.

[0105] As can be seen from Table 1, with Example 1 as a reference, the thermal insulation rate of Comparative Example 5 is 22.78%, and its thermal conductivity is lower than that of Example 1. This is because flake metal aluminum powder is used as a pigment in Example 1. A large number of flake aluminum powder pigments are connected to each other, and the large and small scales fill each other to form a continuous metal film, which can reflect light outside the metal film and improve the cooling performance of the coating. At the same time, the large metal film has a high thermal insulation rate, which can better dissipate the heat of the human body. This is a performance that conventional powdered cooling substances do not have. At the same time, the thermal insulation rate of metal aluminum powder is about 250W / (m·K). The thermal insulation rate of aluminum oxide powder is 35W / (m·K), which is significantly lower than that of flake aluminum powder. Therefore, adding flake aluminum powder to the coating can not only shield external heat sources such as ultraviolet light, but also improve the thermal conductivity of the cooling coating by utilizing its higher thermal conductivity. Moreover, it can fill each other to form a continuous metal film and its thermal insulation rate is significantly higher than that of aluminum oxide powder. Therefore, the cooling effect of adding flake aluminum powder is due to the aluminum oxide powder.

[0106] As shown in Table 1, using Example 1 as a reference, Comparative Example 7 has a thermal insulation rate of 24.68%, a UV protection factor of 28.32, and lower thermal conductivity and UV resistance than Example 1. This is because Comparative Example 7 lacks the addition of flaky aluminum powder metallic pigments, resulting in the absence of interconnected metal layers compared to Example 1. This, on the one hand, prevents the formation of a thermal conductivity pathway within the coating, and on the other hand, lacks the high thermal conductivity and strong UV shielding properties of flaky aluminum powder, resulting in lower thermal conductivity and UV protection.

[0107] As shown in Table 1, compared to Example 1, the thermal insulation rate of Comparative Example 8 was 24.13%, indicating lower thermal conductivity than Example 1. This is because the addition of peppermint essential oil polyurethane microcapsules in Example 1 connects the upper and lower layers of the aluminum powder flaky metal film, forming a thermal path. This reduces the coating's thermal insulation rate, improves thermal conductivity, and simultaneously slowly releases the cooling effect of the peppermint essential oil. Comparative Example 8, however, lacks these microcapsules, failing to form a thermal path between the metal layers, resulting in lower thermal conductivity.

[0108] The fabrics treated with Example 1 and Comparative Example 6 were placed under sunlight at the same time, and their cooling properties were tested every day. The test results are shown in Table 3.

[0109] Table 3 Heat preservation rate after sunlight exposure for different days after preparation

[0110]

[0111] As shown in Table 3, the cooling performance of the fabric treated with Comparative Example 6 decreased significantly after three days, while the cooling performance of the fabric treated with Example 1 remained relatively stable even after 30 days. This is because peppermint essential oil is highly volatile and evaporates rapidly under sunlight and elevated temperatures, causing the coating's cooling performance to decrease. The use of peppermint essential oil microcapsules, in which the polyurethane microcapsules provide a sustained release of the peppermint essential oil, significantly improves its cooling stability.

Claims

1. A nano-inorganic cooling composite material, characterized in that: The invention comprises, by weight, 30 to 40 parts of water-based optically active UV-curable polyurethane, 15 to 20 parts of double-bond grafted cooling inorganic matter, 1 to 5 parts of flaky metal pigment, 5 to 10 parts of mint essential oil polyurethane microcapsules and 5 to 10 parts of defoaming agent; The preparation method of the water-based optically active UV-curable polyurethane is as follows: (1) Synthesize polyurethane prepolymer by taking diisocyanate and diol oligomer under the action of catalyst; (2) Adding a hydrophilic chain extender, polytetrahydrofuran, to react, and then adding a left-handed reagent to react. After the chain extension is completed, end-capping, neutralization, and solvent removal are performed to obtain a water-based optically active UV-curable polyurethane.

2. The optical nano inorganic cool feeling composite material according to claim 1, characterized in that: The flaky metal pigment is a flaky aluminum powder pigment.

3. The optical nano inorganic cool feeling composite material according to claim 1, characterized in that: The cool inorganic substance in the double-bond grafted cool inorganic substance is one or more of nano zinc oxide, boron nitride, nano titanium oxide and nano silicon dioxide.

4. The optical nano inorganic cool feeling composite material according to claim 1, characterized in that: The defoamer is BYK-011 or BYK-028.

5. The nano-inorganic cooling composite material according to claim 1, characterized in that: The polytetrahydrofuran is 1.0 to 1.5 parts.

6. The nano-inorganic cooling composite material according to claim 1, characterized in that: The left-handed reagent is S-binaphthol.

7. A coating comprising the nano-inorganic cooling composite material according to any one of claims 1 to 6.

8. Use of the coating according to claim 7 in modifying the cool feel of fabrics.

9. The use according to claim 8, characterized in that The application method is as follows: the coating is first applied to the surface of the fabric by screen printing, and the fabric is placed under a UV light curing device to initiate a cross-linking reaction between the coating and the fabric surface.

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