Microcapsule wall material as well as preparation method and application thereof

Abstract

The invention discloses a microcapsule wall material and a preparation method thereof. The prepared low-supercooling-degree microcapsule is composed of a shell formed by a wall material and a coated phase change material core material, and meanwhile, inorganic nanoparticles are uniformly loaded on the surface of the shell through the grafting effect of an isocyanate silane coupling agent. The preparation method comprises the following steps: carrying out surface modification on inorganic nanoparticles by using an isocyanate silane coupling agent, preparing an oil phase and a water phase of a microemulsion, preparing the microemulsion and carrying out a synthetic reaction on the microcapsule. According to the invention, an isocyanate silane coupling agent grafting technology is combined with a phase change microcapsule preparation process for the first time, so that the supercooling phenomenon of the microcapsule in the use process is effectively reduced. Compared with other methods in the prior art, the method has the advantages that the prepared low-supercooling-degree microcapsule sample has good physical and chemical stability and mechanical strength, the doped inorganic nanoparticles are not easy to agglomerate, fall off and the like, and the method has very high practical value.

Description

Technical Field

[0001] The present invention relates to a coating technology for a low supercooling phase change material, and specifically relates to a low supercooling phase change microcapsule based on the grafting action of an isocyanate silane coupling agent and a preparation method thereof, belonging to the technical field of phase change materials. Background Art

[0002] Phase change materials are a class of functional materials that absorb and release heat from the environment through the solid-liquid phase transition, have good temperature regulation and constant temperature functions, can be recycled, and have broad application prospects in the fields of energy conservation and energy storage, building materials, textiles, aerospace, and military.

[0003] The development of microcapsule technology has broadened the application scope of phase change materials. Phase change microcapsules with phase change materials as the core material and organic or inorganic materials as the wall material avoid direct contact between the core material and the external environment and solve problems such as core material leakage and pollution. However, after the phase change material is encapsulated into microcapsules, serious supercooling phenomena are prone to occur, making the exothermic peak temperature lower than the endothermic peak temperature, resulting in the inability of the microcapsule material to release heat in a timely manner during actual application, thus directly affecting the sensitivity and accuracy of the temperature control ability of the phase change material. For example, in the textile field, temperature-regulating fabrics cannot provide good heat preservation effects due to supercooling phenomena; in the field of electronic device management, the supercooling problem of thermal interface materials leads to a decrease in their heat transfer efficiency. Therefore, the supercooling phenomenon seriously affects the actual application effect of the phase change microcapsule material.

[0004] The supercooling phenomenon is mainly caused by the low thermal conductivity of the microcapsule shell material and slow heat transfer. At present, the supercooling problem is mainly solved through two ways: one way is to use inorganic ceramics and metal materials with high thermal conductivity as the wall material, but this will greatly increase the preparation difficulty and cost of the microcapsules; the other way is to dope inorganic nanoparticles such as inorganic oxides and metals in the shell to enhance the heat transfer rate of the shell, but this can only improve the supercooling phenomenon to a certain extent, and the inorganic nanoparticles are prone to phenomena such as particle agglomeration and falling off from the shell, and even reduce the mechanical properties and encapsulation properties of the microcapsules. In summary, finding a new way to solve the supercooling problem of microcapsules during use is the key research and development direction in the field of microcapsule preparation.

[0005] Isocyanate group-containing silanes are a type of silane coupling agent with two different reactive groups, isocyanate and alkoxy groups, in their molecules. Among them, the isocyanate group exhibits the chemical properties typical of alkyl isocyanates and is highly reactive with active hydrogens (such as hydroxyl, amino, mercapto groups, etc.) in organic polymers. After hydrolysis and crosslinking of the alkoxy groups, good adhesion to the substrate is provided. Utilizing its properties, different types of organic polymers are end-capped and modified, thereby improving the substrate adhesion and water resistance of the resin coating and enhancing the mechanical and anti-aging properties of the product. It is commonly used in industries such as glass fiber-reinforced composites and surface treatment. Currently, no one has used the properties of isocyanate silane coupling agents to solve the problem of supercooling in phase change microcapsules.

[0006] The present invention combines the grafting technology of isocyanate silane coupling agents with the preparation process of phase change microcapsules, effectively reducing the supercooling phenomenon during the use of microcapsules. Isocyanate silane coupling agents are organosilicon compounds containing two different chemically reactive groups. One end of the isocyanate bond is an important component of the shell material, and the hydrolyzable group at the other end undergoes chemical bonding or physical adsorption with the hydroxyl groups on the surface of inorganic nanoparticles, forming an organic adsorption layer on the particle surface. As a result, the modified nanoparticles can be better dispersed in the organic medium, effectively improving their dispersibility and agglomeration phenomenon. Compared with other existing methods, the prepared low-supercooling microcapsule sample (CHNO-g-NPS) has good physical and chemical stability and mechanical strength, and the doped inorganic nanoparticles are not prone to problems such as easy agglomeration and easy shedding, having high practical value. Summary of the Invention

[0007] The present invention provides a low-supercooling phase change microcapsule based on the grafting effect of isocyanate silane coupling agents and its preparation method. The isocyanate silane coupling agent material has two different chemically reactive groups. One chemically reactive group can undergo chemical bonding or physical adsorption with inorganic nanoparticles on their surface, and together with the chemically reactive group at the other end, form the wall material of the highly dense phase change microcapsule. An ultrasonic cell disruptor is used to assist in emulsification to form a stable water-in-oil microemulsion, and a chain extender is added dropwise to the emulsion. The phase change microcapsules obtained by this ultrasonic cell disruptor microemulsion polymerization method have excellent performance.

[0008] To achieve the above object, the specific technical content adopted in the present invention is as follows:

[0009] One aspect of the present invention provides a microcapsule wall material, which is composed of modified nanoparticles obtained by bonding nanoparticles through the grafting action of an isocyanate silane coupling agent; the modified nanoparticles are prepared by the following method: dissolving the isocyanate silane coupling agent in an ethanol aqueous solution with a mass concentration of 5%-10%, adjusting the pH to 3-6, adding inorganic nanoparticles, ultrasonically dispersing evenly, washing with deionized water, and drying at 50°C - 70°C to obtain modified nanoparticles. The mass ratio of the isocyanate silane coupling agent to the ethanol aqueous solution is 2-10:100, and the mass ratio of the isocyanate silane coupling agent to the inorganic nanoparticles is 1-3:10.

[0010] Preferably, the isocyanate silane coupling agent is one or more of 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, and 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

[0011] Preferably, the inorganic nanoparticles in step (1) are one or more of alumina nanoparticles, silica nanoparticles, titanium dioxide nanoparticles, silicon nitride nanoparticles, zinc oxide nanoparticles, or iron nanoparticles.

[0012] Preferably, dissolve the isocyanate silane coupling agent in an ethanol aqueous solution with a mass concentration of 5%-10%, adjust the pH to 3-6 with acetic acid, add inorganic nanoparticles, ultrasonically disperse evenly, wash with deionized water, and dry at 50°C - 70°C to obtain modified nanoparticles.

[0013] The present invention also provides the use of the above microcapsule wall material for preparing low supercooling phase change microcapsules.

[0014] Preferably, the low supercooling phase change microcapsules are prepared using the microcapsule wall material according to the following steps:

[0015] (1) Mix the modified nanoparticles and the organic phase change material in a mass ratio of 1-3:1 at 30-50°C to obtain an oil phase. The organic phase change material is one or more of n-hexadecane, n-octadecane, n-eicosane, or n-tetracosane.

[0016] (2) Mix the emulsifier, dispersant, and deionized water evenly at room temperature to obtain an aqueous phase. The mass ratio of the emulsifier, dispersant, and deionized water is 1:0.15-1.5:50-150.

[0017] (3) Add the oil phase to the aqueous phase and stir in the same direction to assist emulsification to obtain an oil-in-water microemulsion. The mass ratio of the oil phase to the aqueous phase is 1-2:10.

[0018] (4) Add a chain extender dropwise to the microemulsion described in step (3), heat it to 60 - 85°C under mechanical stirring at 400 - 900 rpm in the same direction, continue stirring, and obtain a microcapsule suspension after 5 - 10 h. The volume of the chain extender is 1 - 2% of the volume of the microemulsion, and the chain extender is an alcohol chain extender;

[0019] (5) Centrifuge the microcapsule suspension at 2000 - 5000 rpm, take the upper white solid, wash it with deionized water, filter to remove the liquid, and dry it at 30 - 50°C to obtain the low supercooling phase change microcapsules.

[0020] Preferably, the emulsifier in step (2) is one or more of Tween, sodium dodecylbenzenesulfonate, polyvinyl alcohol, and styrene maleic anhydride copolymer.

[0021] Preferably, the dispersant in step (2) is one or more of gelatin and polyvinylpyrrolidone.

[0022] Preferably, the chain extender in step (4) is one or more of 1,4 - butanediol, 1,6 - butanediol, diethylene glycol, and triethylene glycol.

[0023] Preferably, the preparation method of the low supercooling phase change microcapsules is as follows:

[0024] (1) Mix the modified nanoparticles and the organic phase change material at a mass ratio of 1 - 2.8:1 at 30 - 50°C to obtain an oil phase. The organic phase change material is one of n - hexadecane and n - octadecane;

[0025] (2) Mix the emulsifier, dispersant, and deionized water uniformly at room temperature to obtain an aqueous phase. Among them, the mass ratio of the emulsifier, dispersant, and deionized water is 1:0.15 - 1.5:50 - 125. The emulsifier is one or more of Tween, sodium dodecylbenzenesulfonate, and styrene maleic anhydride copolymer; the dispersant is one or more of gelatin and polyvinylpyrrolidone;

[0026] (3) Add the oil phase to the aqueous phase and stir in the same direction to assist emulsification for 10 - 30 min to obtain an oil - in - water microemulsion. The mass ratio of the oil phase to the aqueous phase is 1 - 1.5:10;

[0027] (4) Add a chain extender dropwise to the microemulsion described in step (3), heat it to 60 - 85°C under mechanical stirring at 450 - 800 rpm, continue stirring for 5 - 10 h to obtain a microcapsule suspension. The volume of the chain extender is 1 - 1.8% of the volume of the microemulsion, and the chain extender is one or more of 1,4 - butanediol, 1,6 - butanediol, diethylene glycol, and triethylene glycol;

[0028] (5) Centrifuge the microcapsule suspension at a speed of 2500 - 4500 rpm, take the upper white solid, wash it twice with deionized water, filter to remove the liquid, and dry it at 35 - 50 °C to obtain the low supercooling phase change microcapsules.

[0029] For the first time, the present invention combines the isocyanate silane coupling technology with the preparation process of phase change microcapsules to prepare low supercooling microcapsules. The isocyanate silane coupling agent contains two different chemically active groups. One end of the chemically active group, the siloxane bond, forms a chemical bond or physical adsorption with the hydroxyl groups on the surface of the nanoparticles, forming an organic adsorption layer on the particle surface. As a result, the modified nanoparticles are better dispersed in the organic medium, effectively improving their agglomeration phenomenon. It effectively avoids the problems of poor dispersibility and easy agglomeration caused by directly adding nanoparticles to the core material or the shell material, as well as the waste of resources and environmental pollution caused by core material leakage due to direct addition. Together with the isocyanate bond at the other end, it forms part of the microcapsule shell material. Under the action of the chain extender and initiator, a network structure gradually forms on the surface of the core material, and the other end is grafted with inorganic nanoparticles, making the microcapsule shell material denser and avoiding environmental pollution caused by core material leakage. Inorganic nanoparticles have excellent thermal conductivity. As a transfer medium between the core material and the outside world, they greatly improve the heat transfer efficiency of the microcapsules. Therefore, when the core material undergoes a phase change, the processes of heat absorption and heat release can be achieved in a timely manner, effectively reducing the supercooling degree of the microcapsules. At the same time, the introduction of inorganic nanoparticles can increase the mechanical strength and physical and chemical stability of the prepared phase change microcapsule shell. In addition, the isocyanate silane coupling agent endows the phase change microcapsules with good water resistance and weather resistance, enriching the functionality of the phase change microcapsule materials.

[0030] The low supercooling phase change microcapsule material prepared by the present invention does not contain components harmful to the human body and the environment, and does not have the potential hazards of flammability, explosiveness, and corrosiveness. During use, it is not prone to releasing substances harmful to the human body and the environment such as formaldehyde and microplastics. The preparation method described in the present invention does not involve rare and expensive raw materials, does not involve extreme, harsh, and complex process conditions, and no toxic substances and substances requiring special treatment are generated during the preparation process. The above characteristics of the present invention meet the requirements of safety, green environmental protection in industrial production and have high industrial application value. Specific Embodiments

[0031] The implementation scheme of the present invention will be described in detail below in combination with embodiments, and the advantages and features of the present invention will become clearer with the description. The following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Those skilled in the art should understand that without departing from the spirit and scope of the present invention, the details and forms of the technical solution of the present invention can be modified or replaced, but these modifications and replacements all fall within the protection scope of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0032] Example 1

[0033] Mix 2 g of 3-isocyanatopropyltriethoxysilane with 60 g of an ethanol aqueous solution with a mass concentration of 5%, adjust the pH to 3.5 with acetic acid, add 8 g of alumina nanoparticles, perform ultrasonic dispersion for 1 h, wash three times with deionized water, and dry at 50 °C to obtain modified nanoparticles.

[0034] Stir 3 g of modified alumina nanoparticles and 3 g of n-hexadecane at 30 °C to form an oil phase. Weigh 0.5 g of sodium dodecylbenzenesulfonate, 0.15 g of gelatin and 50 g of deionized water and stir to form an aqueous phase. Add the oil phase to the aqueous phase, stir in the same direction, and use an ultrasonic cell disruptor to ultrasonicate for 10 min to form 56.65 ml of an oil-in-water microemulsion. Then add 1 ml of 1,4-butanediol, raise the temperature to 65 °C at a mechanical stirring speed of 500 rpm, and react for 5 h to obtain a microcapsule suspension. Centrifuge the microcapsule suspension at 2500 rpm, take the upper white solid, wash it twice with deionized water, filter to remove the liquid, and dry it at 35 °C to obtain phase change microcapsules. The melting temperature of the obtained microcapsules is 18.51 °C, the melting enthalpy value is 81.98 J / g, the crystallization enthalpy value is 80.54 J / g, the crystallization temperature is 13.78 °C, and the supercooling degree is only 4.73 °C; the thermal conductivity of the microcapsules is 0.2474 W / m·k; the compressive strength of the microcapsules is 6 - 12 kg / cm 2 。

[0035] Example 2

[0036] Mix 2.2 g of 3-isocyanatopropyltriethoxysilane with 60 g of an ethanol aqueous solution with a mass concentration of 6%, adjust the pH to 4.2 with acetic acid, add 9 g of silicon nitride nanoparticles, perform ultrasonic dispersion for 2 h, wash three times with deionized water, and dry at 55 °C to obtain modified nanoparticles.

[0037] 3.5 g of modified silicon nitride nanoparticles and 3 g of n-octadecane were stirred at 40 °C to form an oil phase. 0.55 g of Tween 80, 0.11 g of gelatin, and 60 g of deionized water were weighed and stirred to form an aqueous phase. The oil phase was added to the aqueous phase, and stirred in the same direction. The mixture was sonicated for 15 min with an ultrasonic cell disruptor to form 67.16 ml of microemulsion. Subsequently, 1.2 ml of 1,6-butanediol was added, and the mechanical stirring speed was 600 rpm. The temperature was raised to 70 °C and reacted for 6 h to obtain a microcapsule suspension. The microcapsule suspension was centrifuged at 3000 rpm, and the upper white solid was taken, washed twice with deionized water, filtered to remove the liquid, and dried at 40 °C to obtain phase change microcapsules. The melting temperature of the obtained microcapsules was 28.55 °C, the melting enthalpy value was 213.10 J / g, the crystallization enthalpy value was 215.11 J / g, the crystallization temperature was 24.99 °C, and the supercooling degree was only 3.56 °C; the thermal conductivity of the microcapsules was 0.2592 W / m·k; the compressive strength of the microcapsules was 5.2 - 11.3 kg / cm 2 。

[0038] Example 3

[0039] 3 g of 3-isocyanatopropyltrimethoxysilane was mixed with 80 g of an ethanol aqueous solution with a mass concentration of 6%. The pH was adjusted to 4.5 with acetic acid, 10 g of titanium dioxide nanoparticles were added, and ultrasonic dispersion was carried out for 4 h. It was washed three times with deionized water and dried at 60 °C to obtain modified nanoparticles.

[0040] 4 g of modified titanium dioxide nanoparticles and 3 g of n-hexadecane were stirred at 50 °C to form an oil phase. 0.9 g of sodium dodecylbenzenesulfonate, 0.95 g of polyvinylpyrrolidone, and 70 g of deionized water were weighed and stirred to form an aqueous phase. The oil phase was added to the aqueous phase, and stirred in the same direction. The mixture was sonicated for 20 min with an ultrasonic cell disruptor to form 78.55 ml of oil-in-water microemulsion. Subsequently, 1.4 ml of diethylene glycol was added, and the mechanical stirring speed was 700 rpm. The temperature was raised to 70 °C and reacted for 8 h to obtain a microcapsule suspension. The microcapsule suspension was centrifuged at 3500 rpm, and the upper white solid was taken, washed twice with deionized water, filtered to remove the liquid, and dried at 50 °C to obtain phase change microcapsules. The melting temperature of the obtained microcapsules was 18.76 °C, the melting enthalpy value was 78.79 J / g, the crystallization enthalpy value was 80.42 J / g, the crystallization temperature was 13.81 °C, and the supercooling degree was only 4.95 °C; the thermal conductivity of the microcapsules was 0.2615 W / m·k; the compressive strength of the microcapsules was 6.1 - 13.3 kg / cm 2 。

[0041] Example 4

[0042] 5 g of 3-isocyanatopropyltrimethoxysilane was mixed with 90 g of an 8% ethanol aqueous solution by mass. The pH was adjusted to 5.3 with acetic acid, 18 g of zinc oxide nanoparticles were added, and ultrasonic dispersion was carried out for 3 h. After washing three times with deionized water, drying at 70 °C gave the modified nanoparticles.

[0043] 6 g of the modified zinc oxide nanoparticles and 3 g of n-eicosane were stirred at 40 °C to form an oil phase. 1 g of styrene maleic anhydride copolymer, 0.35 g of gelatin and 100 g of deionized water were weighed and stirred to form an aqueous phase. The oil phase was added to the aqueous phase, and stirring was carried out in the same direction. Ultrasonic cell disruptor was used for ultrasonic treatment for 20 min to form 110.35 ml of oil-in-water microemulsion. Subsequently, 1.1 ml of 1,4-butanediol was added, and the mechanical stirring speed was 800 rpm. The temperature was raised to 75 °C and the reaction was carried out for 7 h to obtain a microcapsule suspension. The microcapsule suspension was centrifuged at 4000 rpm, and the upper white solid was taken, washed twice with deionized water, the liquid was filtered off, and drying at 50 °C gave the phase change microcapsules. The melting temperature of the obtained microcapsules was 36.86 °C, the melting enthalpy value was 175.52 J / g, the crystallization enthalpy value was 176.43 J / g, the crystallization temperature was 32.16 °C, and the supercooling degree was only 4.7 °C; the thermal conductivity of the microcapsules was 0.2911 W / m·k; the compressive strength of the microcapsules was 5.5 - 10.3 kg / cm 2 。

[0044] Example 5

[0045] 6 g of 3-isocyanatopropyltriethoxysilane was mixed with 90 g of an 8% ethanol aqueous solution by mass. The pH was adjusted to 5.3 with acetic acid, 25 g of zinc oxide nanoparticles were added, and ultrasonic dispersion was carried out for 5 h. After washing three times with deionized water, drying at 65 °C gave the modified nanoparticles.

[0046] 6 g of modified silicon nitride nanoparticles and 3 g of n - eicosane were stirred at 45 °C to form an oil phase. 1.5 g of styrene - maleic anhydride copolymer, 0.8 g of gelatin and 90 g of deionized water were weighed and stirred to form an aqueous phase. The oil phase was added to the aqueous phase and stirred in the same direction. Then, it was ultrasonicated for 30 min with an ultrasonic cell disruptor to form 101.3 ml of oil - in - water microemulsion. Subsequently, 1.1 ml of 1,4 - butanediol was added, and the mechanical stirring speed was 800 rpm while heating to 75 °C and reacting for 7 h to obtain a microcapsule suspension. The microcapsule suspension was centrifuged at 4300 rpm, and the upper white solid was taken, washed twice with deionized water, filtered to remove the liquid, and dried at 45 °C to obtain phase - change microcapsules. The melting temperature of the obtained microcapsules was 36.56 °C, the melting enthalpy value was 174.41 J / g, the crystallization enthalpy value was 175.34 J / g, the crystallization temperature was 32.25 °C, and the supercooling degree was only 4.31 °C; the thermal conductivity of the microcapsules was 0.2891 W / m·k; the compressive strength of the microcapsules was 5.4 - 10.6 kg / cm 2 。

[0047] Example 6

[0048] 6 g of 3 - isocyanatopropyltriethoxysilane was mixed with 80 g of an ethanol aqueous solution with a mass concentration of 9%. The pH was adjusted to 4.5 with acetic acid, 20 g of zinc oxide nanoparticles were added, and ultrasonic dispersion was carried out for 4 h. Then it was washed three times with deionized water and dried at 55 °C to obtain modified nanoparticles.

[0049] 7.5 g of modified zinc oxide nanoparticles and 3 g of n - octadecane were stirred at 50 °C to form an oil phase. 0.75 g of Tween 80, 0.15 g of gelatin and 80 g of deionized water were weighed and stirred to form an aqueous phase. The oil phase was added to the aqueous phase and stirred in the same direction. Then, it was ultrasonicated for 25 min with an ultrasonic cell disruptor to form 91.4 ml of microemulsion. Subsequently, 1.2 ml of 1,6 - butanediol was added, and the mechanical stirring speed was 700 rpm while heating to 70 °C and reacting for 6 h to obtain a microcapsule suspension. The microcapsule suspension was centrifuged at 2500 rpm, and the upper white solid was taken, washed twice with deionized water, filtered to remove the liquid, and dried at 40 °C to obtain phase - change microcapsules. The melting temperature of the obtained microcapsules was 28.55 °C, the melting enthalpy value was 211.12 J / g, the crystallization enthalpy value was 213.02 J / g, the crystallization temperature was 24.89 °C, and the supercooling degree was only 3.66 °C; the thermal conductivity of the microcapsules was 0.2589 W / m·k; the compressive strength of the microcapsules was 5.1 - 11.1 kg / cm 2 。

[0050] Example 7

[0051] 8.8 g of 3-isocyanatopropyltrimethoxysilane was mixed with 110 g of an aqueous ethanol solution with a mass concentration of 10%. The pH was adjusted to 3.6 with acetic acid. 30 g of alumina nanoparticles were added, and ultrasonic dispersion was carried out for 1 h. It was washed three times with deionized water and dried at 70 °C to obtain modified nanoparticles.

[0052] 8 g of modified iron nanoparticles and 3 g of n-hexadecane were stirred at 50 °C to form an oil phase. 1 g of sodium dodecylbenzenesulfonate, 1.5 g of polyvinylpyrrolidone and 120 g of deionized water were weighed and stirred to form an aqueous phase. The oil phase was added to the aqueous phase, and stirred in the same direction. The ultrasonic cell disruptor was used for ultrasonic treatment for 22 min to form 133.5 ml of oil-in-water microemulsion. Subsequently, 2.4 ml of 1,4-butanediol was added, and the mechanical stirring speed was 750 rpm and the temperature was raised to 70 °C, and the reaction was carried out for 6 h. The microcapsule suspension was centrifuged at 4500 rpm, and the upper white solid was taken, washed 2 times with deionized water, the liquid was filtered off, and dried at 50 °C to obtain phase change microcapsules. The melting temperature of the obtained microcapsules was 18.42 °C, the melting enthalpy value was 81.68 J / g, the crystallization enthalpy value was 82.14 J / g, the crystallization temperature was 13.81 °C, and the supercooling degree was only 4.61 °C; the thermal conductivity of the microcapsules was 0.2462 W / m·k; the compressive strength of the microcapsules was 6 - 12 kg / cm 2 。

[0053] Comparative Example 1:

[0054] 10 g of titanium dioxide nanoparticles were added to 150 g of deionized water, the pH was adjusted to 4 with acetic acid, and ultrasonic dispersion was carried out for 1 h. Subsequently, 2 g of KH570 was added, the stirring rate was 1000 rpm, and it was heated in a water bath at 60 °C for 2 h. It was washed 2 times with deionized water and dried at room temperature to obtain modified nanoparticles. 3 g of styrene, 2.5 g of n-octadecane, 0.8 g of pentaerythritol triacrylate and 0.04 g of azobisisobutyronitrile were stirred at 40 °C to form an oil phase. 1.5 g of Tween 80 and 50 g of deionized water were weighed and stirred at room temperature to form an aqueous phase. The oil phase was slowly added to the aqueous phase, and stirred at 1500 rpm in the same direction for 15 min to form an oil-in-water microemulsion. The microcapsule suspension was centrifuged at 5000 rpm, and the upper white solid was taken, washed 2 times with deionized water, the liquid was filtered off, and dried at 50 °C to obtain phase change microcapsules. The melting temperature of the obtained microcapsules was 28.95 °C, the melting enthalpy value was 175.22 J / g, the crystallization enthalpy value was 176.52 J / g, the crystallization temperature was 22.61 °C, and the supercooling degree was only 6.34 °C; the thermal conductivity of the microcapsules was 0.2152 W / m·k; the compressive strength of the microcapsules was 4.2 - 9.4 kg / cm 2 。

[0055] Comparative Example 2:

[0056] 8 g of alumina nanoparticles were added to 180 g of deionized water, and the pH was adjusted to 4.5 with acetic acid. After ultrasonic dispersion for 2 h, 1.8 g of KH550 was added, and the stirring rate was 800 rpm. The mixture was heated in a water bath at 70 °C for 2 h, washed twice with deionized water, and dried at room temperature to obtain modified nanoparticles. 3 g of styrene, 2.5 g of n-hexadecane, 0.9 g of pentaerythritol triacrylate, and 0.06 g of azobisisobutyronitrile were stirred at 40 °C to form an oil phase. 2 g of Tween 80 and 50 g of deionized water were weighed and stirred at room temperature to form an aqueous phase. The oil phase was slowly added to the aqueous phase, and the mixture was stirred in the same direction at a rate of 2000 rpm for 15 min to form an oil-in-water microemulsion. The microcapsule suspension was centrifuged at 5000 rpm, and the upper white solid was taken, washed twice with deionized water, filtered to remove the liquid, and dried at 50 °C to obtain phase change microcapsules. The melting temperature of the obtained microcapsules was 18.96 °C, the melting enthalpy value was 77.19 J / g, the crystallization enthalpy value was 78.42 J / g, the crystallization temperature was 11.81 °C, and the supercooling degree was only 7.15 °C; the thermal conductivity of the microcapsules was 0.2085 W / m·k; the compressive strength of the microcapsules was 3.1 - 8.9 kg / cm 2 .

[0057] The applicant declares that the present invention uses the above embodiments to illustrate a low supercooling degree phase change microcapsule based on the grafting effect of isocyanate silane coupling agent and its preparation method. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the products of the present invention, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A microcapsule wall material, characterized in that: The microcapsule wall material is a modified nanoparticle bonded by nanoparticles through the grafting action of an isocyanate silane coupling agent; the modified nanoparticle is prepared by the following method: dissolving the isocyanate silane coupling agent in an ethanol aqueous solution with a mass concentration of 5%-10%, adjusting the pH to 3-6, adding inorganic nanoparticles, dispersing evenly, washing, and drying to obtain the modified nanoparticles, wherein the mass ratio of the isocyanate silane coupling agent to the ethanol aqueous solution is 2-10:100, and the mass ratio of the isocyanate silane coupling agent to the inorganic nanoparticle is 1-3:

10.

2. The microcapsule wall material according to claim 1, characterized in that The isocyanate silane coupling agent is one or more of 3-isocyanate propyl triethoxy silane, 3-isocyanate propyl trimethoxy silane and 1,3,5-tris (trimethoxysilyl propyl) isocyanurate.

3. The microcapsule wall material according to claim 1, characterized in that: The inorganic nanoparticles in step (1) are one or more of aluminum oxide nanoparticles, silicon dioxide nanoparticles, titanium dioxide nanoparticles, silicon nitride nanoparticles, zinc oxide nanoparticles or iron nanoparticles.

4. The microcapsule wall material according to claim 1, characterized in that The isocyanate silane coupling agent is dissolved in an ethanol aqueous solution with a mass concentration of 5%-10%, the pH is adjusted to 3-6 with acetic acid, inorganic nanoparticles are added, ultrasonically dispersed evenly, washed with deionized water, and dried at 50-70°C to obtain modified nanoparticles.

5. Use of the microcapsule wall material according to claim 1 for preparing low supercooling phase change microcapsules.

6. The use according to claim 4, characterized in that The low supercooling phase change microcapsules are prepared by using the microcapsule wall material according to the following steps: (1) mixing the microcapsule wall material and the organic phase change material at a mass ratio of 1-3:1 at 30-50° C. to obtain an oil phase, wherein the organic phase change material is one or more of n-hexadecane, n-octadecane or n-eicosane; (2) uniformly mixing an emulsifier, a dispersant and deionized water at room temperature to prepare an aqueous phase, wherein the mass ratio of the emulsifier, the dispersant and the deionized water is 1:0.15-1.5:50-150; (3) adding the oil phase to the water phase, stirring in the same direction to assist emulsification, to obtain an oil-in-water microemulsion, wherein the mass ratio of the oil phase to the water phase is 1-2:10; (4) adding a chain extender dropwise to the microemulsion described in step (3), heating to 60-85° C. under mechanical stirring at 400-900 rpm in the same direction, and continuing stirring to obtain a microcapsule suspension after 5-10 hours, wherein the volume of the chain extender is 1-2% of the volume of the microemulsion, and the chain extender is an alcohol chain extender; (5) The microcapsule suspension is centrifuged at 2000-5000 rpm, the upper white solid is taken, washed with deionized water, filtered to remove the liquid, and dried at 30-50° C. to obtain the low supercooling phase change microcapsules.

7. The use according to claim 6, characterized in that The emulsifier in step (2) is one or more of Tween, sodium dodecylbenzene sulfonate, polyvinyl alcohol, and styrene maleic anhydride copolymer.

8. The use according to claim 6, characterized in that The dispersant in step (2) is one or more of gelatin or polyvinyl pyrrolidone.

9. The use according to claim 6, characterized in that The chain extender described in step (4) is one or more of 1,4-butanediol, 1,6-butanediol, diethylene glycol or triethylene glycol.

10. The method according to claim 6, characterized in that The preparation method of the low supercooling phase change microcapsules is as follows: (1) uniformly mixing the modified nanoparticles and an organic phase change material at a mass ratio of 1-2.8:1 at 30-50° C. to obtain an oil phase, wherein the organic phase change material is one of n-hexadecane and n-octadecane; (2) uniformly mixing an emulsifier, a dispersant and deionized water at room temperature to obtain an aqueous phase, wherein the mass ratio of the emulsifier, the dispersant and the deionized water is 1:0.15-1.5:50-125, the emulsifier is one or more of Tween, sodium dodecylbenzene sulfonate and styrene maleic anhydride copolymer; the dispersant is one or more of gelatin and polyvinyl pyrrolidone; (3) adding the oil phase to the water phase, stirring in the same direction to assist emulsification for 10-30 minutes to obtain an oil-in-water microemulsion, wherein the mass ratio of the oil phase to the water phase is 1-1.5:10; (4) adding a chain extender dropwise to the microemulsion described in step (4), heating the mixture to 65-80° C. under mechanical stirring at 450-800 rpm, and continuing stirring for 5-10 hours to obtain a microcapsule suspension, wherein the volume of the chain extender is 1-1.8% of the volume of the microemulsion, and the chain extender is one or more of 1,4-butanediol, 1,6-butanediol, diethylene glycol, or triethylene glycol; (5) The microcapsule suspension is centrifuged at 2500-4500 rpm, the upper white solid is taken, washed twice with deionized water, filtered to remove the liquid, and dried at 35-50° C. to obtain the low supercooling phase change microcapsules.