A method for preparing high thermal conductivity phase change microcapsules and their application in nylon materials.

Abstract

This invention discloses a method for preparing high thermal conductivity phase change microcapsules and their application in nylon materials. Diisocyanate and inorganic thermally conductive nanoparticles are dispersed in an organic phase change material to obtain an oil phase solution. The oil phase solution is added to water, ultrasonically emulsified, and then a silane coupling agent is added. The mixture is heated to 50-70°C and ultrasonically treated with stirring for 4-12 hours. After homogenization and emulsification, a Pickering emulsion is obtained. A diamine is added to the Pickering emulsion, heated to 35-55°C, and stirred for 2-8 hours. The mixture is then filtered, washed, and dried to obtain high thermal conductivity phase change microcapsules. This invention obtains Pickering particles by interfacial grafting of thermally conductive nanoparticles in an organic phase change material with a silane coupling agent. The interfacial polymerization of diisocyanate and polyamine on the surface of the phase change material droplets is achieved through the Pickering emulsion method. Phase change microcapsules with good thermal conductivity and heat storage properties can be obtained without the addition of additional emulsifiers. Furthermore, the large number of amine and acyl groups on the wall material exhibits particularly excellent compatibility and adhesion to nylon materials.

Description

Technical Field

[0001] This invention relates to the field of functional phase change energy storage materials, and in particular to a method for preparing high thermal conductivity phase change microcapsules and their application in nylon materials. Background Technology

[0002] Nylon is currently the most produced, widely used, and diverse of the five major engineering plastics. Due to the strong hydrogen bonds between its amide groups, it possesses a high melting point and maintains excellent strength and stiffness even at high temperatures, making it widely used in the automotive, electronics, textile machinery, and chemical industries. However, as market demands for material performance increase, functionalization is being sought in addition to the inherent properties of polymer materials. As one of the most widely used engineering plastics, improving the thermal conductivity of nylon is a crucial research direction to adapt to market development.

[0003] Phase change materials (PCMs) possess large latent heat and heat storage density, attracting significant attention due to their ability to store and release substantial latent heat during isothermal phase transitions. Among them, organic PCMs (especially solid-liquid PCMs) are currently the most widely used due to their non-toxicity, stable physicochemical properties, and non-corrosiveness. However, they suffer from drawbacks such as low thermal conductivity, volume expansion during phase transition, and high leakage, limiting their application in certain fields. Microencapsulation technology can effectively isolate PCMs from their surroundings, delay potential reactions with the environment, increase heat transfer area, control volume changes caused by phase transitions, and exhibit excellent thermal and mechanical stability. However, the wall materials used to prepare microcapsules are mostly organic polymers or biopolymers, resulting in low thermal conductivity of PCM microcapsules, severely limiting their application.

[0004] Introducing inorganic thermally conductive nanoparticles into microcapsule wall materials is one of the effective methods to improve the thermal conductivity of microcapsules. Chinese patent CN113881404 A discloses an organic phase change microcapsule with high encapsulation rate, high thermal conductivity, and high thermal cycling stability, and its preparation method. Modified silicon nitride is introduced into a polymethyl methacrylate (PCM) shell material, resulting in thermally conductive microcapsules with an encapsulation rate of over 82.5% and an increase in thermal conductivity of over 50%. However, to achieve better compatibility with the polymer wall material and solve the distribution problem of thermally conductive particles in the PCM, the preparation process becomes complex. Furthermore, these methods use large amounts of surfactants, which can cause environmental pollution. Summary of the Invention

[0005] Based on the above problems, the purpose of this invention is to provide a method for preparing high thermal conductivity phase change microcapsules and their application in nylon materials.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing high thermal conductivity phase change microcapsules includes the following steps:

[0008] S1. Take 15-30 parts by weight of diisocyanate and 1.5-3 parts by weight of inorganic thermally conductive nanoparticles and disperse them in 70-85 parts by weight of organic phase change material to obtain an oil phase solution;

[0009] S2. Add 10-20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, emulsify by ultrasonication under stirring, add 3-8 parts by weight of silane coupling agent, heat to 50-70°C, and sonicate under continuous stirring for 4-12 hours. Cool to room temperature and obtain Pickering emulsion after homogenization.

[0010] S3. Add 5-20 parts by weight of diamine to the Pickering emulsion prepared in step S2, heat to 35-55°C, stir and react for 2-8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

[0011] The diisocyanate in step S1 is one or a combination of several of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI).

[0012] The inorganic thermally conductive nanoparticles in step S1 are one or a combination of graphene, carbon nanotubes, and boron nitride.

[0013] The organic phase change material in step S1 is one or a combination of several of n-octadecane, paraffin, and stearate.

[0014] The silane coupling agent in step S2 is one or a combination of several of KH550, KH560, KH570, and KH580.

[0015] The diamine in step S3 is one or a combination of several of ethylenediamine (EDA), diethanolamine (DEA), hexamethylenediamine (HMDA), and diethylenetriamine (DETA).

[0016] In step S2, the stirring rate for homogenization and emulsification is 1000-3000 rpm, the ultrasonic frequency is 20 kHz, and the power is 400 W.

[0017] The high thermal conductivity phase change microcapsules can be used to prepare phase change nylon materials or fabrics.

[0018] The present invention employs the above technical solution, which involves interfacial grafting of thermally conductive nanoparticles in organic phase change materials (oil phase) with silane coupling agents to obtain Pickering particles, and then using the Pickering emulsion method to achieve interfacial polymerization of diisocyanate and polyamine on the surface of phase change material droplets to form the wall material of phase change microcapsules, thereby encapsulating the phase change material.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention modifies thermally conductive nanoparticles using a one-pot method and uses them as a Pickering emulsion stabilizer and a thermal conductivity enhancer for microcapsules, obtaining phase change microcapsules with good thermal conductivity and heat storage properties without the need for additional emulsifiers.

[0021] 2. The phase change microcapsules prepared by this invention have high mechanical strength, good chemical stability, and good heat resistance. The large number of amine and acyl groups on their wall material have particularly excellent compatibility and adhesion to nylon materials.

[0022] 3. The preparation method of this invention is simple, the raw material cost is low, it is suitable for continuous production, and it has high application value. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the embodiments.

[0024] Example 1

[0025] (1) Preparation of high thermal conductivity phase change microcapsules

[0026] S1. Take 20 parts by weight of MDI and 3 parts by weight of boron nitride nanoparticles and disperse them in 80 parts by weight of n-octadecane to obtain an oil phase solution;

[0027] S2. Add 20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, and emulsify by ultrasonication under stirring. Add 5 parts by weight of KH560, heat to 70℃, and sonicate under continuous stirring for 8 hours. Cool to room temperature and homogenize under stirring speed of 1500 rpm, ultrasonic frequency of 20 kHz, and power of 400 W to obtain Pickering emulsion.

[0028] S3. Add 5 parts by weight of DEA to the Pickering emulsion prepared in step S2, heat to 35°C, stir and react for 8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

[0029] (2) Preparation of phase change nylon fibers using high thermal conductivity phase change microcapsules

[0030] Weigh out 100 parts PA66, 10 parts high thermal conductivity phase change microcapsules, and 3 parts POE-g-MAH by weight; melt-blend and spin each component to obtain phase change nylon fiber.

[0031] Example 2

[0032] (1) Preparation of high thermal conductivity phase change microcapsules

[0033] S1. Take 20 parts by weight of IPDI and 3 parts by weight of boron nitride nanoparticles and disperse them in 80 parts by weight of n-octadecane to obtain an oil phase solution;

[0034] S2. Add 20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, and emulsify by ultrasonication under stirring. Add 5 parts by weight of KH550, heat to 70°C, and sonicate under continuous stirring for 8 hours. Cool to room temperature and homogenize under stirring speed of 1500 rpm, ultrasonic frequency of 20 kHz, and power of 400 W to obtain Pickering emulsion.

[0035] S3. Add 12 parts by weight of DETA to the Pickering emulsion prepared in step S2, heat to 35 °C and stir for 8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

[0036] (2) Preparation of phase change nylon fibers using high thermal conductivity phase change microcapsules

[0037] Weigh 100 parts PA66, 20 parts high thermal conductivity phase change microcapsules, and 3 parts POE-g-MAH by weight; melt-blend and spin each component to obtain the phase change nylon fiber.

[0038] Example 3

[0039] (1) Preparation of high thermal conductivity phase change microcapsules:

[0040] S1. Take 30 parts by weight of IPDI and 5 parts by weight of boron nitride nanoparticles and disperse them in 70 parts by weight of n-octadecane to obtain an oil phase solution;

[0041] S2. Add 20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, and emulsify by ultrasonication under stirring. Add 5 parts by weight of KH560, heat to 70°C, and sonicate under continuous stirring for 8 hours. Cool to room temperature and homogenize under stirring speed of 1500 rpm, ultrasonic frequency of 20 kHz, and power of 400 W to obtain Pickering emulsion.

[0042] S3. Add 15 parts by weight of DETA to the Pickering emulsion prepared in step S2, heat to 35°C, stir and react for 8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

[0043] (2) Preparation of phase change nylon fibers using high thermal conductivity phase change microcapsules

[0044] Weigh 100 parts PA66, 30 parts high thermal conductivity phase change microcapsules, and 3 parts POE-g-MAH by weight; melt-blend and spin each component to obtain the phase change nylon fiber.

[0045] Example 4

[0046] Preparation of high thermal conductivity phase change microcapsules:

[0047] S1. Take 30 parts by weight of IPDI and 5 parts by weight of boron nitride nanoparticles and disperse them in 70 parts by weight of paraffin to obtain an oil phase solution;

[0048] S2. Add 20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, and emulsify by ultrasonication under stirring. Add 5 parts by weight of KH560, heat to 70°C, and sonicate under continuous stirring for 8 hours. Cool to room temperature and homogenize under stirring speed of 1500 rpm, ultrasonic frequency of 20 kHz, and power of 400 W to obtain Pickering emulsion.

[0049] S3. Add 15 parts by weight of DETA to the Pickering emulsion prepared in step S2, heat to 35°C, stir and react for 8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

[0050] Example 5

[0051] Preparation of high thermal conductivity phase change microcapsules:

[0052] S1. Take 30 parts by weight of IPDI and 5 parts by weight of boron nitride nanoparticles and disperse them in 70 parts by weight of dodecyl stearate to obtain an oil phase solution;

[0053] S2. Add 20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, and emulsify by ultrasonication under stirring. Add 5 parts by weight of KH560, heat to 70°C, and sonicate under continuous stirring for 8 hours. Cool to room temperature and homogenize under stirring speed of 1500 rpm, ultrasonic frequency of 20 kHz, and power of 400 W to obtain Pickering emulsion.

[0054] S3. Add 15 parts by weight of DETA to the Pickering emulsion prepared in step S2, heat to 35°C, stir and react for 8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

[0055] Comparative Example 1

[0056] (1) Preparation of phase change microcapsules

[0057] S1. Take 20 parts by weight of IPDI and 5 parts by weight of boron nitride nanoparticles and disperse them in 80 parts by weight of n-octadecane to obtain an oil phase solution;

[0058] S2. Add 20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of deionized water, add 2 parts by weight of emulsifier polyvinyl alcohol (PVA), and ultrasonically emulsify under stirring. Heat to 70°C and ultrasonically treat for 8 hours under continuous stirring. Cool to room temperature and homogenize under stirring speed of 1500 rpm, ultrasonic frequency of 20 kHz and power of 400 W to obtain an oil-in-water emulsion.

[0059] S3. Add 12 parts by weight of DETA to the emulsion prepared in step S2, heat to 35°C, stir and react for 8 hours. After the reaction is completed, filter, wash and dry to obtain phase change microcapsules.

[0060] In step S2, the stirring rate for homogenization and emulsification is 1500 rpm, and the ultrasonic power is 20 kHz and 400 W.

[0061] Compared with Examples 1-5, Comparative Example 1 requires the addition of an emulsifier but does not add a silane coupling agent during the preparation of phase change microcapsules.

[0062] (2) Preparation of phase change nylon fibers:

[0063] Weigh 100 parts PA66, 10 parts phase change microcapsules, and 3 parts POE-g-MAH by weight; melt-blend and spin the components to obtain the phase change nylon fiber.

[0064] The performance test results of the phase change microcapsules prepared in Examples 1-5 and Comparative Example 1 are shown in Table 1.

[0065] Table 1. Test results of phase change microcapsules

[0066]

[0067] The performance test results of the nylon materials prepared in Examples 1-3 and Comparative Example 1 are shown in Table 2.

[0068] Table 2. Performance test results of phase change microencapsulated nylon materials

[0069]

[0070] As shown in Table 1, the high thermal conductivity phase change microcapsules provided by this invention exhibit phase change temperatures between 27-44℃, depending on the phase change material, which is suitable for human body temperature regulation. The phase change enthalpy is between 87-170 J / g, indicating high latent heat of phase change, making them widely applicable to various textile fibers. In Comparative Example 1, an emulsifier needs to be added during the preparation of the phase change microcapsules. In contrast, Examples 1-5 of this invention use a silane coupling agent to perform interfacial grafting of thermally conductive nanoparticles in the organic phase change material (oil phase) to obtain Pickering particles. The Pickering emulsion method is then used to achieve interfacial polymerization of diisocyanate and polyamine on the surface of the phase change material droplets, forming the wall material of the phase change microcapsules and encapsulating the phase change material. Due to the Pickering emulsifier modification of the thermally conductive filler nano-boron nitride (without the need for additional emulsifier), it is dispersed at the oil-water interface due to interfacial tension. This not only acts as an emulsifier but also achieves uniform dispersion of the thermally conductive filler, resulting in a decrease in the average particle size of the microcapsules and an increase in thermal conductivity (Examples 1, 2, 3 vs. Comparative Example 1).

[0071] The high thermal conductivity phase change microcapsules of the present invention were applied to nylon melt spinning. As can be seen from the results in Table 2, the heat absorption and heat storage performance of nylon fibers is improved with the increase of microcapsule dosage. However, when the dosage exceeds a certain proportion (30% in Example 3), the strength of the fibers decreases significantly. This may be due to the high shear force during melt blending causing the microcapsule walls to break and the phase change core material to leak into the nylon matrix.

[0072] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing high thermal conductivity phase change microcapsules, characterized in that, Includes the following steps: S1. Take 15-30 parts by weight of diisocyanate and 1.5-3 parts by weight of inorganic thermally conductive nanoparticles and disperse them in 70-85 parts by weight of organic phase change material to obtain an oil phase solution; The inorganic thermally conductive nanoparticles are one or a combination of graphene, carbon nanotubes, and boron nitride. S2. Add 10-20 parts by weight of the oil phase solution prepared in step S1 to 100 parts by weight of water, emulsify by ultrasonication under stirring, add 3-8 parts by weight of silane coupling agent, heat to 50-70℃, sonicate under continuous stirring for 4-12 hours, cool to room temperature, and obtain Pickering emulsion after homogenization. The silane coupling agent is one or a combination of several of KH550, KH560, KH570, and KH580; S3. Add 5-20 parts by weight of diamine to the Pickering emulsion prepared in step S2, heat to 35-55℃, stir and react for 2-8 hours. After the reaction is completed, filter, wash and dry to obtain high thermal conductivity phase change microcapsules.

2. The method for preparing a high thermal conductivity phase change microcapsule according to claim 1, characterized in that, The diisocyanate in step S1 is one or a combination of several of diphenylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

3. The method for preparing a high thermal conductivity phase change microcapsule according to claim 1, characterized in that, The organic phase change material in step S1 is one or a combination of several of n-octadecane, paraffin, and stearate.

4. The method for preparing a high thermal conductivity phase change microcapsule according to claim 1, characterized in that, The diamine in step S3 is one or a combination of several of ethylenediamine, diethanolamine, hexamethylenediamine, and diethylenetriamine.

5. The method for preparing a high thermal conductivity phase change microcapsule according to claim 1, characterized in that, In step S2, the stirring rate for homogenization and emulsification is 1000~3000 rpm, the ultrasonic frequency is 20 kHz, and the power is 400 W.

6. A high thermal conductivity phase change microcapsule obtained by the preparation method according to any one of claims 1-5.

7. The application of the high thermal conductivity phase change microcapsules as described in claim 6 in the preparation of phase change nylon materials or fabrics.

Images