Flame-retardant temperature-regulating phase change microcapsules and use thereof in polystyrene foam

Abstract

The present application relates to the field of microcapsules, and discloses a flame-retardant temperature-regulating phase change microcapsule and application thereof in polystyrene foam plastic. The polystyrene foam plastic contains carbon nanotube / magnesium-aluminum layered double hydroxide modified silica coated paraffin phase change microcapsules, the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica wall material has high thermal conductivity, and the magnesium-aluminum layered double hydroxide generates water vapor when decomposed under heat, which dilutes combustible gas, and the decomposition products, silica and carbon nanotubes synergistically promote carbonization to form a dense carbon layer, achieving the effect of flame retardation. When the microcapsules are used as fillers of polystyrene foam plastic, the polystyrene foam plastic has good flame retardation and energy storage temperature regulation effects.

Description

Technical Field

[0001] This invention relates to the field of microcapsules, and more particularly to a flame-retardant temperature-regulating phase change microcapsule and its application in polystyrene foam. Background Technology

[0002] Phase change materials (PCMs), as latent heat storage materials, can maintain their temperature within a certain range by absorbing or releasing latent heat, and are considered a recyclable clean energy material with high energy conversion efficiency. Microencapsulated PCMs are designed to address the leakage problem of PCMs. They are composite PCMs with a core-shell structure, formed by coating the surface of solid-liquid PCM particles with a stable polymer or inorganic material film using microencapsulation technology. Research shows that further surface modification of novel PCM microcapsules with temperature-regulating functions to impart flame-retardant properties, and their incorporation into polymers, not only endows the polymers with temperature-regulating functions but also improves their flame-retardant properties.

[0003] For example, Cheng et al. [Cheng JJ, Niu SS, Kang MY, et al. The thermal behavior and flame retardant performance of phase change material microcapsules with modified carbon nanotubes[J]. Energy, 2022, 240] prepared carbon nanotube / ferric oxide modified polymethyl methacrylate-coated decanoic acid phase change microcapsules and composited them with rigid polyurethane foam. The results showed that the composite material had good temperature regulation performance. However, the shell material of the above-mentioned phase change microcapsule is polymethyl methacrylate, which is a flammable polymer. As the shell of the microcapsule, it will inhibit the further improvement of the flame retardant properties of the microcapsule and the polymer matrix.

[0004] Silica possesses excellent thermal and chemical stability, is readily synthesized through the hydrolysis and condensation of silicone esters, and exhibits a stable and dense structure, making it highly suitable as a shell material for phase change microcapsules. Furthermore, silica is a solid acid that can catalyze polymer degradation, leading to the formation of lower carbon number degradation products. In the presence of metal oxides, these lower carbon number degradation products are more readily catalyzed into char, contributing to improved flame retardant properties of microcapsule composites. However, silica cannot decompose thermally, neither absorbing heat nor generating inert gases to dilute flammable gases, resulting in low flame retardant efficiency. Therefore, synergistic effects with other flame retardants are necessary to enhance the flame retardant properties of the composite material. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a flame-retardant and temperature-regulating phase change microcapsule and its application in polystyrene foam. The polystyrene foam of this invention contains a phase change microcapsule of carbon nanotube / magnesium-aluminum layered double hydroxide modified silica coated with paraffin. The silica wall material modified with carbon nanotube / magnesium-aluminum layered double hydroxide not only possesses high thermal conductivity, but the magnesium-aluminum layered double hydroxide, upon thermal decomposition, generates water vapor to dilute flammable gases. Furthermore, its decomposition products synergistically promote carbonization with silica and carbon nanotubes, forming a dense carbon layer to achieve a flame-retardant effect. Using this as a filler in polystyrene foam imparts excellent flame-retardant and energy-storage temperature-regulating effects to the polystyrene foam.

[0006] The specific technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides a flame-retardant temperature-regulating phase change microcapsule, the preparation method of which includes the following steps:

[0008] (1) Preparation of silica-coated paraffin phase change microcapsules.

[0009] (2) Mix the silica-coated paraffin microcapsules with water in a container and heat and stir. Dissolve magnesium chloride hexahydrate and aluminum chloride hexahydrate in water and add them to the container for reaction. Add ammonia water to continue the reaction. Separate the product to obtain magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0010] (3) The magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules were mixed with anhydrous ethanol in a container and heated and stirred. 3-aminopropyltriethoxysilane was mixed with an alcohol-water solution and stirred before being added dropwise to the container for reaction. A carbon nanotube suspension was added, and an aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added under stirring to continue the reaction. The product was separated to obtain carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0011] The preparation principle of the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules of the present invention is as follows: In step (1), silica-coated paraffin phase change microcapsules are prepared. In step (2), magnesium-aluminum layered double hydroxides are synthesized on the silica surface using electrostatic attraction and in-situ precipitation. When pH > 2.5, silica carries a negative charge, and Mg is attracted to the silica surface by electrostatic force. 2+ And Al 3+ Magnesium-aluminum layered double hydroxides are attracted to the silica surface and aggregate. Then, ammonia is added to the reaction system, and under alkaline conditions, magnesium-aluminum layered double hydroxides are synthesized in situ on the silica surface. 2+ And Al 3+ This makes the layers positively charged, with exchangeable anions (Cl-) between the layers. -With the positive charge balanced by the layers, the magnesium-aluminum layered double hydroxides exhibit a vertical structure distributed on the silica surface. Furthermore, the solvent (water) contains... With Cl, which has low interlayer stability - It readily undergoes ion exchange, and some interlayer pillar-supporting anions are... Based on this, in step (3), 3-aminopropyltriethoxysilane is used to modify the surface of the microcapsules. The silanol bonds of the hydrolysis product of 3-aminopropyltriethoxysilane undergo condensation polymerization with the hydroxyl groups on the surface of the magnesium-aluminum layered double hydroxide. At the same time, self-condensation polymerization occurs between the silanol bonds, coating the surface of the magnesium-aluminum layered double hydroxide, thereby obtaining amino-modified microcapsules. After adding carbon nanotube suspension and aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride reacts with the carboxyl groups on the carbon nanotubes to form an amine-reactive O-acyl isourea intermediate. This intermediate can react with the amino groups on the surface of the modified microcapsules to form amide bonds, finally obtaining carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0012] This invention uses carbon nanotubes / magnesium-aluminum layered double hydroxide modified silica as the wall material to coat paraffin to form microcapsules. The carbon nanotubes form heat transfer channels between the microcapsules, which enables energy to be transferred more quickly inside the paraffin and greatly improves the heat storage rate of the microcapsules.

[0013] Magnesium-aluminum layered double hydroxides can absorb a large amount of heat and generate water vapor when decomposed by heat, reducing the concentration of combustible gases. At the same time, the non-combustible metal oxides produced by the decomposition of the above hydroxides work synergistically with silicon dioxide and carbon nanotubes to promote carbonization and increase the density of the carbon layer, thereby achieving a highly efficient flame retardant effect.

[0014] Preferably, in step (2), the ratio of the amount of silica-coated paraffin microcapsules, water, magnesium chloride hexahydrate, aluminum chloride hexahydrate, and ammonia is (0.5-1)g∶(60-80)ml∶(0.3-0.8)g∶(0.3-0.8)g∶(20-40)ml.

[0015] Preferably, in step (2), the concentration of ammonia water is 0.18 to 0.22 mol / L.

[0016] Preferably, in step (2), the temperature of heating and stirring is 50-60°C.

[0017] Preferably, in step (2), the first reaction takes 3-5 hours and the second reaction takes 1-3 hours.

[0018] In step (2), an ammonia solution diluted to a certain concentration is slowly added dropwise to the reaction system to gradually adjust the pH value. When the pH value is low, Al 3+ First, aluminum hydroxide precipitates on the surface of silica. The colloidal precipitate of aluminum hydroxide has an effect on OH. - Adsorption, accumulation, and induction of Mg 2+ Precipitates on the surface of aluminum hydroxide when the pH is below its individual settling pH, and when the solution pH rises to Mg... 2+ When the alkalinity required for individual sedimentation is reached, magnesium hydroxide precipitates out in large quantities, forming a mixed hydroxide on the silica surface. Further, dehydration and recombination occur between these mixed hydroxides. Based on some of the composite products, during the crystallization stage, adjacent hydroxyl groups in the complex undergo further dehydration and condensation until all the cation octahedral coordinating groups form a closely packed network structure with shared hydroxyl groups. The metal ions in the solution then... and The growth units continuously migrate, adsorb, and associate onto the surface of the complex, thereby increasing the particle size. The specific reaction process is as follows:

[0019]

[0020]

[0021] Al(OH)3·Mg(OH)2→(HO)Mg-O-Al[-O-Mg(OH)]2+2H2O

[0022] (HO)Mg-O-Al[-O-Mg(OH)]2+3H2O→{(HO)Mg-OH-Al[-OH-Mg(OH)]2} 3+ +3OH-

[0023] If the ammonia concentration is too high, it will cause the local pH value in the reaction system to be too high, resulting in rapid and large-scale precipitation of aluminum hydroxide and magnesium hydroxide, preventing the uniform formation of mixed hydroxides on the silica surface. Furthermore, an excessively high pH value will cause unreacted aluminum hydroxide or Al in the -Al-O-Mg-OH complex units to... The form of dissolution hinders the formation of complex hydroxides. If the ammonia concentration is too low, it cannot reach the Mg... 2+ The alkalinity required for individual sedimentation results in a low sedimentation rate for magnesium hydroxide, thereby inhibiting the formation and growth of complex hydroxides.

[0024] Preferably, in step (3), the ratio of the amounts of the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, anhydrous ethanol, 3-aminopropyltriethoxysilane, alcohol-water solution, carbon nanotube suspension, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution is (0.5-1.5)g∶(80-100)ml∶(2-4)ml∶(10-20)ml∶(40-60)ml∶(10-20)ml.

[0025] Preferably, in step (3), the mass ratio of anhydrous ethanol to water in the aqueous alcohol solution is (10-15):(1-1.5); the solid-liquid ratio of carboxylated carbon nanotubes to anhydrous ethanol in the carbon nanotube suspension is 0.1-0.2 g / 40-60 ml; and the concentration of the aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is 0.008-0.012 g / ml.

[0026] In step (3), mixing 3-aminopropyltriethoxysilane with an aqueous alcohol solution is to delay the hydrolysis-condensation reaction, allowing the silanol bonds of the hydrolysis product of 3-aminopropyltriethoxysilane to undergo condensation with the hydroxyl groups on the microcapsule surface, thus modifying its surface with amino groups. Excessive water content will intensify the self-condensation between the silanol bonds of the hydrolysis product, thereby reducing the amino modification effect on the microcapsule surface. Conversely, insufficient water content will lead to incomplete hydrolysis of 3-aminopropyltriethoxysilane, similarly reducing the surface modification effect of the microcapsule.

[0027] Preferably, in step (1), the preparation method of the silica-coated paraffin phase change microcapsules is as follows: paraffin and tetraethyl orthosilicate are mixed, heated and stirred. After the paraffin melts, a formamide solution containing hexadecyltrimethylammonium bromide is added dropwise and stirred to form a microemulsion. Hydrochloric acid solution is added dropwise, and stirring is stopped after the reaction. The product is then aged. The product is separated to obtain silica-coated paraffin phase change microcapsules.

[0028] In step (1), cetyltrimethylammonium bromide (CTAB) is used as an emulsifier, melted paraffin is used as the oil phase, tetraethyl orthosilicate is used as the aqueous phase, and formamide (a non-aqueous medium) is used as the solvent. Under stirring conditions, a stable microemulsion is formed, in which the lipophilic end of CTAB is inserted into the paraffin droplets, and the hydrophilic end is attracted to tetraethyl orthosilicate, forming a micelle system. As hydrochloric acid solution is slowly added, tetraethyl orthosilicate undergoes in-situ hydrolysis and condensation on the surface of the paraffin droplets to form silica. In this way, silica-coated paraffin phase change microcapsules are prepared.

[0029] Preferably, in step (1), the ratio of the amount of paraffin, tetraethyl orthosilicate, hexadecyltrimethylammonium bromide, formamide and hydrochloric acid solution is (5-7g):(5-7)g:(0.75-1.5)g:(100-150)ml:(100-150)ml.

[0030] Secondly, the present invention provides the application of the above-mentioned flame-retardant temperature-regulating phase change microcapsules in the preparation of polystyrene foam: the polystyrene foam comprises the following raw materials in parts by weight: 90-120 parts of polystyrene, 35-45 parts of carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, 5-10 parts of foaming agent, 1-5 parts of nucleating agent, and 1-5 parts of lubricant.

[0031] This invention uses carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules as fillers for polystyrene foam, endowing it with excellent flame retardant properties and temperature regulation functions, greatly improving the functionality and safety of polystyrene foam.

[0032] Preferably, the foaming agent is isobutane and / or n-butane; the nucleating agent is talc and / or citric acid; and the lubricant is glyceryl monostearate.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The polystyrene foam of the present invention contains carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules. The microcapsules use carbon nanotube / magnesium-aluminum layered double hydroxide modified silica as the shell material, which can effectively encapsulate the paraffin phase change material and prevent its leakage. By utilizing its high thermal conductivity and carbon nanotubes as heat transfer channels, the energy storage efficiency of the phase change material is improved. At the same time, the synergistic effect improves the flame retardant performance and increases the safety factor of the polystyrene foam. Attached Figure Description

[0034] Figure 1 A schematic diagram of the preparation mechanism of carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules;

[0035] Figure 2 SEM image of silica-coated paraffin phase change microcapsules;

[0036] Figure 3 SEM images of paraffin phase change microcapsules coated with magnesium-aluminum layered double hydroxide modified silica;

[0037] Figure 4 SEM images of paraffin phase change microcapsules coated with silica and modified with carbon nanotubes / magnesium-aluminum layered double hydroxides;

[0038] Figure 5 XRD patterns of paraffin phase change microcapsules coated with silica and modified with carbon nanotubes / magnesium-aluminum layered double hydroxides;

[0039] Figure 6Fourier transform infrared spectra of silica-coated paraffin microcapsules, magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, and carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules.

[0040] Figure 7 A schematic diagram of the thermal conductivity of carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules prepared in Example 1 and pure paraffin.

[0041] Figure 8 Time-temperature curves for pure paraffin and silica-coated paraffin phase change microcapsules modified with carbon nanotubes / magnesium-aluminum layered double hydroxides. Detailed Implementation

[0042] The present invention will be further described below with reference to embodiments.

[0043] General Implementation Examples

[0044] A method for preparing flame-retardant temperature-regulating phase change microcapsules, the process is as follows: Figure 1 As shown, it includes the following steps:

[0045] (1) Mix paraffin and tetraethyl orthosilicate, heat and stir. After the paraffin melts, add a formamide solution containing hexadecyltrimethylammonium bromide dropwise and stir to form a microemulsion. Add hydrochloric acid solution dropwise and react for 3-5 hours. Stop stirring and age at 50-60℃ for 15-20 hours. Separate the product to obtain silica-coated paraffin phase change microcapsules.

[0046] The ratio of paraffin wax, tetraethyl orthosilicate, hexadecyltrimethylammonium bromide, formamide, and hydrochloric acid solution is (5-7 g): (5-7) g: (0.75-1.5) g: (100-150) ml: (100-150) ml. The concentration of the hydrochloric acid solution is 0.8-1.2 mol / L; the paraffin wax is a single-melting-point paraffin wax or a mixed paraffin wax composed of multiple single-melting-point paraffin waxes, with a melting point of 28-50℃.

[0047] (2) Mix the silica-coated paraffin microcapsules with water in a container and heat and stir at 50-60°C. Dissolve magnesium chloride hexahydrate and aluminum chloride hexahydrate in water and add them dropwise into the container to react for 3-5 hours. Add ammonia water (concentration of 0.18-0.22 mol / L) and continue the reaction for 1-3 hours. Separate the product to obtain magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0048] The ratio of silica-coated paraffin microcapsules, water, magnesium chloride hexahydrate, aluminum chloride hexahydrate, and ammonia is (0.5-1)g∶(60-80)ml∶(0.3-0.8)g∶(0.3-0.8)g∶(20-40)ml.

[0049] (3) The magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules were mixed with anhydrous ethanol in a container and heated and stirred. 3-aminopropyltriethoxysilane was mixed with an alcohol-water solution and stirred before being added dropwise to the container for reaction. A carbon nanotube suspension was added, and an aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added under stirring to continue the reaction. The product was separated to obtain carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0050] The following components were used: magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, anhydrous ethanol, 3-aminopropyltriethoxysilane, an alcohol-water solution, carbon nanotube suspension, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution, in a ratio of (0.5-1.5) g : (80-100) ml : (2-4) ml : (10-20) ml : (40-60) ml : (10-20) ml. The mass ratio of anhydrous ethanol to water in the alcohol-water solution was (10-15) : (1-1.5); the solid-liquid ratio of carboxylated carbon nanotubes to anhydrous ethanol in the carbon nanotube suspension was 0.1-0.2 g / 40-60 ml; and the concentration of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution was 0.008-0.012 g / ml.

[0051] A polystyrene foam plastic comprises the following raw materials in parts by weight: 90-120 parts polystyrene, 35-45 parts carbon nanotube / magnesium aluminum layered double hydroxide modified silica-coated paraffin microcapsules, 5-10 parts foaming agent, 1-5 parts nucleating agent, and 1-5 parts lubricant.

[0052] Preferably, the foaming agent is isobutane and / or n-butane; the nucleating agent is talc and / or citric acid; and the lubricant is glyceryl monostearate.

[0053] The preparation method of polystyrene foam includes the following steps: adding carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules, nucleating agent, polystyrene, and lubricant to a No. 1 single-screw extruder for mixing and stirring, and after high-temperature plasticization and homogenization in the compression section and homogenization section, a foaming agent is injected, and the mixture is initially mixed and homogenized in the mixing section; the resulting molten material is further fully mixed and cooled in a No. 2 single-screw extruder, and then transferred to a mold, shaped by a leveling machine, and after secondary processing and cooling, polystyrene foam is obtained.

[0054] Example 1

[0055] (1) 5g of sliced ​​paraffin (melting point 28-30℃) and 5ml of tetraethyl orthosilicate were placed in a three-necked flask and stirred at 1000rpm at 55℃. After the paraffin melted, 100ml of formamide solution containing 0.75g of hexadecyltrimethylammonium bromide was added dropwise. After stirring, a microemulsion was formed. Then, 100ml of hydrochloric acid solution (1mol / L) was slowly added dropwise. After reacting for 4h, stirring was stopped, and the mixture was aged at 55℃ for 18h. The resulting reaction product was centrifuged at 7000rpm for 8min, washed (3 times with deionized water and 3 times with alcohol), and dried at 60℃ for 24h to obtain silica-coated paraffin phase change microcapsules.

[0056] (2) Take 0.5g of the silica-coated paraffin microcapsules obtained in step (1) and mix them with 50ml of distilled water. After ultrasonic dispersion, place them in a three-necked flask and mechanically stir at 55℃. Dissolve 0.5g of magnesium chloride hexahydrate and 0.5g of aluminum chloride hexahydrate in 30ml of distilled water and slowly add them dropwise to the three-necked flask and react for 4h. Then, slowly add 30ml of ammonia solution (concentration of 0.2mol / L) to the three-necked flask and continue the reaction for 2h. After the reaction is complete, centrifuge the obtained product at 6500rpm for 8min, wash (wash 3 times with deionized water and 3 times with alcohol), and dry at 60℃ for 24h to obtain magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0057] (3) Take 1g of the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules obtained in step (2) and mix them with anhydrous ethanol. Place the mixture in a three-necked flask and stir mechanically at 700 rpm at 55°C. Mix 2ml of 3-aminopropyltriethoxysilane (KH-550) with 10ml (10wt%) of anhydrous ethanol-water solution (a mixture of anhydrous ethanol and distilled water). After stirring mechanically for 30min, slowly add the mixture dropwise to the three-necked flask. After reacting for 24h, mix 0.1g of carboxylated carbon nanotubes with 40ml of anhydrous ethanol and sonicate for 1h to obtain a carbon nanotube suspension. Add the suspension to the three-necked flask and add 10ml (0.01g / ml) of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) aqueous solution under continuous mechanical stirring. Continue the reaction for 24h. After the reaction was completed, the mixture was centrifuged at 6000 rpm for 8 min, washed (3 times with deionized water and 3 times with alcohol), and dried at 60℃ for 24 h to obtain carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0058] (4) The raw materials obtained in step (3), including carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules (40 parts), talc nucleating agent (3 parts), polystyrene (90 parts), and glyceryl monostearate lubricant (5 parts), are stored independently according to their components. They are fed and mixed in the No. 1 extruder (single screw) through an automatic control system. After being uniformly plasticized at high temperature in the compression and homogenization sections, isobutane foaming agent (7 parts) is injected and preliminarily mixed and homogenized in the mixing section. In the No. 2 extruder (single screw), the molten material and foaming agent are further fully mixed and cooled. Then, the temperature is precisely controlled by a heat exchanger and added to the mold. After being shaped by a leveling machine, polystyrene foam with flame-retardant and temperature-regulating functions is obtained after secondary processing and cooling. The No. 1 extruder's high-temperature screw is divided into four zones, with a total length of 15 meters. The temperature of zone 1 is set to 170℃, zone 2 to 180℃, zone 3 to 190℃, and zone 4 to 200℃. The No. 2 extruder's high-temperature screw is 10 meters long, with the temperature of zone 1 set to 200℃, zone 2 to 200℃, zone 3 to 180℃, and zone 4 to 150℃.

[0059] Figure 2 The image shows a SEM image of the silica-coated paraffin microcapsules prepared in Example 1. As shown in the figure, the silica-coated paraffin microcapsules are regular spherical with a smooth and dense surface and a particle size of about 1-3 μm.

[0060] Figure 3 The image shows a SEM image of the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules prepared in Example 1. As shown in the figure, compared with silica-coated paraffin microcapsules, the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules have a rougher surface morphology, and a large number of nanosheets with two-dimensional layered structures are dispersed on the surface of the microcapsules.

[0061] Figure 4 The image shows a SEM image of the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules prepared in Example 1. As shown in the figure, the surface of the microcapsules has a large number of irregularly entangled carbon nanotubes.

[0062] Figure 5The image shows the XRD pattern of the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules prepared in Example 1. As shown in the figure, the diffraction angles 2θ of 22.11° and 24.74° correspond to the (110) and (0014) crystal planes of paraffin (JCPDF 361591), respectively, while the diffraction angles 2θ of 23.48°, 35.84°, and 60.78° correspond to the (006), (009), and (110) crystal planes of magnesium-aluminum layered hydroxide (JCPDF#70-2151), respectively. The diffraction peak intensities are low, which is due to the low reaction temperature and the low crystallinity of the magnesium-aluminum layered hydroxide. In addition, no obvious diffraction peaks of silica and carbon nanotubes are observed in the figure. This is because the peaks of the amorphous silica in the microcapsule shell and the diffraction peaks of carbon nanotubes are superimposed with the diffraction peaks of paraffin.

[0063] Figure 6 The Fourier transform infrared (FTIR) spectra of the silica-coated paraffin, magnesium-aluminum layered double hydroxide-modified silica-coated paraffin, and carbon nanotube / magnesium-aluminum layered double hydroxide-modified silica-coated paraffin microcapsules prepared in Example 1 are shown in the figure. For the silica-coated paraffin microcapsules, the FTIR spectrum is 3444 cm⁻¹. -1 and 1083cm -1 The absorption peaks at 461 cm⁻¹ represent the bending vibration peak and the asymmetric tensile vibration peak of Si-O-Si, respectively. -1 The peak at 3917 cm⁻¹ represents the stretching vibration of Si-OH. -1 and 2850cm -1 The absorption peaks at 1401 cm⁻¹ correspond to the asymmetric and symmetric stretching vibrations of the CH bond in the chemical structure of paraffin, respectively. For magnesium-aluminum layered double hydroxide-modified silica-coated paraffin microcapsules, the absorption peak at 1401 cm⁻¹ corresponds to the asymmetric and symmetric stretching vibrations of the CH bond in the chemical structure of paraffin. -1 and 3450cm -1 A set of tensile vibration peaks were observed at 3450 cm⁻¹ for interlayer carbonates and interlayer water in magnesium-aluminum layered double hydroxides. For carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, [the peak value is missing]. -1 The stretching vibration peak of the hydroxyl group was significantly weakened. This is because after modification with KH-550, some hydroxyl groups were polycondensed with the silanol bonds generated by the hydrolysis of KH-550.

[0064] Figure 7 The figures show the thermal conductivity of paraffin and the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules prepared in Example 1. As shown in the figure, the thermal conductivity of paraffin and the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules are 0.1513 W / m², respectively. -1 ·K -1 and 0.5231Wm -1 ·K -1The results showed that carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules had higher thermal conductivity, making the microcapsules more sensitive to environmental temperature.

[0065] Figure 8 The figures show the time-temperature curves for pure paraffin and carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules in Example 1. The test method involved taking samples of the same mass and using a self-made experimental apparatus under simulated sunlight conditions, recording the relationship between temperature and illumination time. As shown in the figure, for pure paraffin, the sample temperature rose to approximately 28°C after the light exposure began, and then the temperature rose slowly for a period of time. This is because the melting point of paraffin is approximately 28°C; upon reaching this temperature, paraffin undergoes a phase transition until the absorbed heat reaches saturation, after which the sample temperature continues to rise until it reaches ambient temperature. For the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, the sample temperature rose rapidly to approximately 27°C after the light exposure began, and then the curve showed a plateau period until the absorbed heat reached saturation, after which the temperature rose again until it reached ambient temperature. The heating rate of this sample was much higher than that of pure paraffin, indicating that the carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules have a higher thermal conductivity than pure paraffin.

[0066] Example 2

[0067] (1) 5g of sliced ​​paraffin (melting point 48-50℃) and 5ml of tetraethyl orthosilicate were placed in a three-necked flask and stirred at 1000rpm at 55℃. After the paraffin melted, 100ml of formamide solution containing 1g of hexadecyltrimethylammonium bromide was added dropwise. After stirring continued, a microemulsion was formed. Then, 100ml of hydrochloric acid solution (1mol / L) was slowly added dropwise. After reacting for 4h, stirring was stopped, and the mixture was aged at 55℃ for 18h. The resulting reaction product was centrifuged at 7000rpm for 8min, washed (3 times with deionized water and 3 times with alcohol), and dried at 60℃ for 24h to obtain silica-coated paraffin phase change microcapsules.

[0068] (2) Take 0.5g of the silica-coated paraffin microcapsules obtained in step (1) and mix them with 50ml of distilled water. After ultrasonic dispersion, place them in a three-necked flask and mechanically stir at 55℃. Dissolve 0.7g of magnesium chloride hexahydrate and 0.7g of aluminum chloride hexahydrate in 30ml of distilled water and slowly add them dropwise to the three-necked flask and react for 4h. Then, slowly add 30ml of ammonia solution (concentration of 0.2mol / L) to the three-necked flask and continue the reaction for 2h. After the reaction is complete, centrifuge the obtained product at 6500rpm for 8min, wash (wash 3 times with deionized water and 3 times with alcohol), and dry at 60℃ for 24h to obtain magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0069] (3) Take 1.5g of the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules obtained in step (2) and mix them with anhydrous ethanol. Place them in a three-necked flask and stir mechanically at 700 rpm at 55°C. Mix 3ml of 3-aminopropyltriethoxysilane (KH-550) with 15ml (10wt%) of anhydrous ethanol-water solution (a mixture of anhydrous ethanol and distilled water). After stirring mechanically for 30min, slowly add the mixture dropwise to the three-necked flask. After reacting for 24h, mix 0.15g of carboxylated carbon nanotubes with 40ml of anhydrous ethanol and sonicate for 1h to obtain a carbon nanotube suspension. Add the suspension to the three-necked flask and add 15ml (0.01g / ml) of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) aqueous solution under continuous mechanical stirring. Continue the reaction for 24h. After the reaction was completed, the mixture was centrifuged at 6000 rpm for 8 min, washed (3 times with deionized water and 3 times with alcohol), and dried at 60℃ for 24 h to obtain carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0070] (4) The raw materials obtained in step (3) including carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules (35 parts), talc nucleating agent (2 parts), polystyrene (100 parts), and glyceryl monostearate lubricant (3 parts) are stored independently according to their components. They are fed and mixed in the No. 1 extruder (single screw) through an automatic control system. After being uniformly plasticized at high temperature in the compression section and homogenization section, isobutane foaming agent (5 parts) is injected and preliminarily mixed and homogenized in the mixing section. In the No. 2 extruder (single screw), the molten material and foaming agent are further fully mixed and cooled. Then, the temperature is precisely controlled by a heat exchanger and added to the mold. After being shaped by a leveling machine, polystyrene foam with flame retardant and temperature regulating functions is obtained after secondary processing and cooling.

[0071] The No. 1 extruder's high-temperature screw is divided into four zones, with a total length of 15 meters. The temperature of zone 1 is set to 170℃, zone 2 to 180℃, zone 3 to 190℃, and zone 4 to 200℃. The No. 2 extruder's high-temperature screw is 10 meters long, with the temperature of zone 1 set to 200℃, zone 2 to 200℃, zone 3 to 180℃, and zone 4 to 150℃.

[0072] Example 3

[0073] (1) 5g of sliced ​​paraffin (melting point 48-50℃) and 5ml of tetraethyl orthosilicate were placed in a three-necked flask and stirred at 1000rpm at 55℃. After the paraffin melted, 100ml of formamide solution containing 1.5g of hexadecyltrimethylammonium bromide was added dropwise. After stirring continued, a microemulsion was formed. Then, 100ml of hydrochloric acid solution (1mol / L) was slowly added dropwise. After reacting for 4h, stirring was stopped, and the mixture was aged at 55℃ for 18h. The resulting reaction product was centrifuged at 7000rpm for 8min, washed (3 times with deionized water and 3 times with alcohol), and dried at 60℃ for 24h to obtain silica-coated paraffin phase change microcapsules.

[0074] (2) Take 0.5g of the silica-coated paraffin microcapsules obtained in step (1) and mix them with 50ml of distilled water. After ultrasonic dispersion, place them in a three-necked flask and mechanically stir at 55℃. Dissolve 0.3g of magnesium chloride hexahydrate and 0.3g of aluminum chloride hexahydrate in 30ml of distilled water and slowly add them dropwise to the three-necked flask for 4h. Then, slowly add 30ml of ammonia solution (concentration of 0.2mol / L) to the three-necked flask and continue the reaction for 2h. After the reaction is complete, centrifuge the obtained product at 6500rpm for 8min, wash (wash 3 times with deionized water and 3 times with alcohol), and dry at 60℃ for 24h to obtain magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0075] (3) Take 1g of the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules obtained in step (2) and mix them with anhydrous ethanol. Place them in a three-necked flask and stir mechanically at 700rpm at 55℃. Mix 4ml of 3-aminopropyltriethoxysilane (KH-550) with 20ml (10wt%) of anhydrous ethanol-water solution (a mixture of anhydrous ethanol and distilled water). After stirring mechanically for 30min, slowly add the mixture to the three-necked flask. After reacting for 24h, mix 0.2g of carboxylated carbon nanotubes with 60ml of anhydrous ethanol and sonicate for 1h to obtain a carbon nanotube suspension. Add the suspension to the three-necked flask and add 20ml (0.01g / ml) of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) aqueous solution under continuous mechanical stirring. Continue the reaction for 24h. After the reaction was completed, the mixture was centrifuged at 6000 rpm for 8 min, washed (3 times with deionized water and 3 times with alcohol), and dried at 60℃ for 24 h to obtain carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

[0076] (4) The carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules (45 parts), talc nucleating agent (5 parts), polystyrene (120 parts), and glyceryl monostearate lubricant (5 parts) obtained in step (3) are stored independently according to their components. They are fed and mixed in the No. 1 extruder (single screw) through an automatic control system. After being uniformly plasticized at high temperature in the compression section and homogenization section, isobutane foaming agent (8 parts) is injected and preliminarily mixed and homogenized in the mixing section. In the No. 2 extruder (single screw), the molten material and foaming agent are further fully mixed and cooled. Then, the temperature is precisely controlled by a heat exchanger and added to the mold. After being shaped by a leveling machine, polystyrene foam with flame retardant and temperature regulating functions is obtained after secondary processing and cooling.

[0077] The No. 1 extruder's high-temperature screw is divided into four zones, with a total length of 15 meters. The temperature of zone 1 is set to 170℃, zone 2 to 180℃, zone 3 to 190℃, and zone 4 to 200℃. The No. 2 extruder's high-temperature screw is 10 meters long, with the temperature of zone 1 set to 200℃, zone 2 to 200℃, zone 3 to 180℃, and zone 4 to 150℃.

[0078] Table 1 shows the flame retardant properties of polystyrene foam with carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules and polystyrene foam without microcapsules. t1 and t2 represent the average burning time of the specimen after the first and second ignition in the vertical burning test, respectively. LOI% represents the limiting oxygen index of the specimen.

[0079] Table 1

[0080]

[0081]

[0082] As shown in Table 1, polystyrene foam without microcapsules did not exhibit self-extinguishing behavior in the vertical burning test. However, all examples using carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules as fillers exhibited self-extinguishing properties, with Example 1 showing the shortest burning time and the best self-extinguishing ability. Furthermore, compared to polystyrene foam without microcapsules, the limiting oxygen index (LOI) of polystyrene foam with microcapsules was improved, with Example 1 showing the highest LIO. These results indicate that the addition of microcapsules significantly improves the flame-retardant properties of polystyrene foam, and the flame-retardant performance increases with the increase in the proportion of microcapsules.

[0083] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A process for the preparation of flame retardant temperature regulating phase change microcapsules, characterized in that The method comprises the following steps: (1) preparing silica-coated paraffin phase change microcapsules; (2) mixing the silica-coated paraffin microcapsules with water in a container and heating and stirring, dissolving magnesium chloride hexahydrate and aluminum chloride hexahydrate in water and then dropping into the container to react for 3-5 hours; dropping ammonia water with a concentration of 0.18-0.22 mol / L into the container to react for 1-3 hours; and separating the product to obtain magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules; The amount ratio of the silica-coated paraffin microcapsules, water, magnesium chloride hexahydrate, aluminum chloride hexahydrate and ammonia water is (0.5-1) g:(60-80) ml:(0.3-0.8) g:(0.3-0.8) g:(20-40) ml; (3) mixing 0.5-1.5 g of the magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules with 80-100 ml of anhydrous ethanol in a container and heating and stirring, mixing 2-4 ml of 3-aminopropyl triethoxysilane with 10-20 ml of an alcohol water solution and then dropping into the container to react, the mass ratio of anhydrous ethanol to water in the alcohol water solution being (10-15):(1-1.5); adding 40-60 ml of a carbon nanotube suspension with a concentration of 0.1-0.2 g / 40-60 ml and 10-20 ml of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride aqueous solution with a concentration of 0.008-0.012 g / ml to react under stirring; and separating the product to obtain carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin phase change microcapsules.

2. The production method according to claim 1, characterized by: In step (2), the temperature of the heating and stirring is 50-60°C.

3. The production method according to claim 1, characterized by: In step (1), the preparation method of the silica-coated paraffin phase change microcapsules is as follows: mixing paraffin and tetraethyl orthosilicate and heating and stirring, dropping a formamide solution containing cetyltrimethylammonium bromide into the mixture after the paraffin is melted, stirring to form a microemulsion, dropping a hydrochloric acid solution, stopping stirring after reaction, and aging; Separating the product to obtain silica-coated paraffin phase change microcapsules.

4. The production method according to claim 3, characterized by: In step (1), the amount ratio of the paraffin, tetraethyl orthosilicate, cetyltrimethylammonium bromide, formamide and hydrochloric acid solution is (5-7) g:(5-7) g:(0.75-1.5) g:(100-150) ml:(100-150) ml.

5. Application of the flame-retardant temperature-regulating phase change microcapsules obtained by the method of any one of claims 1-4 in the preparation of polystyrene foam plastic.

6. Use according to claim 5, wherein: The polystyrene foam plastic comprises the following raw materials in mass fractions: 90-120 parts of polystyrene, 35-45 parts of carbon nanotube / magnesium-aluminum layered double hydroxide modified silica-coated paraffin microcapsules, 5-10 parts of a foaming agent, 1-5 parts of a nucleating agent and 1-5 parts of a lubricant.

7. Use according to claim 6, wherein: The foaming agent is isobutane and / or n-butane.

8. The use according to claim 6, characterized in that: The nucleating agent is talc and / or citric acid.

9. The use according to claim 6, characterized in that: The lubricant is glycerol monostearate.

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