Microcapsule flame retardant, polystyrene foam material and preparation method of polystyrene foam material

Abstract

The invention provides a microcapsule flame retardant, a polystyrene foam material and a preparation method thereof, and relates to the technical field of polystyrene foam plastics. The microcapsule flame retardant has a core-shell structure; a core material of the microcapsule flame retardant is ammonium polyphosphate; a shell material of the microcapsule flame retardant comprises melamine-formaldehyde resin and zinc carbonate. A framework of the polystyrene foaming material comprises polystyrene, a microcapsule flame retardant and CNTs-SiO2 particles. According to the invention, the microcapsule flame retardant and the CNTs-SiO2 particles are introduced into the polystyrene foaming material, so that the polystyrene foaming material obtains an acid source, carbon source and gas source integrated synergistic flame-retardant effect and a dynamic flame-retardant mechanism, thereby obviously improving the flame-retardant property of the polystyrene foaming material.

Description

Technical Field

[0001] The invention relates to the technical field of polystyrene foam plastics, and in particular to a microcapsule flame retardant, a polystyrene foam material and a preparation method thereof. Background Art

[0002] Expanded polystyrene (EPS) is widely used in the packaging and transportation of large household appliances such as washing machines and dryers due to its lightweight, heat-insulating, shock-resistant, and low-cost properties. However, this material's high flammability has become a significant hazard to warehouse safety management for appliance manufacturers. Traditional EPS materials not only burn rapidly when exposed to fire, but also produce molten material dripping, accelerating the spread of fire and leading to serious warehouse fires. This has led to an increasingly urgent demand for flame-retardant EPS materials.

[0003] Applying flame retardant technology to EPS packaging for washing machines and dryers presents several unique challenges. First, packaging materials are extremely cost-sensitive. Adding flame retardants can increase costs by 30-50%, necessitating the development of cost-effective flame retardant solutions. Second, the packaging EPS must maintain excellent cushioning properties and a low density (typically 20-30 kg / m²). 3 High levels of traditional flame retardants can significantly increase the material's density, affecting its protective properties. Furthermore, packaging materials also have requirements for surface gloss, printability, and other appearance indicators. Certain flame retardants can cause surface defects or affect post-processing performance.

[0004] Currently, flame-retardant EPS materials still suffer from unsatisfactory flame retardancy in practical applications. This problem stems from the complex interaction of multiple factors, including material properties, flame retardant mechanism, processing technology, and application environment. Therefore, the development of EPS materials with excellent flame retardancy is urgently needed. Summary of the Invention

[0005] To address the above technical issues, the present invention provides a microcapsule flame retardant, a polystyrene foam material, and a preparation method thereof. By introducing the microcapsule flame retardant and CNTs-SiO2 particles into the polystyrene foam material, the present invention achieves a synergistic flame retardant effect and a dynamic flame retardant mechanism by integrating acid, carbon, and gas sources, thereby significantly improving the flame retardancy of the polystyrene foam material.

[0006] In a first aspect, the present invention provides a microcapsule flame retardant having a core-shell structure;

[0007] The core material of the microcapsule flame retardant is ammonium polyphosphate;

[0008] The shell material of the microcapsule flame retardant comprises melamine-formaldehyde resin and zinc carbonate.

[0009] In some embodiments of the present invention, in the raw materials for preparing the microcapsule flame retardant, the mass ratio of ammonium polyphosphate, melamine-formaldehyde resin and zinc carbonate is (10-30):(25-30):(1-2).

[0010] In some embodiments of the present invention, the mass ratio of formaldehyde to melamine in the polymerized monomers of the melamine-formaldehyde resin is (7-10):8.

[0011] In some embodiments of the present invention, the particle size of the microcapsule flame retardant is 200-800 μm.

[0012] In a second aspect, the present invention provides a method for preparing the microcapsule flame retardant according to the first aspect, the preparation method comprising the following steps:

[0013] (1) reacting formaldehyde and melamine in water to obtain a melamine-formaldehyde resin prepolymer solution;

[0014] (2) mixing the melamine-formaldehyde resin prepolymer solution with zinc carbonate to obtain a shell material precursor solution;

[0015] (3) adding the shell material precursor solution dropwise to the ammonium polyphosphate solution, reacting under stirring conditions, and drying to obtain the microcapsule flame retardant.

[0016] In some embodiments of the present invention, the reaction temperature in step (1) is 70-80° C., and the reaction time is 1.5-3 h.

[0017] In some embodiments of the present invention, the concentration of the melamine-formaldehyde resin prepolymer solution in step (1) is 50-60 wt %.

[0018] In some embodiments of the present invention, the reaction temperature in step (3) is 80-90° C., the reaction time is 2-4 h, and the stirring speed is 400-800 r / min.

[0019] In some embodiments of the present invention, the concentration of the ammonium polyphosphate solution in step (3) is 25-30 wt%.

[0020] In some embodiments of the present invention, the solvent of the ammonium polyphosphate solution in step (3) is selected from one or both of methanol and ethanol.

[0021] In a third aspect, the present invention provides a composite polystyrene material, comprising polystyrene, a microcapsule flame retardant, and CNTs-SiO2 particles; the microcapsule flame retardant and the CNTs-SiO2 particles are dispersed in the polystyrene;

[0022] The microcapsule flame retardant is the microcapsule flame retardant described in the first aspect or the microcapsule flame retardant prepared by the preparation method described in the second aspect;

[0023] The CNTs-SiO2 particles include silica aerogel particles, carbon nanotubes and a binder, and the carbon nanotubes are adhered to the pores and surface of the silica aerogel particles through the binder.

[0024] In some embodiments of the present invention, in the composite polystyrene material, the mass of the microcapsule flame retardant is 1-2% of the mass of the polystyrene.

[0025] In some embodiments of the present invention, in the composite polystyrene material, the mass of the CNTs-SiO2 particles is 3-4% of the mass of the polystyrene.

[0026] In some embodiments of the present invention, in the CNTs-SiO2 particles, the mass ratio of carbon nanotubes to silica aerogel particles is (3-5):(40-60).

[0027] In some embodiments of the present invention, the silica aerogel particles have a pore size of 2-50 nm, a particle size of 50-200 μm, and a porosity of 40-90%.

[0028] In some embodiments of the present invention, the silica aerogel particles are amino-modified silica aerogel particles.

[0029] In some embodiments of the present invention, the binder is selected from one or more of phenolic resin, furan resin and epoxy resin.

[0030] In a fourth aspect, the present invention provides a method for preparing the composite polystyrene material according to the third aspect, the preparation method comprising the following steps:

[0031] Mixing styrene, microcapsule flame retardant, CNTs-SiO2 particles and initiator to obtain an oil phase solution;

[0032] mixing an emulsifier with water to obtain an aqueous phase solution;

[0033] The oil phase solution is added to the water phase solution, and the mixture is reacted under stirring to obtain the composite polystyrene material.

[0034] In some embodiments of the present invention, the mass of the initiator is 1-1.5% of the mass of the styrene.

[0035] In some embodiments of the present invention, the mass ratio of the emulsifier to water is (1-3):100.

[0036] In some embodiments of the present invention, the emulsifier is sodium lauryl sulfate.

[0037] In some embodiments of the present invention, the volume ratio of the oil phase solution to the aqueous phase solution is 1:(4-8).

[0038] In some embodiments of the present invention, the reaction temperature is 70-100° C. and the reaction time is 2-4 h.

[0039] In some embodiments of the present invention, the stirring speed is 200-400 r / min.

[0040] In a fifth aspect, the present invention provides a polystyrene foam material, wherein the polystyrene foam material comprises a skeleton and foam cells;

[0041] The material of the skeleton is the composite polystyrene material described in the third aspect.

[0042] In some embodiments of the present invention, the content of the microcapsule flame retardant in the surface layer of the styrene foam material is greater than the content of the microcapsule flame retardant in the interior;

[0043] The content of CNTs-SiO2 particles in the surface layer of the styrene foam material is less than that in the interior.

[0044] In a sixth aspect, the present invention provides a method for preparing the polystyrene foam material according to the fifth aspect, the preparation method comprising the following steps:

[0045] S1. placing the composite polystyrene material described in the third aspect in a mold and introducing steam for pre-foaming;

[0046] S2. placing the pre-foamed composite polystyrene material in a mold, introducing steam to foam it, and obtaining the polystyrene foam material after cooling.

[0047] In some embodiments of the present invention, the surface temperature of the mold in step S1 is greater than the center temperature.

[0048] In some embodiments of the present invention, the surface temperature of the mold in step S1 is 100-110°C, and the center temperature is 80-90°C.

[0049] In some embodiments of the present invention, the pressure of the steam in step S1 is 0.4-0.5 MPa.

[0050] In some embodiments of the present invention, the pre-foaming ratio in step S1 is 30-40 times.

[0051] In some embodiments of the present invention, the surface temperature of the mold in step S2 is greater than the center temperature.

[0052] In some embodiments of the present invention, the surface temperature of the mold in step S2 is 110-125°C, and the center temperature is 95-105°C.

[0053] In some embodiments of the present invention, the pressure of the steam in step S2 is 0.4-0.5 MPa.

[0054] In some embodiments of the present invention, in step S2, periodic pressure is applied to the pre-foamed composite polystyrene material during foaming; the valley value of the periodic pressure is 0, the peak value is 0.1-0.3 MPa, and the frequency is 0.3-0.5 Hz.

[0055] The technical solution provided by the embodiment of the present invention has the following advantages compared with the existing technology:

[0056] The embodiment of the present invention constructs a synergistic flame retardant system by introducing microcapsule flame retardants and CNTs-SiO2 particles into polystyrene foam materials, thereby achieving a synergistic flame retardant effect of integrating acid source, carbon source and gas source, as well as a dynamic flame retardant mechanism. The polystyrene foam material triggers different flame retardant mechanisms at different temperature stages: at low temperatures (200-300°C), the shell of the microcapsule flame retardant ruptures, releasing ammonium polyphosphate, which decomposes to form polyphosphoric acid, catalyzing the dehydration of polystyrene into carbon. At medium temperatures (300-400°C), the shell of the microcapsule flame retardant decomposes, releasing inert gases such as nitrogen and ammonia, which dilute the concentration of combustible gases. Simultaneously, zinc carbonate in the shell of the microcapsule flame retardant begins to decompose, and the resulting ZnO forms a glassy melt with polyphosphoric acid, sealing the pores of the carbon layer. The CNTs network in the CNTs-SiO2 particles guides the orderly growth of the carbon layer, forming a continuous protective layer. At high temperatures (>400°C), the zinc carbonate completely decomposes, producing a large amount of CO2, which further dilutes the oxygen. At the same time, the generated ZnO reacts with SiO2 (from the CNTs-SiO2 particles) to form a zinc silicate ceramic phase, significantly increasing the strength of the carbon layer. This significantly improves the flame retardant properties of the polystyrene foam material. DETAILED DESCRIPTION

[0057] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0058] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0061] In a first aspect, an embodiment of the present invention provides a microcapsule flame retardant having a core-shell structure;

[0062] The core material of the microcapsule flame retardant is ammonium polyphosphate;

[0063] The shell material of the microcapsule flame retardant comprises melamine-formaldehyde resin and zinc carbonate.

[0064] The microcapsule flame retardant provided by the embodiment of the present invention realizes the integration of acid source, carbon source and gas source, and has a synergistic flame retardant effect. When the microcapsule flame retardant is used in a polymer, the flame retardant performance of the polymer can be significantly improved. Its flame retardant mechanism is as follows: in the low-temperature stage (200-300°C), the shell of the microcapsule flame retardant ruptures, releasing ammonium polyphosphate, which decomposes to form polyphosphoric acid, catalyzing the dehydration of the polymer into carbon; in the medium-temperature stage (300-400°C), the shell of the microcapsule flame retardant decomposes, releasing inert gases such as nitrogen and ammonia, diluting the concentration of combustible gas, and at the same time, zinc carbonate in the shell of the microcapsule flame retardant begins to decompose, and the generated ZnO forms a glassy melt with polyphosphoric acid, sealing the pores of the carbon layer; in the high-temperature stage (>400°C), the zinc carbonate completely decomposes, generating a large amount of CO2 to further dilute the oxygen.

[0065] In some embodiments of the present invention, the mass ratio of ammonium polyphosphate, melamine-formaldehyde resin and zinc carbonate in the raw materials for preparing the microcapsule flame retardant is (10-30):(25-30):(1-2). For example, it can be 10:25:1, 10:28:1, 10:30:1, 10:25:1.5, 10:28:1.5, 10:30:1.5, 10:25:2, 10:28:2, 10:30:2, 15:25:1, 15:28:1, 15:30:1, 15:25:2, 15:28:2, 15:30:2, 20:25:1 , 20:28:1, 20:30:1, 20:25:2, 20:28:2, 20:30:2, 25:25:1, 25:28:1, 25:30:1, 25:25:2, 25:28:2, 25:30:2, 30:25:1, 30:28:1, 30:30:1, 30:25:2, 30:28:2 or 30:30:2, etc. However, the present invention is not limited to the values ​​listed, and other values ​​not listed within the range are also applicable.

[0066] In the embodiment of the present invention, when the ratio of ammonium polyphosphate, melamine-formaldehyde resin and zinc carbonate is controlled within the above range, the acid source, carbon source and gas source are balanced with each other, and the synergistic effect of the three can be fully exerted, further improving the flame retardant performance of the microcapsule flame retardant.

[0067] In some embodiments of the present invention, the mass ratio of formaldehyde to melamine in the polymerized monomers of the melamine-formaldehyde resin is (7-10):8; for example, the mass ratio may be 7:8, 7.2:8, 7.5:8, 7.8:8, 8:8, 8.2:8, 8.5:8, 8.8:8, 9:8, 9.2:8, 9.5:8, 9.8:8, or 10:8, etc. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0068] In some embodiments of the present invention, the particle size of the microcapsule flame retardant is 200-800 μm; for example, it can be 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 750 μm, or 800 μm. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0069] In the embodiment of the present invention, if the particle size of the microcapsule flame retardant is too large, it is difficult to disperse evenly in the polystyrene matrix and is prone to form local agglomerations, which will lead to a lack of protection in some areas during combustion, forming "weak points" and reducing the overall flame retardant effect; if the particle size of the microcapsule flame retardant is too small, its surface energy is high and secondary agglomeration is prone to occur, which will also lead to uneven dispersion in the polystyrene matrix.

[0070] In a second aspect, the present invention provides a method for preparing the microcapsule flame retardant according to the first aspect, the preparation method comprising the following steps:

[0071] (1) reacting formaldehyde and melamine in water to obtain a melamine-formaldehyde resin prepolymer solution;

[0072] (2) mixing the melamine-formaldehyde resin prepolymer solution with zinc carbonate to obtain a shell material precursor solution;

[0073] (3) adding the shell material precursor solution dropwise to the ammonium polyphosphate solution, reacting under stirring conditions, and drying to obtain the microcapsule flame retardant.

[0074] In some embodiments of the present invention, the mass ratio of formaldehyde to melamine in the preparation method is (7-10):8; the mass ratio of ammonium polyphosphate, melamine-formaldehyde resin and zinc carbonate is (10-30):(25-30):(1-2).

[0075] In some embodiments of the present invention, the reaction temperature in step (1) is 70-80° C., for example, 70° C., 72° C., 73° C., 75° C., 76° C., 78° C., or 80° C., and the reaction time is 1.5-3 h, for example, 1.5 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.3 h, 2.5 h, 2.6 h, 2.8 h, or 3 h, etc. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within the range are also applicable.

[0076] In some embodiments of the present invention, the concentration of the melamine-formaldehyde resin prepolymer solution in step (1) is 50-60 wt %, for example, 50 wt %, 52 wt %, 53 wt %, 55 wt %, 56 wt %, 58 wt %, or 60 wt %. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0077] In some embodiments of the present invention, the reaction temperature in step (3) is 80-90° C., for example, 80° C., 82° C., 83° C., 85° C., 86° C., 88° C., or 90° C.; the reaction time is 2-4 h, for example, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, or 4 h; and the stirring speed is 400-800 r / min, for example, 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, or 800 r / min. However, the present invention is not limited to the values ​​listed, and other values ​​not listed within the range are also applicable.

[0078] It should be noted that the reaction time in step (3) refers to the reaction time after the dropwise addition is completed. In the embodiment of the present invention, there is no particular limitation on the dropwise addition rate of the shell material precursor solution, and those skilled in the art can routinely select it. As a non-limiting example, the dropwise addition rate can be 0.5-2 mL / min.

[0079] In some embodiments of the present invention, the concentration of the ammonium polyphosphate solution in step (3) is 25-30 wt %; for example, it can be 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt % or 30 wt %. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0080] In some embodiments of the present invention, the solvent of the ammonium polyphosphate solution in step (3) is selected from one or both of methanol and ethanol.

[0081] In the embodiment of the present invention, the above-mentioned optimized preparation conditions are adopted to facilitate obtaining a microcapsule flame retardant having a core-shell structure with uniform particle size and good coating.

[0082] In a third aspect, the present invention provides a composite polystyrene material, comprising polystyrene, a microcapsule flame retardant, and CNTs-SiO2 particles; the microcapsule flame retardant and the CNTs-SiO2 particles are dispersed in the polystyrene;

[0083] The microcapsule flame retardant is the microcapsule flame retardant described in the first aspect or the microcapsule flame retardant prepared by the preparation method described in the second aspect;

[0084] The CNTs-SiO2 particles include silica aerogel particles, carbon nanotubes (CNTs) and a binder, wherein the carbon nanotubes are adhered to the pores and surface of the silica aerogel particles through the binder.

[0085] The embodiment of the present invention constructs a synergistic flame retardant system by introducing microcapsule flame retardants and CNTs-SiO2 particles into the composite polystyrene material, obtains a synergistic flame retardant effect integrating acid source, carbon source and gas source, and a dynamic flame retardant mechanism, thereby enabling the composite polystyrene material to obtain good flame retardant properties.

[0086] Specifically, the composite polystyrene material can trigger different flame retardant mechanisms at different temperature stages: in the low-temperature stage (200-300°C), the shell of the microcapsule flame retardant breaks, releasing ammonium polyphosphate, which decomposes to form polyphosphoric acid, catalyzing the dehydration of polystyrene into carbon; in the medium-temperature stage (300-400°C), the shell of the microcapsule flame retardant decomposes, releasing inert gases such as nitrogen and ammonia, diluting the concentration of combustible gases. At the same time, zinc carbonate in the shell of the microcapsule flame retardant begins to decompose, and the generated ZnO forms a glassy melt with polyphosphoric acid, sealing the pores of the carbon layer. The CNTs network in the CNTs-SiO2 particles guides the orderly growth of the carbon layer to form a continuous protective layer; in the high-temperature stage (>400°C), zinc carbonate completely decomposes, producing a large amount of CO2 to further dilute the oxygen. At the same time, the generated ZnO reacts with SiO2 (from CNTs-SiO2 particles) to form a zinc silicate ceramic phase, significantly improving the strength of the carbon layer.

[0087] In some embodiments of the present invention, the mass of the microcapsule flame retardant in the composite polystyrene material is 1-2% of the mass of the polystyrene; for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%. However, the present invention is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0088] In some embodiments of the present invention, the mass of the CNTs-SiO2 particles in the composite polystyrene material is 3-4% of the mass of the polystyrene; for example, it can be 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4%. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0089] In the embodiment of the present invention, if the content of the microcapsule flame retardant and CNTs-SiO2 particles in the composite polystyrene material is too little, the corresponding flame retardant effect is limited and the effect on improving the flame retardant performance is weak; if the content of the microcapsule flame retardant or CNTs-SiO2 particles is too high, it will interfere with the nucleation and growth of bubbles during the foaming process, resulting in uneven pore size, thinning or rupture of the pore wall, and reduced mechanical properties such as compressive strength and toughness of the polystyrene foam material.

[0090] In the embodiment of the present invention, there is no particular limitation on the method for preparing the CNTs-SiO2 particles, and those skilled in the art may select a conventional method. As a non-limiting example, the method for preparing the CNTs-SiO2 particles may be:

[0091] The binder is dissolved in a solvent, carbon nanotubes are added, and ultrasonic dispersion is performed to obtain a dispersion liquid; silica aerogel particles are added to the dispersion liquid, ultrasonic treatment is performed to uniformly load the carbon nanotubes in the pores and on the surface of the silica aerogel particles, and the solid product is collected and thermally cured to obtain CNTs-SiO2 particles.

[0092] In some embodiments of the present invention, the mass ratio of carbon nanotubes to silica aerogel particles in the CNTs-SiO2 particles is (3-5):(40-60); for example, the mass ratio may be 1:8, 1:10, 1:12, 1:13, 1:15, 1:16, 1:18, or 1:20. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0093] In the embodiment of the present invention, if the content of carbon nanotubes in the CNTs-SiO 2 particles is too low, the role of guiding the orderly growth of the carbon layer will be difficult to play.

[0094] In some embodiments of the present invention, the pore size of the silica aerogel particles is 2-50 nm, for example, 2 nm, 3 nm, 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm; the particle size is 50-200 μm, for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 150 μm, 160 μm, 180 μm, or 200 μm; and the porosity is 40-90%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%. However, the present invention is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0095] In some embodiments of the present invention, the silica aerogel particles are amino-modified silica aerogel particles. The amino modification can, on the one hand, improve the bonding strength between the carbon nanotubes and the silica aerogel particles to a certain extent; on the other hand, the decomposition products of polystyrene can react with the amino-modified groups to form a dense, continuous ceramic carbon layer (carbonitride) on the combustion surface. This ceramic carbon layer has self-healing properties and can continuously densify with increasing temperature, thereby further improving the flame retardancy of the material.

[0096] In the embodiments of the present invention, the method for aminated modification of the silica aerogel particles is not particularly limited and can be routinely selected by those skilled in the art. As a non-limiting example, the silica aerogel particles can be added to a solution containing an aminosilane coupling agent to react to obtain amino-modified silica aerogel particles. The aminosilane coupling agent can be, for example, 3-aminopropyltriethoxysilane, and the solvent in the aminosilane coupling agent solution can be, for example, ethanol. The reaction conditions can be, for example, 60°C for 4 hours.

[0097] In some embodiments of the present invention, the binder is selected from one or more of phenolic resin, furan resin, and epoxy resin. In embodiments of the present invention, the binder can improve the bonding between the carbon nanotubes and the silica aerogel particles and form a carbon layer at high temperatures, providing a certain flame retardant effect.

[0098] In some embodiments of the present invention, the solvent used in the preparation process of the CNTs-SiO2 particles is ethanol.

[0099] In some embodiments of the present invention, during the preparation of the CNTs-SiO2 particles, the mass ratio of the binder, carbon nanotubes, silica aerogel particles and solvent is (5-10):(3-5):(40-60):150.

[0100] In some embodiments of the present invention, during the preparation of the CNTs-SiO2 particles, the thermal curing temperature is 100-120°C and the time is 1-3 hours.

[0101] In a fourth aspect, the present invention provides a method for preparing the composite polystyrene material according to the third aspect, the preparation method comprising the following steps:

[0102] Mixing styrene, microcapsule flame retardant, CNTs-SiO2 particles and initiator to obtain an oil phase solution;

[0103] mixing an emulsifier with water to obtain an aqueous phase solution;

[0104] The oil phase solution is added to the water phase solution, and the mixture is reacted under stirring to obtain the composite polystyrene material.

[0105] In some embodiments of the present invention, the mass of the initiator is 1-1.5% of the mass of the styrene; for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0106] In the embodiment of the present invention, the initiator may be a conventional initiator for styrene polymerization reaction, such as benzoyl peroxide.

[0107] In some embodiments of the present invention, the mass ratio of the emulsifier to water is (1-3):100; for example, it can be 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, 2.2:100, 2.5:100, 2.8:100 or 3:100, etc. However, the present invention is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0108] In some embodiments of the present invention, the emulsifier is sodium dodecyl sulfate (SDS).

[0109] In some embodiments of the present invention, the volume ratio of the oil phase solution to the aqueous phase solution is 1:(4-8). However, the present invention is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0110] In some embodiments of the present invention, the reaction temperature is 70-100° C., for example, 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., or 100° C., and the reaction time is 2-4 h, for example, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, or 4 h, etc. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within the range are also applicable.

[0111] In some embodiments of the present invention, the stirring speed is 200-400 r / min; for example, it can be 200 r / min, 220 r / min, 230 r / min, 250 r / min, 260 r / min, 280 r / min, 300 r / min, 320 r / min, 330 r / min, 350 r / min, 360 r / min, 380 r / min or 400 r / min, etc. However, the present invention is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0112] In some embodiments of the present invention, the oil phase solution is added dropwise to the aqueous phase solution. During the dropwise addition, the temperature of the oil phase solution is 85°C, and the temperature of the aqueous phase solution is 45°C.

[0113] In a fifth aspect, the present invention provides a polystyrene foam material, wherein the polystyrene foam material comprises a skeleton and foam cells;

[0114] The material of the skeleton is the composite polystyrene material described in the third aspect.

[0115] The polystyrene foam material provided in an embodiment of the present invention is formed by foaming the composite polystyrene material. In addition to having the flame retardant effect of the composite polystyrene material, it also has a multi-level pore structure from nanometer to micrometer scale, including polystyrene foam cells (50-300μm), silica aerogel mesopores (2-50nm) and macropores (1-5mm). This structure not only optimizes the thermal insulation performance of the material, but also provides a channel for gas release during the flame retardant process.

[0116] In some embodiments of the present invention, the microcapsule flame retardant content of the surface layer of the styrene foam material is greater than the microcapsule flame retardant content inside; the CNTs-SiO2 particle content of the surface layer of the styrene foam material is less than the CNTs-SiO2 particle content inside.

[0117] In the embodiments of the present invention, by creating the aforementioned gradient distribution of microcapsule flame retardants and CNTs-SiO2 particles within the polystyrene foam material, a flame retardant effect that provides both external protection and internal stability can be achieved, further enhancing the flame retardancy of the polystyrene foam material. This gradient distribution can be achieved by controlling the surface temperature of the composite polystyrene material to be higher than the core temperature during the foaming process and applying periodic pressure.

[0118] In a sixth aspect, the present invention provides a method for preparing the polystyrene foam material according to the fifth aspect, the preparation method comprising the following steps:

[0119] S1. placing the composite polystyrene material described in the third aspect in a mold and introducing steam for pre-foaming;

[0120] S2. placing the pre-foamed composite polystyrene material in a mold, introducing steam to foam it, and obtaining the polystyrene foam material after cooling.

[0121] In some embodiments of the present invention, the surface temperature of the mold in step S1 is greater than the center temperature.

[0122] In some embodiments of the present invention, the surface temperature of the mold in step S1 is 100-110°C, for example, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, or 110°C; and the center temperature is 80-90°C, for example, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, or 90°C. However, the present invention is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0123] In some embodiments of the present invention, the steam pressure in step S1 is 0.4-0.5 MPa, for example, 0.4 MPa, 0.42 MPa, 0.43 MPa, 0.45 MPa, 0.46 MPa, 0.48 MPa, or 0.5 MPa, etc. However, the present invention is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0124] In some embodiments of the present invention, the pre-foaming ratio in step S1 is 30-40 times; for example, it can be 30 times, 32 times, 33 times, 35 times, 36 times, 38 times, or 40 times, etc. However, the present invention is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0125] In some embodiments of the present invention, the surface temperature of the mold in step S2 is greater than the center temperature.

[0126] In some embodiments of the present invention, the surface temperature of the mold in step S2 is 110-125°C, for example, 110°C, 112°C, 113°C, 115°C, 116°C, 118°C, 120°C, 122°C, 123°C, or 125°C; and the center temperature is 95-105°C, for example, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, or 105°C. However, the present invention is not limited to the listed values, and other values ​​within this range that are not listed are also applicable.

[0127] In some embodiments of the present invention, in step S2, the steam pressure is 0.4-0.5 MPa, for example, 0.4 MPa, 0.42 MPa, 0.43 MPa, 0.45 MPa, 0.46 MPa, 0.48 MPa, or 0.5 MPa, etc. However, the present invention is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0128] In some embodiments of the present invention, in step S2, a periodic pressure is applied to the pre-foamed composite polystyrene material during foaming; the periodic pressure has a valley value of 0, a peak value of 0.1-0.3 MPa (e.g., 0.1 MPa, 0.12 MPa, 0.15 MPa, 0.18 MPa, 0.2 MPa, 0.22 MPa, 0.25 MPa, 0.28 MPa, or 0.3 MPa), and a frequency of 0.3-0.5 Hz (e.g., 0.3 Hz, 0.32 Hz, 0.35 Hz, 0.38 Hz, 0.4 Hz, 0.42 Hz, 0.45 Hz, 0.48 Hz, or 0.5 Hz). However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within this range are equally applicable.

[0129] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail with reference to the following embodiments. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way serves as any limitation on the present invention and its applications. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0130] The sources of some raw materials in the examples of the present invention are as follows:

[0131] Silica aerogel particles: products of Corpuscular, USA, particle size 50-200 μm, pore size 2-50 nm;

[0132] Ammonium polyphosphate: Sinopharm Chemical Reagent Co., Ltd., CAS No. 68333-79-9, SH-APP-70;

[0133] Carbon nanotubes: Sinopharm Chemical Reagent Co., Ltd., CAS No. 308068-56-6, SH-NM-3080.

[0134] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to conventional techniques or conditions in the art, or those described in the literature, or the product instructions. Reagents or instruments used without manufacturer specified were all commercially available conventional products.

[0135] Example 1

[0136] This embodiment provides a polystyrene foam material, the preparation method of which includes the following steps:

[0137] S1. Styrene monomer, microcapsule flame retardant, CNTs-SiO2 particles and benzoyl peroxide were mixed in a mass ratio of 100:1:3:1 and stirred at 85°C to obtain an oil phase solution;

[0138] S2. Add the emulsifier SDS to water at a mass ratio of SDS to water of 1:100 and stir at 45°C to obtain an aqueous solution.

[0139] S3. Under stirring conditions at a speed of 200 r / min, the 85 ° C oil phase solution was added dropwise to the 45 ° C aqueous phase solution, the volume ratio of the oil phase solution to the aqueous phase solution was 1:4; after the addition was completed, the reaction was stirred at 70 ° C for 4h to obtain composite polystyrene material beads;

[0140] S4. The composite polystyrene beads are placed in a mold having a temperature gradient, the surface temperature of the mold is 100°C, the center temperature is 90°C, and 0.4MPa of water vapor is introduced for pre-foaming, and the pre-foaming expansion ratio is 30 times;

[0141] S5. Transfer the pre-foamed beads to a molding mold and use zoned heating technology to control the temperature of the mold surface area to 110°C and the temperature of the center area to 95°C. The mold is controlled to apply periodic pressure with a valley value of 0, a peak value of 0.1 MPa, and a frequency of 0.5 Hz. Simultaneously, 0.4 MPa of water vapor is introduced for foaming. After molding, cool to room temperature to obtain a polystyrene foam material.

[0142] The preparation method of CNTs-SiO2 particles includes the following steps:

[0143] S11. The silica aerogel particles were immersed in an ethanol solution of 3-aminopropyltriethoxysilane at a concentration of 2 g / L and a solid-liquid ratio of 5 g / L. The reaction was carried out at 60°C for 4 h. The solid product was washed and dried to obtain amino-modified silica aerogel particles.

[0144] S12. The phenolic resin was dissolved in anhydrous ethanol, carbon nanotubes were added, and ultrasonic dispersion was performed to obtain a dispersion;

[0145] S13. Amino-modified silica aerogel particles were added to the dispersion in a mass ratio of phenolic resin, carbon nanotubes, amino-modified silica aerogel particles, and anhydrous ethanol of 5:3:40:150. The dispersion was ultrasonically treated for 2 h. The solid product was thermally cured at 100°C for 3 h to obtain CNTs-SiO2 particles.

[0146] The preparation method of the microcapsule flame retardant comprises the following steps:

[0147] S21. A 37 wt % aqueous formaldehyde solution and melamine were mixed in a mass ratio of 20:8 and reacted at 70 ° C for 3 h to obtain a melamine - formaldehyde resin prepolymer solution;

[0148] S22. The zinc carbonate and melamine - formaldehyde resin prepolymer solution were mixed in a mass ratio of 1:50 to obtain a shell material precursor solution;

[0149] S23. Using a methanol solution of ammonium polyphosphate with a concentration of 25 wt% as the core material solution, the shell material precursor solution is added dropwise to the core material solution under stirring conditions at a rotation speed of 400 r / min. The volume ratio of the shell material precursor solution to the core material solution is 1:1, and the dropping rate is 0.5 mL / min. After the dropwise addition is completed, the reaction is stirred at 90°C for 2 h. After the solid product is dried, a microcapsule flame retardant is obtained.

[0150] Example 2

[0151] This embodiment provides a polystyrene foam material, the preparation method of which includes the following steps:

[0152] S1. Styrene monomer, microcapsule flame retardant, CNTs-SiO2 particles and benzoyl peroxide were mixed in a mass ratio of 100:2:4:1.5 and stirred at 85°C to obtain an oil phase solution;

[0153] S2. Add the emulsifier SDS to water at a mass ratio of 3:100 and stir at 45°C to obtain an aqueous solution.

[0154] S3. Under stirring conditions at a speed of 400 r / min, the 85 ° C oil phase solution was added dropwise to the 45 ° C aqueous phase solution, the volume ratio of the oil phase solution to the aqueous phase solution was 1:8; after the addition was completed, the reaction was stirred at 100 ° C for 2h to obtain composite polystyrene material beads;

[0155] S4. The composite polystyrene beads are placed in a mold having a temperature gradient, the surface temperature of the mold is 110 ℃, the center temperature is 80 ℃, 0.5MPa of water vapor is introduced for pre-foaming, and the pre-foaming expansion ratio is 40 times;

[0156] S5. Transfer the pre-foamed beads to a molding mold and use zoned heating technology to control the temperature of the mold surface area to 125°C and the temperature of the center area to 105°C. The mold is controlled to apply periodic pressure with a valley value of 0, a peak value of 0.3 MPa, and a frequency of 0.3 Hz. Simultaneously, 0.5 MPa of water vapor is introduced for foaming. After molding, cool to room temperature to obtain a polystyrene foam material.

[0157] The preparation method of CNTs-SiO2 particles includes the following steps:

[0158] S11. The silica aerogel particles were immersed in an ethanol solution of 3-aminopropyltriethoxysilane at a concentration of 2 g / L and a solid-liquid ratio of 5 g / L. The reaction was carried out at 60°C for 4 h. The solid product was washed and dried to obtain amino-modified silica aerogel particles.

[0159] S12. The phenolic resin was dissolved in anhydrous ethanol, carbon nanotubes were added, and ultrasonic dispersion was performed to obtain a dispersion;

[0160] S13. Amino-modified silica aerogel particles were added to the dispersion in a mass ratio of phenolic resin, carbon nanotubes, amino-modified silica aerogel particles, and anhydrous ethanol of 10:5:60:150. The dispersion was ultrasonically treated for 2 h. The solid product was thermally cured at 120°C for 3 h to obtain CNTs-SiO2 particles.

[0161] The preparation method of the microcapsule flame retardant comprises the following steps:

[0162] S21. A 37 wt % aqueous formaldehyde solution and melamine were mixed in a mass ratio of 25:8 and reacted at 80 ° C for 1.5 h to obtain a melamine - formaldehyde resin prepolymer solution;

[0163] S22. The zinc carbonate and melamine - formaldehyde resin prepolymer solution were mixed in a mass ratio of 2:50 to obtain a shell material precursor solution;

[0164] S23. Using a methanol solution of ammonium polyphosphate with a concentration of 30 wt% as the core material solution, the shell material precursor solution is added dropwise to the core material solution under a stirring condition of 800 r / min. The volume ratio of the shell material precursor solution to the core material solution is 1:1, and the dropping rate is 2 mL / min. After the dropwise addition is completed, the reaction is stirred at 80°C for 4 h. After the solid product is dried, a microcapsule flame retardant is obtained.

[0165] Example 3

[0166] This embodiment provides a polystyrene foam material, the preparation method of which includes the following steps:

[0167] S1. Styrene monomer, microcapsule flame retardant, CNTs-SiO2 particles and benzoyl peroxide were mixed in a mass ratio of 100:1.2:3.6:1.2 and stirred at 85 ° C to obtain an oil phase solution;

[0168] S2. Add the emulsifier SDS to water at a mass ratio of SDS to water of 2.5:100 and stir at 45°C to obtain an aqueous solution;

[0169] S3. Under stirring conditions at a speed of 250 r / min, the 85 ℃ oil phase solution was added dropwise to the 45 ℃ aqueous phase solution, the volume ratio of the oil phase solution to the aqueous phase solution was 1:5; after the addition was completed, the reaction was stirred at 80 ℃ for 4h to obtain composite polystyrene material beads;

[0170] S4. The composite polystyrene beads are placed in a mold having a temperature gradient, the surface temperature of the mold is 100 ℃, the center temperature is 80 ℃, and 0.45MPa of water vapor is introduced for pre-foaming, and the pre-foaming expansion ratio is 40 times;

[0171] S5. Transfer the pre-foamed beads to a molding mold and use zoned heating technology to control the temperature of the mold surface area to 115°C and the temperature of the center area to 98°C. The mold is controlled to apply periodic pressure with a valley value of 0, a peak value of 0.25 MPa, and a frequency of 0.4 Hz. Simultaneously, 0.45 MPa of water vapor is introduced for foaming. After molding, cool to room temperature to obtain a polystyrene foam material.

[0172] The preparation method of CNTs-SiO2 particles includes the following steps:

[0173] S11. The silica aerogel particles were immersed in an ethanol solution of 3-aminopropyltriethoxysilane at a concentration of 2 g / L and a solid-liquid ratio of 5 g / L. The reaction was carried out at 60°C for 4 h. The solid product was washed and dried to obtain amino-modified silica aerogel particles.

[0174] S12. The phenolic resin was dissolved in anhydrous ethanol, carbon nanotubes were added, and ultrasonic dispersion was performed to obtain a dispersion;

[0175] S13. Amino-modified silica aerogel particles were added to the dispersion in a mass ratio of phenolic resin, carbon nanotubes, amino-modified silica aerogel particles, and anhydrous ethanol of 6:3:45:150. The dispersion was ultrasonically treated for 2 h. The solid product was thermally cured at 105°C for 2.5 h to obtain CNTs-SiO2 particles.

[0176] The preparation method of the microcapsule flame retardant comprises the following steps:

[0177] S21. A 37 wt % aqueous formaldehyde solution and melamine were mixed in a mass ratio of 22:8 and reacted at 75 ° C for 2 h to obtain a melamine - formaldehyde resin prepolymer solution;

[0178] S22. The zinc carbonate and melamine - formaldehyde resin prepolymer solution were mixed in a mass ratio of 1.5:50 to obtain a shell material precursor solution;

[0179] S23. Using a methanol solution of ammonium polyphosphate with a concentration of 25 wt% as the core material solution, the shell material precursor solution is added dropwise to the core material solution at a stirring speed of 600 r / min. The volume ratio of the shell material precursor solution to the core material solution is 1:1, and the dropping rate is 1 mL / min. After the dropwise addition is completed, the reaction is stirred at 80°C for 3.5 hours. After the solid product is dried, a microcapsule flame retardant is obtained.

[0180] Example 4

[0181] This embodiment provides a polystyrene foam material, the preparation method of which includes the following steps:

[0182] S1. Styrene monomer, microcapsule flame retardant, CNTs-SiO2 particles and benzoyl peroxide were mixed in a mass ratio of 100:1.8:3.6:1.4 and stirred at 85 ° C to obtain an oil phase solution;

[0183] S2. Add the emulsifier SDS to water at a mass ratio of SDS to water of 1.5:100 and stir at 45°C to obtain an aqueous solution;

[0184] S3. Under stirring conditions at a speed of 350 r / min, the 85 ° C oil phase solution was added dropwise to the 45 ° C aqueous phase solution, the volume ratio of the oil phase solution to the aqueous phase solution was 1:7; after the addition was completed, the reaction was stirred at 90 ° C for 3h to obtain composite polystyrene material beads;

[0185] S4. The composite polystyrene beads are placed in a mold having a temperature gradient, the surface temperature of the mold is 110 ℃, the center temperature is 90 ℃, 0.4MPa of water vapor is introduced for pre-foaming, and the pre-foaming expansion ratio is 30 times;

[0186] S5. The pre-foamed beads are transferred to a molding mold. Using zoned heating technology, the surface temperature of the mold is controlled to 120°C and the center temperature is controlled to 102°C. The mold is also controlled to apply periodic pressure with a valley value of 0, a peak value of 0.15 MPa, and a frequency of 0.3 Hz. Simultaneously, 0.4 MPa of water vapor is introduced for foaming. After molding, the beads are cooled to room temperature to obtain a polystyrene foam material.

[0187] The preparation method of CNTs-SiO2 particles includes the following steps:

[0188] S11. The silica aerogel particles were immersed in an ethanol solution of 3-aminopropyltriethoxysilane at a concentration of 2 g / L at a solid-liquid ratio of 5 g / L g / mL. The reaction was carried out at 60°C for 4 h. The solid product was washed and dried to obtain amino-modified silica aerogel particles.

[0189] S12. The phenolic resin was dissolved in anhydrous ethanol, carbon nanotubes were added, and ultrasonic dispersion was performed to obtain a dispersion;

[0190] S13. Amino-modified silica aerogel particles were added to the dispersion in a mass ratio of phenolic resin, carbon nanotubes, amino-modified silica aerogel particles, and anhydrous ethanol of 9:4:55:150. The dispersion was ultrasonically treated for 2 h. The solid product was thermally cured at 115°C for 2 h to obtain CNTs-SiO2 particles.

[0191] The preparation method of the microcapsule flame retardant comprises the following steps:

[0192] S21. A 37 wt % aqueous formaldehyde solution and melamine were mixed in a mass ratio of 24:8 and reacted at 75 ° C for 2 h to obtain a melamine - formaldehyde resin prepolymer solution;

[0193] S22. The zinc carbonate and melamine - formaldehyde resin prepolymer solution were mixed in a mass ratio of 1:50 to obtain a shell material precursor solution;

[0194] S23. Using a methanol solution of ammonium polyphosphate with a concentration of 25 wt% as the core material solution, the shell material precursor solution is added dropwise to the core material solution under a stirring condition of 600 r / min. The volume ratio of the shell material precursor solution to the core material solution is 1:1, and the dropping rate is 1 mL / min. After the dropwise addition is completed, the reaction is stirred at 85°C for 3.5 hours. After the solid product is dried, a microcapsule flame retardant is obtained.

[0195] Example 5

[0196] This embodiment provides a polystyrene foam material, the preparation method of which differs from that of Example 4 only in that: in step S4, the surface and center temperatures of the mold are both 100°C; in step S5, the surface and center area temperatures of the mold are both 110°C, and no periodic pressure is applied.

[0197] Example 6

[0198] This embodiment provides a polystyrene foam material, and the preparation method thereof is different from that of Example 4 only in that the volume ratio of the shell material precursor solution to the core material solution is 1:2.

[0199] Example 7

[0200] This embodiment provides a polystyrene foam material, and the preparation method thereof is different from that of Example 4 only in that the volume ratio of the shell material precursor solution to the core material solution is 3:1.

[0201] Comparative Example 1

[0202] This comparative example provides a polystyrene foam material, the preparation method of which differs from that of Example 4 only in that the CNTs-SiO2 particles in step S1 are replaced with silica aerogel particles.

[0203] Comparative Example 2

[0204] This comparative example provides a polystyrene foam material, the preparation method of which is different from that of Example 4 only in that no phenolic resin is added in step S12.

[0205] Comparative Example 3

[0206] This comparative example provides a polystyrene foam material, the preparation method of which is different from that of Example 4 only in that zinc carbonate is not added in step S22.

[0207] Comparative Example 4

[0208] This comparative example provides a polystyrene foam material, the preparation method of which is different from that of Example 4 only in that carbon nanotubes are not added in step S12.

[0209] Comparative Example 5

[0210] This comparative example provides a polystyrene foam material, the preparation method of which differs from that of Example 4 only in that the CNTs-SiO2 particles in step S1 are replaced with microcapsule flame retardants of the same mass.

[0211] Comparative Example 6

[0212] This comparative example provides a polystyrene foam material, the preparation method of which differs from that of Example 4 only in that the microcapsule flame retardant in step S1 is replaced by CNTs-SiO2 particles of the same mass.

[0213] Performance Testing

[0214] The flame retardant properties of the polystyrene foam materials provided in the above examples and comparative examples were tested using the following test methods:

[0215] Self-extinguishing time: According to the self-extinguishing test method of SG-232-81, place the sample at a 45° angle to the horizontal plane, ignite it with a candle flame for 5 seconds, and measure the time the sample continues to burn after the flame is removed. If it extinguishes within two seconds, it is qualified.

[0216] Limiting Oxygen Index: The minimum oxygen concentration required for a material to sustain combustion in a mixture of O₂ and N₂ under specified test conditions, expressed as a percentage by volume. Limiting Oxygen Index test standard: GBT2406-2008. Specimen size: 100mm × 10mm × 10mm strip.

[0217] The results of the above performance tests are shown in Table 1.

[0218] Table 1

[0219]

[0220]

[0221] It can be seen from the data in Table 1 that the polystyrene foam materials provided by Examples 1-4 of the present invention have shorter self-extinguishing times and higher limiting oxygen indexes, indicating that they have good flame retardant properties.

[0222] Among them, compared with Example 4, in Example 5, since zoned heating was not used and periodic pressure was not applied during the foaming process, the microcapsule flame retardant and CNTs-SiO2 particles did not form a gradient distribution, and therefore the flame retardant properties of the obtained polystyrene foam material were reduced.

[0223] Compared with Example 4, the core material content of the microcapsule flame retardant in Example 6 is relatively high, and the shell material content is relatively low. The core material content of the microcapsule flame retardant in Example 7 is relatively low, and the shell material content is relatively high. Both lead to unbalanced contents of acid source, carbon source and gas source in the microcapsule flame retardant, affecting the synergistic flame retardant effect. Therefore, the flame retardant properties of the polystyrene foam materials obtained in Examples 6 and 7 are both reduced.

[0224] Compared with Example 4, Comparative Example 1 uses silica aerogel particles instead of CNTs-SiO2 particles, and the aerogel particles used in Comparative Example 4 do not contain carbon nanotubes and do not have the function of guiding the orderly growth of the carbon layer. Therefore, both lead to a significant decrease in the flame retardant properties of the polystyrene foam material.

[0225] Compared with Example 4, no phenolic resin was added when preparing CNTs-SiO2 particles in Comparative Example 2, resulting in poor bonding between carbon nanotubes and silica aerogel particles. At the same time, phenolic resin can also form a carbon layer at high temperature to play a certain flame retardant role. Therefore, the flame retardant properties of the polystyrene foam material prepared in Comparative Example 2 are significantly reduced.

[0226] Compared with Example 4, the microcapsule flame retardant used in Comparative Example 3 does not contain zinc carbonate and cannot generate CO2 and ZnO at high temperature to exert its flame retardant function, thereby causing a significant decrease in the flame retardant properties of the polystyrene foam material.

[0227] Compared with Example 4, the polystyrene foam material provided in Comparative Example 5 only adds microcapsule flame retardant, and the polystyrene foam material provided in Comparative Example 6 only adds CNTs-SiO2 particles. Both do not have the synergistic flame retardant effect of microcapsule flame retardant and CNTs-SiO2 particles, and therefore both lead to a significant decrease in the flame retardant properties of the polystyrene foam material.

[0228] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments described herein, but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A microcapsule flame retardant, characterized in that: The microcapsule flame retardant has a core-shell structure; The core material of the microcapsule flame retardant is ammonium polyphosphate; The shell material of the microcapsule flame retardant comprises melamine-formaldehyde resin and zinc carbonate.

2. The microcapsule flame retardant according to claim 1, characterized in that In the raw materials for preparing the microcapsule flame retardant, the mass ratio of ammonium polyphosphate, melamine-formaldehyde resin and zinc carbonate is (10-30):(25-30):(1-2); Preferably, in the polymerized monomers of the melamine-formaldehyde resin, the mass ratio of formaldehyde to melamine is (7-10):8; Preferably, the particle size of the microcapsule flame retardant is 200-800 μm.

3. A method for preparing a microcapsule flame retardant according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) reacting formaldehyde and melamine in water to obtain a melamine-formaldehyde resin prepolymer solution; (2) mixing the melamine-formaldehyde resin prepolymer solution with zinc carbonate to obtain a shell material precursor solution; (3) adding the shell material precursor solution dropwise to the ammonium polyphosphate solution, reacting under stirring conditions, and drying to obtain the microcapsule flame retardant.

4. The preparation method according to claim 3, characterized in that The reaction temperature in step (1) is 70-80°C and the reaction time is 1.5-3h; Preferably, the concentration of the melamine-formaldehyde resin prepolymer solution in step (1) is 50-60 wt %; Preferably, the reaction temperature in step (3) is 80-90°C, the reaction time is 2-4h, and the stirring speed is 400-800r / min; Preferably, the concentration of the ammonium polyphosphate solution in step (3) is 25-30 wt%; Preferably, the solvent of the ammonium polyphosphate solution in step (3) is selected from one or both of methanol and ethanol.

5. A composite polystyrene material, characterized in that: The composite polystyrene material comprises polystyrene, a microcapsule flame retardant and CNTs-SiO2 particles; the microcapsule flame retardant and the CNTs-SiO2 particles are dispersed in the polystyrene; The microcapsule flame retardant is the microcapsule flame retardant according to claim 1 or 2 or the microcapsule flame retardant prepared by the preparation method according to claim 3 or 4; The CNTs-SiO2 particles include silica aerogel particles, carbon nanotubes and a binder, and the carbon nanotubes are adhered to the pores and surface of the silica aerogel particles through the binder; Preferably, in the composite polystyrene material, the mass of the microcapsule flame retardant is 1-2% of the mass of the polystyrene; Preferably, in the composite polystyrene material, the mass of the CNTs-SiO2 particles is 3-4% of the mass of the polystyrene; Preferably, in the CNTs-SiO2 particles, the mass ratio of carbon nanotubes to silica aerogel particles is (3-5):(40-60); Preferably, the silica aerogel particles have a pore size of 2-50 nm, a particle size of 50-200 μm, and a porosity of 40-90%; Preferably, the silica aerogel particles are amino-modified silica aerogel particles; Preferably, the binder is selected from one or more of phenolic resin, furan resin and epoxy resin.

6. A method for preparing a composite polystyrene material according to claim 5, characterized in that: The preparation method comprises the following steps: Mixing styrene, microcapsule flame retardant, CNTs-SiO2 particles and initiator to obtain an oil phase solution; mixing an emulsifier with water to obtain an aqueous phase solution; adding the oil phase solution to the water phase solution, and reacting under stirring to obtain the composite polystyrene material; Preferably, the mass of the initiator is 1-1.5% of the mass of the styrene; Preferably, the mass ratio of the emulsifier to water is (1-3):100; Preferably, the emulsifier is sodium lauryl sulfate; Preferably, the volume ratio of the oil phase solution to the aqueous phase solution is 1:(4-8); Preferably, the reaction temperature is 70-100°C and the reaction time is 2-4h; Preferably, the stirring speed is 200-400 r / min.

7. A polystyrene foam material, characterized in that: The polystyrene foam material comprises a skeleton and pores; The material of the skeleton is the composite polystyrene material according to claim 5 or 6.

8. The polystyrene foam material according to claim 7, characterized in that: The content of the microcapsule flame retardant in the surface layer of the styrene foam material is greater than the content of the microcapsule flame retardant in the interior; The content of CNTs-SiO2 particles in the surface layer of the styrene foam material is less than that in the interior.

9. A method for preparing a polystyrene foam material according to claim 7 or 8, characterized in that: The preparation method comprises the following steps: S1. placing the composite polystyrene material according to claim 5 or 6 in a mold and introducing steam for pre-foaming; S2. placing the pre-foamed composite polystyrene material in a mold, introducing steam to foam it, and obtaining the polystyrene foam material after cooling.

10. The preparation method according to claim 9, characterized in that In step S1, the surface temperature of the mold is greater than the center temperature; Preferably, the surface temperature of the mold in step S1 is 100-110°C, and the center temperature is 80-90°C; Preferably, the pressure of the steam in step S1 is 0.4-0.5 MPa; Preferably, the pre-foaming ratio in step S1 is 30-40 times; Preferably, in step S2, the surface temperature of the mold is greater than the center temperature; Preferably, the surface temperature of the mold in step S2 is 110-125°C, and the center temperature is 95-105°C; Preferably, the pressure of the steam in step S2 is 0.4-0.5 MPa; Preferably, in step S2, periodic pressure is applied to the pre-foamed composite polystyrene material during foaming; the valley value of the periodic pressure is 0, the peak value is 0.1-0.3 MPa, and the frequency is 0.3-0.5 Hz.

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