Flame-retardant polystyrene beads, flame-retardant polystyrene insulation board and preparation method

Abstract

The present invention relates to flame-retardant polystyrene beads, flame-retardant polystyrene insulation boards, and a preparation method. The method comprises the following steps: pre-foaming and aging the polystyrene beads; the raw material of the polystyrene beads includes 10-15% by mass of a flame retardant; adding the aged pre-foamed polystyrene beads to ungelled SiO2 hydrogel and mechanically stirring until the SiO2 hydrogel completely covers the surface of the polystyrene beads; adding a phosphoric acid solution until gelation occurs and reacting for 10-20 minutes; then adding a NaOH solution to adjust the pH of the system to 9.5-10 to obtain polystyrene beads coated with SiO2 wet gel; aging the polystyrene beads coated with SiO2 wet gel, surface-modifying them, and supercritical drying them to obtain the flame-retardant polystyrene beads. The technical problem to be solved is how to improve the flame retardancy and thermal insulation properties of polystyrene insulation materials so that their thermal conductivity is ≤0.026W / (m·K), their limiting oxygen index is ≥35%, their vertical combustion grade reaches V0, and their horizontal combustion grade reaches V2 to V1.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation materials, and in particular relates to flame-retardant polystyrene beads, a flame-retardant polystyrene insulation board and a preparation method thereof. Background Art

[0002] Currently, my country's traditional polystyrene insulation materials have poor fire resistance, and their combustion performance is mostly Class B. They produce a large amount of toxic and harmful gases when burned, which poses a great safety hazard. Their mechanical strength is low, and their application is also limited.

[0003] SiO2 aerogels have been extensively researched in recent years as flame retardants because they effectively transmit sunlight while blocking ambient infrared radiation and are inherently inorganic and non-combustible. However, the hydrophobic modification required in aerogel preparation and the introduction of organic functional groups can degrade the thermal stability of the aerogel material, and these organic components also pose a potential fire risk.

[0004] To date, there have been many studies on aerogel materials as flame retardant modifiers. The application of aerogel materials as flame retardant modifiers in polystyrene insulation materials mainly includes the following two methods: one is to use aerogel particles as the core and use suspension polymerization to prepare aerogel / polystyrene expandable beads. For example, Chang'an University's master's thesis "Preparation and Molding Research of SiO2 Aerogel PS Core-Shell Composite Insulation Materials" made relevant records. However, the production process of this method is relatively cumbersome and not suitable for large-scale promotion and application. In addition, the flame retardant and thermal insulation properties of the polystyrene insulation materials prepared by this technical means are not significantly improved. The second method is to simply physically add aerogel particles during the molding process. However, the flame retardant and thermal insulation properties of the polystyrene insulation materials prepared by this technical means are not significantly improved. In addition, the thermal conductivity coefficient of the polystyrene insulation materials prepared by this method varies greatly at different measuring points. There are many flammable points in the material, which cannot solve the problem of poor fire resistance and combustion performance of polystyrene insulation materials. Summary of the Invention

[0005] The main purpose of the present invention is to provide flame-retardant polystyrene beads, flame-retardant polystyrene insulation board and preparation method. The technical problem to be solved is how to improve the flame retardancy and thermal insulation properties of polystyrene insulation materials so that their thermal conductivity is ≤0.026W / (m·K), the limiting oxygen index is ≥35%, the vertical combustion level reaches V0, and the horizontal combustion level reaches V2 to V1, so as to be more suitable for practical use.

[0006] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. According to the present invention, a method for preparing flame retardant polystyrene beads is proposed, which comprises the following steps:

[0007] 1) pre-foaming polystyrene beads and aging; the raw material of the polystyrene beads includes 10 to 15% of a flame retardant by weight;

[0008] 2) adding the matured pre-expanded polystyrene beads to the ungelled SiO2 hydrogel and mechanically stirring until the SiO2 hydrogel completely covers the surface of the polystyrene beads; adding phosphoric acid solution until gelation occurs and reacting for 10 to 20 minutes; then adding NaOH solution to adjust the pH value of the system to 9.5 to 10 to obtain polystyrene beads coated with SiO2 wet gel;

[0009] 3) aging the polystyrene beads coated with the SiO2 wet gel, performing surface modification, and supercritical drying to obtain flame-retardant polystyrene beads.

[0010] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0011] Preferably, in the aforementioned preparation method, the flame retardant is selected from at least one of expanded graphite, high polyammonium phosphate, pentaerythritol, microcapsule red phosphorus, aluminum hydroxide, and zinc borate.

[0012] Preferably, in the aforementioned preparation method, the pre-foaming is to place the polystyrene beads in water vapor at 100°C and maintain it at a saturated vapor pressure of 0.4 to 0.6 MPa for 30 to 40 seconds; and the aging is to place the pre-foamed polystyrene beads in a place with air circulation at room temperature for 20 to 30 hours.

[0013] Preferably, in the aforementioned preparation method, the SiO2 hydrogel is prepared according to the following steps: adding anhydrous ethanol and deionized water to inorganic sodium silicate, adjusting the pH value to 3.0-4.0 with 0.1-1 mol / L phosphoric acid solution, and stirring for 5-10 minutes; the molar ratio of the inorganic sodium silicate, anhydrous ethanol and deionized water is 1:8:20.

[0014] Preferably, in the aforementioned preparation method, the aging step is to heat the SiO2 wet gel-coated polystyrene beads to 45-55° C. and keep the temperature in anhydrous ethanol for 12-24 hours.

[0015] Preferably, in the aforementioned preparation method, the surface modification is performed by adding aged polystyrene beads to a mixture of hexamethyldisilazane and ethanol and reacting for 12 to 24 hours; the molar ratio of hexamethyldisilazane to ethanol in the mixture is 1:1.

[0016] Preferably, in the aforementioned preparation method, the supercritical drying is to place the surface-modified polystyrene beads in a supercritical drying kettle, introduce carbon dioxide gas therein for drying, increase the pressure for 1.5 hours, and maintain the pressure at 15-16 MPa for 8-10 hours.

[0017] The purpose of the present invention and the technical problems solved therein are also achieved by adopting the following technical solutions: The present invention provides flame retardant polystyrene beads prepared according to the above-mentioned method for preparing flame retardant polystyrene beads.

[0018] The objectives of the present invention and the technical problems solved therein are also achieved by the following technical solutions. A method for preparing a flame-retardant polystyrene insulation board according to the present invention comprises the following steps: filling a mold with the aforementioned flame-retardant polystyrene beads, introducing high-pressure steam at a pressure of 0.4 to 0.6 MPa for steam molding for 180 seconds, and demolding the board; and drying and aging the demolded board at 60 to 70°C.

[0019] The purpose of the present invention and the technical problems solved therein are also achieved by adopting the following technical solutions: According to the present invention, a flame retardant polystyrene insulation board is prepared according to the above-mentioned method for preparing the flame retardant polystyrene insulation board.

[0020] By means of the above technical solution, the present invention provides a flame-retardant polystyrene bead, a flame-retardant polystyrene insulation board, and a preparation method thereof, which have at least the following advantages:

[0021] The flame retardant polystyrene beads, flame retardant polystyrene insulation board and preparation method proposed in the present invention prepare polystyrene beads by suspension polymerization, and improve the flame retardancy of the polystyrene beads themselves by controlling the addition of 10-15% of flame retardant to the polystyrene raw material; at the same time, a layer of SiO2 aerogel is evenly and firmly coated on the surface of the polystyrene beads to further enhance the flame retardancy and thermal insulation of the polystyrene material; further, the present invention adopts non-flammable inorganic sodium silicate as a silicon source and phosphoric acid as an acid catalyst and flame retardant. On the one hand, the inorganic sodium silicate and phosphoric acid themselves have good flame retardancy, and on the other hand, the introduction of organic components into the SiO2 aerogel can be avoided, thereby significantly improving the flame retardancy and thermal stability of the SiO2 aerogel from two dimensions; as can be seen from the above, in the technical solution of the present invention, hydrophobic SiO2 aerogel is micro-composite and coated on the surface of the multi-element flame retardant primary foamed polystyrene beads, The flame retardancy and thermal insulation properties of polystyrene are synergistically modified through the combined effects of the composite flame retardant and the inorganic silicon source SiO2 aerogel, thereby maximizing the advantages of the super insulating material SiO2 aerogel and the organic thermal insulation material polystyrene, thereby preparing a molded polystyrene thermal insulation material with low thermal conductivity and Class A combustion performance; specifically, the flame retardant polystyrene beads and flame retardant polystyrene insulation board prepared by the present invention have a thermal conductivity of ≤0.026W / (m·K), a limiting oxygen index of ≥35%, a vertical combustion grade of V0, and a horizontal combustion grade of V2 to V1; and the preparation method in the above technical scheme of the present invention is simple to operate. On the basis of preparing polystyrene by suspension polymerization and preparing inorganic silicon source SiO2 aerogel, the two are composited to form a core-shell structure with "polystyrene beads" as the core and "SiO2 aerogel" as the shell, which is then used to make boards for large-scale industrial production.

[0022] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the preparation process of flame-retardant polystyrene beads and insulation boards. DETAILED DESCRIPTION

[0024] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following, in combination with the accompanying drawings and preferred embodiments, describes in detail a flame retardant polystyrene bead, a flame retardant polystyrene insulation board and a preparation method proposed in accordance with the present invention, as well as its specific implementation method, structure, characteristics and effects.

[0025] The present invention provides a method for preparing flame retardant polystyrene beads, as shown in the attached Figure 1As shown, it includes the following steps: pre-foaming polystyrene beads and aging; then adding the aging pre-foamed polystyrene beads into ungelled SiO2 hydrogel and mechanically stirring until the SiO2 hydrogel completely wraps the surface of the polystyrene beads; adding phosphoric acid solution until gelation occurs and reacting for 10 to 20 minutes; then adding NaOH solution to adjust the pH value of the system to 9.5 to 10 to obtain SiO2 wet gel-coated polystyrene beads; aging the SiO2 wet gel-coated polystyrene beads, surface modifying, and supercritical drying to obtain flame-retardant polystyrene beads.

[0026] In the above technical solution, polystyrene beads are polymerized by suspension polymerization. The specific polymerization process can be found in the prior art document "Zhang Tao, Pan Wei, Cheng Feifei, Yu Yanghui, Lai Wei, Experimental Study on Preparation of Flame Retardant Graphite / Polystyrene Insulation Material [J], Non-metallic Minerals, 2022, 1(45): 34-36.)", which will not be described in detail in this patent. Among them, the polymerization raw materials include styrene and flame retardant; in the technical solution of the present invention, the polymerization raw materials include 10-15% flame retardant in terms of mass percentage. The flame retardant can be a single flame retardant or a composite flame retardant. The flame retardant is selected from at least one of expanded graphite, high polyammonium phosphate, pentaerythritol, microcapsule red phosphorus, aluminum hydroxide, and zinc borate. Furthermore, the flame retardant is selected from at least two of expanded graphite, high polyammonium phosphate, pentaerythritol, microcapsule red phosphorus, aluminum hydroxide, and zinc borate, that is, the product prepared using the composite flame retardant has better performance.

[0027] When a composite flame retardant is used, the above technical solution can achieve better flame retardant effect.

[0028] Preferably, the flame retardant is a composite flame retardant of expanded graphite, high polyammonium phosphate and pentaerythritol, wherein the mass ratio of expanded graphite, high polyammonium phosphate and pentaerythritol is preferably 5:2:3; at this time, the thermal conductivity of the polystyrene insulation board prepared by the technical solution of the present invention can be as low as 0.024W / (m·K), the limiting oxygen index can reach 41%, the vertical combustion grade reaches V0, and the horizontal combustion grade reaches V1.

[0029] Preferably, the flame retardant is a composite flame retardant of expanded graphite, aluminum hydroxide and zinc borate, wherein the mass ratio of expanded graphite, aluminum hydroxide and zinc borate is preferably 5:3:2; at this time, the thermal conductivity of the polystyrene insulation board prepared by the technical solution of the present invention can be as low as 0.025W / (m·K), the limiting oxygen index can reach 38%, the vertical combustion grade reaches V0, and the horizontal combustion grade reaches V1.

[0030] The polystyrene beads prepared by the suspension polymerization are pre-foamed and aged. The pre-foaming and aging requirements in this step can be based on the existing polystyrene bead pre-foaming and aging processes. Preferably, the pre-foaming step involves exposing the polystyrene beads to water vapor at 100°C and maintaining it at a saturated vapor pressure of 0.4-0.6 MPa for 30-40 seconds. The aging step involves placing the pre-foamed polystyrene beads at room temperature in a well-ventilated location for 20-30 hours.

[0031] In the above technical solution, the preparation technology of the SiO2 hydrogel is crucial. The specific steps are as follows: adding anhydrous ethanol and deionized water to inorganic sodium silicate, controlling the molar ratio of the inorganic sodium silicate, anhydrous ethanol, and deionized water to be 1:8:20; then adjusting the pH of the mixture to 3.0-4.0 with a 0.1-1 mol / L phosphoric acid solution and stirring for 5-10 minutes to form the SiO2 hydrogel. The choice of inorganic sodium silicate as the silicon source in the present invention is based on its low cost and, more importantly, on reducing or avoiding the introduction of organic components into the hydrogel, thereby improving its thermal stability and reducing the potential fire risk of organic components. The choice of phosphoric acid solution to adjust the pH of the system in the present invention is based on the flame retardancy of phosphoric acid, which not only creates an acidic environment for the hydrolysis reaction but also improves its thermal stability and reduces its potential fire risk.

[0032] According to the above steps, the polystyrene beads are pre-foamed and matured to prepare the SiO2 hydrogel. The matured pre-foamed polystyrene beads are added to the ungelled SiO2 hydrogel and mechanically stirred to completely wrap the surface of the polystyrene beads with the SiO2 hydrogel, forming a core-shell structure with the "matured pre-foamed polystyrene beads" as the core and the "SiO2 hydrogel" as the shell. Then, phosphoric acid solution is added to the system as an acid catalyst to cause a hydrolysis reaction in the system until gelation occurs, and the reaction is continued for 10 to 20 minutes. NaOH solution is then added to the system to adjust the pH value of the system to 9.5 to 10, so that the gel undergoes a condensation reaction to obtain polystyrene beads coated with SiO2 wet gel. At this time, the product structure is a core-shell structure with the "matured pre-foamed polystyrene beads" as the core and the "SiO2 wet gel" as the shell.

[0033] The polystyrene beads coated with the SiO2 wet gel are then aged, surface modified, and supercritically dried. The SiO2 wet gel coated on the surface of the polystyrene beads is converted into SiO2 aerogel through sol-gel reaction and supercritical carbon dioxide drying, thereby obtaining flame-retardant polystyrene beads. The structure of the flame-retardant polystyrene beads is a core-shell structure with "matured pre-foamed polystyrene beads" as the core and "SiO2 aerogel" as the shell. Through the core-shell structure, the SiO2 aerogel is evenly and firmly wrapped in the polystyrene beads, and the silicon source of the SiO2 aerogel itself adopts inorganic sodium silicate, so that the introduction of organic components can be avoided or reduced as much as possible. At the same time, during the suspension polymerization of the polystyrene beads, a flame retardant with a mass percentage of 10 to 15% is added to the raw materials to enhance its own flame retardancy. Through the comprehensive application of the above-mentioned technical means, the flame retardant polystyrene beads prepared by the present invention have excellent flame retardant and thermal insulation properties. It can be seen from the test data of the embodiment that the thermal conductivity of the flame retardant polystyrene beads prepared by the present invention is ≤0.026W / (m·K), the vertical combustion level reaches V0, and the horizontal combustion level reaches V2 to V1.

[0034] The aging method described in the above technical solution is preferably to raise the temperature of the SiO2 wet gel-coated polystyrene beads to 45-55°C and maintain the temperature in anhydrous ethanol for 12-24 hours. The surface modification method is preferably to add the aged polystyrene beads to a mixture of hexamethyldisilazane and ethanol and react for 12-24 hours; the molar ratio of hexamethyldisilazane to ethanol in the mixture is 1:1. The present invention preferably uses an alkaline system when performing the surface modification of the SiO2 wet gel to avoid the possibility of damaging the alkaline coating formed on the particle surface due to the alkaline polycondensation reaction during surface modification under acidic conditions, thereby effectively protecting the SiO2 wet gel layer coated on the surface of the polystyrene beads. The supercritical drying is to place the surface-modified polystyrene beads in a supercritical drying kettle, introduce carbon dioxide gas into it for drying treatment, increase the pressure for 1.5 hours, and maintain the pressure reaction at a pressure of 15 to 16 MPa for 8 to 10 hours; the temperature of the supercritical drying is controlled by the conventional temperature of carbon dioxide drying, generally 30 to 60°C, which is not specifically limited in this patent.

[0035] The present invention also provides flame-retardant polystyrene beads prepared according to the aforementioned method for preparing flame-retardant polystyrene beads. The flame-retardant polystyrene beads have excellent flame retardancy and thermal insulation properties and can be used to prepare flame-retardant polystyrene insulation boards, thereby imparting excellent flame retardancy and thermal insulation properties to the polystyrene insulation board.

[0036] The present invention also proposes a method for preparing a flame-retardant polystyrene insulation board, which includes the following steps: filling the aforementioned flame-retardant polystyrene beads into a mold, introducing high-pressure water vapor with a pressure of 0.4 to 0.6 MPa for steam molding for 180 seconds, and demolding; and placing the demolded board at 60 to 70°C for drying and aging.

[0037] The present invention also provides a flame-retardant polystyrene insulation board produced according to the aforementioned method. The flame-retardant polystyrene insulation board exhibits excellent flame retardancy and thermal insulation properties. Its thermal conductivity is ≤0.026 W / (m·K), its limiting oxygen index is ≥35%, and its vertical combustion rating reaches V0, while its horizontal combustion rating reaches V2 to V1.

[0038] The present invention will be further described below with reference to specific embodiments, but this should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0039] Unless otherwise specified, the materials and reagents mentioned below are commercially available products familiar to those skilled in the art. Unless otherwise specified, the methods described are all well-known methods in the art. Unless otherwise defined, technical or scientific terms used shall have the same meanings as those commonly understood by those skilled in the art.

[0040] Example 1

[0041] This embodiment prepares a multi-component modified flame-retardant polystyrene insulation board, and the specific steps are as follows:

[0042] Preparation of expandable polystyrene beads:

[0043] Expandable polystyrene beads are prepared by suspension polymerization using expanded graphite as a flame retardant and styrene as a polymerization monomer; the specific process of the suspension polymerization method in this embodiment is as described in the document "Zhang Tao, Pan Wei, Cheng Feifei, Yu Yanghui, Lai Wei, Experimental study on the preparation of flame-retardant graphite / polystyrene insulation materials [J], "Non-metallic Minerals" 2022, 1(45): 34-36.)"; the mass percentage of the flame retardant in the polymerization raw material is 10wt%.

[0044] Polystyrene beads pre-foamed, cured:

[0045] A certain amount of expandable polystyrene beads were placed in 100°C water vapor and pre-foamed for 40 seconds at a saturated vapor pressure of 0.6 MPa. The pre-foamed polystyrene beads were then placed at room temperature in a location with good air circulation for 20 hours for aging.

[0046] Preparation of SiO2 hydrogel:

[0047] Inorganic sodium silicate is used as a silicon source, and appropriate amounts of anhydrous ethanol and deionized water are added, wherein the molar ratio of inorganic sodium silicate, anhydrous ethanol and deionized water is 1:8:20; then the pH value of the solution is adjusted to the range of 3.0 to 4.0 with a 1 mol / L dilute phosphoric acid solution, and stirred for 5 to 10 minutes.

[0048] Polystyrene beads coating:

[0049] Pre-foamed polystyrene beads are added to an excess of ungelled SiO2 hydrogel and mechanically stirred until the surface of the polystyrene beads is completely wrapped by the SiO2 hydrogel; then, 1 mol / L phosphoric acid solution is added to the system until gelation occurs and the reaction is carried out for 10 minutes; 1 mol / L NaOH solution is then added to adjust the pH value of the system to alkaline 9.5-10, and then the temperature is raised to 45-55°C and aged in anhydrous ethanol for 12 hours; after aging, the aged polystyrene beads are transferred to a modification container, and a mixture of hexamethyldisilazane and ethanol in a molar ratio of 1:1 is added for surface modification, and the reaction is carried out for 24 hours; finally, the surface-modified polystyrene beads are placed in a supercritical drying kettle, carbon dioxide gas is introduced for drying, the pressure is increased for 1.5 hours, and after the pressure reaches 15 MPa, the pressure is maintained for reaction for 8 hours, and then the air is released to normal pressure and the kettle is opened to obtain coated modified polystyrene beads.

[0050] Preparation of flame retardant polystyrene insulation board:

[0051] The coated, modified polystyrene beads prepared above were placed in a mold, and high-pressure steam at 0.4 MPa was introduced for 180 seconds. The mold was then demolded. The demolded sample was then dried and aged at 60°C to produce a multi-componently modified flame-retardant polystyrene insulation board. The technical specifications are shown in Table 1.

[0052] Example 2

[0053] This embodiment prepares a multi-component modified flame-retardant polystyrene insulation board, and the specific steps are as follows:

[0054] Preparation of expandable polystyrene beads:

[0055] Same as Example 1, except that: the mass percentage of the flame retardant in the polymer raw material is 15wt%, and the flame retardant is a composite flame retardant of expanded graphite, high polyammonium phosphate and pentaerythritol, wherein the mass ratio of expanded graphite, high polyammonium phosphate and pentaerythritol is preferably 5:2:3.

[0056] Polystyrene beads pre-foamed, cured:

[0057] Same as Example 1, except that the pre-foaming is carried out at a saturated steam pressure of 0.4 MPa for 30 seconds and the aging time is 30 hours.

[0058] Preparation of SiO2 hydrogel:

[0059] Same as Example 1, except that a 0.5 mol / L dilute phosphoric acid solution was used to adjust the pH value of the solution.

[0060] Polystyrene beads coating:

[0061] The same as Example 1, except that: the gel reaction time is 20 minutes; the aging time is 24 hours; the surface modification time is 12 hours; and the supercritical drying is carried out at a pressure of 16 MPa and then the reaction is maintained for 10 hours.

[0062] Preparation of flame retardant polystyrene insulation board:

[0063] Same as Example 1. After testing, its technical indicators are shown in Table 1.

[0064] Example 3

[0065] This embodiment prepares a multi-component modified flame-retardant polystyrene insulation board, and the specific steps are as follows:

[0066] Preparation of expandable polystyrene beads:

[0067] Same as Example 1, except that: the mass percentage of the flame retardant in the polymer raw material is 12wt%, and the flame retardant is a composite flame retardant of expanded graphite, aluminum hydroxide, and zinc borate, wherein the mass ratio of expanded graphite, aluminum hydroxide, and zinc borate is preferably 5:3:2.

[0068] Polystyrene beads pre-foamed, cured:

[0069] Same as Example 1, except that the pre-foaming is carried out at a saturated steam pressure of 0.5 MPa for 35 seconds and the aging time is 25 hours.

[0070] Preparation of SiO2 hydrogel:

[0071] Same as Example 1, except that a 0.1 mol / L dilute phosphoric acid solution was used to adjust the pH value of the solution.

[0072] Polystyrene beads coating:

[0073] The same as Example 1, except that: the gel reaction time is 15 minutes; the aging time is 24 hours; the surface modification time is 24 hours; and the supercritical drying is carried out by maintaining the pressure at 15 MPa for 10 hours.

[0074] Preparation of flame retardant polystyrene insulation board:

[0075] Same as Example 1. After testing, its technical indicators are shown in Table 1.

[0076] Comparative Example 1

[0077] This comparative example prepares a flame retardant polystyrene insulation board, and the specific steps are as follows:

[0078] Preparation of expandable polystyrene beads:

[0079] Same as Example 1.

[0080] Polystyrene beads pre-foamed, cured:

[0081] Same as Example 1.

[0082] Preparation of flame retardant polystyrene insulation board:

[0083] Same as Example 1. After testing, its technical indicators are shown in Table 1.

[0084] Comparative Example 2

[0085] This comparative example prepares a flame retardant polystyrene insulation board, and the specific steps are as follows:

[0086] Preparation of expandable polystyrene beads:

[0087] Same as Example 1.

[0088] Polystyrene beads pre-foamed, cured:

[0089] Same as Example 1.

[0090] Preparation of flame retardant polystyrene insulation board:

[0091] The pre-expanded polystyrene beads prepared above were mixed with 5% by weight of SiO2 aerogel hydrophobic powder having a size of 40 to 50 μm, the two were stirred evenly and then filled into a mold, and the subsequent process was the same as in Example 1.

[0092] The SiO2 aerogel hydrophobic powder added in this comparative example will produce a clustering effect along with the airflow when water vapor is introduced into the steam molding, resulting in uneven dispersion of the SiO2 aerogel hydrophobic powder in the flame retardant polystyrene insulation board. Therefore, the performance indicators of the flame retardant polystyrene insulation board prepared by the method of this comparative example have large differences in parameters at different positions; during the test of this comparative example, 5 points were randomly selected to measure the thermal conductivity data, and the results were 0.027W / (m·K), 0.032W / (m·K), 0.030W / (m·K), 0.029W / (m·K), and 0.031W / (m·K), respectively. The performance of each point has large fluctuations, and the flame retardant performance decreases in the area with high thermal conductivity.

[0093] Table 1

[0094]

[0095]

[0096] The technical features in the claims and / or the specification of the present invention may be combined, and the manner of combination is not limited to the combination obtained by reference in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the scope of protection of the present invention.

[0097] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing flame retardant polystyrene beads, characterized in that: It includes the following steps: 1) pre-foaming polystyrene beads and aging them; the raw material of the polystyrene beads includes 10-15% by weight of a flame retardant; the flame retardant is selected from at least one of expanded graphite, high polyammonium phosphate, pentaerythritol, microcapsule red phosphorus, aluminum hydroxide, and zinc borate; 2) Adding mature pre-expanded polystyrene beads to ungelled SiO2 hydrogel and mechanically stirring until the SiO2 hydrogel completely covers the surface of the polystyrene beads; adding phosphoric acid solution until gelation occurs and reacting for 10-20 minutes; then adding NaOH solution to adjust the pH value of the system to 9.5-10 to obtain SiO2 wet gel-coated polystyrene beads; 3) aging, surface modifying, and supercritically drying the polystyrene beads coated with the SiO2 wet gel to obtain flame-retardant polystyrene beads coated with SiO2 aerogel; The SiO2 hydrogel is prepared according to the following steps: adding anhydrous ethanol and deionized water to inorganic sodium silicate, adjusting the pH value to 3.0-4.0 with 0.1-1 mol / L phosphoric acid solution, and stirring for 5-10 minutes; the molar ratio of the inorganic sodium silicate, anhydrous ethanol and deionized water is 1:8:

20.

2. The preparation method according to claim 1, characterized in that The pre-foaming step is to place the polystyrene beads in water vapor at 100° C. and maintain the temperature at a saturated vapor pressure of 0.4-0.6 MPa for 30-40 seconds. The aging step is to place the pre-foamed polystyrene beads in a well-ventilated location at room temperature for 20-30 hours.

3. The preparation method according to claim 1, characterized in that The aging step comprises heating the SiO2 wet gel-coated polystyrene beads to 45-55° C. and keeping the temperature in anhydrous ethanol for 12-24 hours.

4. The preparation method according to claim 1, characterized in that The surface modification comprises adding aged polystyrene beads into a mixed solution of hexamethyldisilazane and ethanol and reacting the mixture for 12 to 24 hours; the molar ratio of hexamethyldisilazane to ethanol in the mixed solution is 1:

1.

5. The preparation method according to claim 1, characterized in that The supercritical drying is to place the surface-modified polystyrene beads in a supercritical drying kettle, introduce carbon dioxide gas into the kettle for drying, increase the pressure for 1.5 hours, and maintain the pressure at 15-16 MPa for 8-10 hours. 6 . Flame retardant polystyrene beads prepared according to the method for preparing flame retardant polystyrene beads according to any one of claims 1 to 5 .

7. A method for preparing a flame retardant polystyrene insulation board, characterized in that: It includes the following steps: The flame-retardant polystyrene beads according to claim 6 are filled into a mold, high-pressure steam with a pressure of 0.4-0.6 MPa is introduced for 180 seconds of steam molding, and the mold is removed; the demolded plate is placed at 60-70° C. for drying and aging.

8. A flame retardant polystyrene thermal insulation board prepared according to the method for preparing a flame retardant polystyrene thermal insulation board according to claim 7.

Images