Preparation method of polyurethane hollow glass microsphere thermal insulation fire-retardant board
By using a synergistic flame-retardant system of alumina hydroxya, modified jadar stone powder, and expandable graphite, along with the application of modified hollow glass microspheres, the problem of balancing flame retardancy, thermal insulation, and mechanical strength in polyurethane insulation materials has been solved, achieving highly efficient flame retardant and thermal insulation effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING UNIV OF TECH
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-02
AI Technical Summary
Existing polyurethane insulation materials cannot simultaneously achieve flame retardancy, thermal insulation performance, and mechanical strength. The addition of traditional flame retardants can lead to fire safety hazards, high heat release rate, increased thermal conductivity, and decreased mechanical properties.
Alumina hydroxyl, modified jadar stone powder, and expandable graphite are used as flame retardants to form a multi-stage, three-dimensional flame retardant system through synergistic effects. Combined with modified hollow glass microspheres, a multi-scale thermal insulation network is constructed to improve compressive strength and thermal insulation effect.
The polyurethane hollow glass microsphere insulation and flame retardant board achieves a balance between high flame retardancy rating (A2 grade), low thermal conductivity (≤0.022W/(m·K)) and good compressive strength (≥0.39MPa), making it suitable for building exterior walls and other fields.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer composite material preparation technology, and in particular to a method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board. Background Technology
[0002] Rigid polyurethane foam is widely used as an insulation material for building exterior walls, cold storage, refrigerators, and other applications due to its excellent thermal insulation performance, low thermal conductivity, high specific strength, and convenient molding process. Its insulation mechanism mainly relies on its numerous closed-cell structures, where the foaming agent gas has extremely low thermal conductivity, effectively blocking heat transfer.
[0003] However, due to the nature of its organic polymers, traditional polyurethane insulation materials typically have a low limiting oxygen index (LOI), classifying them as flammable materials. When exposed to fire, they burn, releasing large amounts of heat and toxic fumes, posing a significant fire hazard. This severely limits their application in building applications with stringent fire safety requirements. To improve the flame-retardant properties of polyurethane materials, a common practice is to add flame retardants. Currently widely used flame retardants include additive flame retardants such as halogenated flame retardants, phosphorus-based flame retardants, intumescent flame retardants (IFR), and inorganic flame-retardant fillers such as aluminum hydroxide and magnesium hydroxide. While these flame retardants can improve the oxygen index to some extent, they often present the following problems: difficulty in achieving high flame-retardant ratings: While adding large amounts of traditional flame retardants can barely achieve a B1 rating (flame-retardant), it is difficult to reach the A2 rating (non-combustible). Furthermore, the peak heat release rate (pHRR) and total heat release (THR) during combustion remain high, leading to excessively rapid temperature rise in a fire. Decreased Mechanical and Thermal Insulation Properties: The excessive addition of flame retardants to achieve flame retardancy damages the cell structure of polyurethane foam, leading to a significant decrease in its compressive and flexural mechanical strength. Simultaneously, many solid flame-retardant fillers form thermal bridges, increasing the material's thermal conductivity and sacrificing its core thermal insulation performance. Decreased Environmental Safety and Processing Performance: Halogenated flame retardants produce large amounts of toxic fumes and corrosive gases during combustion; hydroxide fillers require extremely high addition amounts to be effective, severely impairing processability and material physical properties. Furthermore, common inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide primarily rely on endothermic decomposition, resulting in limited flame-retardant efficiency and poor suppression of dense smoke and toxic gases produced during combustion. Therefore, developing a composite insulation material that can synergistically address the poor flame retardancy, thermal insulation, and mechanical strength of existing polyurethane materials has become a pressing technical challenge for those skilled in the art. Summary of the Invention
[0004] In view of this, the present invention provides a method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board.
[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board, comprising the following steps: Step 1: Mix polyurethane white material, modified hollow glass microspheres and flame retardant evenly to obtain premixed slurry; Step 2: Mix the premixed slurry and polyphenyl polymethylene polyisocyanate and then foam it to obtain polyurethane hollow glass microsphere thermal insulation and flame retardant board. In step 1, the flame retardant includes aluminum hydroxide, modified jadalite powder, and expandable graphite; the modified jadalite powder is silane coupling agent modified jadalite powder. In step 1, the modified hollow glass microspheres are silane coupling agent modified hollow glass microspheres.
[0006] Commonly used inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide mainly rely on endothermic decomposition during combustion, thus their flame retardant efficiency is limited, and they are not effective in suppressing the dense smoke and toxic gases produced during combustion. Therefore, finding new flame retardant materials is of great significance for improving the flame retardant effect.
[0007] Jadarite undergoes an endothermic dehydration reaction when heated, generating magnesium silicon oxide residues that provide some insulation and barrier properties. Therefore, the inventors attempted to use jadarite as a flame-retardant material. However, research revealed significant limitations when using jadarite alone: ① While the endothermic dehydration effect of jadarite can lower the temperature, it lacks the ability to catalyze polymer char formation, making it difficult to form a continuous and dense early protective char layer; ② The residues from the thermal decomposition of jadarite have poor compatibility with the polymer matrix, resulting in uneven dispersion within the matrix and potential stress concentration, negatively impacting the material's mechanical properties; ③ Relying solely on the endothermic and physical barrier properties of jadarite results in limited flame-retardant efficiency, making it difficult to meet the stringent requirements of the A2 flame-retardant rating.
[0008] During their research, the inventors discovered that, compared to jadal stone powder, modified jadal stone powder, when used as a flame retardant, exhibits a more significant effect in reducing the thermal conductivity of the flame-retardant board and improving its flame-retardant performance and compressive strength through a synergistic effect with alumina hydroxyl and expandable graphite. This invention utilizes specific modified jadal stone powder, whose silicon-magnesium oxide residue generated after thermal decomposition possesses higher hardness and density. This residue can tightly bond with the char layer formed by alumina hydroxyl, constructing a stable ceramic reinforcing skeleton. This ensures the high flame-retardant performance of the flame-retardant board while significantly improving its compressive strength.
[0009] Through extensive experimental research, the inventors discovered that when aluminum hydroxide, modified jadar stone powder, and expandable graphite are selected as flame retardants, aluminum hydroxide preferentially decomposes and absorbs heat in the initial heating stage at around 220℃, releasing water vapor. This not only cools the matrix but also dilutes combustible gases. Furthermore, the decomposition products catalyze the rapid formation of an early dense char layer on the flame-retardant board. When the temperature is ≥350℃, modified jadar stone powder undergoes endothermic decomposition and dehydration reactions, releasing water vapor and absorbing a large amount of heat, continuously cooling the flame-retardant board. The thermal decomposition residue of modified jadar stone powder can also form a dense and hard magnesium silicate ceramic or glassy barrier. This barrier is tightly bonded to the early char layer, greatly enhancing the heat insulation and barrier effect of the condensed phase and improving the mechanical properties of the flame-retardant board to a certain extent. In the high-temperature stage, expandable graphite expands rapidly upon heating, forming a dense worm-like expanded graphite layer. This layer firmly covers the previously formed char and ceramic layers, forming a physical sealing layer that isolates heat, oxygen, and combustible volatiles.
[0010] This invention selects alumina hydroxyaluminate, modified jadar stone powder, and expandable graphite as flame retardants. The three components complement each other and have interconnected operating temperature ranges, forming a multi-stage, three-dimensional, highly efficient flame retardant system. This significantly reduces the thermal conductivity of polyurethane hollow glass microsphere insulation flame retardant boards and improves their flame retardant performance and compressive strength.
[0011] The polyurethane hollow glass microsphere insulation and flame retardant board provided by this invention further incorporates specific modified hollow glass microspheres. The gas trapped inside the microspheres has an extremely low thermal conductivity. After being uniformly dispersed, it forms a large number of microscopic insulation units in the insulation and flame retardant board, effectively blocking the three heat transfer paths of heat conduction, convection and radiation. Together with the closed-cell structure of the polyurethane white material, it constructs a multi-scale insulation network, significantly improving the insulation effect.
[0012] In this invention, the polyurethane white material and modified hollow glass microspheres facilitate the formation of a uniform and dense foam microsphere composite structure, thereby reducing the thermal conductivity of the polyurethane hollow glass microsphere insulation and flame retardant board. Simultaneously, the hollow glass microspheres modified with silane coupling agents achieve interfacial strengthening between the microspheres and the polyurethane matrix, moving from physical filling to chemical bonding. Furthermore, the uniformly dispersed rigid microspheres act as anchors and load-bearing elements in the polyurethane hollow glass microsphere insulation and flame retardant board, effectively dispersing stress and improving the compressive strength of the board to a certain extent. In addition, the modified hollow glass microspheres exhibit good dispersion in the polyurethane hollow glass microsphere insulation and flame retardant board, which facilitates the formation of a more uniform and stable cell-carbon layer composite structure between the polyurethane white material and the flame retardant, thereby improving flame retardant performance.
[0013] Preferably, in step 1, the mass ratio of the alumina hydroxyl oxide, modified jadar stone powder and expandable graphite is (20~30):(8~15):(3~8).
[0014] This invention further improves the performance of flame-retardant boards by limiting the mass ratio of alumina hydroxyl, modified jadar stone powder, and expandable graphite, thereby reducing the thermal conductivity of the flame-retardant boards and increasing their flame-retardant strength and compressive strength.
[0015] More preferably, in step 1, the mass ratio of the alumina hydroxyl oxide, modified jadar stone powder, and expandable graphite is 25:10:5.
[0016] Preferably, in step 1, the preparation method of the modified jadarite powder includes the following steps: Jadar stone powder and silane coupling agent are added to an aqueous ethanol solution and reacted at 60-80°C to obtain the modified jadar stone powder.
[0017] The method for preparing modified jadarite powder provided by this invention is simple, has mild reaction conditions, and requires no complex equipment.
[0018] For example, the Jadar stone powder also needs to undergo pretreatment, including crushing and purification.
[0019] For example, the pulverization condition is: pulverization to a particle size D50 ≤ 10 μm.
[0020] For example, the purification includes the following steps: soaking the pulverized jadar stone powder in an acid solution, washing, and drying.
[0021] For example, the acid solution is a hydrochloric acid solution or a nitric acid solution with a mass concentration of 5% to 10%.
[0022] For example, the soaking temperature is 60~80℃ and the soaking time is 2~4h.
[0023] For example, the drying temperature is 100~120℃, and drying is carried out until constant weight is achieved.
[0024] For example, the purity of LiNaSiB3O7(OH) in the Jadar stone powder is ≥95%, wherein the Li2O content is ≥8%, the B2O3 content is ≥35%, and the SiO2 content is ≥25%.
[0025] More preferably, the silane coupling agent includes, but is not limited to, γ-aminopropyltriethoxysilane.
[0026] More preferably, the mass ratio of the jadarite powder to the silane coupling agent is 100:(1~5).
[0027] More preferably, the mass-to-volume ratio of the jadarite powder and the ethanol aqueous solution is 1 g: (8~9) mL, wherein the mass concentration of the ethanol aqueous solution is 80%~82%.
[0028] More preferably, the reaction time is 2-4 hours.
[0029] For example, after the reaction is complete, filtration, washing and drying are also required.
[0030] Preferably, in step 1, the modified jadar stone powder has a particle size D50 ≤ 5 μm and an initial decomposition temperature ≥ 350℃.
[0031] More preferably, the particle size D50 of the modified jadarite powder is 1~5μm.
[0032] Preferably, in step 1, the particle size D50 of the aluminum hydroxyaluminate is ≤500nm.
[0033] More preferably, the particle size D50 of the aluminum hydroxyaluminate is 50~300nm.
[0034] More preferably, the aluminum hydroxyaluminate has an AlOOH content of ≥95% and an initial decomposition temperature of ≥220℃.
[0035] Preferably, in step 1, the expandable graphite has a particle size of 80-100 mesh, an initial expansion temperature of 180-220℃, and an expansion volume ≥300mL / g.
[0036] For example, in step 1, the mixing can be carried out by stirring at a speed of 2300~2700 rpm for 7~9 minutes until the slurry is uniform.
[0037] Preferably, in step 1, the polyurethane white material comprises the following raw material components by mass percentage: 69%~78% polyether polyol, 0.7%~2.2% surfactant, 0.3%~1.1% composite catalyst, 6.5%~11% cyclopentane, 6.5%~15% dimethyl methylphosphonate, and 1%~1.8% water.
[0038] More preferably, the composite catalyst comprises bis(2-dimethylaminoethyl) ether and dibutyltin dilaurate.
[0039] More preferably, the mass ratio of the bis(2-dimethylaminoethyl) ether to dibutyltin dilaurate is (1~2):1.
[0040] More preferably, the polyether polyol has a functionality of 3 to 5 and a hydroxyl value of 400 to 500 mg KOH / g.
[0041] More preferably, the polyether polyol has a functionality of 4 and a hydroxyl value of 450 mg KOH / g.
[0042] More preferably, the polyether polyol is purchased from Wanhua Chemical Group Co., Ltd., and its brand name is 4110.
[0043] More preferably, the surfactant has a kinematic viscosity of 500~1500 mmHg at 25°C. 2 / s.
[0044] More preferably, the surfactant is a polyether-modified polysiloxane surfactant.
[0045] More preferably, the surfactant is purchased from Momentive Advanced Materials Group and its brand name is B8870.
[0046] Preferably, in step 1, the preparation method of the polyurethane white material includes the following steps: Weigh each raw material component according to the mass ratio, and mix the polyether polyol, surfactant, composite catalyst, cyclopentane, dimethyl methylphosphonate and water evenly at 35~40℃ to obtain the polyurethane white material.
[0047] For example, the water content of the polyether polyol is ≤0.05wt%.
[0048] Preferably, in step 1, the method for preparing the modified hollow glass microspheres includes the following steps: Hollow glass microspheres were added to an alcoholic solution of silane coupling agent, and ultrasonically treated at 40-50°C. The mixture was then filtered, washed, and dried to obtain the modified hollow glass microspheres.
[0049] The method for preparing modified hollow glass microspheres provided by this invention does not require complex equipment, is easy to operate, and is suitable for large-scale production. Furthermore, applying the prepared modified hollow glass microspheres to thermal insulation and flame-retardant boards can significantly improve the performance of the flame-retardant boards.
[0050] More preferably, the alcohol solution includes ethanol.
[0051] More preferably, the silane coupling agent comprises γ-aminopropyltriethoxysilane.
[0052] More preferably, the mass concentration of the alcohol solution of the silane coupling agent is 1% to 3%.
[0053] More preferably, the hollow glass microspheres have a particle size of 10~100μm and a true density of 0.1~0.3g / cm³. 3 Compressive strength ≥15MPa.
[0054] For example, the hollow glass microspheres are composed of borosilicate glass.
[0055] More preferably, the mass-to-volume ratio of the hollow glass microspheres and the silane coupling agent in the alcohol solution is 1 g: (5-15) mL.
[0056] More preferably, the ultrasonic treatment power is 400~600W and the ultrasonic treatment time is 30~60min.
[0057] For example, the drying temperature can be 70~90℃ and the time can be 6~12h.
[0058] Preferably, in step 1, the mass ratio of the polyurethane white material to the modified hollow glass microspheres is 100:(5~30).
[0059] Preferably, in step 1, the mass ratio of the polyurethane white material to the flame retardant is 100:(5~20).
[0060] Preferably, in step 2, the mass ratio of the polyurethane white material to polyphenyl polymethylene polyisocyanate is 100:(100~130).
[0061] More preferably, in step 2, the isocyanate (NCO) mass fraction in the polyphenyl polymethylene polyisocyanate is 30%~32%, and the viscosity at 25°C is 150~250 mPa·s.
[0062] More preferably, the polyphenyl polymethylene polyisocyanate can be selected from at least one of PM-200 produced by Wanhua Chemical Group Co., Ltd., 44V20 produced by Covestro Polymer Co., Ltd., or 5005 produced by Huntsman Corporation.
[0063] Preferably, in step 2, the mixing conditions are: stirring at a speed of 1500~2500 rpm for 10~15 seconds.
[0064] Preferably, in step 2, the foaming temperature is 60~80℃ and the foaming time is 1~2h.
[0065] This invention successfully solves the technical contradiction of existing flame-retardant boards that are difficult to balance thermal insulation performance, flame retardant performance and mechanical strength by optimizing the formulation design and process of polyurethane hollow glass microsphere thermal insulation and flame retardant board. It significantly reduces the thermal conductivity of polyurethane hollow glass microsphere thermal insulation and flame retardant board and improves its compressive strength and flame retardant performance. Detailed Implementation
[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0067] In this invention, the particle size D50 of alumina hydroxyl is 50~100nm, the AlOOH content in alumina hydroxyl is ≥95%, and the initial decomposition temperature is ≥220℃; the particle size of expandable graphite is 80~100 mesh, the initial expansion temperature is 180~220℃, and the expansion volume is ≥300mL / g; the particle size D50 of modified jadar stone powder is 1~5μm, and the initial decomposition temperature is ≥350℃; the polyether polyol is purchased from Wanhua Chemical Group Co., Ltd., with the grade 4110; the surfactant is purchased from Momentive Advanced Materials Group, with the grade B8870; and the polyphenyl polymethylene polyisocyanate is PM-200 produced by Wanhua Chemical Group Co., Ltd.
[0068] Unless otherwise specified, the raw materials and reagents used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.
[0069] Example 1 This embodiment provides a method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board, including the following steps: Step 1: Stir the polyurethane white material, modified hollow glass microspheres and flame retardant at 2300 rpm for 7 minutes until the slurry is homogeneous to obtain the premixed slurry. Step 2: Mix the premixed slurry and polyphenyl polymethylene polyisocyanate, stir at 2000 rpm for 10 seconds, and foam at 60°C for 1 hour to obtain polyurethane hollow glass microsphere insulation and flame retardant board. The flame retardant consists of aluminum hydroxide, modified jadar stone powder, and expandable graphite in a mass ratio of 25:10:5. The preparation method of modified jadar stone powder includes the following steps: Jadar stone powder was pulverized to a particle size D50≤10μm, then added to a 5% hydrochloric acid solution, soaked at 60℃ for 4h, washed, and dried at 100℃ to constant weight to obtain pretreated Jadar stone powder. Based on the following calculations: the ratio of pretreated jadarite powder to γ-aminopropyltriethoxysilane is 100:1, and the solid-liquid ratio of pretreated jadarite powder to 80% ethanol aqueous solution is 1 g: 8 mL, the pretreated jadarite powder and γ-aminopropyltriethoxysilane are added to the ethanol aqueous solution and reacted at 60℃ for 4 h. After the reaction is completed, the mixture is filtered, washed and dried to obtain modified jadarite powder. The modified Jadar stone powder has a LiNaSiB3O7(OH) purity of ≥95%, with Li2O content ≥8%, B2O3 content ≥35%, and SiO2 content ≥25%.
[0070] The polyurethane hollow glass microsphere insulation and flame retardant board comprises the following raw material components in parts by weight: 100 parts of polyurethane white material, 5 parts of modified hollow glass microspheres, 130 parts of polyphenyl polymethylene polyisocyanate, and 10 parts of flame retardant. The polyurethane white component comprises the following raw material components by weight percentage: 70% polyether polyol, 2% surfactant, 1% composite catalyst, 11% cyclopentane, 15% dimethyl methylphosphonate, and 1% water; wherein, the composite catalyst comprises a mixture of bis(2-dimethylaminoethyl) ether and dibutyltin dilaurate in a mass ratio of 1:1. The preparation method of polyurethane white material includes the following steps: Weigh each raw material component according to the mass ratio, and mix the polyether polyol, surfactant, composite catalyst, cyclopentane, dimethyl methylphosphonate and water with a water content of 0.03wt% at 40℃. Stir at 800rpm for 40min to obtain the polyurethane white material. The preparation method of modified hollow glass microspheres includes the following steps: S1. Mix γ-aminopropyltriethoxysilane and ethanol evenly to obtain a silane coupling agent solution with a mass concentration of 1%. S2. The hollow glass microspheres and silane coupling agent solution were mixed at a mass-to-volume ratio of 1 g:5 mL. The mixture was then ultrasonically treated at 50°C with a power of 400 W for 60 min, filtered, washed, and dried at 70°C for 12 h to obtain modified hollow glass microspheres. The particle size of the hollow glass microspheres was 10–30 μm, and the true density was 0.1–0.3 g / cm³. 3 It has a compressive strength of ≥15MPa and is made of borosilicate glass.
[0071] Example 2 This embodiment provides a method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board, including the following steps: Step 1: Stir the polyurethane white material, modified hollow glass microspheres and flame retardant at 2500 rpm for 9 minutes until the slurry is homogeneous to obtain the premixed slurry. Step 2: After mixing the premixed slurry and polyphenyl polymethylene polyisocyanate, stir at 1500 rpm for 12 seconds and foam at 80°C for 2 hours to obtain polyurethane hollow glass microsphere insulation and flame retardant board. The flame retardant consists of alumina hydroxide, modified jadar stone powder, and expandable graphite in a mass ratio of 20:15:3. The preparation method of modified jadar stone powder includes the following steps: Jadar stone powder was pulverized to a particle size D50≤10μm, then added to a 10% hydrochloric acid solution, soaked at 80℃ for 2h, washed, and dried at 120℃ to constant weight to obtain pretreated jadar stone powder. Based on the following calculations: the ratio of pretreated jadarite powder to γ-aminopropyltriethoxysilane is 100:3, and the solid-liquid ratio of pretreated jadarite powder to 82% ethanol aqueous solution is 1 g:9 mL, the pretreated jadarite powder and γ-aminopropyltriethoxysilane are added to the ethanol aqueous solution and reacted at 80℃ for 2 h. After the reaction is completed, the mixture is filtered, washed and dried to obtain modified jadarite powder. The modified Jadar stone powder has a LiNaSiB3O7(OH) purity of ≥95%, with Li2O content ≥8%, B2O3 content ≥35%, and SiO2 content ≥25%.
[0072] The polyurethane hollow glass microsphere insulation and flame retardant board comprises the following raw material components in parts by weight: 100 parts of polyurethane white material, 15 parts of modified hollow glass microspheres, 100 parts of polyphenyl polymethylene polyisocyanate and 20 parts of flame retardant. The polyurethane white component comprises the following raw material components by mass percentage: 76% polyether polyol, 1% surfactant, 1.1% composite catalyst, 10.1% cyclopentane, 10% dimethyl methylphosphonate, and 1.8% water; wherein the composite catalyst comprises a mixture of bis(2-dimethylaminoethyl) ether and dibutyltin dilaurate in a mass ratio of 2:1. The preparation method of polyurethane white material includes the following steps: Weigh each raw material component according to the mass ratio, and mix the polyether polyol, surfactant, composite catalyst, cyclopentane, dimethyl methylphosphonate and water with a water content of 0.02wt% at 35℃. Stir at 800rpm for 40min to obtain the polyurethane white material. The preparation method of modified hollow glass microspheres includes the following steps: S1. Mix γ-aminopropyltriethoxysilane and ethanol evenly to obtain a silane coupling agent solution with a mass concentration of 2%. S2. The hollow glass microspheres and silane coupling agent solution were mixed at a mass ratio of 1 g:10 mL. The microspheres were added to the silane coupling agent solution and ultrasonically treated at 50°C with 600 W for 40 min. The mixture was then filtered, washed, and dried at 90°C for 8 h to obtain modified hollow glass microspheres. The particle size of the microspheres was 50–80 μm, and the true density was 0.1–0.3 g / cm³. 3 It has a compressive strength of ≥15MPa and is made of borosilicate glass.
[0073] Example 3 This embodiment provides a method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board, comprising the following steps: Step 1: Stir the polyurethane white material, modified hollow glass microspheres and flame retardant at 2700 rpm for 8 minutes until the slurry is homogeneous to obtain the premixed slurry. Step 2: Mix the premixed slurry and polyphenyl polymethylene polyisocyanate, stir at 2500 rpm for 10 seconds, and foam at 70°C for 2 hours to obtain a heat-insulating and flame-retardant board. The flame retardant consists of aluminum hydroxide, modified jadar stone powder, and expandable graphite in a mass ratio of 30:10:7. The preparation method of modified jadar stone powder includes the following steps: Jadar stone powder was pulverized to a particle size D50≤10μm, then added to an 8% hydrochloric acid solution, soaked at 70℃ for 3h, washed, and dried at 110℃ to constant weight to obtain pretreated jadar stone powder. Based on the following calculations: the ratio of pretreated jadarite powder to γ-aminopropyltriethoxysilane is 100:5, and the solid-liquid ratio of pretreated jadarite powder to 80% ethanol aqueous solution is 1g:8mL, the pretreated jadarite powder and γ-aminopropyltriethoxysilane are added to the ethanol aqueous solution and reacted at 70℃ for 3h. After the reaction is completed, the mixture is filtered, washed and dried to obtain modified jadarite powder. The modified Jadar stone powder has a LiNaSiB3O7(OH) purity of ≥95%, with Li2O content ≥8%, B2O3 content ≥35%, and SiO2 content ≥25%.
[0074] The polyurethane hollow glass microsphere insulation and flame retardant board comprises the following raw material components in parts by weight: 100 parts of polyurethane white material, 25 parts of modified hollow glass microspheres, 110 parts of polyphenyl polymethylene polyisocyanate and 7 parts of flame retardant. The polyurethane white component comprises the following raw material components by mass percentage: 78% polyether polyol, 2.2% surfactant, 1% composite catalyst, 8% cyclopentane, 9% dimethyl methylphosphonate, and 1.8% water; wherein, the composite catalyst comprises a mixture of bis(2-dimethylaminoethyl) ether and dibutyltin dilaurate in a mass ratio of 2:1. The preparation method of polyurethane white material includes the following steps: Weigh each raw material component according to the mass ratio, and mix the polyether polyol, surfactant, composite catalyst, cyclopentane, dimethyl methylphosphonate and water with a water content of 0.02wt% at 38℃. Stir at 800rpm for 40min to obtain the polyurethane white material. The preparation method of modified hollow glass microspheres includes the following steps: S1. Mix γ-aminopropyltriethoxysilane and ethanol evenly to obtain a silane coupling agent solution with a mass concentration of 2%. S2. Using a mass ratio of 1 g:13 mL for hollow glass microspheres and silane coupling agent solution, the hollow glass microspheres were added to the silane coupling agent solution and ultrasonically treated at 50°C with a power of 500 W for 50 min. The mixture was then filtered, washed, and dried at 90°C for 8 h to obtain modified hollow glass microspheres. The particle size of the hollow glass microspheres was 80–100 μm, and the true density was 0.1–0.3 g / cm³. 3 It has a compressive strength of ≥15MPa and is made of borosilicate glass.
[0075] Comparative Example 1 This comparative example provides a method for preparing a heat-insulating and flame-retardant board, which differs from Example 1 in that: the modified jadar stone powder is replaced with an equal amount of magnesium hydroxide, with a particle size D50≤2μm and a purity ≥95%; The remaining components and preparation methods are the same as in Example 1, and will not be repeated here.
[0076] Comparative Example 2 This comparative example provides a method for preparing a thermal insulation and flame retardant board, which differs from Example 1 in that aluminum hydroxide is replaced with an equal amount of ammonium polyphosphate. The ammonium polyphosphate is a type II product with a degree of polymerization n>1000, specifically Exolit AP 422 manufactured by Clariant, with a particle size D50≤10μm and a thermal decomposition temperature ≥275℃. The remaining components and preparation methods are the same as in Example 1, and will not be repeated here.
[0077] Comparative Example 3 This comparative example provides a method for preparing a heat-insulating and flame-retardant board, which differs from Example 1 in that: expandable graphite is replaced with an equal amount of expandable microspheres. The expandable microspheres are thermoplastic physically expandable microspheres, and Expansionl 031 DU 40 produced by AkzoNobel is selected. Its initial expansion temperature is about 120~140℃ and its maximum expansion temperature is about 180~200℃. The remaining components and preparation methods are the same as in Example 1, and will not be repeated here.
[0078] Comparative Example 4 This comparative example provides a method for preparing a heat-insulating and flame-retardant board, which differs from Example 1 in that: the hollow glass microspheres are not modified. The remaining components and preparation methods are the same as in Example 1, and will not be repeated here.
[0079] Example of effect The performance of the thermal insulation and flame retardant boards provided in the examples and comparative examples was tested, and the specific test indicators and standards are as follows: All tests were conducted under a standard environment of (23±2)℃ and (50±5)% relative humidity, and all samples were conditioned under this environment for at least 48 hours. The specific test standards are as follows: Apparent density: Determined according to GB / T 6343-2009 "Determination of Apparent Density of Foamed Plastics and Rubber". The geometric dimensions and mass of the sample are measured, and the apparent density is calculated.
[0080] Thermal conductivity: The thermal conductivity was determined according to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method". A protective hot plate thermal conductivity meter was used to measure the thermal conductivity of the sample at an average temperature of 25℃.
[0081] Compressive strength: Tested according to GB / T 8813-2020 "Determination of compressive properties of rigid foamed plastics". The sample size is 100mm×100mm×50mm, the compression speed is 10% of the sample thickness / min, and the compressive stress at 10% relative deformation is taken as the compressive strength.
[0082] Oxygen index: determined according to GB / T 2406.2-2009 "Determination of flammability by oxygen index method for plastics - Part 2: Room temperature test". The sample size was 150mm × 10mm × 4mm. The top-side ignition method was used to determine the minimum oxygen concentration that could support the continuous combustion of the sample.
[0083] Combustion rating: The rating is determined comprehensively according to GB 8624-2012 "Classification of Combustion Performance of Building Materials and Products". The combustion performance rating is determined based on the indicators specified in the standard by measuring the calorific value (GB / T 14402-2007), non-combustibility (GB / T 5464-2010), and individual combustion performance (if necessary) of the sample.
[0084] The specific test results are shown in Table 1: Table 1
[0085] As shown in Table 1, this invention achieves an optimal balance between high flame retardant rating (A2 grade), low thermal conductivity (≤0.022W / (m·K)) and good compressive strength (≥0.39MPa) in polyurethane insulation boards through the synergistic effect of the constructed compound flame retardant system and surface-modified hollow glass microspheres, utilizing the catalytic char formation of alumina hydroxyaluminate, the heat absorption and ceramic barrier construction of modified jadar stone powder, and the high-temperature physical sealing of expandable graphite. It is particularly suitable for the field of building exterior wall insulation with strict requirements for fire safety and energy-saving performance.
[0086] Comparative Example 1 used magnesium hydroxide, which has a stronger endothermic capacity, to directly replace the modified jadalite powder. The test results showed that its oxygen index (29.0%) and flammability rating (B1) were much lower than those of the preferred embodiment (35.0%, A2). Although magnesium hydroxide has a greater endothermic decomposition, its decomposition product MgO is a loose powder, which is difficult to effectively combine with the carbon layer formed by alumina hydroxyl catalysis. It cannot form a dense ceramic-like thermal insulation barrier like that produced by the decomposition of modified jadalite powder, nor can it provide a reinforcing skeleton. At the same time, the compressive strength (0.28 MPa) and thermal conductivity (0.028 W / (m·K)) of Comparative Example 1 also deteriorated.
[0087] Comparative Example 2 directly replaced alumina with ammonium polyphosphate, which has significant catalytic charring and expansion effects. Test results showed that although its oxygen index reached 31.5%, its flame retardant rating still failed to reach A2 level. The key issue is that ammonium polyphosphate has a low decomposition temperature, which highly overlaps with the expansion temperature range of expandable graphite. This causes the catalytic charring and physical expansion steps to occur almost simultaneously, preventing the formation of a sequential synergistic protective layer structure where charring precedes coating. Furthermore, the strong acidity of ammonium polyphosphate severely interferes with the curing reaction and interfacial compatibility of the polyurethane matrix, resulting in Comparative Example 2 having the worst mechanical strength (0.25 MPa) and thermal insulation performance (0.030 W / (m·K)) among the comparative examples.
[0088] Comparative Example 3 used expandable microspheres that physically expand at low temperatures to replace expandable graphite. The test results showed that its overall performance was poor: the oxygen index (28.5%) and flammability rating (B1) were significantly reduced; the compressive strength (0.24 MPa) was severely deteriorated; and the thermal conductivity (0.029 W / (m·K)) was significantly increased. The key mechanism is that the expandable microspheres expand in the early stage of polyurethane foaming (about 80~120℃), which seriously disrupts the formation of the cell structure. Secondly, the foam ball structure formed by its expansion is very easy to fail at high temperatures and cannot provide the ultimate high-temperature stable sealing protection like expandable graphite.
[0089] The comparative data from Examples 1-3 strongly demonstrate that alumina hydroxyl, modified jadar stone powder, and expandable graphite form an optimal combination with complementary functions, seamless timing, and compatible interfaces. Replacing any one of these components will result in a failure to achieve the A2 flame retardant rating, and a significant reduction in compressive strength and thermal insulation performance.
[0090] Comparative Example 4 used unmodified hollow glass microspheres, which had a thermal conductivity of 0.028 W / (m·K), a compressive strength of only 0.27 MPa, an oxygen index of 30.5%, and a flame retardant rating of B1, all of which were significantly lower than those of the Example Group. This further proves that only by combining surface-modified hollow glass microspheres with a specific compound flame retardant can a synergistic reduction in thermal conductivity be achieved. Moreover, the surface modification treatment of hollow glass microspheres effectively enhances its interfacial bonding with the matrix, avoids the aggravation of heat conduction caused by interfacial defects, and further improves compressive strength and flame retardant performance.
[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a polyurethane hollow glass microsphere thermal insulation and flame retardant board, characterized in that, Includes the following steps: Step 1: Mix polyurethane white material, modified hollow glass microspheres and flame retardant evenly to obtain premixed slurry; Step 2: Mix the premixed slurry and polyphenyl polymethylene polyisocyanate and then foam it to obtain polyurethane hollow glass microsphere thermal insulation and flame retardant board. In step 1, the flame retardant includes aluminum hydroxide, modified jadalite powder, and expandable graphite; the modified jadalite powder is silane coupling agent modified jadalite powder. In step 1, the modified hollow glass microspheres are silane coupling agent modified hollow glass microspheres.
2. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1, characterized in that, In step 1, the mass ratio of the alumina hydroxyl oxide, modified jadar stone powder, and expandable graphite is 25:10:
5.
3. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1 or 2, characterized in that, The preparation method of the modified jadar stone powder includes the following steps: Jadar stone powder and silane coupling agent are added to an aqueous ethanol solution and reacted at 60-80°C to obtain the modified jadar stone powder.
4. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 3, characterized in that, The mass ratio of the jadarite powder to the silane coupling agent is 100:(1~5). The mass-to-volume ratio of the jadarite powder to the ethanol aqueous solution is 1 g: (8~9) mL, wherein the mass concentration of the ethanol aqueous solution is 80%~82%. The reaction time is 2-4 hours.
5. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1 or 2, characterized in that, In step 1, the modified jadar stone powder has a particle size D50 ≤ 5 μm and an initial decomposition temperature ≥ 350℃; In step 1, the particle size D50 of the aluminum hydroxyaluminate is ≤500nm; In step 1, the expandable graphite has a particle size of 80-100 mesh, an initial expansion temperature of 180-220℃, and an expansion volume ≥300mL / g.
6. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1, characterized in that, In step 1, the preparation method of the modified hollow glass microspheres includes the following steps: Hollow glass microspheres were added to an alcoholic solution of silane coupling agent, and ultrasonically treated at 40-50°C. The mixture was then filtered, washed, and dried to obtain the modified hollow glass microspheres.
7. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 6, characterized in that, The silane coupling agent includes γ-aminopropyltriethoxysilane; The mass concentration of the alcohol solution of the silane coupling agent is 1% to 3%; The hollow glass microspheres have a particle size of 10~100μm and a true density of 0.1~0.3g / cm³. 3 Compressive strength ≥15MPa; The mass-to-volume ratio of the hollow glass microspheres and the silane coupling agent in the alcohol solution is 1 g: (5-15) mL.
8. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1, characterized in that, In step 1, the mass ratio of the polyurethane white material to the modified hollow glass microspheres is 100:(5~30). In step 1, the mass ratio of the polyurethane white material to the flame retardant is 100:(5~20).
9. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1, characterized in that, In step 2, the mass ratio of the polyurethane white material to polyphenyl polymethylene polyisocyanate is 100:(100~130).
10. The method for preparing polyurethane hollow glass microsphere thermal insulation and flame retardant board as described in claim 1, characterized in that, In step 2, the isocyanate (NCO) mass fraction in the polyphenyl polymethylene polyisocyanate is 30%~32%, and the viscosity at 25°C is 150~250 mPa·s; In step 2, the foaming temperature is 60~80℃ and the foaming time is 1~2h.