A halogen-free flame-retardant rigid polyurethane foam composite material, its preparation method and application

Abstract

This invention provides a halogen-free flame-retardant rigid polyurethane foam composite material, its preparation method, and its application, belonging to the technical field of flame-retardant and thermal insulation materials. This invention prepares borosilicate-modified expandable graphite and phytic acid-modified layered trimetallic hydroxide using organic modification technology, and simultaneously introduces modified expandable graphite and modified layered trimetallic hydroxide into rigid polyurethane foam, further constructing a multi-component composite catalytic synergistic flame-retardant and smoke-suppressing system, thus obtaining a halogen-free flame-retardant rigid polyurethane foam composite material, achieving a balance between the mechanical properties, thermal insulation, and flame-retardant and smoke-suppressing properties of rigid polyurethane foam.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant and heat-insulating materials technology, and in particular to a halogen-free flame-retardant rigid polyurethane foam composite material, its preparation method, and its application. Background Technology

[0002] Rigid polyurethane foam (RPUF) holds a significant position in the building insulation market due to its excellent mechanical strength, superior thermal insulation performance, and good sound insulation properties. However, like most organic polymer materials, untreated RPUF is highly flammable, with extremely rapid flame spread. During combustion, it releases large amounts of toxic gases such as HCN, CO, and nitrogen oxides, along with copious amounts of black smoke, which are major contributors to casualties in fires. Furthermore, the dense smoke produced during combustion severely obstructs visibility, complicating fire rescue efforts and hindering escape. Therefore, it is necessary to conduct research on the flame retardancy and smoke suppression of RPUF to significantly improve fire safety in the building insulation field.

[0003] Currently, the effective methods for imparting or enhancing the flame retardancy of RPUF mainly include physical blending modification (additive flame retardants) and chemical copolymerization modification (reactive flame retardants). Additive flame retardants are introduced during the RPUF foaming process through physical blending, existing in a physically dispersed form within the polyurethane matrix. They are mainly divided into organic and inorganic categories. Organic flame retardants are primarily phosphorus, nitrogen, and silicon-based. While halogen-based flame retardants, widely used in the early stages, have high flame retardant efficiency, they easily release large amounts of dense smoke, corrosive gases, and toxic products during combustion, posing a serious threat to the environment and human health, and have been gradually replaced by halogen-free systems. Inorganic flame retardants, such as aluminum hydroxide, magnesium hydroxide, and zinc borate, while possessing excellent thermal stability and smoke suppression properties, often require high addition amounts to achieve the ideal flame retardant effect. Furthermore, the difference in interface properties between the polyurethane matrix and inorganic fillers often disrupts the foam's cell morphology, adversely affecting mechanical and thermal insulation properties. In addition, additive flame retardants are prone to migration and leaching during use, thus failing to guarantee the long-term flame retardant effect of the material. Reactive flame retardants introduce flame-retardant elements (such as phosphorus and nitrogen) into the polyurethane molecular chain through chemical bonding, resulting in a longer-lasting flame-retardant effect and good interfacial compatibility with the polyurethane matrix. Therefore, the dispersibility of inorganic fillers in the polyurethane matrix can be improved by organically modifying them.

[0004] Expandable graphite (EG), as a highly efficient, environmentally friendly, and inexpensive intumescent flame retardant, expands upon heating to form a "worm-like" char layer, which prevents the transfer of heat and combustible gases, and is widely used in RPUF (Reduced Polyurethane Foam). Chinese invention patent CN110527053 A prepared a halogen-free flame-retardant RPUF using EG and phosphate flame retardants, exhibiting good flame-retardant properties, but with high peak heat release rate and total heat release, and smoke production needs further reduction. Chinese invention patent CN118638345 A used silane coupling agents and phytic acid to organically modify EG to improve its dispersibility in polyurethane foam, and combined it with a reactive phosphorus-nitrogen flame retardant to prepare a halogen-free flame-retardant RPUF. This RPUF showed high flame retardancy and mechanical properties, effectively reducing the drawbacks of flame retardant function degradation due to migration and precipitation, but its thermal insulation and smoke suppression / toxicity reduction performance still need improvement. Furthermore, the expanded char layer of EG after heating is relatively loose and easily detached, making it difficult to sustain its flame-retardant and smoke-suppressing effects.

[0005] Layered metal hydroxides (LDHs), due to their unique layered structure, possess characteristics such as adjustable cation types / valence states in the main layer and controllable interlayer anions, allowing for the preparation of various metal-doped hydroxide composites. LDHs containing transition metal elements exhibit excellent flame retardant and smoke-suppressing effects in polymer materials; their catalytic char formation ability can effectively improve the density of the char layer, thereby further reducing smoke emissions. However, due to their strong interlayer electrostatic interactions and surface inertness, LDHs are prone to agglomeration in polymers, making uniform dispersion difficult. Chinese invention patent CN118878775 A utilizes modified chitosan quaternary ammonium salt grafted magnesium-aluminum-based LDH as a flame-retardant filler to prepare modified biomass polyurethane foam materials, effectively improving the thermal insulation and flame retardant properties of polyurethane foam materials. However, due to the relatively low proportion of flame-retardant and smoke-suppressing elements, the smoke-suppressing and toxicity-reducing performance still needs further improvement.

[0006] Therefore, existing rigid polyurethane foams have the problem of not being able to simultaneously achieve mechanical properties, thermal insulation, and flame retardant and smoke suppression properties, which urgently needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to provide a halogen-free flame-retardant rigid polyurethane foam composite material, its preparation method, and its application. By simultaneously introducing modified expandable graphite and modified layered trimetallic hydroxide, the halogen-free flame-retardant rigid polyurethane foam composite material has the characteristics of being lightweight, high-strength, low-smoke, and low-toxicity. It also has good thermal insulation properties. After being eroded by flames, it can form a dense expanded char layer, which can effectively suppress the release of toxic fumes. It exhibits excellent flame-retardant properties and low smoke toxicity, solving the problem in the prior art that it is difficult to simultaneously achieve the mechanical properties, thermal insulation, and flame-retardant and smoke-suppressing properties of rigid polyurethane foam.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a halogen-free flame-retardant rigid polyurethane foam composite material, comprising the following raw materials by total mass fraction (100%): Polyether polyol 30-35%, isocyanate 45-60%, modified expandable graphite 5-14%, modified layered trimetallic hydroxide 0.9-3.5%, ammonium polyphosphate 2.5-4.5%, amine catalyst 0.5-1.5%, foam stabilizer 0.3-0.5%, water 0.5-0.9%; The method for preparing the modified expandable graphite includes the following steps: Expandable graphite, a first dispersant, a boron source, a silicon source, and a first aminosilane coupling agent are mixed and borosilicate modified to obtain modified expandable graphite. The method for preparing the modified layered trimetallic hydroxide includes the following steps: The second aminosilane coupling agent was mixed with an alcohol-water mixed solvent and hydrolyzed to obtain a silane hydrolysate. The layered trimetallic hydroxide was mixed with the silane hydrolysate for the first modification to obtain a modified intermediate product. The modified intermediate product, the second dispersant, and the phytic acid solution were mixed to carry out a second modification, resulting in a modified layered trimetallic hydroxide.

[0009] Preferably, the hydroxyl value of the polyether polyol is 350~500 mgKOH / g; The isocyanate includes polymethylene polyphenyl isocyanate; the NCO group content in the isocyanate is 30~32 wt%.

[0010] Preferably, the degree of polymerization of the ammonium polyphosphate is 1000~1500.

[0011] Preferably, the foam stabilizer comprises silicone oil AK-8805.

[0012] Preferably, the boron source includes one or more of trimethoxyboroxy ester, trimethyl borate, boric acid, and trimethylcyclotriboroxy alkane; the silicon source includes one or more of tetraethyl orthosilicate, acetoxypropyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane. The mass ratio of the expandable graphite, boron source, and silicon source is 20:(3.0~4.5):(1.4~3.0); The first aminosilane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, and 3-aminopropyltrimethoxysilane; the mass ratio of the first aminosilane coupling agent to expandable graphite is (2.5~3.5):20; The borosilicate modification was performed at a temperature of 80-90 °C for 5-6 h, with a pH of 3.5-4.0.

[0013] Preferably, the layered trimetallic hydroxide contains divalent and trivalent metal ions, wherein the divalent metal ions include Ni. 2+ Zn 2+ Co 2+ Cu 2+ Mg 2+ Any one of the following, wherein the trivalent metal ion includes Fe 3 + Ce 3+ and La 3+ Any two of them; The second aminosilane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane and 3-aminopropyltrimethoxysilane; The mass ratio of the layered trimetallic hydroxide, the second aminosilane coupling agent, and the phytic acid solution is 10:(1.2~2.2):(0.5~1.5); the mass concentration of the phytic acid solution is 50~70%.

[0014] Preferably, the hydrolysis temperature is 30~35 ℃ and the time is 0.5~1.5 h; The first modification was performed at a temperature of 85-90 °C for 4.5-6 h. The second modification includes reacting at 30~35 °C for 0.5~1.5 h, followed by reacting at 85~90 °C for 0.5~1.5 h.

[0015] This invention provides a method for preparing the halogen-free flame-retardant rigid polyurethane foam composite material described above, comprising the following steps: After mixing polyether polyol, modified expandable graphite, modified layered trimetallic hydroxide, ammonium polyphosphate, amine catalyst, foam stabilizer and water, isocyanate is added, and the mixture is polymerized-foamed and then cured to obtain halogen-free flame-retardant rigid polyurethane foam composite material.

[0016] Preferably, the polymerization-foaming temperature is 65~70 ℃ and the time is 30~40 min; the curing temperature is 65~75 ℃ and the time is 40~50 h.

[0017] The present invention provides the application of the halogen-free flame-retardant rigid polyurethane foam composite material described in the above technical solution or the halogen-free flame-retardant rigid polyurethane foam composite material prepared by the preparation method described in the above technical solution in the field of building insulation.

[0018] This invention provides a halogen-free flame-retardant rigid polyurethane foam composite material. By simultaneously introducing modified expandable graphite and modified layered trimetallic hydroxide, and further constructing a multi-component composite catalytic synergistic flame-retardant and smoke-suppressing system, a balance can be achieved in the mechanical properties, thermal insulation, and flame-retardant and smoke-suppressing performance of the RPUF. Specifically, this invention prepares borosilicate-modified expandable graphite and phytic acid-modified layered trimetallic hydroxide using organic modification technology. This not only improves the dispersibility of both in the RPUF matrix but also simultaneously leverages the physical expansion effect of the borosilicate organically modified expandable graphite and the reinforcing effect of the borosilicate ceramic precursor on the carbon layer structure. On the other hand, by simultaneously utilizing the catalytic char-forming ability of the phytic acid organically modified layered trimetallic hydroxide and the gas-phase / condensed-phase dual-phase flame-retardant effect of phosphorus-containing phytic acid, a composite catalytic synergistic flame-retardant and smoke-suppressing system is constructed in the RPUF, resulting in a high-performance halogen-free flame-retardant rigid polyurethane foam composite material. This rigid polyurethane foam composite material not only has good mechanical and thermal insulation properties, but also forms a dense expanded char layer during combustion, which can effectively suppress the release of toxic fumes. It exhibits excellent flame retardant properties and low smoke toxicity, which can significantly improve the inherent fire safety in the field of building insulation.

[0019] Compared to layered bimetallic hydroxides, the layered trimetallic hydroxides prepared by the co-precipitation method in this invention contain a wider variety of metal ions, which is more conducive to their catalytic char formation and smoke suppression and detoxification effects within the RPUF matrix. Furthermore, the layered trimetallic hydroxides are modified using aminosilane modifiers and phytic acid. The introduction of siloxane and phytic acid organic components improves their compatibility with the RPUF matrix, effectively ensuring the uniformity of the prepared RPUF composite material and reducing negative impacts on overall performance. On the other hand, the introduction of phosphorus-containing phytic acid increases the content of flame-retardant elements in the RPUF composite material, further enhancing its gas-phase / condensed-phase dual-phase flame-retardant effect and expanding the application scope of biomass resources, aligning with the concept of green and sustainable development.

[0020] Unlike existing flame-retardant technologies for RPUFs, the composite catalytic synergistic flame-retardant and smoke-suppressing system based on borosilicate-modified expandable graphite and phytic acid-modified layered trimetallic hydroxides provided by this invention exhibits superior flame-retardant and smoke-suppressing performance. Specifically, the borosilicate flame-retardant element in the modified expandable graphite can serve as a ceramic precursor. The ceramic body can melt at high temperatures to form a dense ceramic structure, which, in conjunction with the expandable graphite, effectively compensates for the looseness of the worm-like expanded char layer, thereby better preventing the flame from spreading inward and significantly improving the fire resistance of the RPUF. Furthermore, the products of the thermal decomposition of the introduced modified layered trimetallic hydroxides can also participate in the ceramicization process, further enhancing the catalytic synergistic effect and improving the ceramicization performance. Borosilicate-modified expandable graphite and phytic acid-modified layered trimetallic hydroxide exhibit higher dispersibility in the RPUF matrix, significantly reducing the negative impact of inorganic fillers on the mechanical properties and thermal conductivity of the foam material. Their synergistic effect better blocks heat transfer during combustion and effectively reduces the release of combustible gases and particulate matter (especially highly toxic gases such as HCN and CO), significantly improving fire safety in building insulation. The halogen-free flame-retardant rigid polyurethane foam composite material described in this invention achieves a balance between low thermal conductivity, high mechanical properties, and excellent flame-retardant and smoke-suppressing effects. Its comprehensive performance is well-balanced, and the raw materials used are halogen-free, inexpensive, and have a relatively simple production process, making it suitable for commercial production and possessing high practical application value. Attached Figure Description

[0021] Figure 1 The images show the FT-IR (a) and XPS (b) spectra of expandable graphite before and after modification in Example 1. Figure 2 The images show the microstructure of expandable graphite before and after modification in Example 1, as well as the elemental distribution diagram of EG-SB. Figure 3 Images showing the dispersion state of expandable graphite before and after modification in Example 1; Figure 4 The images show the FT-IR (a) and XPS (b) spectra of CeCoFe-LDH before and after modification in Example 1. Figure 5 The images show the microstructure of CeCoFe-LDH before and after modification, and the elemental distribution of LDH-SP in Example 1. Figure 6 The thermal conductivity (a) and mechanical property curves (b) of the rigid polyurethane foam composite materials in Examples 1-3 and Comparative Examples 1-3 are shown. Figure 7The curves show the heat release rate (a), total heat release (b), smoke generation rate (c), total smoke generation (d), HCN concentration (e), and CO concentration (f) of the rigid polyurethane foam composite materials in Example 1 and Comparative Examples 1-3. Figure 8 Images showing the morphology of the char residue after combustion of the rigid polyurethane foam composite materials in Example 1 and Comparative Example 1; Figure 9 The images show the Raman spectra of the char residues after combustion of the rigid polyurethane foam composite materials in Example 1(a) and Comparative Example 1(b). Detailed Implementation

[0022] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0023] This invention provides a halogen-free flame-retardant rigid polyurethane foam composite material, comprising the following raw materials by total mass fraction (100%): Polyether polyol 30-35%, isocyanate 45-60%, modified expandable graphite 5-14%, modified layered trimetallic hydroxide 0.9-3.5%, ammonium polyphosphate 2.5-4.5%, amine catalyst 0.5-1.5%, foam stabilizer 0.3-0.5%, water 0.5-0.9%.

[0024] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 30-35% polyether polyol, preferably 32-33%, and more preferably 32.29-32.93%.

[0025] In this invention, the hydroxyl value of the polyether polyol is preferably 350~500 mgKOH / g.

[0026] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 45-60% isocyanate, preferably 48.43-49.39%.

[0027] In this invention, the isocyanate preferably includes polymethylene polyphenyl isocyanate, and the polymethylene polyphenyl isocyanate is preferably PM400; the NCO group content in the isocyanate is preferably 30~32 wt%.

[0028] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 5-14% modified expandable graphite, preferably 11.79-13.3%.

[0029] In this invention, the preparation method of the modified expandable graphite includes the following steps: Expandable graphite, a first dispersant, a boron source, a silicon source, and a first aminosilane coupling agent are mixed and borosilicate modified to obtain modified expandable graphite.

[0030] In this invention, the particle size of the expandable graphite is preferably 80-200 mesh, more preferably 80-100 mesh; before use, the expandable graphite is preferably ultrasonicated in anhydrous ethanol for 30 min and dried at 80 °C for 24 h.

[0031] In this invention, the first dispersant is preferably a mixture of ethanol and water, wherein the mass ratio of ethanol to water is preferably 351:39; and the mass ratio of the first dispersant to expandable graphite is preferably 390:20.

[0032] In this invention, the boron source preferably includes one or more of trimethoxyborooxy ester, trimethyl borate, boric acid, and trimethylcyclotriboroxane; the silicon source preferably includes one or more of tetraethyl orthosilicate, acetoxypropyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane. When the boron source or silicon source is two or more of the above, this invention does not have a special limitation on the proportion of different types of boron sources or silicon sources, and can be adjusted according to requirements.

[0033] In this invention, the mass ratio of expandable graphite, boron source and silicon source is preferably 20:(3.0~4.5):(1.4~3.0), more preferably 20:(3.5~4):2.2.

[0034] In this invention, the first aminosilane coupling agent preferably includes one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, and 3-aminopropyltrimethoxysilane; when the first aminosilane coupling agent is two or more of the above, this invention does not have a special limitation on the proportion of different types of first aminosilane coupling agents, and can be adjusted according to requirements.

[0035] In this invention, the preferred mass ratio of the first aminosilane coupling agent to expandable graphite is (2.5~3.5):20, more preferably 3:20. This invention utilizes the reaction between the amino group and isocyanate in the first aminosilane coupling agent to enhance its binding force in RPUF, while the introduction of organosiloxane segments improves the dispersibility of expandable graphite. Furthermore, the first aminosilane coupling agent serves as both a modifier and a silicon source, providing silicon.

[0036] In this invention, expandable graphite is dispersed in a first dispersant, followed by the addition of a boron source, a silicon source, and a first aminosilane coupling agent. The mixture is then mechanically stirred at 30 °C for 3 h. After adjusting the pH of the system with a 35% hydrochloric acid solution, the temperature is raised to the borosilicate modification temperature, and the mixture is stirred to carry out the borosilicate modification.

[0037] In this invention, the temperature for borosilicate modification is preferably 80-90 °C, more preferably 85-90 °C, the time is preferably 5-6 h, more preferably 5.5-6 h, and the pH is preferably 3.5-4.0, more preferably 3.5.

[0038] After completing the borosilicate modification, the present invention preferably filters the obtained product and washes it three times with ethanol, and then dries it at 80 °C for 24 h to obtain modified expandable graphite.

[0039] This invention modifies expandable graphite with borosilicate flame-retardant elements, which on the one hand improves its dispersibility in a polyurethane matrix, and on the other hand, strengthens the carbon layer structure by introducing borosilicate ceramic precursors.

[0040] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 0.9-3.5% modified layered trimetallic hydroxide, preferably 0.97-2.9%, and more preferably 0.99-1.96%.

[0041] In this invention, the preparation method of the modified layered trimetallic hydroxide includes the following steps: The second aminosilane coupling agent was mixed with an alcohol-water mixed solvent and hydrolyzed to obtain a silane hydrolysate. The layered trimetallic hydroxide was mixed with the silane hydrolysate for the first modification to obtain a modified intermediate product. The modified intermediate product, the second dispersant, and the phytic acid solution were mixed to carry out a second modification, resulting in a modified layered trimetallic hydroxide.

[0042] In this invention, the second aminosilane coupling agent preferably includes one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, and 3-aminopropyltrimethoxysilane. When the second aminosilane coupling agent is two or more of the above, this invention does not have a special limitation on the proportion of different types of second aminosilane coupling agents, and can be adjusted according to requirements. This invention utilizes the acid-base reaction between the amino group in the second aminosilane coupling agent and the phosphate group in phytic acid to bind phytic acid to the layered trimetallic hydroxide.

[0043] In this invention, the alcohol-water mixed solvent is preferably a mixture of anhydrous ethanol and water, wherein the volume ratio of anhydrous ethanol to water is preferably 9:1. This invention does not impose any particular limitation on the ratio of the alcohol-water mixed solvent to the second aminosilane coupling agent; it can be adjusted according to requirements to ensure complete hydrolysis.

[0044] In this invention, the hydrolysis temperature is preferably 30~35 ℃, more preferably 30 ℃, and the time is preferably 0.5~1.5 h, more preferably 1 h; hydrolyzing the second aminosilane coupling agent into silanol is beneficial to the subsequent condensation reaction.

[0045] In this invention, the metal ions in the layered trimetallic hydroxide preferably include divalent and trivalent metal ions, and the divalent metal ions preferably include Ni. 2+ Zn 2+ Co 2+ Cu 2+ Mg 2+ Any one of the following, wherein the trivalent metal ion preferably includes Fe. 3+ Ce 3+ and La 3+ Any two of them.

[0046] In this invention, the method for preparing the layered trimetallic hydroxide preferably includes the following steps: The divalent and trivalent metal salts required for the layered trimetallic hydroxide are mixed with water to obtain a mixed metal salt solution; The mixed metal salt solution and sodium hydroxide aqueous solution were simultaneously added dropwise to sodium carbonate aqueous solution to maintain the pH value at 12-12.5, and a co-precipitation reaction was carried out. After drying, layered trimetallic hydroxide was obtained.

[0047] The present invention does not limit the specific types of the divalent and trivalent metal salts, and any water-soluble metal salts well known in the art are acceptable.

[0048] In this invention, the molar ratio of divalent metal ions to trivalent metal ions in the layered trimetallic hydroxide is preferably 2~4:1, more preferably 2~3:1; this invention does not have a special limitation on the ratio of the two trivalent metal ions, and can be adjusted according to requirements.

[0049] In this invention, the preferred ratio of the amount of metal salt in the mixed metal salt solution, sodium hydroxide in the sodium hydroxide aqueous solution, and sodium carbonate in the sodium carbonate aqueous solution is (0.05~0.15)mol:(5~10)g:(2~5)g, and more preferably 0.09mol:8g:2.38g.

[0050] The present invention does not impose any special limitations on the concentrations of the sodium carbonate aqueous solution and the sodium hydroxide aqueous solution; they can be adjusted according to requirements.

[0051] In this invention, the temperature of the coprecipitation reaction is preferably room temperature, and the time is preferably 3.5~4.5h, more preferably 4h.

[0052] After the coprecipitation reaction is completed, the present invention preferably centrifuges the obtained mixture, washes the precipitate repeatedly with deionized water until the supernatant is neutral, dries the washed product at 80 °C to constant weight, grinds it to obtain layered trimetallic hydroxide.

[0053] In this invention, the layered trimetallic hydroxide is preferably CeCoFe-LDH, CeNiFe-LDH, CeCuFe-LDH or CeZnFe-LDH.

[0054] In this invention, the mass ratio of the layered trimetallic hydroxide, the second aminosilane coupling agent, and the phytic acid solution is preferably 10:(1.2~2.2):(0.5~1.5), more preferably 10:1.5~2:1; the mass concentration of the phytic acid solution is preferably 50~70%, more preferably 60~65%.

[0055] In this invention, the silane hydrolysate is preferably mixed with a layered trimetallic hydroxide, ultrasonically dispersed for 30 min, and then heated to carry out the first modification reaction.

[0056] In this invention, the temperature for the first modification is preferably 85~90 ℃, more preferably 90 ℃, and the time is preferably 4.5~6 h, more preferably 5~6 h.

[0057] After the first modification reaction is completed, the present invention preferably collects the modified product by centrifugation, and after washing and drying, obtains the modified intermediate product.

[0058] In this invention, the second dispersant is preferably an ethanol-water mixture, wherein the volume ratio of ethanol to water is preferably 9:1. This invention does not impose any particular limitation on the amount of the second dispersant, as long as the modified intermediate product is evenly dispersed.

[0059] In this invention, the modified intermediate product is preferably dispersed in a second dispersant, followed by the addition of phytic acid solution and stirring to carry out the second modification.

[0060] In this invention, the second modification preferably includes: reacting at 30~35 °C for 0.5~1.5 h, followed by reacting at 85~90 °C for 0.5~1.5 h, more preferably reacting at 30 °C for 1 h, followed by reacting at 90 °C for 1 h.

[0061] After the second modification reaction is completed, the product is collected by centrifugation, washed and dried to obtain the modified layered trimetallic hydroxide.

[0062] This invention utilizes silane modifiers and phytic acid to modify layered trimetallic hydroxides, which improves their dispersibility, increases the content of flame retardant elements in the system, and expands the application scope of biomass resources.

[0063] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 2.5-4.5% ammonium polyphosphate, preferably 2.93-3.07%.

[0064] In this invention, the degree of polymerization of the ammonium polyphosphate is preferably 1000-1500.

[0065] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 0.5-1.5% amine catalyst, preferably 0.97-0.99%.

[0066] This invention does not specifically limit the amine catalyst; any amine catalyst known in the art for the preparation of rigid polyurethane foam is acceptable. In the embodiments of this invention, the amine catalyst CAT-171, manufactured by Wanhua Chemical Group Co., Ltd., is specifically used.

[0067] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 0.3~0.5% foam stabilizer, preferably 0.32~0.33%.

[0068] In this invention, the foam stabilizer preferably includes silicone oil AK-8805.

[0069] Based on a total mass fraction of 100%, the raw materials for preparing the halogen-free flame-retardant rigid polyurethane foam composite material provided by the present invention include 0.5~0.9% water, preferably 0.65~0.66%.

[0070] This invention provides a method for preparing the halogen-free flame-retardant rigid polyurethane foam composite material described above, comprising the following steps: After mixing polyether polyol, modified expandable graphite, modified layered trimetallic hydroxide, ammonium polyphosphate, amine catalyst, foam stabilizer and water, isocyanate is added, and the mixture is polymerized-foamed and then cured to obtain halogen-free flame-retardant rigid polyurethane foam composite material.

[0071] In this invention, polyether polyol, modified expandable graphite, modified layered trimetallic hydroxide, ammonium polyphosphate, amine catalyst, foam stabilizer and water are mixed at room temperature and a stirring speed of 1200 r / min for 30 s. After adding isocyanate, the mixture is immediately stirred at 1200 r / min for 8 s and then polymerized and foamed in a closed foaming chamber.

[0072] In this invention, the polymerization-foaming temperature is preferably 65~70 ℃, more preferably 70 ℃, and the time is preferably 30~40 min, more preferably 30~35 min.

[0073] After the polymerization-foaming process is completed, the present invention preferably removes the obtained product and cures it in an oven to obtain a halogen-free flame-retardant rigid polyurethane foam composite material; the curing temperature is preferably 65~75 ℃, more preferably 70 ℃, and the curing time is preferably 40~50 h, more preferably 45~48 h.

[0074] This invention provides the application of the halogen-free flame-retardant rigid polyurethane foam composite material described in the above-described technical solution, or the halogen-free flame-retardant rigid polyurethane foam composite material prepared by the preparation method described in the above-described technical solution, in the field of building insulation. This invention does not impose any particular limitation on the method of application; any method well-known in the art can be used.

[0075] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0076] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0077] Example 1

[0078] (1) Preparation of modified expandable graphite

[0079] 20 g of expandable graphite (EG, 80 mesh, Qingdao Tianheda Graphite Co., Ltd.) was sonicated in 100 mL of anhydrous ethanol for 30 min, and then dried at 80 ℃ for 24 h. The dried expandable graphite was dispersed in a mixture of 351 g of anhydrous ethanol and 39 g of deionized water, followed by the addition of 4 g of trimethoxyboroxyester (Shanghai Maclean Biochemical Technology Co., Ltd.), 2.2 g of tetraethyl orthosilicate (Shanghai Aladdin Biochemical Technology Co., Ltd.), and 3 g of γ-aminopropyltriethoxysilane (Shanghai Aladdin Biochemical Technology Co., Ltd.). The mixture was mechanically stirred at 30 ℃ for 3 h, and the pH of the system was adjusted to 3.5 using a 35% hydrochloric acid solution. The temperature was then raised to 90 ℃ and stirred continuously for 6 h. After the modification reaction was complete, the product was filtered and washed three times with ethanol, and finally dried at 80 ℃ for 24 h to obtain modified expandable graphite, denoted as EG-SB.

[0080] (2) Preparation of modified layered trimetallic hydroxides

[0081] Dissolve 2.38 g of anhydrous sodium carbonate (Sinopharm Chemical Reagent Co., Ltd.) in 300 mL of deionized water to prepare a sodium carbonate solution; dissolve 9.69 g (0.024 mol) of ferric nitrate nonahydrate (Shanghai Maclean Biochemical Technology Co., Ltd.), 2.61 g (0.006 mol) of cerium nitrate hexahydrate (Shanghai Maclean Biochemical Technology Co., Ltd.), and 17.46 g (0.06 mol) of cobalt nitrate hexahydrate (Shanghai Maclean Biochemical Technology Co., Ltd.) in 100 mL of deionized water to prepare a mixed metal salt solution; dissolve 8 g of sodium hydroxide (Shanghai Maclean Biochemical Technology Co., Ltd.) in 100 mL of deionized water to prepare a sodium hydroxide solution; use two constant pressure dropping funnels to hold the mixed metal salt solution and the sodium hydroxide solution respectively, and add them dropwise to the sodium carbonate solution simultaneously with stirring at room temperature, adjusting the dropping rate to maintain the pH of the system at 12. After the addition was complete, stirring was continued for 4 hours. The resulting mixture was centrifuged and the precipitate was repeatedly washed with deionized water until the supernatant was neutral. The washed product was dried at 80 °C to constant weight and ground to obtain a layered trimetallic hydroxide, denoted as CeCoFe-LDH.

[0082] 1.5 g of γ-aminopropyltriethoxysilane was dissolved in a mixture of 90 mL of anhydrous ethanol and 10 mL of deionized water and hydrolyzed at 30 °C for 1 h to obtain a hydrolyzed mixture. The above mixture was mixed with 10 g of CeCoFe-LDH and sonicated for 30 min to ensure uniform dispersion. Then, the mixture was reacted at 90 °C for 6 h. After the reaction was completed, the modified product was collected by centrifugation, washed, and dried. The modified intermediate product was denoted as LDH-S.

[0083] Subsequently, LDH-S was dispersed in a mixture of 90 mL anhydrous ethanol and 10 mL deionized water, followed by the addition of 1 g phytic acid solution (70% by mass, Shanghai Aladdin Biochemical Technology Co., Ltd.), and stirred at 30 ℃ for 1 h. The temperature was then raised to 90 ℃ and stirred for another 1 h. After the reaction was completed, the modified product was collected by centrifugation, washed, and dried to obtain the modified layered trimetallic hydroxide, denoted as LDH-SP.

[0084] (3) Preparation of rigid polyurethane foam composite materials

[0085] First, 3.58 g EG-SB, 0.89 g ammonium polyphosphate (CF-APP201, degree of polymerization 1000~1500, Shifang Changfeng Chemical Co., Ltd.), 0.3 g LDH-SP, 0.3 g amine catalyst (CAT-171, Wanhua Chemical Group Co., Ltd.), 0.1 g foam stabilizer (AK-8805, Xuzhou Yihuiyang New Material Co., Ltd.), and 0.2 g water were added to 10 g polyether polyol (7011, hydroxyl value 480±20 mgKOH / g, Wanhua Chemical Group Co., Ltd.). The mixture was stirred at room temperature and a stirring speed of 1200 r / min for 30 s until completely mixed. Then, 15 g polymethylene polyphenyl isocyanate (PM400, NCO group content 30~32 wt%, Wanhua Chemical Group Co., Ltd.) was added, and the mixture was immediately stirred at 1200 r / min for 8 s. After all components were thoroughly mixed, the mixture was foamed in a closed foaming chamber maintained at 70 ℃ for 30 seconds. After being removed from the oven, the product was cured in a 70 °C oven for 48 h to obtain a rigid polyurethane foam composite material.

[0086] Example 2

[0087] (1) The preparation of modified expandable graphite is the same as in Example 1.

[0088] (2) The preparation of the modified layered trimetallic hydroxide is the same as in Example 1.

[0089] (3) The preparation of rigid polyurethane foam composite material is the same as in Example 1, except that the amount of modified layered trimetallic hydroxide LDH-SP added in step (3) is 0.6 g.

[0090] Example 3

[0091] (1) The preparation of modified expandable graphite is the same as in Example 1.

[0092] (2) The preparation of the modified layered trimetallic hydroxide is the same as in Example 1.

[0093] (3) The preparation of rigid polyurethane foam composite material is the same as in Example 1, except that the amount of modified layered trimetallic hydroxide LDH-SP added in step (3) is 0.9 g.

[0094] Example 4

[0095] (1) Preparation of modified expandable graphite, the source of the reagents used is the same as in Example 1: 20 g of expandable graphite (80 mesh) was sonicated in 100 mL of anhydrous ethanol for 30 min, and then dried at 80 °C for 24 h. The dried expandable graphite was dispersed in a mixture of 351 g of anhydrous ethanol and 39 g of deionized water, followed by the addition of 3.5 g of trimethoxyboroxyester, 3.0 g of tetraethyl orthosilicate, and 3.5 g of γ-aminopropyltriethoxysilane. The mixture was mechanically stirred at 30 °C for 3 h, and the pH of the system was adjusted to 4 using a 35% hydrochloric acid solution. The temperature was then raised to 90 °C and stirred continuously for 6 h. After the modification reaction was complete, the product was filtered and washed three times with ethanol, and finally dried at 80 °C for 24 h to obtain borosilicate-modified expandable graphite.

[0096] (2) The preparation of the modified layered trimetallic hydroxide is the same as in Example 1.

[0097] (3) The preparation of rigid polyurethane foam composite material is the same as in Example 1.

[0098] Example 5

[0099] (1) The preparation of modified expandable graphite is the same as in Example 1.

[0100] (2) The preparation of the modified layered trimetallic hydroxide is the same as in Example 1.

[0101] (3) Preparation of rigid polyurethane foam composite materials: First, 4.12 g EG-SB, 0.95 g ammonium polyphosphate (same type and source as in Example 1), 0.3 g LDH-SP, 0.3 g amine catalyst (same type and source as in Example 1), 0.1 g foam stabilizer (same type and source as in Example 1), and 0.2 g water were added to 10 g polyether polyol (4110, hydroxyl value 430±20 mgKOH / g, Wanhua Chemical Group Co., Ltd.). After mixing completely at room temperature and a stirring speed of 1200 r / min for 30 s, 15 g polymethylene polyphenyl isocyanate (same type and source as in Example 1) was added, and the mixture was immediately stirred at 1200 r / min for 8 s. After all components were mixed evenly, the mixture was foamed in a closed foaming chamber at a temperature maintained at 70 ℃ for 30 min. After removal, the mixture was cured in a 70 ℃ oven for 48 h to obtain a rigid polyurethane foam composite material.

[0102] Example 6

[0103] (1) The preparation of modified expandable graphite is the same as in Example 1.

[0104] (2) Preparation of modified layered trimetallic hydroxides, the reagents used were from the same sources as in Example 1: 2.38 g of anhydrous sodium carbonate was dissolved in 300 mL of deionized water to prepare a sodium carbonate solution. In 100 mL of deionized water, 9.69 g of ferric nitrate nonahydrate, 2.61 g of cerium nitrate hexahydrate, and 17.45 g (0.06 mol) of nickel nitrate hexahydrate were dissolved to prepare a mixed metal salt solution. 8 g of sodium hydroxide was dissolved in 100 mL of deionized water to prepare a sodium hydroxide solution. Using two constant-pressure dropping funnels, the mixed metal salt solution and the sodium hydroxide solution were placed in the funnels respectively. Both were simultaneously added dropwise to the sodium carbonate solution while stirring at room temperature. The pH of the system was maintained at 12 by adjusting the dropping rate. After the addition was complete, stirring was continued for 4 hours. The resulting mixture was centrifuged, and the precipitate was repeatedly washed with deionized water until the supernatant was neutral. The washed product was dried at 80 °C to constant weight, ground, and a layered trimetallic hydroxide, denoted as CeNiFe-LDH, was obtained.

[0105] The modification method for layered trimetallic hydroxide CeNiFe-LDH is the same as in Example 1.

[0106] (3) The preparation of rigid polyurethane foam composite material is the same as in Example 1.

[0107] Example 7

[0108] (1) The preparation of modified expandable graphite is the same as in Example 1.

[0109] (2) Preparation of modified layered trimetallic hydroxides, the reagents used were from the same sources as in Example 1: 2.38 g of anhydrous sodium carbonate was dissolved in 300 mL of deionized water to prepare a sodium carbonate solution. 9.69 g of ferric nitrate nonahydrate, 2.61 g of cerium nitrate hexahydrate, and 14.50 g (0.06 mol) of copper nitrate trihydrate were dissolved in 100 mL of deionized water to prepare a mixed metal salt solution. 8 g of sodium hydroxide was dissolved in 100 mL of deionized water to prepare a sodium hydroxide solution. The mixed metal salt solution and sodium hydroxide solution were placed in two constant-pressure dropping funnels, respectively, and simultaneously added dropwise to the sodium carbonate solution while stirring at room temperature. The pH of the system was maintained at 12 by adjusting the dropping rate. After the addition was complete, stirring was continued for 4 hours. The resulting mixture was centrifuged, and the precipitate was repeatedly washed with deionized water until the supernatant was neutral. The washed product was dried at 80 °C to constant weight, ground, and a layered trimetallic hydroxide, denoted as CeCuFe-LDH, was obtained.

[0110] The modification method for the layered trimetallic hydroxide CeCuFe-LDH is the same as in Example 1.

[0111] (3) The preparation of rigid polyurethane foam composite material is the same as in Example 1.

[0112] Example 8

[0113] (1) The preparation of modified expandable graphite is the same as in Example 1.

[0114] (2) Preparation of modified layered trimetallic hydroxides, the reagents used were from the same sources as in Example 1: 2.38 g of anhydrous sodium carbonate was dissolved in 300 mL of deionized water to prepare a sodium carbonate solution. In 100 mL of deionized water, 9.69 g of ferric nitrate nonahydrate, 2.61 g of cerium nitrate hexahydrate, and 17.85 g (0.06 mol) of zinc nitrate hexahydrate were dissolved to prepare a mixed metal salt solution. 8 g of sodium hydroxide was dissolved in 100 mL of deionized water to prepare a sodium hydroxide solution. Using two constant-pressure dropping funnels, the mixed metal salt solution and the sodium hydroxide solution were placed separately and simultaneously added dropwise to the sodium carbonate solution while stirring at room temperature. The pH of the system was maintained at 12.5 by adjusting the dropping rate. After the addition was complete, stirring was continued for 4 h. The resulting mixture was centrifuged, and the precipitate was repeatedly washed with deionized water until the supernatant was neutral. The washed product was dried at 80 °C to constant weight, ground, and a layered trimetallic hydroxide, denoted as CeZnFe-LDH, was obtained.

[0115] The modification method of layered trimetallic hydroxide CeZnFe-LDH is the same as in Example 1.

[0116] (3) The preparation of rigid polyurethane foam composite material is the same as in Example 1.

[0117] Comparative Example 1

[0118] Compared to Example 1, this comparative example uses unmodified expandable graphite instead of EG-SB and does not add LDH-SP. The types and sources of ammonium polyphosphate, amine catalyst, foam stabilizer, polyether polyol, and polymethylene polyphenyl isocyanate are the same as in Example 1. First, 3.58 g of expandable graphite, 0.89 g of ammonium polyphosphate, 0.3 g of amine catalyst, 0.1 g of foam stabilizer, and 0.2 g of water were added to 10 g of polyether polyol. The mixture was stirred at room temperature and a stirring speed of 1200 r / min for 30 s until it was completely mixed. Then, 15 g of polymethylene polyphenyl isocyanate was added, and the mixture was immediately stirred at 1200 r / min for 8 s. After all components were mixed evenly, the mixture was foamed in a closed foaming chamber at a temperature of 70 ℃ for 30 min. After being removed, the mixture was cured in a 70 ℃ oven for 48 h to obtain a rigid polyurethane foam composite material.

[0119] Comparative Example 2

[0120] Compared to Example 1, this comparative example only adds EG-SB as in Example 1, but does not add LDH-SP. The types and sources of ammonium polyphosphate, amine catalyst, foam stabilizer, polyether polyol, and polymethylene polyphenyl isocyanate are the same as in Example 1. First, 3.58 g EG-SB, 0.89 g ammonium polyphosphate, 0.3 g amine catalyst, 0.1 g foam stabilizer and 0.2 g water were added to 10 g polyether polyol. After mixing for 30 s at room temperature and a stirring speed of 1200 r / min, 15 g polymethylene polyphenyl isocyanate was added and immediately stirred at 1200 r / min for 8 s. After all components were mixed evenly, the mixture was foamed in a closed foaming chamber at a temperature of 70 ℃ for 30 min. After removal, it was cured in an oven at 70 ℃ for 48 h to obtain rigid polyurethane foam composite material.

[0121] Comparative Example 3

[0122] Compared to Example 1, this comparative example only adds EG-SB and unmodified CeCoFe-LDH as in Example 1. The types and sources of ammonium polyphosphate, amine catalyst, foam stabilizer, polyether polyol, and polymethylene polyphenyl isocyanate are the same as in Example 1. First, 3.58 g EG-SB, 0.3 g CeCoFe-LDH, 0.89 g ammonium polyphosphate, 0.3 g amine catalyst, 0.1 g foam stabilizer, and 0.2 g water were added to 10 g polyether polyol. The mixture was stirred at room temperature and a stirring speed of 1200 r / min for 30 s until homogeneous. Then, 15 g polymethylene polyphenyl isocyanate was added, and the mixture was immediately stirred at 1200 r / min for 8 s. After all components were mixed evenly, the mixture was foamed in a closed foaming chamber at a temperature of 70 ℃ for 30 min. After being removed, the mixture was cured in a 70 ℃ oven for 48 h to obtain a rigid polyurethane foam composite material.

[0123] Structural and morphological analysis

[0124] 1) The chemical structures of EG before and after modification in Example 1 were characterized by FT-IR and XPS, and the results are as follows: Figure 1 As shown.

[0125] Figure 1 The images show the FT-IR (a) and XPS (b) spectra of expandable graphite before and after modification in Example 1; from Figure 1 As can be seen in (a), at 3430 cm -1 The characteristic peak at 1630 cm⁻¹ originates from the stretching vibration of -OH groups between graphite sheets, while the peak at 1630 cm⁻¹ is due to the stretching vibration of -OH groups between graphite sheets. -1The characteristic peak at 2920 cm⁻¹ originates from the stretching vibration of the C=C bond. Compared with unmodified EG, the FT-IR spectrum of EG-SB shows significant changes, with a peak at 2920 cm⁻¹. -1 and 2850 cm -1 A stretching vibration peak of the CH bond appears at 1100 cm⁻¹. -1 The characteristic peak of the stretching vibration of the Si-O-Si bond appears at 930 cm⁻¹. Furthermore, a characteristic peak of the stretching vibration of the Si-O-Si bond appears at 930 cm⁻¹. -1 The presence of characteristic absorption peaks at the BO-Si bond indicates that the borosilicate ceramic precursor has been successfully modified onto the EG surface via a hydrolysis-condensation reaction. From the XPS spectra of EG and EG-SB (… Figure 1 As can be seen in (b) of the spectrum, compared with the unmodified EG, the EG-SB spectrum shows Si at 103 eV and 191 eV, respectively. 2p and B 1s The characteristic peaks further confirmed the successful construction of borosilicate ceramic precursors on EG surfaces.

[0126] 2) The microstructure of expandable graphite EG before and after modification in Example 1 was characterized using scanning electron microscopy (SEM). The results are as follows: Figure 2 As shown.

[0127] Figure 2 The images show the microstructure of expandable graphite before and after modification in Example 1, as well as the elemental distribution diagram of EG-SB; from Figure 2 It can be observed that EG itself has a distinct layered structure and a relatively smooth surface. For EG-SB, the introduction of the borosilicate ceramic precursor did not change its original layered structure; only the surface was covered by irregular particles and milky protrusions. Furthermore, the elemental distribution image of EG-SB shows the presence and uniform distribution of O, Si, B, C, and N elements, fully demonstrating that the EG surface has been successfully modified with the borosilicate ceramic precursor.

[0128] 3) The modified and unmodified EG from Example 1 were dispersed in deionized water by ultrasonication (100 W, 20 min), and then allowed to stand for 10 min to observe its sedimentation state. The results are shown in [Figure 1]. Figure 3 .

[0129] Figure 3 Images showing the dispersion state of expandable graphite before and after modification in Example 1; from Figure 3 As can be seen, the dispersibility of EG improved significantly after organic modification, and no significant sedimentation occurred after 10 minutes of standing, while most of the unmodified EG settled to the bottom. Therefore, EG modified with borosilicate organic compounds lays the foundation for the further preparation of RPUF composite materials with good comprehensive performance.

[0130] 4) The chemical structures of CeCoFe-LDH before and after modification in Example 1 were characterized by FT-IR and XPS. The results are as follows: Figure 4 As shown.

[0131] Figure 4 The images show the FT-IR (a) and XPS (b) spectra of CeCoFe-LDH before and after modification in Example 1; from... Figure 4 As can be seen in (a), at 3374 cm -1 and 1640 cm -1 The absorption peak appearing at 750–430 cm⁻¹ originates from the stretching and bending vibrations of the -OH groups in water molecules within the CeCoFe-LDH layer; -1 The absorption peaks appearing within this range can be attributed to the lattice vibration peaks of the metal-oxygen bonds (MO, MOM) in CeCoFe-LDH. In the FT-IR spectrum of LDH-S, the peak at 2920 cm⁻¹... -1 and 2850 cm -1 The absorption peak at 1100 cm⁻¹ is attributed to the asymmetric and symmetric stretching vibrations of the CH bond; -1 The characteristic peak at 1530 cm⁻¹ is due to the stretching vibration of Si-O-Si; -1 The absorption peak at 1230 cm⁻¹ corresponds to the bending vibration of NH₄⁺, indicating that γ-aminopropyltriethoxysilane was successfully grafted onto the CeCoFe-LDH surface. Compared to LDH-S, the FT-IR spectrum of LDH-SP shows a peak at 1230 cm⁻¹. -1 An asymmetric stretching vibration peak, attributed to the P=O bond, appears at 1050 cm⁻¹. -1 A stretching vibration peak of PO appears at 1530 cm⁻¹; in addition, a peak of PO stretching vibration appears at 1530 cm⁻¹. -1 The decrease in the peak intensity of the bending vibration absorption peak attributed to NH further indicates that phytic acid and γ-aminopropyltriethoxysilane have been bonded through ionic bonding, confirming the successful preparation of organically modified LDH-SP. XPS spectra of CeCoFe-LDH before and after modification (…) Figure 4 As can be seen in (b), characteristic peaks at 713 eV, 781 eV, and 929 eV, respectively, belonging to Fe, Co, and Ce, originating from CeCoFe-LDH layers. 3+ Co 2+ Fe 3+ Ions. In the XPS spectrum of LDH-S, ions corresponding to Si appear at 102 eV and 400 eV, respectively. 2p and N 1sThe absorption peaks confirmed that γ-aminopropyltriethoxysilane successfully modified CeCoFe-LDH. Compared with LDH-S, an absorption peak at 134 eV, attributed to phosphorus in phytic acid, appeared in the XPS spectrum of LDH-SP, further indicating that γ-aminopropyltriethoxysilane and phytic acid have successfully modified CeCoFe-LDH.

[0132] 5) The microstructure of CeCoFe-LDH before and after modification in Example 1 was characterized using SEM and transmission electron microscopy (TEM). The results are as follows: Figure 5 As shown.

[0133] Figure 5 The images show the microstructure of CeCoFe-LDH before and after modification, and the elemental distribution of LDH-SP in Example 1; from Figure 5 SEM images revealed that unmodified CeCoFe-LDH exhibited a typical layered stacking structure with sharp, clear lamellar edges. LDH-SP retained its layered structure, but the lamellar edges became more rounded, and a distinct coating layer morphology appeared on the surface. SEM-EDS surface scanning analysis showed that Si and P elements were uniformly distributed on the LDH-SP surface, preliminarily confirming the successful modification of the LDH surface with γ-aminopropyltriethoxysilane and phytic acid. Further TEM observation showed that unmodified CeCoFe-LDH exhibited a clear layered structure with sharp lamellar edges, but poor particle dispersion and obvious agglomeration. After two-step modification, the layered structure of LDH-SP remained, but the lamellar thickness increased significantly, and the particle dispersion improved significantly. TEM-EDS elemental surface scanning analysis showed that Si and P elements were uniformly distributed on the surface of individual LDH-SP particles, further demonstrating the successful grafting of γ-aminopropyltriethoxysilane and phytic acid onto the CeCoFe-LDH surface at the microscopic level. Based on the above analysis results, it can be confirmed that the functionalization modification of CeCoFe-LDH was successfully achieved using γ-aminopropyltriethoxysilane and phytic acid.

[0134] Performance testing

[0135] 1) The thermal conductivity and mechanical properties of rigid polyurethane foam composites were tested in accordance with GB / T 21558-2008.

[0136] Figure 6 The thermal conductivity (a) and compression-strain curves (b) of the rigid polyurethane foam composites in Examples 1-3 and Comparative Examples 1-3 are shown; Figure 6As shown in Figure (a), compared to Comparative Example 1, the thermal conductivity of Comparative Example 2 decreased to 0.032 W / (m·k) after the introduction of EG-SB. This is mainly because the surface of expandable graphite after organic modification contains active groups such as amino groups, which can further react with isocyanate, improving its dispersibility in the polyurethane matrix and effectively avoiding the destruction of the cell structure caused by the agglomeration of expandable graphite. In Comparative Example 3, the thermal conductivity decreased slightly to 0.031 W / (m·k) after the introduction of unmodified CeCoFe-LDH, possibly due to the increase in nucleation sites. Importantly, in Example 1, the thermal conductivity decreased to 0.028 W / (m·k) after the introduction of EG-SB and LDH-SP; with the increase of LDH-SP, the thermal conductivity of Example 2 further decreased to 0.027 W / (m·k). This is mainly due to the combined effect of the increase in nucleation sites and the enhanced dispersibility of the modified inorganic filler, which effectively avoids the destruction of the cell structure caused by agglomeration. However, when the amount of LDH-SP introduced was further increased, the thermal conductivity of Example 3 increased slightly. This is because too many nucleation sites destroyed the integrity of the foam cells, causing thermal convection, and the excessive filler content deteriorated the insulation performance of the foam to some extent.

[0137] like Figure 6 As shown in Figure (b), the compressive strength of Example 1 at 10% compressive strain was 0.25 MPa. With increasing LDH-SP content, the compressive strengths of Examples 2 and 3 decreased to 0.24 MPa and 0.21 MPa, respectively. The main reason for this is that although the dispersibility of the inorganic filler in the polyurethane matrix was improved, excessive use inevitably led to partial agglomeration. As stress concentration points, these agglomerates were prone to localized failure in the early stages of stress, resulting in a decrease in the mechanical properties of the foam composite material. The compressive strength of Comparative Example 1 at 10% compressive strain was only 0.16 MPa. After introducing EG-SB, the compressive strength of Comparative Example 2 increased to 0.19 MPa. This was mainly due to the significant improvement in the dispersibility of modified EG-SB in the polyurethane matrix, which effectively alleviated the formation of large agglomerates, resulting in a more uniform stress distribution and avoiding premature localized failure, thus significantly improving the mechanical properties of the composite material. Compared to Example 1, the compressive strength of Comparative Example 3 decreased to 0.18 MPa because unmodified CeCoFe-LDH was introduced. This can be attributed to the significant difference in polarity between CeCoFe-LDH, an inorganic nanosheet material, and the organic polyurethane matrix, leading to poor dispersibility and a pronounced tendency to agglomerate. These agglomerates act as stress concentration points, inducing early material failure. The above results indicate that organically modified EG-SB and LDH-SP can be well dispersed in the polyurethane matrix, thus imparting good mechanical properties.

[0138] 2) The vertical combustion rating, limiting oxygen index and flue gas toxicity of rigid polyurethane foam composites were tested according to GB / T 2406.2-2009, GB / T 8333-2022 and GB / T 20285-2006 respectively. The results are shown in Table 1.

[0139] Table 1. Limiting oxygen index, vertical combustion, and smoke toxicity levels of the rigid polyurethane foam composite materials in Examples 1-3 and Comparative Examples 1-3.

[0140] As shown in Table 1, the vertical flammability rating of the prepared rigid polyurethane foam composite materials was V-0, demonstrating good flame retardant properties. The limiting oxygen index (LOI) of Example 1 was 30.4%. With the increase of modified LDH-SP content, the LIOI of Examples 2 and 3 decreased slightly to 29.9% and 29.2%, respectively. This may be because transition metal oxides may catalyze the thermal degradation of polyurethane foam at high temperatures, thus exacerbating the combustion reaction to some extent. Compared with Comparative Examples 1 and 2, the LIOI of Example 1 was slightly lower due to the addition of LDH-SP. However, the LIOI of Comparative Example 2 was higher than that of Comparative Example 1. This is mainly because the dispersion of expandable graphite in the polyurethane matrix was improved after borosilicate organic modification. On the other hand, the borosilicate ceramic structure also helps to form a denser and more continuous protective layer with expandable graphite, effectively blocking the transfer of oxygen and heat, thus improving the flame retardancy of the material. Compared with Comparative Example 3, the limiting oxygen index of Example 1 was improved. This was mainly because the dispersion of CeCoFe-LDH in the polyurethane matrix was enhanced after organic modification, which improved the density and continuity of the formed char layer and improved the flame retardancy.

[0141] Furthermore, the flue gas toxicity of the samples in Examples 1-3 all reached ZA2 level, which is the result of the combined effect of organically modified expandable graphite and layered trimetallic hydroxide. On the one hand, expandable graphite expands immediately upon heating, forming a porous carbon layer that can adsorb particulate matter in the flue gas; on the other hand, the introduction of borosilicate ceramic precursors can further synergize with the expanded carbon layer, thereby improving the continuity of the carbon layer; in addition, the catalytic carbonization ability of CeCoFe-LDH can also effectively increase the density of the carbon layer, and combined with its ability to catalyze the conversion of highly toxic gases into less toxic gases, it can further reduce the amount of smoke released. In Comparative Examples 1 and 2, because no modified LDH-SP was added, the smoke suppression and toxicity reduction capabilities were reduced, and therefore the flue gas toxicity could only reach ZA3 level.

[0142] 3) The combustion behavior of rigid polyurethane foam composites was analyzed using an FTT cone calorimeter according to ISO 5660-1, with a thermal radiation power of 35 kW·m.-2 .

[0143] Figure 7 The figures show the heat release rate (a), total heat release (b), smoke generation rate (c), total smoke generation (d), HCN concentration (e), and CO concentration (f) curves of the rigid polyurethane foam composite materials in Examples 1 and Comparative Examples 1-3. Figure 7 As can be seen from (a) and (b), the peak heat release rate and total heat release of Comparative Examples 1, 2, and 3 are 124.8 kW·m³, respectively. -2 and 16.6 MJ·m -2 114.1 kW·m -2 and 15.7 MJ·m -2 113.6 kW·m -2 and 14.1 MJ·m -2 The peak heat release rate and total heat release of Example 1 were 111.8 kW·m³, respectively. -2 and 13.4 MJ·m -2 This indicates that the combined introduction of organically modified EG-SB and LDH-SP can produce a good synergistic flame-retardant effect on polyurethane foam. Furthermore, from... Figure 7 As can be seen from (c) and (d), the peak smoke generation rate and total smoke generation of Comparative Examples 1, 2, and 3 are 0.091 m³, respectively. 2 ·s -1 and 2.51m 2 0.078 m 2 ·s -1 and 2.43 m 2 0.073 m 2 ·s -1 and 2.06 m 2 The peak smoke generation rate and total smoke generation in Example 1 were 0.072 m³. 2 ·s -1 and 1.87 m 2 This can be mainly attributed to the fact that the borosilicate ceramic phase formed on the surface of EG-SB effectively promotes the formation of a continuous char layer composite barrier during combustion, thereby inhibiting the release of pyrolysis products and the generation of flue gas particles. Furthermore, LDH-SP, through its layered physical barrier effect, the release of non-combustible gases during combustion, and its catalytic detoxification capabilities, better synergizes with EG-SB in flame retardancy and smoke suppression. Therefore, as... Figure 7As shown in (e) and (f), Example 1 exhibited lower toxic fume release compared to Comparative Examples 1, 2, and 3. The HCN and CO concentrations of Comparative Examples 1, 2, and 3 were 26.9 ppm and 132.6 ppm, 25.1 ppm and 125.5 ppm, and 23.7 ppm and 118.2 ppm, respectively, while the HCN and CO concentrations of Example 1 were 21.5 ppm and 111.8 ppm, respectively.

[0144] 4) The microstructure of the char residue after combustion of rigid polyurethane foam composite material was observed using SEM.

[0145] Figure 8 Images showing the morphology of the char residue after combustion of the rigid polyurethane foam composite materials in Example 1 and Comparative Example 1; from Figure 8 As can be seen, compared with Comparative Example 1, the char residue of the rigid polyurethane foam composite material in Example 1 after combustion is dense and continuous, exhibiting better integrity. It can act as a physical barrier to provide heat insulation, oxygen isolation, and limit the release of flue gas particles. This is mainly due to the combined effect of modified EG-SB and LDH-SP introduced in Example 1. On the one hand, the dispersibility of inorganic fillers is improved after organic modification; on the other hand, borosilicate ceramic precursors, expandable graphite, and metal oxides jointly participate in the construction of the ceramicized char layer, promoting the formation of a complete and dense char layer containing composite flame-retardant elements.

[0146] 5) Raman spectroscopy was used to characterize the graphitization degree of the carbon residue after combustion of rigid polyurethane foam composite materials.

[0147] Figure 9 Raman spectra of the char residue after combustion of the rigid polyurethane foam composite materials in Example 1(a) and Comparative Example 1(b). 1360 cm⁻¹ -1 The D band at 1580 cm⁻¹ is attributed to amorphous carbon. -1 The G-band at that location is attributed to crystalline graphite, I D / I G It is the intensity ratio of the D peak to the G peak. The smaller the value, the higher the degree of graphitization, that is, the fewer defects in the carbon layer. It can be seen that in Example 1, I D / I G The value is 0.99, while I in Comparative Example 1 D / I G The value of 1.33 indicates that the combined introduction of modified EG-SB and LDH-SP enables rigid polyurethane foam composites to form more complete char residues during combustion, thus achieving good flame retardant and smoke suppression effects.

[0148] Furthermore, for Example 4, by changing the amount of raw materials and reaction conditions in the preparation process of EG-SB, its chemical structure remained unchanged. The resulting rigid polyurethane foam composite material had a thermal conductivity of 0.028 W / (m·k), a compressive strength of 0.26 MPa, a vertical combustion rating of V-0, a limiting oxygen index of 30.5%, and a flue gas toxicity of ZA2 level. The relevant properties were similar to those of Example 1.

[0149] Compared to Example 1, Example 5 increased the amounts of EG-SB and ammonium polyphosphate, and proportionally replaced 7011 with polyether polyol 4110. The resulting rigid polyurethane foam composite material exhibited a thermal conductivity of 0.029 W / (m·K) and a compressive strength of 0.27 MPa. This is because the increased filler content altered the cell structure of the polyurethane foam, increasing the open area or connectivity, promoting gas convection and thermal radiation, thus increasing the thermal conductivity. Furthermore, the filler acts as a dispersed phase, and its increased amount can bear some of the external force. Its inhibitory effect on foaming also thickens the cell walls, improving the material's rigidity and compressive strength. Example 5 showed slightly improved flame retardant performance, with a vertical burning rating of V-0, a limiting oxygen index of 31.5%, and smoke toxicity reaching ZA2 level. The improvement in limiting oxygen index is mainly due to the increased proportion of flame retardant elements in the system. Both EG-SB and ammonium polyphosphate can play a flame retardant role in the gas phase and condensed phase. When combined with LDH-SP, they can effectively improve the flame retardant performance of rigid polyurethane foam composites.

[0150] Compared to Example 1, different types of modified layered trimetallic hydroxides were prepared in Examples 6-8, and the LDH-SP dosage was replaced proportionally according to that in Example 1. The thermal conductivity, compressive strength, combustion performance, and smoke toxicity of the resulting rigid polyurethane foam composite materials did not change significantly. Example 5 had a thermal conductivity of 0.027 W / (m·K), a compressive strength of 0.24 MPa at 10% compressive strain, a vertical combustion rating of V-0, a limiting oxygen index of 31.7%, and smoke toxicity reaching ZA2 level. Example 6 had a thermal conductivity of 0.027 W / (m·K), a compressive strength of 0.25 MPa at 10% compressive strain, a vertical combustion rating of V-0, a limiting oxygen index of 31.3%, and smoke toxicity reaching ZA2 level. Example 7 exhibits a thermal conductivity of 0.028 W / (m·K), a compressive strength of 0.26 MPa at 10% compressive strain, a vertical combustion rating of V-0, a limiting oxygen index of 31.9%, and a smoke toxicity level of ZA2. These results demonstrate that EG-SB can form a good synergistic effect with different types of modified layered trimetallic hydroxides, endowing rigid polyurethane foam materials with excellent comprehensive properties.

[0151] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A halogen-free flame-retardant rigid polyurethane foam composite material, characterized in that, Based on a total mass fraction of 100%, the preparation materials include the following: Polyether polyol 30-35%, isocyanate 45-60%, modified expandable graphite 5-14%, modified layered trimetallic hydroxide 0.9-3.5%, ammonium polyphosphate 2.5-4.5%, amine catalyst 0.5-1.5%, foam stabilizer 0.3-0.5%, water 0.5-0.9%; The method for preparing the modified expandable graphite includes the following steps: Expandable graphite, a first dispersant, a boron source, a silicon source, and a first aminosilane coupling agent are mixed and borosilicate modified to obtain modified expandable graphite. The method for preparing the modified layered trimetallic hydroxide includes the following steps: The second aminosilane coupling agent was mixed with an alcohol-water mixed solvent and hydrolyzed to obtain a silane hydrolysate. The layered trimetallic hydroxide was mixed with the silane hydrolysate for the first modification to obtain a modified intermediate product. The modified intermediate product, the second dispersant, and the phytic acid solution were mixed to carry out a second modification, resulting in a modified layered trimetallic hydroxide.

2. The halogen-free flame-retardant rigid polyurethane foam composite material according to claim 1, characterized in that, The hydroxyl value of the polyether polyol is 350~500 mgKOH / g; The isocyanate includes polymethylene polyphenyl isocyanate; the NCO group content in the isocyanate is 30~32wt%.

3. The halogen-free flame-retardant rigid polyurethane foam composite material according to claim 1, characterized in that, The degree of polymerization of the ammonium polyphosphate is 1000~1500.

4. The halogen-free flame-retardant rigid polyurethane foam composite material according to claim 1, characterized in that, The foam stabilizer includes silicone oil AK-8805.

5. The halogen-free flame-retardant rigid polyurethane foam composite material according to claim 1, characterized in that, The boron source includes one or more of trimethoxyboroxy ester, trimethyl borate, boric acid, and trimethylcyclotriboroxy alkane; the silicon source includes one or more of tetraethyl orthosilicate, acetoxypropyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane. The mass ratio of the expandable graphite, boron source, and silicon source is 20:(3.0~4.5):(1.4~3.0); The first aminosilane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, and 3-aminopropyltrimethoxysilane; the mass ratio of the first aminosilane coupling agent to expandable graphite is (2.5~3.5):20; The borosilicate modification was performed at a temperature of 80-90 °C for 5-6 h, with a pH of 3.5-4.

0.

6. The halogen-free flame-retardant rigid polyurethane foam composite material according to claim 1, characterized in that, The layered trimetallic hydroxide contains both divalent and trivalent metal ions, with the divalent metal ions including Ni. 2+ Zn 2+ Co 2+ Cu 2+ Mg 2+ Any one of the following, wherein the trivalent metal ion includes Fe 3+ Ce 3+ and La 3+ Any two of them; The second aminosilane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane and 3-aminopropyltrimethoxysilane; The mass ratio of the layered trimetallic hydroxide, the second aminosilane coupling agent, and the phytic acid solution is 10:(1.2~2.2):(0.5~1.5); the mass concentration of the phytic acid solution is 50~70%.

7. The halogen-free flame-retardant rigid polyurethane foam composite material according to claim 1 or 6, characterized in that, The hydrolysis temperature is 30~35 ℃, and the time is 0.5~1.5 h; The first modification was performed at a temperature of 85-90 °C for 4.5-6 h. The second modification includes reacting at 30~35 °C for 0.5~1.5 h, followed by reacting at 85~90 °C for 0.5~1.5 h.

8. The method for preparing the halogen-free flame-retardant rigid polyurethane foam composite material according to any one of claims 1 to 7, characterized in that, Includes the following steps: After mixing polyether polyol, modified expandable graphite, modified layered trimetallic hydroxide, ammonium polyphosphate, amine catalyst, foam stabilizer and water, isocyanate is added, and the mixture is polymerized-foamed and then cured to obtain halogen-free flame-retardant rigid polyurethane foam composite material.

9. The preparation method according to claim 8, characterized in that, The polymerization-foaming temperature is 65~70 ℃ and the time is 30~40 min; the curing temperature is 65~75 ℃ and the time is 40~50 h.

10. The application of the halogen-free flame-retardant rigid polyurethane foam composite material according to any one of claims 1 to 7 or the halogen-free flame-retardant rigid polyurethane foam composite material prepared by the preparation method according to any one of claims 8 to 9 in the field of building insulation.

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