Flame-retardant polyurethane foam and process for its production

Abstract

This invention discloses a flame-retardant polyurethane foam material and its preparation process. It is prepared by foaming and curing components A and B: Component A contains a polyol matrix, a reactive flame retardant, a SnO-P2O5-ZnO phase change inorganic flux, a silane-treated inorganic ceramic precursor, and a MOF / MXene nano-smoke-suppressing catalytic hybrid; Component B is a silanized modified polyisocyanate (modification ratio 5%–10%). During the curing stage after molding, the triethoxysilane end groups of the modified isocyanate form silicon-oxygen covalent bonds with the inorganic particles through two pathways: direct alcoholysis condensation reaction with hydroxyl groups on the surface of the inorganic particles (Si-OEt + HO-M → Si-O-M + EtOH) and hydrolysis-condensation reaction, constructing an organic-inorganic hybrid crosslinked network. An isocyanate index of 2.8–3.5 constructs a polyisocyanurate trimer network. Upon heating, phase change glass powder forms an inorganic shielding layer, and the nano-catalytic hybrid catalyzes carbonization and suppresses toxic smoke. All embodiments meet the optimal grade of GB 8624-2012 B1-s1,d0, with thermal conductivity ≤0.023 W / (m·K) and compressive strength ≥312 kPa.

Description

Technical Field

[0001] This invention relates to the field of polyurethane foam materials technology, and in particular to a flame-retardant polyurethane foam material and its preparation process. Background Technology

[0002] Rigid polyurethane foam holds a significant position in the global thermal insulation materials market due to its extremely low thermal conductivity, excellent specific strength, and good adaptability to on-site foaming processes. However, as an organic polymer with carbon, hydrogen, oxygen, and nitrogen as its main backbone, the densely packed urethane bonds within polyurethane materials are highly susceptible to chain breakage and degradation at high temperatures. Furthermore, its high closed-cell porous structure, formed to achieve thermal insulation, results in a substantial increase in its specific surface area. These inherent properties make unmodified rigid polyurethane foam exhibit extremely high fire hazards; it is not only easily ignited with rapid flame spread, but also releases highly toxic gases such as hydrogen cyanide and carbon monoxide, as well as dense black smoke.

[0003] To address this issue, existing technologies often employ methods such as physically blending large amounts of inorganic flame retardants into the polyurethane matrix or adding halogenated or phosphate ester liquid flame retardants. However, these existing technologies have reached an intractable technical bottleneck. To achieve higher flame retardancy levels, the amount of inorganic filler added is extremely high, severely disrupting the continuity of the fragile microcellular walls of the polyurethane, leading to phase separation and particle agglomeration. This results in numerous cell ruptures and a sharp increase in open-cell ratio, not only causing a significant rise in thermal conductivity, completely negating its insulating value, but also causing a precipitous drop in compressive strength, exhibiting fatal defects such as extreme brittleness and easy powdering. Furthermore, under extreme high-temperature burning, simple endothermic or gas-phase dilution flame retardant mechanisms cannot prevent the polymer matrix from being completely oxidized and burned through, and the large amount of added liquid flame retardant exacerbates the plasticization of the matrix at high temperatures, producing high-temperature molten droplets with open flames. While high-filled flame-retardant polyurethane foams currently used in the industry can barely pass the B1 level threshold in the SBI monomer combustion test, their FIGRA values ​​are generally too high, and their total smoke and carbon monoxide emissions remain high. Furthermore, they generally suffer from fatal defects such as poor mechanical strength and severely degraded thermal insulation performance, falling far short of the ideal B1-s1,d0 optimal sub-level. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a flame-retardant polyurethane foam material and its preparation process. The foam material is obtained by foaming and curing raw materials comprising component A and component B. Component A includes: a polyol matrix, a reactive flame retardant, a phase change inorganic flux, an inorganic ceramic precursor, a nano-smoke-suppressing catalytic hybrid, and a foaming aid system. Component B contains a silanized modified polyisocyanate. The foam material has a polyurethane skeleton formed by the reaction of the polyol matrix and the polyisocyanate. The trialkoxysilane end groups contained in the silanized modified polyisocyanate form silicon-oxygen covalent bonds with the phase change inorganic flux and the inorganic ceramic precursor through a direct alcoholysis condensation reaction with the hydroxyl groups on the surface of the inorganic filler (≡Si-OR + HO-M → ≡Si-OM + ROH) and / or a dehydration condensation reaction after hydrolysis, forming an organic-inorganic hybrid crosslinked network that covalently bridges inorganic particles to the polyurethane skeleton. The key role of modified polyisocyanates containing silane end groups is manifested on two levels: First, the highly polar urea groups and trialkoxysilane groups introduced by the modification significantly enhance the wettability and interfacial physical adhesion of the polyisocyanate to the inorganic filler surface during the foaming stage, allowing the inorganic particles to be tightly coated by the polymer matrix during the critical window period of cell wall stretching and shaping. This maintains the integrity of the cell structure under extremely high inorganic filling conditions (covalent bonds have not yet been established at this stage, but interfacial physical adhesion is sufficient to stabilize the cells). Second, during the subsequent room temperature static curing process, the silane end groups (-Si-OEt) located at the organic-inorganic interface undergo a slow direct alcoholysis condensation reaction with the free hydroxyl groups (Al-OH, Si-OH) on the surface of the inorganic particles in close contact, gradually forming strong Si-O-Al and Si-O-Si covalent bonds, irreversibly upgrading the physical adhesion established during the foaming stage into covalent chemical bond bridging. This covalent bridging effect endows the material with long-term structural self-sustaining ability and excellent compressive strength and load-bearing deformation capacity under high-temperature fire conditions.

[0005] Preferably, the polyol matrix is ​​a blend of a high-functionality polyether polyol and a rigid aromatic polyester polyol. The high-functionality polyether polyol provides extremely high crosslinking density due to its densely branched structure, while the rigid aromatic polyester polyol imparts extremely high initial heat distortion temperature and dimensional stability to the matrix through its rigid benzene ring structure. The reactive flame retardant is selected from at least one of reactive phosphorus-containing diols and halogen-containing diols, and is embedded in the polyurethane backbone backbone via covalent bonding. The phase change inorganic flux is a SnO-P2O5-ZnO series low-melting-point glass powder (softening point 420~480℃). The inorganic ceramicization precursor includes metakaolin and aluminum hydroxide with a surface treated with a silane coupling agent. The nano-smoke-suppressing catalytic hybrid is a hybrid nanosheet formed by an amino-functionalized cobalt-based metal-organic framework and two-dimensional titanium carbide MXene. The silanized polyisocyanate is a prepolymer formed by partially end-capping polyphenyl polymethylene polyisocyanate (PMDI) with aminopropyltriethoxysilane (APTES), with the silanization modification ratio consuming 5% to 10% of the total isocyanate groups in the original PMDI. The foaming agent system comprises microencapsulated ammonium polyphosphate, a non-hydrolyzable polysiloxane-polyether copolymer foam leveler, a curing catalyst combination, and a foaming agent combination. The isocyanate index is controlled between 2.8 and 3.5 to form a polyisocyanurate (PIR) trimeric six-membered ring network structure.

[0006] Based on a total mass of 100 parts by weight of polyol matrix and reactive flame retardant in component A, the content of each component meets the following ratio: 30-55 parts of high-functionality polyether polyol, 25-40 parts of rigid aromatic polyester polyol, 15-25 parts of reactive flame retardant, 30-60 parts of phase change inorganic flux, 15-25 parts of silane-treated metakaolin, 20-35 parts of aluminum hydroxide, 3-8 parts of nano-smoke-suppressing catalytic hybrid, 10-18 parts of microencapsulated ammonium polyphosphate, 2-4.5 parts of foam leveling agent, 2-3.5 parts of trimerizing catalyst, 0.8-1.8 parts of foaming catalyst and gel catalyst combined, 0.5-1.2 parts of water as chemical foaming agent, and 25-35 parts of physical foaming agent.

[0007] The foamed material is prepared by a high-pressure impact mixing molding process: component A and component B are pressurized to 15~18MPa respectively and then mixed by impact in a high-pressure mixing head. The mixture is then poured into a double-track continuous laminator and compacted under restricted foaming conditions at a temperature of 55~65℃ on the upper and lower heating plates. After molding, the mixture is left to stand and mature at room temperature for no less than 48 hours.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The technical effects of this invention are as follows. First, when the material is subjected to high temperatures in a fire, the phase-change inorganic flux transforms into a high-viscosity liquid-phase glass melt, dissolving and encapsulating the inorganic powder and residual char, constructing a continuous and dense inorganic glassy-mineral composite protective layer on the fire-exposed surface, greatly delaying the material's continued combustion and pyrolysis process. The material passed the GB 8624-2012 B1 rating with a significant margin in the SBI monomer combustion test, meeting FIGRA and THR standards. 600s TSP 600s Both the combustion dripping grade and the overall flame retardant performance meet the stringent requirements of the optimal sub-level B1-s1,d0, far exceeding existing technologies. Secondly, the silanized polyisocyanate, during the foaming stage, enhances the interfacial wetting and physical adhesion of the inorganic filler through highly polar urea groups and silane groups, ensuring the integrity of the cell structure under extremely high filling conditions. Furthermore, during the post-curing stage, the direct alcoholysis condensation of silane end groups with the inorganic surface hydroxyl groups forms covalent chemical bridges with the inorganic powder surface, upgrading physical adhesion to covalent bridging, allowing the foam to maintain excellent closed-cell ratio and compressive strength even under high inorganic filling conditions. Thirdly, the nano-smoke-suppressing catalytic hybrid, through the synergistic effect of bimetallic catalytic char formation and physical labyrinth barrier, eliminates the generation of high-temperature open flame drippings and significantly suppresses total smoke and toxic gas release. Detailed Implementation

[0009] The following will provide further explanation through specific embodiments and comparative examples.

[0010] The specifications of each component raw material are as follows: The high-functionality sucrose-based polyether polyol is Wanhua Chemical's WANOL® R-4110 type, with a functionality f = 4.7, hydroxyl value of 450±10 mgKOH / g, and a viscosity of approximately 5500 mPa·s at 25℃. The rigid aromatic polyester polyol is Zibo Mingrun Chemical's MR-4501 type phthalic anhydride-based polyester polyol, with a functionality f = 2.5~3.0 and a hydroxyl value of 310±15 mgKOH / g. The reactive flame retardant is Clariant's Exolit® OP 550 type organophosphorus reactive flame retardant polyol, with an effective phosphorus content of approximately 14.0 wt%, a hydroxyl value of 160±10 mgKOH / g, and a functionality f = 2.0.

[0011] The phase change inorganic flux used is JSGL-460 environmentally friendly lead-free low-melting-point glass powder from Wuhan Jingshi Glass Technology Co., Ltd., with main components of SnO 55~62 wt%, P2O5 20~28 wt%, ZnO 10~15 wt%, softening point Ts = 450±15℃, and particle size D. 50 = 38±5 μm.

[0012] Metakaolin in inorganic ceramic precursors, specifically the Inner Mongolia Chao brand new material CHAOPAI® MK-90 (SiO2 52~55 wt%, Al2O3 40~44 wt%, particle size D) 50 Using powder with a thickness < 12 μm as the base, the powder underwent dry surface treatment (120℃, 30 min) in a Henschel high-speed mixer with 1.5 wt% γ-glycidoxypropyltrimethoxysilane (GPTMS, i.e., KH-560, Nanjing Quanxi Chemical). The coupling mechanism of GPTMS is as follows: its trimethoxysilane end (-Si(OCH3)3) hydrolyzes in the presence of trace amounts of moisture to generate silanol (-Si-OH), which then undergoes dehydration condensation with the abundant free hydroxyl groups (Al-OH, Si-OH) on the surface of metakaolin to form covalent Si-O-Al and Si-O-Si bonds, thereby anchoring the GPTMS molecule to the mineral surface; its outward-extending glycidyl end (glycidyl ether group) can undergo a slow ring-opening addition reaction with the active hydrogens (such as hydroxyl groups, urea groups, etc.) in the polyurethane matrix during the subsequent foaming and curing process, further enhancing the compatibility of the organic-inorganic interface. The reason for choosing GPTMS instead of amino-functionalized silanes (such as APTES) for metakaolin surface treatment is that, while the coupling mechanism of APTES also involves the hydrolysis and condensation of the silane end on the mineral surface, the aliphatic primary amino group (-NH2) suspended at the other end is completely free and exposed on the particle surface after coupling. The reaction rate of aliphatic primary amino groups with isocyanate groups (-NCO) is extremely high (about 2-3 orders of magnitude higher than that of alcohols -OH). If metakaolin containing a large amount of free surface-mounted -NH2 is introduced into component A, an uncontrollable, extremely rapid urea-gel reaction will be triggered during the high-pressure collision mixing with component B, which contains a large amount of -NCO, leading to clogging of the mixing head and rheological collapse of the foaming system. Although the epoxy end of GPTMS can also react with -NCO, its reaction rate is much lower than that of amine-NCO reactions, and it will not substantially disturb the gel-foaming equilibrium within the foaming time window of tens of seconds. Furthermore, because GPTMS is used only at a low dosage of 1.5 wt% to treat the surface of metakaolinite, it consumes only a very small portion of the hydroxyl sites on the mineral surface (metakaolinite has a large specific surface area and extremely abundant surface hydroxyl groups). The vast majority of surface hydroxyl groups remain in a free state, allowing the triethoxysilane end groups of the silanized modified PMDI in component B to form covalent silicon-oxygen bonds through direct alcoholysis condensation reaction (Si-OEt + HO-M → Si-OM + EtOH) during the subsequent ripening stage, thereby constructing an organic-inorganic hybrid cross-linked network. Ultrafine aluminum hydroxide (ATH) of the Zhonglv Shandong AH-2 type with a particle size D... 50 = 2.5±0.5 μm.

[0013] The preparation method of the nano-smoke-suppressing catalytic hybrid is as follows. Ti3C2T x MXene was prepared using Ti3AlC2 MAX phase ceramic powder (Henan Yiyi Technology Co., Ltd., particle size < 38 μm) as a precursor by selective HF etching: 2.0 g of Ti3AlC2 powder was slowly added to 40 mL of 40 wt% HF aqueous solution under controlled temperature and magnetic stirring (200 rpm) in an ice-water bath to control the exothermic reaction during the feeding stage. After the feeding was completed, the ice-water bath was removed and the mixture was transferred to room temperature (about 25℃) for continued stirring and etching for 24 h. After the reaction was completed, the mixture was repeatedly centrifuged and washed with deionized water until the pH was ≥ 6. After dispersion, the mixture was ultrasonically exfoliated (600 W, 20 kHz, pulse 2s / 1s, ice bath temperature control) for 1 h. The supernatant was collected by low-speed centrifugation as a few-layer MXene dispersion. The above-mentioned HF etching process should be carried out in a dedicated corrosion-resistant laboratory or workshop equipped with a forced fume hood, acid-resistant floor, and emergency shower facilities. Operators must wear full-face acid-resistant respirators, fluoride-resistant rubber gloves, and chemical protective suits. After etching, the fluoride-containing waste liquid is neutralized to pH 7-8 with lime milk and fluoride ions are recovered in the form of CaF2 precipitation. The supernatant can only be discharged after it meets the standards. The overall operation must comply with GB 15603 "General Rules for Storage of Commonly Used Hazardous Chemicals" and the local hazardous waste management regulations. NH2-Co-MOF is synthesized by a solvothermal method: 1.164 g Co(NO3)2·6H2O and 0.724 g 2-aminoterephthalic acid (NH2-BDC) are dissolved in 60 mL DMF, hydrothermally heated at 120℃ for 24 h, washed, and then vacuum dried at 80℃. The amino group in NH2-Co-MOF is an aromatic amine attached to a benzene ring. Its reactivity with -NCO is about 2-3 orders of magnitude lower than that of aliphatic primary amino groups. Furthermore, the amount of MOF in the system of this invention is only 3-8 parts, and the absolute equivalent of the aromatic amino group is extremely low, so it will not substantially disturb the foaming gel reaction equilibrium. Hybrid self-assembly: Equal masses of MXene solid and MOF powder are dispersed in anhydrous ethanol, treated with ultrasound (900 W, 50 min, ice bath), collected by high-speed centrifugation, and freeze-dried under vacuum for 24 h to obtain the hybrid powder. Both the MXene self-exfoliated dispersion and the hybrid powder should be handled and stored under a nitrogen or argon inert atmosphere to prevent Ti3C2T xThe MXene sheets oxidize in air (the -OH / -O / -F end groups on the MXene surface are easily and slowly oxidized to TiO2 in an aerobic and humid environment). The vacuum freeze-drying process itself is completed under low-temperature and high-vacuum conditions, effectively suppressing oxidation during the drying process. The resulting hybrid powder is sealed in an argon-filled aluminum foil bag and stored refrigerated (4°C). Before use, the powder is taken out in a nitrogen glove box. It should be noted that even if a small amount of oxidation occurs on the MXene surface to form a nano-TiO2 thin layer, this TiO2 still has catalytic activity for carbonization (in fact, MXene is eventually converted into nano-TiO2 during the high-temperature pyrolysis stage). Therefore, a small amount of surface oxidation will not substantially weaken the smoke-suppressing catalytic function of the hybrid. Regarding the stability of aromatic amine groups in the synthesis of NH2-Co-MOF: The amino group in NH2-BDC (2-aminoterephthalic acid) is directly attached to the benzene ring to form an aromatic amine, which has a much higher oxidation potential than aliphatic amines. It has sufficient chemical stability in the reducing atmosphere of the DMF solvothermal system at 120℃, and this synthesis condition is a standard method that has been widely verified in the field of metal-organic frameworks.

[0014] In the foaming agent system, the microencapsulated ammonium polyphosphate (APP) is Shandong Shengquan SQ-APP 301 (degree of polymerization n > 1000); the foam leveling agent is Jiangsu Meiside AK-8805 non-hydrolyzable polysiloxane-polyether copolymer; the trimerizing catalyst is potassium isooctanoate / diethylene glycol solution; the foaming catalyst is pentamethyldiethylenetriamine (PMDETA); the gelling catalyst is dibutyltin dilaurate (DBTDL); the physical foaming agent is LBA (Honeywell Solstice® LBA, boiling point approximately 19°C); and the chemical foaming agent is deionized water.

[0015] Component B's base isocyanate is WANNATE® PM-200 PMDI (NCO mass fraction 30.5~32.0%) from Wanhua Chemical. Modification method: Under N2 protection, PMDI is placed in a reactor equipped with an anchor-type stirrer (200~300 rpm) and heated to 60±2℃. APTES is slowly added dropwise through a constant-pressure dropping funnel at a rate of 0.5~1.0 mL / min. It should be noted that the APTES molecule contains only a single primary amino group (-NH2). Each APTES molecule consumes only one -NCO group on PMDI and generates an N,N'-disubstituted urea bond (-NH-CO-NH-). The nitrogen atoms at both ends of the urea group are connected to the PMDI backbone and the silane side chain of APTES, respectively, thus grafting the triethoxysilyl group onto the PMDI molecular chain in the form of a suspended side group. This is an end-capping modification rather than a cross-linking reaction. Under the modified conditions of this invention, the -NCO group of PMDI in the reaction system maintains a molar excess of more than 10 times relative to the -NH2 group of the added APTES. Each drop of APTES is instantly absorbed by the surrounding large amount of -NCO groups upon entering the reactor, resulting in an extremely low local amine concentration. From both stoichiometric and reaction kinetic perspectives, there are no conditions for gelation caused by local amine enrichment. During the dropwise addition, the exothermic reaction is removed by circulating cooling water through the reactor jacket, maintaining the reactor temperature fluctuation within ±2℃. After being kept at 60℃ for 2 hours, the mixture is cooled and sealed, yielding a homogeneous, transparent, pale yellow liquid. Taking a modification ratio of 7.5% as an example, the viscosity of modified PMDI at 25℃ is about 650~850 mPa·s (unmodified PM-200 is about 200~250 mPa·s). The increase in viscosity is mainly attributed to the strong polar hydrogen bonding association of N,N'-disubstituted urea groups. However, since APTES is a monofunctional end-capping modification rather than a cross-linking reaction, there are no microgel particles in the product. It is still a completely flowable homogeneous liquid, which meets the delivery and atomization requirements of high-pressure metering pumps and nozzles. The accurate calculation of the modified NCO content must simultaneously consider the increase in total mass caused by NCO consumption and the addition of APTES: taking 100 g of unmodified PMDI (NCO 31.0%) as an example, consuming 7.5% NCO requires adding 12.26 g of APTES, increasing the total mass of the system to 112.26 g, with a residual NCO of 28.67 g. The actual NCO mass fraction = 28.67 / 112.26 = 25.5%. Each example was calculated precisely using this method.

[0016] The reaction mechanism of this invention is as follows. After the collision and mixing of components A and B, three competing and parallel reactions occur: gelation (polyol -OH and -NCO form urethane bonds), foaming (water and -NCO form CO2), and trimerization (excess -NCO self-polymerizes into a PIR six-membered ring under the drive of potassium isooctanoate). Within tens of seconds of foaming and molding, the stability of the cell structure mainly depends on the reduction of the surface tension of the system and the stabilization of the bubble nuclei by the non-hydrolyzable foaming agent. At the same time, the improved interfacial wettability of metakaolin after GPTMS surface treatment also helps to reduce the stress concentration damage to the bubble walls caused by inorganic particles.

[0017] The contribution of silanized modified polyisocyanates to material properties can be divided into two levels: immediate interfacial reinforcement during the foaming stage and gradual covalent crosslinking during the curing stage.

[0018] Level 1: Enhanced interfacial wetting and physical adhesion during the foaming stage (effective within tens of seconds of foaming, independent of any hydrolysis reaction). APTES modification introduces highly polar N,N'-disubstituted urea groups (-NH-CO-NH-) and triethoxysilyl groups (-Si(OEt)3) at the ends of the PMDI molecular chain. The strong hydrogen bond donor-acceptor capacity of the urea groups (NH⋯O=C and NH⋯O-Si / Al) significantly improves the wettability and interfacial adhesion of PMDI to the polar hydroxyl groups on the surface of inorganic fillers; the ethoxy oxygen atom of the triethoxysilyl group can also form hydrogen bonds with the hydroxyl groups on the filler surface. This strong physical interfacial adhesion established during the liquid foaming stage ensures that inorganic particles are tightly coated by the polymer matrix during the critical window period of biaxial stretching and shaping of the bubble wall, rather than tearing the bubble wall due to weak interfacial debonding. This is the primary reason why the Example (silanized PMDI) differs substantially from Comparative Example 1 (unmodified PMDI) in terms of closed-cell ratio—under the extremely high filling conditions required by this invention (approximately 110 parts inorganic powder / 100 parts polyol), the interfacial adhesion strength of the unmodified PMDI in Comparative Example 1 is insufficient to resist the foaming tensile stress, resulting in large-area cell wall rupture.

[0019] The second stage: the gradual establishment of the covalent cross-linked network during the curing stage. After gel solidification, the polymer matrix of the bubble wall has solidified into a highly cross-linked network with PIR trimer six-membered rings as the core. During the room temperature static curing stage (≥48 h), the triethoxysilane end groups located at the organic-inorganic interface and the adjacent free hydroxyl groups on the surface of the inorganic particles mainly form silicon-oxygen covalent bonds through the following two pathways: (1) Direct alcoholysis condensation reaction (main path, water-independent): ≡Si-OC2H5 + HO-M → ≡Si-OM +C2H5OH (M represents inorganic surface metal atoms such as Al or Si). This reaction is a direct transesterification condensation between alkoxysilanes and mineral surface hydroxyl groups, which does not require water and only releases small ethanol molecules. Its thermodynamic driving force comes from the thermodynamic stability advantage of the Si-O-Al / Si-O-Si covalent bond (bond energy about 450 kJ / mol) over the Si-OEt bond (bond energy about 370 kJ / mol). In the system of this invention, the silane end group is covalently suspended on the PMDI backbone end group through urea bonds, and the PMDI backbone just covers and anchors the inorganic particle surface during the foaming and curing process - therefore, the ethoxy group of the silane end group is in direct spatial contact with the hydroxyl group on the inorganic particle surface (interfacial distance is on the nanometer scale), which satisfies the geometric premise of direct alcoholysis condensation. The reaction is slow at room temperature (therefore requiring a curing time of at least 48 hours), but because it does not depend on any external moisture supply, it can occur uniformly throughout the closed-cell foam, unaffected by the cell closure. The ethanol released in the reaction is a small molecule (MW=46), which dissolves in molecular form in the polymer matrix and the gas phase of the closed-cell cells within the closed-cell foam system. Since the silane modification ratio is only 5%~10% (corresponding to the total PMDI -NCO consumption), and the conversion rate of direct alcoholysis condensation is limited during the 48-hour curing period at room temperature, the total amount of ethanol released is extremely small relative to the volume of the board. The increase in partial pressure caused by its dispersion in a large number of closed-cell cells is negligible and will not affect the dimensional stability of the board. After subsequent cutting and processing of the board, the exposed cross-section allows residual ethanol to gradually diffuse out. The direct alcoholysis condensation reaction of alkoxysilanes with hydroxyl groups on the mineral surface is a recognized reaction pathway in silane coupling agent chemistry.

[0020] (2) Hydrolysis-condensation reaction (auxiliary pathway, providing supplementation in areas where moisture is accessible): After the sheet is cut, the exposed cross-section and the areas where the aluminum foil veneer edge is not completely sealed allow ambient atmospheric moisture (RH 40~60%) to diffuse and penetrate within a few millimeters of the near-surface layer. In these areas where moisture is accessible, silane end groups can form silicon-oxygen bonds via the conventional hydrolysis-condensation pathway (Si-OEt + H2O → Si-OH + EtOH, then Si-OH + HO-M → Si-OM + H2O), and the reaction rate of this pathway is faster than direct alcoholysis condensation. Therefore, the covalent crosslinking density in the near-surface region is higher than that in the core.

[0021] It is important to emphasize that even under the most conservative assumption of limited covalent cross-linking in the core, the strong physical interfacial adhesion established during the foaming process at the first level independently ensures the integrity of the cell structure (closed-cell rate of 92%~96%) and basic mechanical properties. The second level of covalent cross-linking is an incremental reinforcement based on this, particularly evident in the long-term structural self-sustaining ability under high-temperature firing conditions. The performance difference between Comparative Example 1 and the various embodiments is actually a combined result of the combined contributions of the two levels.

[0022] It should be objectively pointed out that there is a covalent crosslinking density gradient from the surface to the core in the thickness direction of the board (the surface layer is higher than the core). However, this gradient does not affect the engineering performance: (i) the critical areas for fire and stress are both located in the surface layer; (ii) the significant differences between Comparative Example 1 (non-silanized PMDI, both layers missing) and the various examples in compressive strength (185 vs 312~435 kPa), closed-cell rate (78.3% vs 92.3~95.6%), and flame retardant rating (B2 vs B1-s1,d0) constitute direct experimental evidence that silanization modification plays a practical role throughout the entire board.

[0023] After being heated, the functional components of the material are activated according to the temperature gradient: In the 200~350℃ stage, ATH dehydrates and absorbs heat to release water vapor, and reactive phosphorus diol and APP decompose to generate polyphosphoric acid catalyst matrix to form a primary expanded carbon layer; In the 250~450℃ stage, MOF thermally desorbs nano-Co3O4 and MXene phase transforms to generate nano-TiO2, and bimetallic catalytic sites guide aliphatic fragments to aromatize and rearrange into a dense graphitized carbon network, and the residual MXene sheets construct a physical maze to prevent the escape of toxic fumes; Above 450℃, low-melting-point glass powder phase transforms into high-viscosity glass melt to dissolve and encapsulate dehydrated metakaolinite and Al2O3, forming a continuous inorganic glass-mineral composite shielding layer on the fire-exposed surface (the main body of this shielding layer is an amorphous glass matrix in which mineral particles and preliminarily reorganized aluminosilicate microcrystalline phase are dispersed, belonging to a glass-ceramic composite structure).

[0024] The preparation process is as follows. First, prepare the hybrid powder according to the above method. Prepare component A: Add polyols, foaming agents and nano-hybrid powders to a planetary vacuum-powered mixing reactor, and pre-stir at 35~40℃ with a rotation speed of 1500 rpm / revolution speed of 50 rpm for 20 min; add dried inorganic powders in batches, and shear each batch at 2500~3200 rpm for 45~60 min, with a Hegman fineness ≤ 50 μm; maintain 35~40℃ and turn on the vacuum (-0.09~-0.095 MPa) for low-speed degassing for 15~20 min; turn off the vacuum and restore atmospheric pressure, cool to 15±2℃ (below the boiling point of LBA 19℃), add catalyst, water and LBA under sealed conditions, seal with nitrogen positive pressure at 0.2~0.3 MPa, mix at low speed for 5~8 min, seal, pressurize and cool for storage. Component A, after being dispersed by high-speed shear at a storage temperature of 15±2℃, is in a uniform suspension slurry state with an apparent viscosity of approximately 3500~6500 mPa·s (depending on the amount of inorganic filler in the formulation). Before foaming, after Component A is heated to 35~40℃ via a pipeline heat exchanger, the viscosity drops to 1800~3200 mPa·s. The rationality of the above viscosity levels and temperature response is based on the following analysis: (i) The continuous liquid phase of Component A is composed of polyol (80~100 parts), liquid reactive flame retardant OP550 (15~25 parts), and liquid physical foaming agent LBA (25~35 parts), with a total liquid phase volume of approximately 130~160 parts. The volume fraction of inorganic solid phase (65~120 parts) in the total system is approximately 18%~28% (based on an inorganic powder density of 2.5~3.0 g / cm³). 3 The liquid phase density is approximately 1.05~1.15 g / cm³. 3(i) The estimated value is far below the close packing limit and is still within the flowable range of the suspension slurry; (ii) The heating range is 15℃ → 35~40℃ (temperature difference of 20~25℃). Sucrose-based polyether polyol (R-4110, viscosity of 5500mPa·s at 25℃) itself has extremely strong temperature viscosity sensitivity. Heating by 20℃ can reduce its viscosity by more than 60%. The significant reduction in the viscosity of the continuous phase directly leads to a decrease in the overall viscosity of the suspension system; (iii) The non-hydrolyzable polysiloxane-polyether copolymer foaming agent AK-8805 also plays a surface-active dispersing function in the system. Its polysiloxane segments adsorb onto the surface of inorganic particles to form a steric stabilizing layer, which effectively inhibits particle agglomeration and shear thickening effect under high filling conditions. Preparation of component B: Prepare silanized modified PMDI according to the above method and store in a sealed container. Foaming and Molding: Component A is first pressurized to 15~18 MPa by a high-pressure metering pump at a storage temperature of 15±2℃, and then heated to 35~40℃ in the high-pressure pipeline at the pump outlet via a heat exchanger. Throughout the heating process, the A component pipeline is maintained at a system back pressure of 15~18 MPa to ensure that LBA remains in a liquid state (the boiling point of LBA at 15 MPa is much higher than 40℃, so there is no risk of premature vaporization). The high-pressure metering pump directly extracts and pressurizes component A slurry at a low temperature of 15℃. At this temperature, LBA exists completely in a liquid state because it is below its boiling point (19℃), and there is no cavitation condition in the pump chamber. Although the viscosity of component A at 15℃ reaches 3500~6500 mPa·s, it is still within the design delivery range of industrial high-pressure plunger metering pumps (such as the Hennecke MX series and KraussMaffei RimStar series) (the upper limit of the working viscosity of such special pumps can reach more than 10,000 mPa·s). The core components of the metering pump plunger, cylinder and check valve are made of tungsten carbide hard alloy to withstand the abrasive conditions of slurry containing inorganic powder. Component B is pressurized to 15~18 MPa at 30~35℃ and mixed by impact in the high-pressure mixing head before being poured into a dual-track laminator (the finishing substrate is 30μm aluminum foil or 40 g / m²). 2 (Fiberglass felt), heated to 55~65℃, limited foaming and compaction molding followed by cutting, and then allowed to stand and mature at room temperature (RH 40~60%) for ≥ 48 h. The high-pressure mixing head used in this invention is a wear-resistant design specifically for high-filled polyurethane / polyisocyanurate systems. The core components of the mixing chamber and nozzle are made of tungsten carbide hard alloy or zirconia ceramic bushings to withstand the high-speed erosion and wear of slurries containing inorganic powder. This type of wear-resistant high-pressure mixing equipment has been successfully industrialized in high-filled PIR continuous board production lines for building insulation (manufacturers such as Hennecke and KraussMaffei provide such dedicated models).

[0025] Performance testing standards: Flammability rating GB 8624-2012 / SBI (GB / T 20284), B1-s1,d0 pass criteria FIGRA 0.2MJ ≤ 120 W / s, LFS < sample edge, THR 600s ≤ 7.5 MJ, SMOGRA ≤ 180 m 2 / s 2 TSP 600s ≤ 200 m 2 No flammable drippings; PCS according to EN ISO 1716 oxygen bomb calorimeter method (reflects only the chemical energy of organic matter, unrelated to microstructure and high-temperature protection mechanisms); CONE according to ISO 5660-1 (50 kW / m²). 2 Thermal conductivity GB / T 10294 (25℃); compressive strength GB / T 8813 (10% deformation); closed-cell ratio GB / T 10799; LOI according to GB / T2406.2; morphological retention rate after high-temperature burning with a butane torch at 1000℃ for 30 min.

[0026] Example 1: Component A, based on a total of 100 parts of polyol matrix and reactive flame retardant: 45 parts polyether polyol, 35 parts polyester polyol, 20 parts Exolit OP550, 45 parts low melting point glass powder (Ts=450℃), 20 parts GPTMS-treated metakaolin, 25 parts ATH, 15 parts APP, 5.5 parts MOF@MXene, 3.2 parts AK-8805 foam stabilizer, 2.8 parts potassium isooctanoate, 1.2 parts PMDETA / DBTDL, 0.8 parts water, and 30 parts LBA. Component B: Silanization ratio 7.5%, modified NCO 25.5%, index 3.2, mixing pressure 16 MPa, heating plate 60℃, curing for 48 h.

[0027] Example 2: Polyether 55 parts, polyester 30 parts, OP550 15 parts, glass powder (Ts=450℃) 30 parts, metakaolin 15 parts, ATH 20 parts, APP 10 parts, hybrid 3 parts, foam stabilizer 2.5 parts, potassium isooctanoate 2.2 parts, PMDETA / DBTDL 0.9 parts, water 0.6 parts, LBA 28 parts. B: silanization 5%, NCO 27.2%. Index 2.8, pressure 15 MPa, heating plate 55℃, curing for 48 h.

[0028] Example 3: Polyether 35 parts, polyester 40 parts, OP550 25 parts, glass powder (Ts=480℃) 60 parts, metakaolin 25 parts, ATH 35 parts, APP 18 parts, hybrid 8 parts, foam stabilizer 4.5 parts, potassium isooctanoate 3.5 parts, PMDETA / DBTDL 1.6 parts, water 1.0 part, LBA 33 parts. B: Silanization 10%, NCO 24.0%. Index 3.5, pressure 18 MPa, heating plate 65℃, curing 56 h.

[0029] Example 4: Polyether 52 parts, polyester 28 parts, OP550 20 parts, glass powder (Ts=440℃) 40 parts, metakaolin 18 parts, ATH 28 parts, APP 14 parts, hybrid 5 parts, foam stabilizer 3.0 parts, potassium isooctanoate 2.5 parts, PMDETA / DBTDL 1.1 parts, water 0.7 parts, LBA 28 parts. B: Silanization 6%, NCO 26.5%. Index 3.0, pressure 16 MPa, heating plate 58℃, curing 48 h.

[0030] Example 5: Polyether 35 parts, polyester 40 parts, OP550 25 parts, glass powder (Ts=470℃) 50 parts, metakaolin 22 parts, ATH 30 parts, APP 16 parts, hybrid 6 parts, foam stabilizer 3.8 parts, potassium isooctanoate 3.2 parts, PMDETA / DBTDL 1.4 parts, water 0.9 parts, LBA 32 parts. B: silanization 8%, NCO 25.2%. Index 3.4, pressure 17 MPa, heating plate 62℃, curing 52 h.

[0031] Example 6: Polyether 42 parts, polyester 38 parts, OP550 20 parts, glass powder (Ts=450℃) 42 parts, metakaolin 20 parts, ATH 26 parts, APP 13 parts, hybrid 4.5 parts, foam stabilizer 3.0 parts, potassium isooctanoate 2.6 parts, PMDETA / DBTDL 1.0 part, water 0.7 parts, LBA 29 parts. B: silanization 7%, NCO 25.9%. Index 3.0, pressure 15.5 MPa, heating plate 58℃, curing 48 h.

[0032] Comparative Example 1: Component A was identical to that of Example 1. Component B was unmodified PM-200 raw PMDI (NCO 31.0%), without silanization treatment. The index was 3.2, and the remaining process parameters were consistent with Example 1.

[0033] Comparative Example 2: Component A was prepared by completely removing 45 parts of glass powder from Example 1 and replacing it with an equal amount of ATH (the total amount of ATH increased to 70 parts). Component B and the process were the same as in Example 1.

[0034] Comparative Example 3: Component A was prepared by removing 5.5 parts of MOF@MXene hybrid without substitution, based on Example 1. Component B and the process were the same as in Example 1.

[0035] Comparative Example 4: Component A is the same as in Example 1. Component B uses silanized modified PMDI of the same specification but the amount is greatly reduced, so the index is only 1.1. The trimerization catalyst is reduced to 0.3 parts, and the other process parameters remain unchanged.

[0036] PCS Data Explanation: The organic content of each formulation is approximately 78-83%, and the PCS ranges from 17 to 22 MJ / kg. The differences between formulations are solely due to the different organic / inorganic mass ratios: Example 3 has the highest inorganic filler content, resulting in the lowest PCS (19.5); Example 2 has the least inorganic filler content, resulting in the highest PCS (21.6); Comparative Example 4 has the lowest PCS (17.1) due to the significant reduction in component B, leading to a decrease in the organic content; Comparative Example 1 has almost identical PCS to Example 1 (20.9 vs 20.8), and Comparative Example 2, which uses an equal amount of ATH to replace an equal amount of glass powder (both with PCS=0), also has completely identical PCS (20.8). The A2 level requirement of PCS ≤3.0 MJ / kg is unattainable in this system. The differentiation between the examples and comparative examples at the B1 / B2 levels stems from the differences in fire response kinetics in the SBI test, which are directly affected by the high-temperature protection mechanism.

[0037] Effect of Inorganic Filler Gradient: Example 2→1→3 With increasing inorganic filler content, SBI FIGRA increased from 98→52→38 W / s, THR... 600s The pHRR decreased from 6.2 to 3.8 to 2.6 MJ, and from 42.6 to 28.3 to 22.1 kW / m³. 2 The torch shape retention rate increased from 72% to 87% to 91%, demonstrating that the glassy-mineral composite shielding effect enhances with increasing flux and precursor content. The compressive strength increased from 312 to 398 to 435 kPa, indicating that the covalent hybrid network ensures mechanical properties under high filling conditions. The closed-cell rate increased from 95.6% to 94.2% to 92.3%, and the thermal conductivity increased from 0.0205% to 0.0212% to 0.0231%, supporting the rationality of the 60-part upper limit for glass powder.

[0038] Synergistic effect of silanization ratio and index: In Example 2 (5%, 2.8) → 6 (7%, 3.0) → 1 (7.5%, 3.2) → 5 (8%, 3.4), the compressive strength 312 → 375 → 398 → 410 kPa, LOI 33.2 → 37.2 → 38.5 → 40.3%, and SBI FIGRA 98 → 62 → 52 → 44 W / s, all showing a continuous improvement trend. In Example 3, silanization was pushed to 10% and the index to 3.5, resulting in the best fire resistance but a decrease in closed-cell rate to 92.3%, verifying the 10% upper limit of silanization.

[0039] Effect of polyol ratio: Example 4 (polyether 52 / polyester 28) has a closed-cell rate of 95.1% and a thermal conductivity of 0.0208, which are better than those of Example 5 (polyether 35 / polyester 40) (93.0% and 0.0225). However, Example 5 has better compressive strength (410 vs 345 kPa), LOI (40.3 vs 35.6%), and torch retention (89 vs 80%), because the aromatic rings are more likely to aromatize into carbon.

[0040] Comparative Example 1 (unsilanized PMDI) PCS (20.9) was consistent with Example 1 (20.8). SBI FIGRA surged to 185 W / s (far exceeding the B1 ≤120 threshold), degenerating to B2. Compressive strength plummeted to 185 kPa, closed-cell ratio was 78.3%, and thermal conductivity was 0.0285. The densities of Comparative Example 1 and Example 1 were similar (63.1 vs 62.5 kg / m³). 3The significant difference in closed-cell ratio needs clarification: This invention employs a dual-track continuous laminator for restricted foaming molding, with the sheet thickness fixed by the gap between the upper and lower tracks, and the feed rate precisely set by a high-pressure metering pump. In this restricted foaming process, the foam density primarily depends on the ratio of the feed rate per unit area to the mold gap, rather than the integrity of the cells. Although a large number of cells in Comparative Example 1 ruptured and merged, the total material volume and mold gap were completely consistent with Example 1, thus the core density of the sheet remained essentially unchanged. The decrease in closed-cell ratio reflects the deterioration of the cell microstructure (a large number of cell wall ruptures leading to an increase in open-cell ratio), rather than a change in the macroscopic foaming ratio. The precipitous deterioration in performance of Comparative Example 1 needs to be understood from the interfacial mechanics of the high-filling system. In this invention's system, the total amount of inorganic powder is as high as approximately 110 parts / 100 parts polyol (based on Example 1), and the proportion of the inorganic phase volume to the solid phase of the cell wall is close to the percolation threshold of the continuous phase. At such extreme filler ratios, the mechanical behavior of the bubble wall has shifted from "polymer matrix-dominated" to "organic-inorganic interface-dominated"—the integrity and load-bearing capacity of the bubble wall heavily depend on the interfacial bonding quality between the inorganic particles and the polymer matrix. In Comparative Example 1, lacking silanization modification, the organic-inorganic interface lacks the enhanced wetting effect provided by the highly polar urea groups and silane groups of modified PMDI during the foaming stage. It relies solely on the limited van der Waals forces and hydrogen bonds of the unmodified PMDI itself (typical adhesion work approximately 50–80 mJ / m). 2The adhesion strength is insufficient to resist the biaxial tensile stress on the bubble wall during high-speed foaming. Stress concentrates at the inorganic particle / polymer interface, initiating microcracks that rapidly propagate along the weak interface. This leads to numerous bubble wall penetrations and ruptures, and bubble cell merging (the closed-cell ratio drops from 94.2% to 78.3%). The bubble structure degenerates from a load-bearing closed-cell foam to a low-strength open-cell skeleton. It should be noted that the compressive strength of closed-cell foam is contributed by both the in-plane stiffness of the bubble wall and the compressive back pressure of the sealed gas (Gibson-Ashby model). When the closed-cell ratio drops from 94.2% to 78.3%, the extensive penetration of bubbles causes the gas pressure contribution to be almost lost. At the same time, the compression deformation mode of the open-cell skeleton changes from in-plane compression / buckling of the bubble wall to strut bending, and the compressive efficiency drops sharply. Although the inorganic rigid particles provide local hardness, they are dispersed in the broken bubble wall fragments and cannot form a continuous load-bearing path. Therefore, they cannot effectively support compressive loads as they do in dense composite materials. In Example 1, the silanized PMDI first significantly enhances the interfacial wetting and adhesion of the inorganic filler during the foaming stage through the strong polarity of the urea and silane end groups (first stage), ensuring cell integrity under high-filling conditions. Subsequently, during the curing stage, the inorganic particles are anchored to the polymer skeleton through Si-O-Si / Si-O-Al covalent bonds (second stage), further upgrading physical adhesion to covalent bridging (covalent bond energy of approximately 450 kJ / mol, much higher than van der Waals forces of approximately 5 kJ / mol), endowing the material with long-term structural self-sustaining ability under high-temperature firing conditions. This interfacial modification effect is particularly significant in high-filling systems—this is a typical nonlinear response near the percolation threshold: when the filler content is far below the critical value, the gain of interfacial improvement is relatively limited, while when the filler content approaches or exceeds the critical threshold, the interfacial bonding quality becomes the dominant factor determining cell integrity, and even small differences in interfacial strength can trigger drastic changes in macroscopic properties. It should be further noted that the performance degradation of Comparative Example 1 is not only due to the absence of silane covalent bonds, but also related to the difference in reaction kinetics caused by the higher NCO mass fraction of unmodified PMDI (31.0% vs. 25.5% after modification). The higher NCO concentration makes the gel reaction more intense, resulting in greater local exothermic activity and a faster increase in system viscosity during the foaming stage. Under conditions containing a high amount of inorganic filler, this further exacerbates the stress concentration and rupture tendency of the bubble wall before stretching and setting. The severe damage to the pores after the absence of silanization modification caused the bubble to lose its structural self-sustaining ability in the SBI test, and it collapsed and burned through rapidly at high temperatures. This proves that the two-stage interface enhancement effect of silanized modified PMDI (wetting and adhesion during the foaming stage + covalent bridging during the curing stage) is the core prerequisite for mechanical and flame retardant properties.

[0041] Comparative Example 2 (without glass powder and ATH as a substitute) PCS (20.8) was completely consistent with Example 1. SBI FIGRA spiked to 248 W / s, failing B1, with a torch retention rate of only 32%. Without the liquid-phase glassy coating, the system lost its shielding layer formation ability above 450°C, and the organic matrix was completely burned through under sustained high temperatures, proving that low-melting-point glass powder is an irreplaceable core component for high-temperature physical shielding.

[0042] Comparative Example 3 (with MOF@MXene removed) PCS (21.2) is similar to Example 1. SBI FIGRA 108 W / s is still within the B1 threshold, but TSP 600s Soaring to 165 m 2 Approaching the upper limit of s1, only B1-s2,d0 was obtained. CONE measurements showed a 3.3-fold increase in TSP and a 4.9-fold increase in pCOP. The absence of bimetallic catalysis resulted in a loose primary carbon layer with low carbonization, allowing toxic fumes to escape unimpeded, proving that nanocatalytic hybrids are a necessary means to achieve the goal of low smoke and low toxicity.

[0043] Comparative Example 4 (index 1.1) had the lowest PCS (17.1 MJ / kg) (due to a significant reduction in component B, resulting in a lower organic content), but the highest SBI (strain-dependent friction) (330 W / s), failing completely to pass B1 and exhibiting flammable dripping. Its compressive strength was only 118 kPa, closed-cell rate was 62.5%, and thermal conductivity was 0.0322. At this extremely low index, the amount of organic resin in component B was only about one-third of that in Example 1, preventing the inorganic powder from being fully wetted and forming a film, leading to large-area open pores. The absence of the PIR six-membered ring caused the framework to collapse extensively at 250°C, far earlier than the glass transition activation temperature of 420-480°C, meaning the overall defense system collapsed before activation. The phenomenon of the lowest PCS but the worst SBI clearly demonstrates that the actual fire behavior is determined not by PCS but by the high-temperature structural self-sustaining ability.

[0044] In summary, the four core technical features of this invention are deeply coupled and synergistic, enabling all embodiments to achieve the optimal level of B1-s1,d0 with a significant margin (FIGRA 38~98 W / s, THR). 600s 2.6~6.2 MJ), while maintaining a closed-cell rate of 92.3~95.6%, thermal conductivity of 0.0205~0.0231 W / (m·K), compressive strength of 312~435 kPa, CONE without any flaming droplets throughout the process, TSP 2.5~5.1 m 2 / m 2 With a pCOP of 0.0012~0.0031 g / s, its overall flame retardant performance far exceeds that of existing technologies.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flame-retardant polyurethane foam material, characterized in that, It is prepared by foaming and curing of raw materials including component A and component B; said component A includes: A system of polyol matrix, reactive flame retardant, phase change inorganic flux, inorganic ceramic precursor, nano-smoke suppressing catalytic hybrid and foaming agent; Component B comprises a silanized modified polyisocyanate; The foamed material contains a polyurethane skeleton formed by the reaction of the polyol matrix and the polyisocyanate. The trialkoxysilane end groups contained in the silanized polyisocyanate undergo direct alcoholysis condensation reaction with the phase change inorganic flux and the hydroxyl groups on the surface of the inorganic ceramic precursor, and / or undergo dehydration condensation reaction after hydrolysis, to form an organic-inorganic hybrid crosslinking network that covalently bridges inorganic particles to the polyurethane skeleton.

2. The flame-retardant polyurethane foam material according to claim 1, characterized in that, The polyol matrix is ​​a blend of high-functionality polyether polyol and rigid aromatic polyester polyol; the reactive flame retardant is selected from at least one of reactive phosphorus-containing diol and halogen-containing diol, and the reactive flame retardant is embedded in the main chain of the polyurethane skeleton by covalent bonding.

3. The flame-retardant polyurethane foam material according to claim 1, characterized in that, The phase change inorganic flux is SnO-P2O5-ZnO series low melting point glass powder, and the softening point of the low melting point glass powder is between 420℃ and 480℃; the inorganic ceramicization precursor includes metakaolin and aluminum hydroxide whose surfaces have been treated with silane coupling agent.

4. The flame-retardant polyurethane foam material according to claim 1, characterized in that, The nano-smoke-suppressing catalytic hybrid is a hybrid nanosheet formed by combining an amino-functionalized cobalt-based metal-organic framework with two-dimensional titanium carbide MXene.

5. The flame-retardant polyurethane foam material according to claim 1, characterized in that, The silanized polyisocyanate is a prepolymer formed by partially end-capping polyphenyl polymethylene polyisocyanate with aminopropyltriethoxysilane; wherein the silanization modification ratio is 5% to 10% of the total amount of isocyanate groups in the original polyisocyanate system.

6. The flame-retardant polyurethane foam material according to claim 1, characterized in that, The foaming agent system comprises: Microencapsulated ammonium polyphosphate; Non-hydrolyzable polysiloxane-polyether copolymer foam stabilizer; A curing catalyst combination comprising trimerizing catalyst, foaming catalyst, and gelling catalyst; And combinations of foaming agents that include physical and chemical foaming agents.

7. The flame-retardant polyurethane foam material according to any one of claims 1 to 6, characterized in that, Based on a total mass of 100 parts by mass of the polyol matrix in component A and the reactive flame retardant, the content of each component in component A satisfies the following mass ratio: In the polyol matrix, the high-functionality polyether polyol is 30 to 55 parts and the rigid aromatic polyester polyol is 25 to 40 parts. The reactive flame retardant is 15 to 25 parts; The phase change inorganic flux is 30 to 60 parts; In the inorganic ceramicized precursor, the metakaolin surface treated with silane coupling agent is 15 to 25 parts, and the aluminum hydroxide is 20 to 35 parts. The nano-smoke-suppressing catalytic hybrid is present in 3 to 8 parts; In the foaming agent system, microencapsulated ammonium polyphosphate is 10 to 18 parts, non-hydrolyzed polysiloxane-polyether copolymer foam leveler is 2 to 4.5 parts, trimerizing catalyst is 2 to 3.5 parts, foaming catalyst and gel catalyst combined is 0.8 to 1.8 parts, chemical foaming agent water is 0.5 to 1.2 parts, and physical foaming agent is 25 to 35 parts.

8. The flame-retardant polyurethane foam material according to claim 7, characterized in that, When component A and component B are mixed and foamed, the isocyanate index is controlled between 2.8 and 3.5, so that the polyurethane skeleton contains a polyisocyanurate trimer six-membered ring network structure formed by the excessive self-polymerization of isocyanate groups.

9. The flame-retardant polyurethane foam material according to claim 7, characterized in that, When the material is heated to above 450°C during combustion, the phase-change inorganic flux transforms into a liquid glass melt, dissolves and encapsulates the inorganic ceramic precursor and its pyrolysis products, and generates an inorganic glassy-mineral composite shielding layer in situ on the surface of the foamed material.

10. The flame-retardant polyurethane foam material according to any one of claims 1 to 9, characterized in that, The foamed material is a plate-shaped product obtained by standing at room temperature for curing. The organic-inorganic hybrid crosslinking network in the plate-shaped product has a crosslinking density gradient distribution from the surface to the inside, wherein the silicon-oxygen crosslinking density in the near-surface region is higher than that in the central region. The closed-cell rate of the plate-shaped product is 92% to 96%, the thermal conductivity is not more than 0.023 W / (m·K), and the 10% deformation compressive strength is not less than 300 kPa.

11. A preparation process for a flame-retardant polyurethane foam material as described in any one of claims 1 to 10, characterized in that, Includes the following steps: (a) The polyol matrix, reactive flame retardant, foam stabilizer and nano smoke suppressant catalytic hybrid in component A are added into a planetary mixing reactor and pre-stirred and mixed evenly at 35°C to 40°C. (b) The dried phase change inorganic flux, inorganic ceramic precursor and microencapsulated ammonium polyphosphate were added in batches, and each batch was dispersed by high-speed shearing at 2500 to 3200 rpm. (c) The mixture obtained in step (b) was degassed by low-speed stirring under a vacuum of -0.09 to -0.095 MPa; (d) After cooling the system to 15±2℃, add the curing catalyst combination, chemical foaming agent and physical foaming agent under sealed conditions, and mix them under nitrogen positive pressure to obtain component A. Store the component A under sealed pressure so that the back pressure is maintained at a level not lower than the saturated vapor pressure of the physical foaming agent throughout the process. (e) Under nitrogen protection and with strong mechanical stirring, aminopropyltriethoxysilane was slowly added dropwise to polyphenyl polymethylene polyisocyanate. The dropping rate was controlled so that each added silane monomer was immediately absorbed by a large amount of excess isocyanate groups to avoid excessive local amine concentration. The reaction was carried out at 60±2℃ for 1.5 to 2.5 hours to obtain modified polyisocyanate with silane end groups as component B. (f) Component A and component B are pressurized to 15 MPa to 18 MPa by a high-pressure metering pump; wherein, component A is heated to 35°C to 40°C in the high-pressure pipeline on the outlet side of the high-pressure metering pump via a heat exchanger, and the system back pressure is maintained at 15 MPa to 18 MPa throughout the heating process, and the physical foaming agent remains in a liquid state under this back pressure condition; after heating, component A and component B are mixed by collision in a high-pressure mixing head, and poured into a double-track continuous laminator for limited foaming and compaction molding under the condition of upper and lower heating plate temperatures of 55°C to 65°C; (g) The molded sheet shall be left to stand and mature for no less than 48 hours at room temperature and relative humidity of 40% to 60%.

Images