Reaction type polyurethane hot melt adhesive, its preparation method and application in preparing fire ventilation pipe

Abstract

The application provides a reactive polyurethane hot melt adhesive, a preparation method thereof and application in preparation of fire ventilation pipes, and relates to the technical field of adhesives. The reactive polyurethane hot melt adhesive comprises polyester polyol, polyether polyol, halogen-free flame-retardant polyol, flame retardant, isocyanate, stabilizer, catalyst and coupling agent, wherein the isocyanate is compounded by aromatic diisocyanate and aliphatic diisocyanate, and the flame retardant is halogen-free phosphorus-nitrogen flame retardant. The isocyanate system is compounded in the application, so that the adhesive layer has high initial adhesion to galvanized steel plates, fast curing capacity, good wetting property to glass fiber composite pipe plate and aging resistance, and effectively relieves internal stress caused by the difference in thermal expansion of double substrates. In addition, the halogen-free phosphorus-nitrogen flame retardant in the application can realize flame-retardant performance, avoid the generation of toxic and corrosive gases, and fully meet the requirements of environmental protection, safety and long-term reliability of fire ventilation pipes.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a reactive polyurethane hot melt adhesive, its preparation method, and its application in the preparation of fire ventilation ducts. Background Technology

[0002] In the fresh air and fire smoke exhaust systems of large buildings such as shopping malls, office buildings, and factories, ventilation ducts are generally made of galvanized steel sheets and fiberglass composite duct panels. Galvanized steel sheets have the characteristics of high strength, good rigidity, and non-flammability, making them an essential structural layer for fire smoke exhaust ducts. Fiberglass composite duct panels, as the core layer, have advantages such as light weight, heat insulation, noise reduction, and non-flammability, making them the mainstream supporting material in this scenario.

[0003] The aforementioned fire ventilation ducts operate under complex conditions for extended periods, including ambient temperature, high temperature, high humidity, alternating hot and cold environments, and some areas with oil fumes and dust. The system is required to maintain stability and reliability during long-term operation. Therefore, higher technical requirements are placed on the bonding materials between the galvanized steel sheet and the fiberglass composite duct panel.

[0004] Currently, the bonding materials for steel sheet and fiberglass board in this scenario are mainly solvent-based adhesives and EVA hot melt adhesives, but both have obvious technical defects: (1) Solvent-based adhesives have problems such as high VOC emissions, slow curing speed, and low construction efficiency; (2) EVA hot melt adhesives have shortcomings such as poor fire resistance and flame retardancy, easy creep or brittleness under wide temperature range conditions, and easy delamination after long-term use, which makes it difficult to meet the long-term reliability requirements of fire ventilation ducts.

[0005] To address the aforementioned issues, related technologies have proposed several reactive polyurethane hot melt adhesive solutions involving flame retardancy and heat resistance. For example, Chinese patent applications CN117363303A and CN117070180A disclose PUR hot melt adhesive technologies with certain flame retardant and heat resistance properties. However, these existing technologies do not specifically design formulations for the surface characteristics of the galvanized steel sheet and fiberglass composite duct panels, nor do they optimize for compatibility with the wide-temperature-range service requirements, vibration-resistant operation, and automated construction needs of fire ventilation ducts in shopping malls and office buildings. Therefore, they still cannot fundamentally solve the technical problems of adhesion failure, insufficient flame retardancy, and poor durability in this application scenario.

[0006] Therefore, the research and development of a reactive polyurethane hot melt adhesive that can adapt to the bonding of galvanized steel sheet and fiberglass composite duct board with two heterogeneous substrates, and has excellent resistance to damp heat, high and low temperature cycling, and vibration, while meeting the requirements of flame retardancy and environmentally friendly construction, remains an urgent technical problem to be solved in this field.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The first objective of this invention is to provide a reactive polyurethane hot melt adhesive, which, through the synergistic effect of a compound of aromatic and aliphatic diisocyanates and a halogen-free phosphorus and nitrogen flame retardant system, can form a stable adhesive layer between galvanized steel sheet and fiberglass composite duct sheet that has high bonding reliability, environmental aging resistance and safety.

[0009] The second objective of this invention is to provide a method for preparing a reactive polyurethane hot melt adhesive.

[0010] A third objective of this invention is to provide an application of a reactive polyurethane hot melt adhesive.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: According to one aspect of the present invention, a reactive polyurethane hot melt adhesive comprises the following raw materials: polyester polyol, polyether polyol, halogen-free flame-retardant polyol, flame retardant, isocyanate, stabilizer, catalyst, and coupling agent, wherein: The isocyanate is obtained by compounding aromatic diisocyanate and aliphatic diisocyanate; The flame retardant is a halogen-free phosphorus-nitrogen flame retardant.

[0012] The reactive polyurethane hot melt adhesive provided by this invention mainly consists of polyester polyol, polyether polyol, halogen-free flame-retardant polyol, flame retardant, isocyanate, stabilizer, catalyst, and coupling agent. This reactive polyurethane hot melt adhesive utilizes an isocyanate system composed of aromatic and aliphatic diisocyanates, fully leveraging the synergistic advantages of both types of isocyanates. Aromatic diisocyanates impart high initial adhesion strength and rapid curing characteristics to galvanized steel sheets, while aliphatic diisocyanates significantly improve the adhesive layer's weather resistance, yellowing resistance, and resistance to damp heat aging, solving the problem that a single isocyanate system cannot simultaneously achieve both metal adhesion strength and environmental durability. Furthermore, this invention selects a halogen-free phosphorus-nitrogen flame retardant, avoiding the risk of toxic fumes and corrosive gases produced during combustion of traditional halogenated flame retardants. While meeting mandatory environmental and safety standards for fire ventilation ducts, the synergistic effect of other components in the formulation ensures the structural stability and flame-retardant durability of the adhesive layer under long-term complex working conditions.

[0013] In a preferred embodiment of the present invention, the reactive polyurethane hot melt adhesive comprises, by weight percentage: Polyester polyol 10%~30%, polyether polyol 20%~50%, halogen-free flame retardant polyol 5%~10%, flame retardant 10%~15%, stabilizer 0.05%~0.2%, catalyst 0.01%~0.5%, coupling agent 0.1%~1%, balance is isocyanate; The amount of isocyanate added results in a certain amount of free isocyanate groups in the polyurethane prepolymer obtained from the reaction. The NCO content accounts for 2-5 wt% of the prepolymer mass.

[0014] In a preferred embodiment, the present invention controls the polyester polyol, polyether polyol, halogen-free flame-retardant polyol, flame retardant, stabilizer, catalyst, and coupling agent within the stated mass percentage range, and allows free [elements] in the prepolymer. The NCO content is maintained at 2-5 wt%, which balances the melt flowability, initial tack establishment speed, moisture curing reactivity and long-term storage stability of the colloid, while ensuring the synergistic effect of the compatibility and adhesion performance of the two heterogeneous substrates of galvanized steel sheet and fiberglass composite duct board and the flame retardant function.

[0015] As an optional embodiment, the mass percentage of the polyester polyol is 10% to 30%, for example, it can be 10%, 15%, 20%, 25%, 30%, or any value between 10% and 30%; the mass percentage of the polyether polyol is 20% to 50%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value between 20% and 50%; the mass percentage of the halogen-free flame-retardant polyol is 5% to 10%, for example, it can be 5%, 7%, 10%, or any value between 5% and 10%; the mass percentage of the flame retardant is 10% to 15%, for example, it can be 10%, 12%, 15%, or any value between 10% and 15%. The mass percentage of the stabilizer is 0.05% to 0.2%, for example, it can be 0.05%, 0.10%, 0.15%, 0.20%, or any value between 0.05% and 0.2%; the mass percentage of the catalyst is 0.01% to 0.5%, for example, it can be 0.01%, 0.10%, 0.25%, 0.40%, 0.50%, or any value between 0.01% and 0.5%; the mass percentage of the coupling agent is 0.1% to 1%, for example, it can be 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, or any value between 0.1% and 1%; the balance is isocyanate.

[0016] As an optional implementation, the amount of isocyanate added is such that the free isocyanate in the polyurethane prepolymer obtained from the reaction is reduced. The content of NCO groups is 2wt% to 5wt%, for example, it can be 2wt%, 3wt%, 4wt%, 5wt%, or any value between 2wt% and 5wt%.

[0017] In a preferred embodiment of the present invention, the polyester polyol is selected from aliphatic or aromatic polyester diols, and the weight-average molecular weight is 400-5000.

[0018] As a preferred embodiment, the present invention selects aliphatic or aromatic polyester diols with a weight-average molecular weight of 400-5000, which ensures that the polyurethane prepolymer has a certain segment rigidity and reactivity, while having good melt flowability and penetration ability into the porous interface of the fiberglass composite duct plate, and helps to adjust the adhesive layer modulus to adapt to the internal stress caused by the difference in thermal expansion coefficients between the galvanized steel plate and the fiberglass plate.

[0019] Preferably, the polyester polyol is formed by polycondensation of one or more of adipic acid, sebacic acid, terephthalic acid, and isophthalic acid with one or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentyl glycol, 3-methyl-1,5-pentyl glycol, and 1,8-octanediol. In a preferred embodiment of the present invention, the weight-average molecular weight of the polyether polyol is 1000-3500.

[0020] In a preferred embodiment, the present invention selects polyether polyols with a weight-average molecular weight of 1000-3500, which helps to improve the wetting and spreading performance of the colloid on the surface of the fiberglass composite duct plate, and endows the prepolymer with suitable flexibility and cohesive strength, thereby improving the deformation resistance of the adhesive layer under complex working conditions and the interfacial bonding stability with the porous substrate.

[0021] Preferably, the polyether polyol is selected from one or more of polyethylene oxide polyol, polypropylene oxide polyol, polytetrahydrofuran ether diol, glycerol polyether polyol, and trimethylolpropane polyether polyol.

[0022] In a preferred embodiment of the present invention, the halogen-free flame-retardant polyol is a phosphorus-based halogen-free flame-retardant polyol; In a preferred embodiment, the present invention uses phosphorus-based halogen-free flame-retardant polyols as reactants, allowing them to participate in chemical reactions during the synthesis of polyurethane prepolymers. This introduces flame-retardant elements into the polymer backbone in the form of covalent bonds, thereby achieving effective flame-retardant function while maintaining the integrity of the cross-linked structure and interfacial adhesion performance of the adhesive layer.

[0023] Preferably, the halogen-free flame-retardant polyol is selected from one or more of Exolit OP550, Exolit OP560, and Baiyuan BY3009.

[0024] It should be noted that this invention introduces phosphorus-based halogen-free flame-retardant polyols and uses them as reactive monomers in the synthesis of polyurethane prepolymers, thereby covalently binding flame-retardant elements into the polymer molecular chain. In combination with halogen-free phosphorus and nitrogen flame retardants, it can ensure flame-retardant performance while maintaining reliable adhesion of the adhesive layer to galvanized steel sheets and fiberglass composite duct panels, and avoid generating toxic and corrosive gases such as hydrogen halides.

[0025] In a preferred embodiment of the present invention, the isocyanate is a combination of diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI); Preferably, the flame retardant is a compound of high polyphosphate ammonium and ultrafine melamine cyanurate in a mass ratio of (2~3):1.

[0026] In a preferred embodiment, the present invention employs a combination of diphenylmethane diisocyanate and hexamethylene diisocyanate, which balances the rapid anchoring capability of galvanized steel sheets with the flexible wetting performance of fiberglass composite duct panels. Preferably, the flame retardant system, which is a compound of high-polymer ammonium polyphosphate and ultrafine melamine cyanurate in a ratio of (2-3):1, can synergistically exert gas phase dilution, condensed phase char formation, and heat absorption and cooling effects during combustion, thereby improving flame retardant efficiency and helping to form a dense and stable heat-insulating char layer.

[0027] In a preferred embodiment of the present invention, the stabilizer is selected from antioxidant composite stabilizers; Preferably, the stabilizer is one or a combination of two of antioxidant 1010 and antioxidant 168; In a preferred embodiment of the present invention, the catalyst is an environmentally friendly organic bismuth composite catalyst; In a preferred embodiment of the present invention, the coupling agent is a silane coupling agent, which is selected from one or more of KH540, KH550, KH560, and KH570.

[0028] According to one aspect of the present invention, a method for preparing the above-mentioned reactive polyurethane hot melt adhesive, the method comprising: (A) Preparation of prepolymer: Polyester polyol, polyether polyol, halogen-free flame retardant polyol and stabilizer are mixed and dehydrated, and then isocyanate is added to react to obtain polyurethane prepolymer; In this process, the halogen-free flame-retardant polyol participates in the polymerization reaction as a reactive monomer in the prepolymer preparation step. The amount of isocyanate added results in a certain amount of free isocyanate groups in the polyurethane prepolymer obtained from the reaction. The NCO content accounts for 2-5 wt% of the prepolymer mass.

[0029] (B) Modification: A halogen-free phosphorus and nitrogen flame retardant and a coupling agent are added to the polyurethane prepolymer to carry out a grafting reaction; (C) Post-treatment: Add catalyst and mix evenly to obtain the reactive polyurethane hot melt adhesive.

[0030] The present invention provides a method for preparing a reactive polyurethane hot melt adhesive, wherein the preparation method controls the reaction process in stages: in the prepolymer preparation stage, a halogen-free flame-retardant polyol is used as a reactive monomer to participate in polymerization, achieving chemical bonding of flame-retardant groups on the polyurethane backbone; in the modification stage, a halogen-free phosphorus-nitrogen flame retardant is introduced and a coupling agent is used for grafting reaction to promote its directional distribution at the prepolymer end groups and interfaces; in the post-treatment stage, a catalyst is added to complete the homogenization of the system. The above-mentioned preparation method of this application helps to coordinate the relationship between reactivity, storage stability and final curing performance, and ensures the structural integrity and functional synergy of the adhesive layer at the interface of two heterogeneous substrates.

[0031] In a preferred embodiment of the present invention, in the preparation of the (A) prepolymer, the temperature of the mixing and dehydration is 100°C to 130°C, and the dehydration time is 60 min to 120 min.

[0032] As an optional implementation, the temperature for mixing and dehydration is 100℃~130℃, for example, it can be 100℃, 110℃, 120℃, 130℃, or any temperature value between 100℃ and 130℃; the dehydration time is 60min~120min, for example, it can be 60min, 80min, 100min, 120min, or any time value between 60min and 120min.

[0033] In a preferred embodiment of the present invention, the mixing and dehydration is carried out under a vacuum of -0.08MPa to 0.1MPa and a stirring speed of 150 r / min to 300 r / min.

[0034] As an optional implementation, the mixing and dehydration is carried out under a vacuum of -0.08MPa to -0.1MPa, for example, -0.08MPa, -0.09MPa, -0.1MPa, or any vacuum value between -0.08MPa and -0.1MPa; the stirring speed is 150r / min to 300r / min, for example, 150r / min, 200r / min, 250r / min, 300r / min, or any rotational speed value between 150r / min and 300r / min.

[0035] In a preferred embodiment of the present invention, in the prepolymer preparation step, the temperature for adding isocyanate and reacting is 70°C to 100°C, and the reaction time is 60 min to 90 min.

[0036] As an optional implementation, in the prepolymer preparation step, the temperature at which isocyanate is added for reaction is 70℃~100℃, for example, 70℃, 85℃, 100℃, or any temperature value between 70℃ and 100℃; the reaction time is 60 min~90 min, for example, 60 min, 75 min, 90 min, or any time value between 60 min and 90 min.

[0037] In a preferred embodiment of the present invention, in the modification (B), the grafting reaction temperature is 70°C to 80°C and the reaction time is 0.5h to 1.5h.

[0038] As an optional implementation, the grafting reaction temperature is 70℃~80℃, for example, it can be 70℃, 75℃, 80℃, or any temperature value between 70℃ and 80℃; the grafting reaction time is 0.5h~1.5h, for example, it can be 0.5h, 1.0h, 1.5h, or any time value between 0.5h and 1.5h.

[0039] In a preferred embodiment of the present invention, the (B) modification is carried out under stirring conditions, wherein the stirring speed is 200 r / min to 400 r / min.

[0040] As an optional implementation, the modification (B) is carried out under stirring conditions, and the stirring speed is 200 r / min to 400 r / min, for example, it can be 200 r / min, 300 r / min, 400 r / min, or any rotation speed value between 200 r / min and 400 r / min.

[0041] In a preferred embodiment of the present invention, in the (C) post-treatment, the catalyst is an environmentally friendly organic bismuth composite catalyst.

[0042] In a preferred embodiment of the present invention, the mixing temperature in the post-processing step (C) is 70°C to 80°C, and the mixing time is 20 min to 40 min.

[0043] As an optional implementation, the mixing temperature in the post-processing step (C) is 70°C to 80°C, for example, it can be 70°C, 75°C, or 80°C, or any temperature value between 70°C and 80°C; the mixing time is 20 min to 40 min, for example, it can be 20 min, 30 min, or 40 min, or any time value between 20 min and 40 min.

[0044] According to one aspect of the present invention, a reactive polyurethane hot melt adhesive is provided, which can be widely used in the preparation process of fire ventilation ducts.

[0045] In a preferred embodiment of the present invention, the fire ventilation duct includes a metal layer, a fiberglass composite duct plate layer, and an adhesive layer; wherein, by using the reactive polyurethane hot melt adhesive of the present invention as the adhesive layer, the fire ventilation duct achieves a firm bond between the galvanized steel plate and the fiberglass composite duct plate, while meeting the requirements of the fire protection system for flame retardancy, low smoke toxicity, and long-term reliability.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows: The reactive polyurethane hot melt adhesive provided by this invention mainly consists of polyester polyol, polyether polyol, halogen-free flame-retardant polyol, flame retardant, isocyanate, stabilizer, catalyst, and coupling agent. This reactive polyurethane hot melt adhesive utilizes an isocyanate system composed of aromatic and aliphatic diisocyanates, fully leveraging the synergistic advantages of both types of isocyanates. Aromatic diisocyanates impart high initial adhesion strength and rapid curing characteristics to galvanized steel sheets, while aliphatic diisocyanates significantly improve the adhesive layer's weather resistance, yellowing resistance, and resistance to damp heat aging, solving the problem that a single isocyanate system cannot simultaneously achieve both metal adhesion strength and environmental durability. Furthermore, this invention selects a halogen-free phosphorus-nitrogen flame retardant, avoiding the risk of toxic fumes and corrosive gases produced during combustion of traditional halogenated flame retardants. While meeting mandatory environmental and safety standards for fire ventilation ducts, the synergistic effect of other components in the formulation ensures the structural stability and flame-retardant durability of the adhesive layer under long-term complex working conditions.

[0047] The present invention provides a method for preparing a reactive polyurethane hot melt adhesive, wherein the preparation method controls the reaction process in stages: in the prepolymer preparation stage, a halogen-free flame-retardant polyol is used as a reactive monomer to participate in polymerization, achieving chemical bonding of flame-retardant groups on the polyurethane backbone; in the modification stage, a halogen-free phosphorus-nitrogen flame retardant is introduced and a coupling agent is used for grafting reaction to promote its directional distribution at the prepolymer end groups and interfaces; in the post-treatment stage, a catalyst is added to complete the homogenization of the system. The above-mentioned preparation method of this application helps to coordinate the relationship between reactivity, storage stability and final curing performance, and ensures the structural integrity and functional synergy of the adhesive layer at the interface of two heterogeneous substrates.

[0048] This invention provides a reactive polyurethane hot melt adhesive, which can be widely used in the preparation process of fire ventilation ducts. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] The technical solution of the present invention will be further described below with reference to the embodiments.

[0051] Examples 1-3 A reactive polyurethane hot melt adhesive, comprising the following raw materials by weight percentage:

[0052] The reactive polyurethane hot melt adhesive of the present invention is prepared by the following method: (1) Add polyester polyol, polyether polyol, halogen-free flame retardant polyol and stabilizer into a sealed reaction vessel, turn on the heating jacket to 120°C, turn on the stirring speed to 200r / min, stir for 20min, and after all raw materials are completely mixed, slowly turn on the vacuum equipment, and after the vacuum of the reaction vessel reaches -0.09MPa±0.01, maintain it for 90 minutes. (2) Cool the material down to 80°C, break the vacuum, and while stirring (200~300r / min), quickly add the isocyanate into the reaction vessel, seal the vessel, evacuate to -0.09MPa±0.01, keep at 80°C for 60 minutes, and take a sample to test the -NCO content; In this process, the halogen-free flame-retardant polyol participates in the polymerization reaction of step (2) as a reactive monomer, thereby grafting the flame-retardant component into the polyurethane prepolymer molecular chain.

[0053] (3) Add phosphorus and nitrogen halogen-free synergistic flame retardant and silane coupling agent to the prepolymer in sequence, stir at 200~300r / min, and react at a constant temperature of 75℃ for 1h to allow the flame retardant and coupling agent to be initially grafted onto the prepolymer. (4) Slowly add the catalyst, mix for 30 minutes, discharge the material, and seal the package.

[0054] Example 4 Except for the fact that the mass ratio of "high polyphosphate ammonium (APP): ultrafine melamine cyanurate (MCA)" in the raw materials is 2:1, the rest of this embodiment is the same as in Example 1.

[0055] Example 5 Except for the fact that the mass ratio of "high polyphosphate ammonium (APP): ultrafine melamine cyanurate (MCA)" in the raw materials is 3:1, the rest of this embodiment is the same as in Example 1.

[0056] Example 6 The difference between this embodiment and Embodiment 1 is that the weight-average molecular weight of the polyester polyol is 300, while the rest is the same as in Embodiment 1.

[0057] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: All the isocyanates used were diphenylmethane diisocyanate (MDI), without the addition of hexamethylene diisocyanate (HDI) for compounding, and the rest were the same as in Example 1.

[0058] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: No halogen-free flame-retardant polyol was added, and its mass fraction was replaced with ordinary polyether polyol (Bluestar Dongda DL-2000D). At the same time, the amount of flame retardant (the composition of the flame retardant is the same as in Example 1) was increased to maintain the total flame-retardant element content. The rest was the same as in Example 1.

[0059] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: The flame retardant used is tris(2-chloropropyl) phosphate TCPP (halogenated flame retardant), and the halogen-free phosphorus-nitrogen compound system of high polyphosphate ammonium and ultrafine melamine cyanurate is not used. The rest is the same as in Example 1.

[0060] Experimental Example 1 The reactive polyurethane hot melt adhesives prepared in Examples 1-6 and Comparative Examples 1-3 were heated to 120°C to melt and uniformly applied to the bonding surface of the galvanized steel sheet and the fiberglass composite duct panel. The adhesive thickness was controlled at 0.5 mm. A pressure of 0.5 MPa was applied and held for 30 seconds. After curing at room temperature for 48 hours, the following performance tests were performed. The specific test methods are as follows: (1) Peel strength test: Refer to GB / T 2790-2021.

[0061] (2) Flame retardancy rating test: Refer to GB 8624-2017, GB / T 8626-2017 and GB / T 8627-2019.

[0062] (3) Moist heat aging test: Refer to GB / T 27934-2011.

[0063] (4) High and low temperature cycling test: Refer to GB / T 38261-2019.

[0064] The specific experimental results are as follows:

[0065] As can be seen from the above, the reactive polyurethane hot melt adhesives prepared in Examples 1-5 all have a peel strength greater than 35N / 25mm, a flame retardancy rating of B1, and pass a 500-hour damp heat resistance test at 85℃ / 85%RH. After 50 cycles of high and low temperature cycling from 20℃ to 80℃, no delamination, peeling, or cracking occurred, fully meeting the stringent requirements for the use of composite structures in fire ventilation ducts. In Example 6, due to the polyester polyol's weight-average molecular weight of 300, the molecular chain segments were too short, resulting in excessively high rigidity and insufficient elasticity after cross-linking of the adhesive layer. Localized microcracks appeared after thermal cycling, and the peel strength decreased significantly.

[0066] Comparative Example 1, lacking hexamethylene diisocyanate (HDI), exhibited deterioration in the adhesive layer's resistance to damp heat and yellowing. After damp heat aging, the interface underwent hydrolysis, resulting in a significant decline in strength. Comparative Example 2, lacking reactive flame-retardant polyols for chemical bonding and relying solely on additive APP / MCA, suffered from easy migration and precipitation of flame-retardant components. This led to a decrease in flame-retardant rating after prolonged heating, insufficient interfacial wetting, and low peel strength of the fiberglass board. Comparative Example 3, employing halogenated flame retardants, released corrosive hydrogen halide fumes during combustion, resulting in excessive smoke density and failing to meet the mandatory low-smoke and non-toxic fire safety requirements for public places like shopping malls.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reactive polyurethane hot melt adhesive, characterized in that, The reactive polyurethane hot melt adhesive comprises the following raw materials: polyester polyol, polyether polyol, halogen-free flame-retardant polyol, flame retardant, isocyanate, stabilizer, catalyst, and coupling agent, wherein: The isocyanate is obtained by compounding aromatic diisocyanate and aliphatic diisocyanate; The flame retardant is a halogen-free phosphorus-nitrogen flame retardant.

2. The reactive polyurethane hot melt adhesive according to claim 1, characterized in that, The reactive polyurethane hot melt adhesive comprises, by weight percentage: Polyester polyol 10%~30%, polyether polyol 20%~50%, halogen-free flame retardant polyol 5%~10%, flame retardant 10%~15%, stabilizer 0.05%~0.2%, catalyst 0.01%~0.5%, coupling agent 0.1%~1%, balance is isocyanate; The amount of isocyanate added results in a certain amount of free isocyanate groups in the polyurethane prepolymer obtained from the reaction. The NCO content accounts for 2-5 wt% of the prepolymer mass.

3. The reactive polyurethane hot melt adhesive according to claim 1, characterized in that, The polyester polyol is selected from aliphatic or aromatic polyester diols, with a weight-average molecular weight of 400-5000. Preferably, the polyester polyol is formed by polycondensation of one or more of adipic acid, sebacic acid, terephthalic acid, and isophthalic acid with one or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentyl glycol, 3-methyl-1,5-pentyl glycol, and 1,8-octanediol. Preferably, the polyether polyol is selected from one or more of polyethylene oxide polyol, polypropylene oxide polyol, polytetrahydrofuran ether diol, glycerol polyether polyol, and trimethylolpropane polyether polyol; Preferably, the weight-average molecular weight of the polyether polyol is 1000~3500; Preferably, the halogen-free flame-retardant polyol is a phosphorus-based halogen-free flame-retardant polyol; Preferably, the halogen-free flame-retardant polyol is selected from one or more of Exolit OP550, Exolit OP560, and Baiyuan BY3009.

4. The reactive polyurethane hot melt adhesive according to claim 1, characterized in that, The isocyanate is a combination of diphenylmethane diisocyanate and hexamethylene diisocyanate; Preferably, the flame retardant is a mixture of ammonium polyphosphate and melamine cyanurate in a mass ratio of (2~3):

1.

5. The reactive polyurethane hot melt adhesive according to claim 1, characterized in that, The stabilizer is an antioxidant composite stabilizer; Preferably, the stabilizer is one or a combination of two of antioxidant 1010 and antioxidant 168; Preferably, the catalyst is an environmentally friendly organic bismuth composite catalyst; Preferably, the coupling agent is a silane coupling agent, and the silane coupling agent is selected from one or more of KH540, KH550, KH560, and KH570.

6. A method for preparing a reactive polyurethane hot melt adhesive according to any one of claims 1 to 5, characterized in that, The preparation method includes: (A) Preparation of prepolymer: Polyester polyol, polyether polyol, halogen-free flame retardant polyol and stabilizer are mixed and dehydrated, and then isocyanate is added to react to obtain polyurethane prepolymer; In this process, the halogen-free flame-retardant polyol participates in the polymerization reaction as a reactive monomer in the prepolymer preparation step. The amount of isocyanate added results in a certain amount of free isocyanate groups in the polyurethane prepolymer obtained from the reaction. The NCO content accounts for 2~5 wt% of the prepolymer mass; (B) Modification: A halogen-free phosphorus and nitrogen flame retardant and a coupling agent are added to the polyurethane prepolymer to carry out a grafting reaction; (C) Post-treatment: Add catalyst and mix evenly to obtain the reactive polyurethane hot melt adhesive.

7. The method for preparing the reactive polyurethane hot melt adhesive according to claim 6, characterized in that, In the preparation of the prepolymer (A), the temperature for mixing and dehydration is 100℃~130℃, and the dehydration time is 60min~120min; Preferably, the mixing and dehydration is carried out under a vacuum of -0.08MPa to 0.1MPa, and the stirring speed is 150 r / min to 300 r / min. Preferably, in the prepolymer preparation step, the temperature for adding isocyanate and reacting is 70℃~100℃, and the reaction time is 60 min~90 min.

8. The method for preparing the reactive polyurethane hot melt adhesive according to claim 6, characterized in that, In the modification described in (B), the grafting reaction temperature is 70℃~80℃, and the reaction time is 0.5h~1.5h; Preferably, the (B) modification is carried out under stirring conditions, with a stirring speed of 200 r / min to 400 r / min.

9. The method for preparing the reactive polyurethane hot melt adhesive according to claim 6, characterized in that, In the post-treatment described in (C), the catalyst is an environmentally friendly organic bismuth composite catalyst; Preferably, the mixing temperature in the post-processing step (C) is 70°C to 80°C, and the mixing time is 20 min to 40 min.

10. The application of a reactive polyurethane hot melt adhesive according to any one of claims 1 to 5 in the preparation of fire ventilation ducts.

Images