Single-component polyurethane adhesive modified by ionic liquid hybridized nano MOF material and preparation method of single-component polyurethane adhesive

Abstract

The invention discloses a single-component polyurethane adhesive modified by an ionic liquid hybrid nano MOF material and a preparation method of the single-component polyurethane adhesive, and belongs to the technical field of wood adhesives. According to the technical scheme, specific ionic liquid is introduced into nano-MOF to obtain an ionic liquid hybridized nano-MOF material, and the ionic liquid hybridized nano-MOF material reacts with raw materials such as oligomer polyol, polyisocyanate and a binary chain extender to obtain the ionic liquid hybridized nano-MOF material modified single-component polyurethane adhesive. The active and efficient adsorption capacity of the hybrid nano MOF material on CO2 is utilized, the stress problem caused by expansion and foaming problems of an adhesive layer in the moisture curing process is solved, and the adhesive film tensile strength, bonding strength and other properties of the adhesive are remarkably improved. Meanwhile, the hybrid nano MOF material plays a role in reinforcing and heat-resistant filling, so that the adhesive film is endowed with excellent high-temperature resistance, and the adhesive can meet the bonding use requirements of hardwood in the high-temperature and high-humidity processing process and has a wide application prospect.

Description

Technical Field

[0001] This application relates to a single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF materials and its preparation method, belonging to the technical field of wood adhesives. Background Technology

[0002] One-component polyurethane adhesives are adhesives containing a highly polar, chemically active urethane structure (—NHCOO—). They possess characteristics such as room temperature curing, high bond strength, and good film flexibility, impact resistance, abrasion resistance, and low-temperature resistance, leading to their rapid increase in use in the wood processing industry, especially in the hardwood furniture industry. One-component polyurethane adhesives primarily rely on moisture for curing. During the curing process, the terminal isocyanate groups first react with water to generate amine groups and carbon dioxide. The generated amine groups continue to react with the isocyanate groups to form cross-linking points, increasing bond strength. However, once the adhesive surface has cured into a film, the carbon dioxide gas generated inside the adhesive layer cannot escape from the surface in time, resulting in the formation of bubbles inside and on the surface of the adhesive layer, thus reducing the adhesive strength.

[0003] On the other hand, in the production of hardwood furniture, the wood needs to be baked in a high-temperature drying oven to control the moisture content of the wood at 8-12% to prevent cracking caused by changes in temperature and humidity during use. Therefore, the wood processing industry has placed higher demands on the bonding strength, water resistance, and heat resistance of wood adhesives. However, due to the poor heat resistance and low thermal decomposition temperature of some groups such as urethane and biuret produced during the curing of single-component polyurethane adhesives, the adhesive layer is prone to softening and decomposition at high temperatures, leading to a sharp decline in bonding strength. The long-term usable temperature of ordinary polyurethane polymers is only 80℃, and the short-term use temperature cannot exceed 120℃. When the temperature exceeds 150℃, polyurethane will degrade rapidly, greatly limiting its application. Therefore, how to improve the heat resistance of single-component polyurethane adhesives so that they can still meet the bonding needs of hardwood furniture production under long-term high-temperature conditions is an urgent problem to be solved.

[0004] Existing technologies disclose a latent-curing one-component polyurethane adhesive and its preparation method. Modification with a latent curing agent effectively solves the problem of air bubbles generated during the curing process of one-component moisture-curing polyurethane adhesives, improving the mechanical and adhesive properties of the polyurethane adhesive. However, this technology cannot completely eliminate air bubbles generated during the curing process, especially when the coating is thick, where foaming of the adhesive layer is still significant. Existing technologies also disclose a heat-resistant one-component polyurethane sealant and its preparation method. By adding hydroxyl-terminated epoxy-modified polymers and fillers such as nano-calcium carbonate, heavy calcium carbonate, carbon black, or kaolin, the heat resistance of the one-component polyurethane sealant is improved. However, this technology cannot completely solve the compatibility problem between inorganic fillers and polyurethane organic polymers, and the adhesive's storage stability is less than three months. Summary of the Invention

[0005] To address the problems of poor heat resistance, insufficient storage stability, and bubble generation during the wet curing process in existing one-component polyurethane adhesives, this application proposes a technical solution for one-component polyurethane adhesives modified with ionic liquid hybrid nano-MOF materials. This involves encapsulating an ionic liquid within an amino-containing nano-MOF using a "ship-in-a-bottle" method to obtain a hybrid material. This hybrid material can actively adsorb CO2 generated during the wet curing of polyurethane, eliminating bubbles. When used to modify one-component polyurethane adhesives, it also serves as a reinforcing filler to improve the adhesive's bonding strength and heat resistance.

[0006] The technical solution adopted in this application is as follows: According to a first aspect of this application, a one-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material is provided, comprising one-component polyurethane modified with ionic liquid hybrid nano-MOF material, a diluent, and a tertiary amine catalyst; The single-component polyurethane modified with ionic liquid hybrid nano-MOF material is prepared by reacting raw materials containing the following components under the action of an organobismuth or organotin catalyst: polyurethane prepolymer and ionic liquid hybrid nano-MOF material. The ionic liquid hybrid nano-MOF material is obtained by reacting nano-MOFs and ionic liquid precursors, wherein the ionic liquid precursors include cation source precursors and anion source precursors. The ionic liquid is encapsulated within the porous cage structure of the nano-MOF.

[0007] Optionally, the nano-MOF contains active amino groups.

[0008] Optionally, the nano MOF is selected from at least one of NH2-MIL-53(Fe), NH2-MIL-100(Fe), NH2-MIL-101(Fe), NH2-Uio-66(Zr), and NH2-Uio-67(Zr).

[0009] Optionally, the cation source precursor is selected from at least one of 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butylpyridine chloride, 1-butylpyridine bromide, 1-butyl-2,3-dimethylimidazolium chloride, and 1-butyl-2,3-dimethylimidazolium bromide.

[0010] Optionally, the anion source precursor is at least one of sodium acetate, sodium tetrafluoroborate, potassium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

[0011] Optionally, the molar ratio of the cation source precursor to the anion source precursor is 1:1-1.2.

[0012] In the single-component polyurethane adhesive, the mass fraction of the ionic liquid hybrid nano-MOF material is 2.5~25wt%.

[0013] Optionally, the one-component polyurethane adhesive modified with the ionic liquid hybrid nano-MOF material has at least one of the following properties: The room temperature moisture curing time at 25℃ is ≤4h; Storage time at 25℃ is ≥240 days; The tensile strength of the adhesive film is ≥22.5MPa; The tensile strength of the adhesive film is ≥22.5MPa; The normal compressive shear strength (wood to wood) of the adhesive film is ≥22.0 MPa; The wet compressive shear strength (wood to wood) of the adhesive film is ≥12.5 MPa; The 50% thermal weight loss temperature of the film is ≥460℃.

[0014] It can meet the bonding requirements of hardwood in high temperature and high humidity processing and has broad application prospects.

[0015] The single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material of this application is a high-solids single-component moisture-curing adhesive. Specifically, it can be rapidly cured at room temperature and has stable storage performance. At the same time, due to the use of ionic liquid hybrid nano-MOF material, the problems of adhesive layer expansion and bubble formation during the moisture curing process are effectively solved, significantly improving the adhesive performance and endowing the adhesive film with high-temperature resistance. It can meet the bonding requirements of hardwood in high-temperature and high-humidity processing and has broad application prospects.

[0016] According to a second aspect of this application, a method for preparing a single-component polyurethane adhesive modified with the above-mentioned ionic liquid hybrid nano-MOF material is provided, comprising the following steps: S1. Add nano-MOF to the cation source precursor and stir. Then add anion source precursor to carry out reaction I. Centrifuge and wash the product of reaction I to obtain ionic liquid hybrid nano-MOF material. S2. The dispersion of the ionic liquid hybrid nano-MOF material is added to a mixture containing polyurethane prepolymer for modification reaction. After the NCO content of polyurethane in the mixture reaches a stable value, a diluent and a tertiary amine catalyst are added to the mixture to obtain the single-component polyurethane adhesive modified by the ionic liquid hybrid nano-MOF material.

[0017] Optionally, the tertiary amine catalyst is selected from at least one of bis(2,6-dimethylmorpholine ethyl) ether, 1,2,4-trimethylpiperazine, 1,3-dimethyl-2-imidazolinone, and triethylamine.

[0018] Optionally, in step S1, the nano-MOF is further degassed before being added.

[0019] Optionally, in step S1, the stirring conditions include: a stirring temperature of 15~40°C and a stirring time of 30~240 min.

[0020] Optionally, in step S1, the conditions for reaction I include: being carried out under stirring, with a reaction temperature of 20~30°C and a reaction time of 1-2 hours.

[0021] Optionally, in step S1, the ratio of the cationic source precursor to the nano MOF is 0.01 mol: 1~10 g.

[0022] Optionally, in step S1, the molar ratio of the cation source precursor to the anion source precursor is 1:1 to 1.2.

[0023] Add diluent and tertiary amine catalyst to the mixture and then cool the mixture to room temperature (15~35°C).

[0024] Optionally, in step S2, the preparation steps of the mixture containing the polyurethane prepolymer include: A mixture containing polyisocyanate, oligomeric polyol, organobismuth or organotin catalyst is heated to react in reaction I until the NCO content of the polyurethane prepolymer in the mixture reaches the theoretical design value. Then, the mixture is cooled down to react in reaction I, and a small molecule diol chain extender is slowly added before heating to react in reaction II until the NCO content of the polyurethane prepolymer in the mixture reaches the theoretical design value. The mixture is then cooled down to react in reaction II to obtain a mixture containing polyurethane prepolymer.

[0025] Optionally, in step S2, the amounts of each component, in total parts, are as follows: 55-75 parts by weight of polyisocyanate; 55-100 parts by weight of oligomeric polyols; 0.05-0.3 parts by weight of organobismuth or organotin catalyst; 5-20 parts by weight of small molecule diol chain extender; 10-25 parts by weight of ionic liquid hybrid nano-MOF materials; 20-50 parts by weight of diluent; Tertiary amine catalysts: 0.05-0.5 parts by weight.

[0026] Optionally, the conditions for the modification reaction include: a reaction temperature of 35-40℃ and a reaction time of 2-6h.

[0027] Optionally, the conditions for heating reaction I include: a reaction temperature of 80-90℃ and a reaction time of 2-6h.

[0028] Optionally, the conditions for cooling I include: cooling to 60-65℃; cooling I can be achieved by purging with nitrogen.

[0029] Optionally, the temperature of the mixture during the slow addition of the small molecule diol chain extender is less than or equal to 75°C.

[0030] Optionally, the slow addition of the small molecule diol chain extender is done by dripping.

[0031] Optionally, the conditions for heating reaction II include: a reaction temperature of 75-80℃ and a reaction time of 2-3 hours.

[0032] Optionally, the conditions for Cooling II include cooling to 35-40°C. Cooling II can be achieved by purging with nitrogen.

[0033] Optionally, the organotin catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, and stannous octoate; The organic bismuth catalyst is selected from at least one of bismuth neodecanoate and bismuth isooctanoate.

[0034] The oligomeric polyol is selected from at least one of polypropylene glycol, polytetrahydrofuran ether glycol, polyethylene adipate glycol, and poly(1,4-butanediol adipate).

[0035] Optionally, the average molecular weight of the oligomeric polyol is 2000-5000.

[0036] Optionally, the polyisocyanate is selected from at least one of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane-4,4'-diisocyanate.

[0037] Optionally, the small molecule diol chain extender is selected from at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and diethylene glycol.

[0038] Optionally, the tertiary amine catalyst is selected from at least one of bis(2,6-dimethylmorpholine ethyl) ether, 1,2,4-trimethylpiperazine, 1,3-dimethyl-2-imidazolinone, and triethylamine.

[0039] Optionally, the diluent is at least one of acetone, butanone, ethyl acetate, butyl acetate, N,N-dimethylformamide, and tetrahydrofuran.

[0040] Optionally, in step S2, the oligomeric polyol undergoes vacuum degassing treatment. For example, the conditions for vacuum degassing treatment include a temperature of 110~130°C and dehydration for 1.5~3 hours until no bubbles are generated.

[0041] The beneficial effects of this application include: (1) The ionic liquid hybrid nano-MOF materials prepared by the method described in this application can systematically control their pore size, specific surface area, framework structure, and surface chemical properties within a relatively wide range, enabling certain MOF materials with specific structures to exhibit excellent gas adsorption capacity and selectivity. Furthermore, the hybrid nano-MOF materials modified with ionic liquids form new CO2 adsorption sites through Lewis acid-base interactions, van der Waals forces, and intermolecular interactions, and synergistically interact with unsaturated metal sites or organic ligands in the framework, which is beneficial for improving CO2 adsorption rate and adsorption initiative. Therefore, this characteristic can be utilized to achieve active and efficient adsorption of CO2 generated during the wet curing process of single-component polyurethane adhesives by nano-MOF particles, effectively avoiding the rapid decline in adhesive strength caused by adhesive layer expansion and bubble formation. (2) The ionic liquid hybrid nano MOF material prepared by the preparation method described in this application has high thermal stability and a thermal decomposition temperature greater than 400℃. When MOF materials are introduced into the polymer system as heat-resistant fillers, they can play a role in blocking heat transfer and protecting the polymer molecular chains from thermal decomposition at high temperatures, which significantly improves the adhesion performance of the adhesive layer under high temperature conditions. (3) The ionic liquid hybrid nano MOF material prepared by the preparation method described in this application is produced by the chemical bonding effect of the active hydrogen reactive functional groups contained in the organic ligands on the MOF and the isocyanate groups on the polyurethane chain, which effectively solves the compatibility problem between MOF materials and polymer systems and improves the storage stability of composite adhesives. 4) The ionic liquid hybrid nano-MOF material prepared by the preparation method described in this application has an amino functionality >2 on its nanoparticles, which increases the crosslinking network sites and the content of rigid benzene ring segments in the molecular hard segments, enhances the polymer cohesive strength and intermolecular forces, and plays a synergistic role in improving the adhesive strength and heat resistance of the adhesive.

[0042] (5) The single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material prepared by the method described in this application can be rapidly cured by moisture in the air at room temperature without the need for additional adhesive, thus improving the production efficiency of downstream industries. At the same time, the adhesive has stable storage performance and excellent heat resistance. It can also efficiently adsorb and eliminate carbon dioxide generated during the wet curing of the adhesive, avoiding the expansion and foaming problems of the adhesive layer. This significantly improves the bonding strength and heat resistance of the adhesive. Its room temperature wet curing time (25℃) is ≤2 hours, storage time (25℃) is ≥300 days, film tensile strength is ≥22.5MPa, normal compressive shear strength is ≥21.0MPa, wet compressive shear strength is ≥12.0MPa, and 50% thermal decompression temperature is ≥455℃. It can meet the bonding requirements of hardwood in high temperature and high humidity processing and manufacturing. Attached Figure Description

[0043] Figure 1 The image shows the FTIR spectrum of a one-component polyurethane adhesive modified with an ionic liquid hybrid nano-MOF material obtained in Example 1 of this application. Detailed Implementation

[0044] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0045] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0046] Additives were purchased from BYK Additives (Shanghai) Co., Ltd.; catalysts were purchased from Guangzhou Yourun Synthetic Materials Co., Ltd.; polyisocyanates were purchased from Wanhua Chemical Group Co., Ltd.; oligomeric polyols were purchased from Asahikawa Chemical (Suzhou) Co., Ltd.; solvents were purchased from Fuqing Federal Chemical Co., Ltd.; binary chain extenders were purchased from Tianjin Yongda Chemical Reagent Co., Ltd.; and MOF nanomaterials were all purchased from Shanghai Kaishu Chemical Technology Co., Ltd.

[0047] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0048] Thermal stability was determined using a NETZSCH STGA 449C integrated thermal analyzer (Germany). The tensile properties of the adhesive film were determined using an Instron 3367 testing machine from Instron, UK. The compressive shear strength of wood was tested using a compressive shear strength tester from Dongri Instruments Co., Ltd.

[0049] The technical solution of this application first utilizes the "shipbuilding in a bottle" method to introduce an ionic liquid with a high active adsorption capacity for CO2 gas into a nano-MOF material containing active amino groups and having a porous cage structure, thereby preparing an ionic liquid hybrid nano-MOF material; then, using raw materials such as vacuum-dehydrated oligomeric polyols, polyisocyanates, binary chain extenders, and the above-mentioned hybrid nano-MOF material, a single-component moisture-curing polyurethane adhesive modified with ionic liquid hybrid nano-MOF material is prepared. This application addresses three key technical challenges in adhesives. First, it utilizes the active and efficient CO2 adsorption capacity of hybrid nano-MOF materials to effectively solve the problems of adhesive layer expansion and bubbling during the wet curing process. Second, it leverages the reactive functional groups containing active hydrogen on the organic ligands of MOF materials to react with the isocyanate groups on the polyurethane chains, forming covalent bonds. This effectively solves the compatibility problem between MOF materials and polymer systems, improving the storage stability of composite adhesives. Furthermore, the reactive functional groups (functionality > 2) on the organic ligands increase crosslinking network sites and introduce a higher content of rigid benzene ring structures, further enhancing the adhesive strength and heat resistance of polyurethane adhesives. Third, by introducing MOF materials as heat-resistant fillers into the polymer system, they can block heat transfer at high temperatures and protect the polymer molecular chains from thermal decomposition, significantly improving the high-temperature resistance of adhesives and enhancing their adhesive performance under high-temperature conditions.

[0050] Example 1 1) Preparation of ionic liquid hybrid nano-MOF materials 20g of NH2-MIL-53(Fe) powder was placed into a 20ml sample vial and pre-degassed. 5g of the ionic liquid precursor 1-ethyl-3-methylimidazolium chloride was added to the vial and magnetically stirred at 25°C for 2 hours. Then, 3g of the precursor sodium acetate was added and magnetically stirred again at 25°C for 2 hours. After the reaction was completed, the solid was centrifuged and washed with ethanol several times. After drying, the ionic liquid hybrid nano-MOF material powder, namely [EMIm][OAc]@NH2-MIL-53(Fe) powder, was obtained.

[0051] 2) Synthesis of one-component modified polyurethane adhesives Raw material components:

[0052] 80g of polyethylene adipate diol 3000 was added to a four-necked flask equipped with a mechanical stirrer and thermometer. The mixture was heated to 120°C and then vacuum-dehydrated for 2 hours until no bubbles were generated. Nitrogen gas was then introduced to lower the temperature to 60°C. 60g of toluene diisocyanate and 0.2g of stannous octoate (the first catalyst) were added sequentially to the flask. The temperature was raised to 90°C and reacted for 2 hours until the NCO content of the polyurethane prepolymer reached the theoretical design value. The temperature was then lowered to 60°C, and 15g of 1,4-butanediol (the chain extender) was slowly added, controlling the system temperature to not exceed 75°C. After the addition was complete, the temperature was raised to 80°C and held for 2 hours until the NCO content of the prepolymer reached the theoretical design value. The temperature was then lowered to 35°C, and 20g of the ionic liquid hybrid nano-MOF material [EMIm][OAc]@ prepared above was added. The acetone ultrasonic dispersion of NH2-MIL-53(Fe) was reacted with the polyurethane prepolymer for another 6 hours. When the NCO content of the polymer reached a stable value, the mixture was cooled to room temperature, and 35g of butyl acetate diluent and 0.15g of 1,2,4-trimethylpiperazine second catalyst were added to obtain a single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material.

[0053] Figure 1 This is the infrared spectrum of the one-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material in Example 1. It can be seen that at 1440 cm⁻¹... -1 and 1400cm -1 A symmetrical absorption peak appeared at 1500 cm⁻¹ on the carbonyl group of the organic ligand. -1 An asymmetric absorption peak for the carbonyl group appeared at 1600 cm⁻¹, while a peak appeared at 1572 cm⁻¹. -1 and 1328cm -1 The presence of stretching vibration absorption peaks at C=N and CN at 3365 cm⁻¹ indicates the synthesis of ionic liquid hybrid nano-MOF materials; while at 3365 cm⁻¹... -1 1730cm -1 Characteristic absorption peaks for the stretching vibrations of -NH and C=O appeared at 1557 cm⁻¹. -1 The peak at 1262 cm⁻¹ is the bending vibration peak of -NH⁻. -1 and 1170 cm -1 The peaks at the left and right positions represent the stretching vibrations of -COO-, indicating the formation of carbamate structures during the reaction; from Figure 1 The results demonstrate the successful synthesis of a one-component polyurethane adhesive modified with an ionic liquid hybrid nano-MOF material.

[0054] Example 2 1) Preparation of ionic liquid hybrid nano-MOF materials 15g of NH2-MIL-100(Fe) powder was placed into a 20ml sample vial and pre-degassed. 4g of the ionic liquid precursor 1-butylpyridine chloride was added to the vial and magnetically stirred at 23°C for 1 hour. Then, 3g of the precursor sodium tetrafluoroborate was added and magnetically stirred again at 23°C for 1.5 hours. After the reaction was completed, the solid was centrifuged and washed repeatedly with ethanol. After drying, the ionic liquid hybrid nano-MOF material powder, namely [C4Py][BF4]@NH2-MIL-100(Fe) powder, was obtained.

[0055] 2) Synthesis of one-component modified polyurethane adhesives Raw material components:

[0056] 100g of polytetrahydrofuran ether glycol 2000 was added to a four-necked flask equipped with a mechanical stirrer and a thermometer. The mixture was heated to 120°C and then vacuum-dehydrated for 2 hours until no bubbles were generated. Nitrogen gas was then introduced to lower the temperature to 60°C. 70g of diphenylmethane-4,4'-diisocyanate and 0.3g of dibutyltin dilaurate (the first catalyst) were added sequentially to the flask. The temperature was raised to 85°C and reacted for 3 hours until the NCO content of the polyurethane prepolymer reached the theoretical design value. The temperature was then lowered to 60°C, and 12g of ethylene glycol (a chain extender) was slowly added, controlling the system temperature to not exceed 75°C. After the addition was complete, the temperature was raised to 80°C and held for 3 hours until the NCO content of the prepolymer reached the theoretical design value. The temperature was then lowered to 40°C, and 15g of the aforementioned ionic liquid hybrid nano-MOF material [C4Py][BF4]@ was added. The acetone ultrasonic dispersion of NH2-MIL-100(Fe) was reacted with the polyurethane prepolymer for another 5 hours. When the NCO content of the polymer reached a stable value, the mixture was cooled to room temperature, and 20g of ethyl acetate and 0.2g of bis(2,6-dimethylmorpholinoethyl) ether were added to obtain a single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material.

[0057] Example 3 1) Preparation of ionic liquid hybrid nano-MOF materials 12g of NH2-Uio-66(Zr) powder was placed into a 20ml sample vial and pre-degassed. 3g of the ionic liquid precursor 1-butyl-2,3-dimethylimidazolium bromide was added to the vial and magnetically stirred at 27°C for 1.5 hours. Then, 2.5g of the precursor potassium hexafluorophosphate was added, and magnetic stirring was continued at 27°C for 2 hours. After the reaction was completed, the solid was centrifuged and washed repeatedly with ethanol. After drying, the ionic liquid hybrid nano-MOF material powder, namely [BMMIm][PF6]@NH2-Uio-66(Zr) powder, was obtained.

[0058] 2) Synthesis of one-component modified polyurethane adhesives Raw material components:

[0059] 65g of polytetrahydrofuran ether diol 2000 was added to a four-necked flask equipped with a mechanical stirrer and thermometer. The mixture was heated to 120°C and then vacuum-dehydrated for 2 hours until no bubbles were generated. Nitrogen gas was then introduced to lower the temperature to 60°C. 70g of hexamethylene diisocyanate and 0.15g of dibutyltin maleate (the first catalyst) were added sequentially to the flask. The temperature was raised to 80°C and reacted for 4 hours until the NCO content of the polyurethane prepolymer reached the theoretical design value. The temperature was then lowered to 60°C, and 20g of 1,3-propanediol (the chain extender) was slowly added, controlling the system temperature to not exceed 75°C. After the addition was complete, the temperature was raised to 75°C and maintained for 2 hours. When the NCO content of the prepolymer reached the theoretical design value, the temperature was lowered to 37°C, and 12g of the aforementioned ionic liquid hybrid nano-MOF material [BMMIm][PF6] was added. The acetone ultrasonic dispersion of NH2-Uio-66(Zr) was reacted with the polyurethane prepolymer for another 6 hours. When the NCO content of the polymer reached a stable value, the mixture was cooled to room temperature, and 25g of diluent N,N-dimethylformamide and 0.25g of second catalyst 1,3-dimethyl-2-imidazolinone were added to obtain a one-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material.

[0060] Example 4 1) Preparation of ionic liquid hybrid nano-MOF materials 30g of NH2-MIL-101(Fe) powder was placed into a 20ml sample vial and pre-degassed. 7.5g of the ionic liquid precursor 1-ethyl-3-methylimidazolium bromide was added to the vial and magnetically stirred at 25°C for 1 hour. Then, 5g of the precursor lithium bis(trifluoromethanesulfonyl)imide was added and magnetically stirred at 25°C for another 2 hours. After the reaction was completed, the solid was centrifuged and washed with ethanol several times. After drying, the ionic liquid hybrid nano-MOF material powder, namely [EMIm][Tf2N]@NH2-MIL-101(Fe) powder, was obtained.

[0061] 2) Synthesis of one-component modified polyurethane adhesives Raw material components:

[0062] 100g of polyethylene adipate diol 4000 was added to a four-necked flask equipped with a mechanical stirrer and thermometer. The mixture was heated to 120°C and then vacuum-dehydrated for 2 hours until no more bubbles were generated. Nitrogen gas was then introduced to lower the temperature to 60°C. 55g of isophorone diisocyanate and 0.2g of dibutyltin diacetate (the first catalyst) were added sequentially to the flask. The temperature was raised to 90°C and reacted for 6 hours until the NCO content of the polyurethane prepolymer reached the theoretical design value. The temperature was then lowered to 60°C, and 18g of 1,6-hexanediol (the chain extender) was slowly added, while controlling the system temperature to not exceed 75°C. The mixture was then added dropwise. The temperature was raised to 80℃ and held for 3 hours. When the NCO content of the prepolymer reached the theoretical design value, the temperature was lowered to 40℃ and an acetone ultrasonic dispersion containing 25g of the ionic liquid hybrid nano-MOF material [EMIm][Tf2N]@NH2-MIL-101(Fe) prepared above was added to the polyurethane prepolymer and the reaction continued for 5 hours. When the NCO content of the polymer reached a stable value, the temperature was lowered to room temperature, and 30g of ethyl acetate diluent and 0.4g of triethylamine second catalyst were added to obtain a single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material.

[0063] Example 5 1) Preparation of ionic liquid hybrid nano-MOF materials 20g of NH2-Uio-67(Zr) powder was placed into a 20ml sample vial and pre-degassed. 5g of the ionic liquid precursor 1-butylpyridine bromide was added to the vial and magnetically stirred at 24℃ for 1.5 hours. Then, 3.2g of the precursor sodium tetrafluoroborate was added, and magnetic stirring was continued at 24℃ for another 1.5 hours. After the reaction was completed, the solid was centrifuged and washed several times with ethanol. After drying, the ionic liquid hybrid nano-MOF material powder, namely [C4Py][BF4]@NH2-Uio-67(Zr) powder, was obtained.

[0064] 2) Synthesis of one-component modified polyurethane adhesives Raw material components:

[0065] 70g of poly(1,4-butanediol adipate) 1000 was added to a four-necked flask equipped with a mechanical stirrer and thermometer. The mixture was heated to 120°C and then vacuum-dehydrated for 2 hours until no more bubbles were generated. Nitrogen gas was then introduced to lower the temperature to 60°C. 75g of toluene diisocyanate and 0.3g of stannous octoate (the first catalyst) were added sequentially to the flask. The temperature was raised to 82°C and reacted for 6 hours until the NCO content of the polyurethane prepolymer reached the theoretical design value. The temperature was then lowered to 60°C, and 17g of 1,4-butanediol (the chain extender) was slowly added, controlling the system temperature to not exceed 75°C. After the addition was complete, the temperature was raised to 78°C. The mixture was kept at ℃ for 2.5 hours. When the NCO content of the prepolymer reached the theoretical design value, the temperature was lowered to 36℃ and an acetone ultrasonic dispersion containing 20g of the above-prepared ionic liquid hybrid nano-MOF material [C4Py][BF4]@NH2-Uio-67(Zr) was added to the polyurethane prepolymer and the reaction continued for 5 hours. When the NCO content of the polymer reached a stable value, the temperature was lowered to room temperature, and 20g of ethyl acetate diluent and 0.1g of bis(2,6-dimethylmorpholinoethyl) ether second catalyst were added to obtain a single-component polyurethane adhesive modified with ionic liquid hybrid nano-MOF material.

[0066] Comparative Example 1 Synthesis of one-component polyurethane adhesives Raw material components:

[0067] 80g of polytetrahydrofuran ether diol 3000 was added to a four-necked flask equipped with a mechanical stirrer and a thermometer. The mixture was heated to 120°C and then vacuum-dehydrated for 2 hours until no bubbles were generated in the flask. Nitrogen gas was then introduced and the temperature was lowered to 60°C. 75g of diphenylmethane-4,4'-diisocyanate and 0.3g of dibutyltin dilaurate (the first catalyst) were added to the flask sequentially. The temperature was raised to 85°C and reacted for 4 hours until the NCO content of the polyurethane prepolymer reached the theoretical design value. The temperature was then lowered to 60°C, and 12g of 1,3-propanediol (the chain extender) was slowly added while controlling the system temperature to not exceed 75°C. After the addition was complete, the temperature was raised to 75°C and maintained for 3 hours until the NCO content of the prepolymer reached the theoretical design value. The temperature was then lowered to room temperature, and 35g of butyl acetate (the diluent) and 0.45g of 1,2,4-trimethylpiperazine (the second catalyst) were added to obtain a one-component polyurethane adhesive.

[0068] Comparative Example 2 A latent curing type one-component polyurethane adhesive is prepared according to the method described in Example 1 of the patent with publication number CN109251715A.

[0069] Comparative Example 3 A phenolic resin modified polyurethane / polyurea coating is prepared according to the method described in Example 2 of the patent with publication number CN109554152A.

[0070] Test Example 1 The analytical methods used in the samples prepared in Examples 1-5 and Comparative Examples 1-3 of this application are as follows: Moist curing time: The samples were placed in an environment of 25±2℃ and 50±10% relative humidity for wet curing. The normal compressive shear strength of the samples was tested at regular intervals, and the time required for the adhesive strength of the samples to reach its maximum was recorded.

[0071] Storage time: The storage time of the samples was evaluated in accordance with GB / T14074.9-1993 Test Methods for Wood Adhesives and Resins.

[0072] Normal and wet compressive shear strength: The normal and wet compressive shear strength of the samples were evaluated according to the method of LY / T 1601-2011 Water-based polymer-isocyanate wood adhesives.

[0073] Film tensile strength: The film tensile strength of the samples was evaluated in accordance with GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0074] Thermal stability: Thermogravimetric analysis was performed using a nitrogen-protected thermogravimetric analyzer. The temperature range was 30-600℃, the heating rate was 10℃ / min, and the sample mass was 10mg.

[0075] NCO (solid content) determination: The percentage of NCO in the reaction system is determined by titration every 30 minutes.

[0076] Furthermore, in the embodiments described in this application, all raw materials are expressed in weight (g).

[0077] The performance of the samples prepared in Examples 1-5 and Comparative Examples 1-3 was analyzed according to the above test methods, and the results are shown in Table 1 below:

[0078] The technical solution of this application mainly solves two key technical problems. First, it utilizes the highly efficient active adsorption capacity of a hybrid nano-MOF material modified with an ionic liquid to CO2 gas, solving the technical problem of rapid decline in adhesive performance caused by CO2 generated during the wet curing process in existing single-component moisture-curing polyurethane adhesives. Second, it utilizes the excellent heat resistance of MOF materials to solve the technical problem of easy cracking of polyurethane adhesives under high-temperature conditions due to poor heat resistance. As shown in Table 1, compared with comparative examples 1-3 prepared using existing technologies, the single-component polyurethane adhesives modified with ionic liquid hybrid nano-MOF materials prepared according to examples 1-5 of this application show significant improvements in overall performance. These adhesives exhibit good storage stability, effectively solve the bubble problem generated during the wet curing process, significantly improve the adhesive film performance and adhesive properties, and endow the adhesive film with excellent heat resistance.

[0079] Compared to existing technologies, this application utilizes the active and efficient adsorption of CO2 by hybrid nano-MOF materials modified with ionic liquids, effectively solving the rapid decline in film and adhesive properties caused by bubbles generated during the wet curing process of adhesives. Furthermore, it leverages the covalent bonding between the reactive functional groups (functionality > 2) containing active hydrogen in the organic ligands of the MOF materials and the isocyanate groups on the polyurethane chains to effectively address the compatibility issues between the MOF materials and the polymer system, improving the storage stability of the composite adhesive. Simultaneously, MOF materials possess high thermal stability, with a thermal decomposition temperature greater than 400℃; introducing them as heat-resistant fillers into the polymer system imparts excellent heat resistance to the adhesive. Finally, the reaction between the reactive functional groups (functionality > 2) containing active hydrogen in the organic ligands of the nano-MOF materials and the isocyanate groups increases the crosslinking network sites, improves the crosslinking density of the adhesive, and forms a more complex three-dimensional crosslinking network structure, thereby enhancing the tensile strength, adhesive strength, and water and thermal stability of the adhesive.

[0080] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A one-component polyurethane adhesive modified with ionic liquid hybrid nano MOF material, characterized in that, The single-component polyurethane modified by the ionic liquid hybrid nano MOF material, a diluent, and a tertiary amine catalyst; The single-component polyurethane modified by the ionic liquid hybrid nano MOF material is prepared by reacting raw materials including a polyurethane prepolymer and the ionic liquid hybrid nano MOF material under the action of an organic bismuth or tin catalyst; The ionic liquid hybrid nano MOF material is obtained by reacting a nano MOF and an ionic liquid precursor, wherein the ionic liquid precursor includes a cation source precursor and an anion source precursor; The ionic liquid is encapsulated in the pore cage structure of the nano MOF.

2. The one-component polyurethane adhesive modified with ionic liquid hybrid nano MOF material according to claim 1, characterized in that, The nano MOF contains active amino groups; Preferably, the nano MOF is at least one of NH2-MIL-53 (Fe), NH2-MIL-100 (Fe), NH2-MIL-101 (Fe), NH2-Uio-66 (Zr), and NH2-Uio-67 (Zr). Preferably, the cation source precursor is at least one of 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butylpyridinium chloride, 1-butylpyridinium bromide, 1-butyl-2,3-dimethylimidazolium chloride, and 1-butyl-2,3-dimethylimidazolium bromide. Preferably, the anion source precursor is at least one of sodium acetate, sodium tetrafluoroborate, potassium hexafluorophosphate, and lithium bis(trifluoromethylsulfonyl)imide.

3. The one-component polyurethane adhesive modified with ionic liquid hybrid nano MOF material according to claim 1, characterized in that, The molar ratio of the cation source precursor to the anion source precursor is 1:1-1.

2. In the single-component polyurethane adhesive, the mass fraction of the ionic liquid hybrid nano MOF material is 2.5-25 wt%.

4. The one-component polyurethane adhesive modified with ionic liquid hybrid nano MOF material according to claim 1, characterized in that, The single-component polyurethane adhesive modified by the ionic liquid hybrid nano MOF material has at least one of the following properties: The room temperature moisture curing time at 25°C is ≤4 h; The storage time at 25°C is ≥240 days; The tensile strength of the adhesive film is ≥22.5 MPa; The normal compression shear strength of the adhesive film is ≥22.0 MPa; The wet compression shear strength of the adhesive film is ≥12.5 MPa; The 50% thermal weight loss temperature of the adhesive film is ≥460°C.

5. The method for preparing the one-component polyurethane adhesive modified by the ionic liquid hybrid nano MOF material according to any one of claims 1 to 4, characterized in that, The method includes the following steps: S1. Stirring the nano MOF in the cation source precursor, then adding the anion source precursor to react I, centrifuging and washing the reaction I product to obtain the ionic liquid hybrid nano MOF material; S2. Adding the dispersion of the ionic liquid hybrid nano MOF material to the mixture containing the polyurethane prepolymer to perform a modification reaction, then adding a diluent and a tertiary amine catalyst to the mixture after the NCO content of the polyurethane in the mixture reaches a stable value to obtain the single-component polyurethane adhesive modified by the ionic liquid hybrid nano MOF material.

6. The production method according to claim 5, characterized by, The tertiary amine catalyst is at least one of bis(2,6-dimethylmorpholinoethyl) ether, 1,2,4-trimethylpiperazine, 1,3-dimethyl-2-imidazolidinone, and triethylamine. Preferably, in step S1, the nano MOF is further subjected to a degassing treatment before being added. Preferably, in step S1, the stirring conditions include: the stirring temperature is 15-40°C, and the stirring time is 30-240 min. Preferably, in step S1, the reaction I conditions include: the reaction is carried out under stirring, the reaction temperature is 20-30°C, and the reaction time is 1-2 h. Preferably, in step S1, the ratio of the amount of the cation source precursor to the amount of the nano MOF is 0.01 mol: 1-10 g. Preferably, in step S1, the molar ratio of the cation source precursor to the anion source precursor is 1: 1-1.

2.

7. The preparation method according to claim 5, characterized in that, In step S2, the preparation of the mixture containing the polyurethane prepolymer includes: The mixture containing polyisocyanate, oligomer polyol, and organic bismuth or organic tin catalyst is heated to carry out reaction I until the NCO content of the polyurethane prepolymer in the mixture reaches the theoretical design value, then the mixture is cooled I and the small molecule dihydric alcohol chain extender is slowly added to carry out heating reaction II until the NCO content of the polyurethane prepolymer in the mixture reaches the theoretical design value, and then the mixture is cooled II to obtain the mixture containing the polyurethane prepolymer.

8. The preparation method according to claim 7, characterized in that, In step S2, the amount of each component is as follows based on the total amount: Polyisocyanate 55-75 parts by weight; Oligomer polyol 55-100 parts by weight; Organic bismuth or organic tin catalyst 0.05-0.3 parts by weight; Small molecule dihydric alcohol chain extender 5-20 parts by weight; Ionic liquid hybrid nano MOF material 10-25 parts by weight; Diluent 20-50 parts by weight; Tertiary amine catalyst 0.05-0.5 parts by weight.

9. The preparation method according to claim 7, characterized in that, The modification reaction conditions include: the reaction temperature is 35-40°C, and the reaction time is 2-6 h; Preferably, the heating reaction I conditions include: the reaction temperature is 80-90°C, and the reaction time is 2-6 h; Preferably, the cooling I conditions include: cooling to 60-65°C; Preferably, the temperature of the mixture during the slow addition of the small molecule dihydric alcohol chain extender is less than or equal to 75°C; Preferably, the slow addition of the small molecule dihydric alcohol chain extender is by dropwise addition; Preferably, the heating reaction II conditions include: the reaction temperature is 75-80°C, and the reaction time is 2-3 h; Preferably, the cooling II conditions include: cooling to 35-40°C.

10. The preparation method according to claim 7, characterized in that, The organic tin catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, and stannous octoate; The organic bismuth catalyst is selected from at least one of bismuth neodecanoate and bismuth iso-octoate; The oligomer polyol is selected from at least one of polypropylene oxide glycol, polytetrahydrofuran ether glycol, polyethylene glycol adipate glycol, and poly-1,4-butanediol adipate glycol; Preferably, the average molecular weight of the oligomer polyol is 2000-5000; Preferably, the polyisocyanate is selected from at least one of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane-4,4'-diisocyanate; Preferably, the small molecule diol chain extender is selected from at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol; Preferably, the tertiary amine catalyst is selected from at least one of bis(2,6-dimethylmorpholinoethyl)ether, 1,2,4-trimethylpiperazine, 1,3-dimethyl-2-imidazolidinone, triethylamine; Preferably, the diluent is at least one of acetone, butanone, ethyl acetate, butyl acetate, N,N-dimethylformamide, tetrahydrofuran.

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