Modified polyurethane adhesive with high bonding strength and high temperature resistance

Abstract

The invention discloses a modified polyurethane adhesive with high bonding strength and high temperature resistance, and relates to the technical field of high polymer materials. The invention discloses a modified polyurethane adhesive with high bonding strength and high temperature resistance. The modified polyurethane adhesive is prepared from the following components in parts by mass: 45-60 parts of polyether polyol, 15-20 parts of diisocyanate, 7-15 parts of an organic silicon modifier, 5-10 parts of an isocyanate curing agent, 8-12 parts of high-temperature-resistant filler, 1-3 parts of a silane coupling agent, 0.5-2 parts of an antioxidant and 10-20 parts of a solvent. By introducing the inorganic filler and organic silicon for modification, the stability of the polyurethane adhesive under a high-temperature condition is greatly enhanced. By virtue of the specially designed antioxidant, the oxidation and aging resistance of the polyurethane adhesive is remarkably improved. Through the high-temperature-resistant filler, the silane coupling agent and the optimized formula design, it is ensured that the polyurethane adhesive can still keep excellent bonding strength in a high-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a modified polyurethane adhesive with high bonding strength and high temperature resistance. Background Technology

[0002] Polyurethane adhesives, as an important polymer material, are widely used in industries such as automotive manufacturing, electronic packaging, aerospace, and construction due to their excellent flexibility, bonding properties, and process adaptability. However, the performance of traditional polyurethane adhesives in high-temperature environments is often unsatisfactory. They have poor heat resistance and are prone to softening and decomposition at high temperatures, leading to a significant decrease in bond strength and limiting their application in high-temperature conditions.

[0003] To improve the high-temperature resistance of polyurethane adhesives, the industry typically employs methods such as introducing heat-resistant segments, adding inorganic fillers, or modifying with organosilicon. For example, adding high-temperature resistant fillers such as aluminum hydroxide and silica can improve thermal stability to some extent, but often affects the flowability and bonding performance of the adhesive. While organosilicon modification can improve heat resistance and flexibility, it may lead to compatibility issues with other components, thus reducing overall bond strength. On the other hand, polyurethane adhesives are also susceptible to oxidative aging during long-term use, especially in high-temperature and aerobic environments, where molecular chains break or cross-link, further accelerating performance degradation. Therefore, developing a polyurethane adhesive that possesses both high bonding strength and excellent heat resistance and anti-aging properties in high-temperature environments has become an urgent need for technological development in this field.

[0004] Therefore, there is an urgent need to develop a new type of modified polyurethane adhesive that can simultaneously achieve high bonding strength and excellent high-temperature resistance, and overcome the shortcomings of existing technologies in terms of component compatibility, antioxidant properties and process control. Summary of the Invention

[0005] To address the problems of insufficient heat resistance, significant decrease in bond strength, and poor antioxidant properties of existing polyurethane adhesives in high-temperature environments, a modified polyurethane adhesive with high bond strength and high-temperature resistance is provided. Through optimized component design and preparation process, this adhesive significantly improves bond strength, heat resistance, and mechanical properties, making it suitable for high-temperature applications and bonding to various substrates.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a modified polyurethane adhesive with high bonding strength and high temperature resistance, which is made of the following components in parts by weight: 45-60 parts of polyether polyol, 15-20 parts of diisocyanate, 7-15 parts of organosilicon modifier, 5-10 parts of isocyanate curing agent, 8-12 parts of high temperature resistant filler, 1-3 parts of silane coupling agent, 0.5-2 parts of antioxidant, and 10-20 parts of solvent; The antioxidant is a compound represented by Formula 1 below: Formula 1: ; R1 in Formula 1 is a substituent selected from methyl, hydroxyl, amino, and phenyl.

[0007] Furthermore, the polyether polyol is at least one of polypropylene glycol or polytetrahydrofuran glycol.

[0008] Furthermore, the diisocyanate is at least one of toluene diisocyanate or hexamethylene diisocyanate.

[0009] Furthermore, the organosilicon modifier is at least one of hydroxyl-terminated polydimethylsiloxane or aminopropyl-terminated polydimethylsiloxane.

[0010] Furthermore, the isocyanate curing agent is at least one of the blocked isocyanate curing agent DXB-3375E or blocked isocyanate curing agent DXB-3360A.

[0011] Furthermore, the high-temperature resistant filler is at least one of aluminum hydroxide or silicon dioxide.

[0012] Furthermore, the silane coupling agent is at least one of KH-560 or KH-550.

[0013] Furthermore, the antioxidant is one or more of the compounds shown in the following structures: ; .

[0014] Furthermore, the solvent is at least one of ethyl acetate or toluene.

[0015] A method for preparing a modified polyurethane adhesive with high bonding strength and high temperature resistance includes the following steps: S1. Preparation of prepolymer: The polyether polyol and diisocyanate are added to a reaction vessel, heated to 75-85℃ under a nitrogen inert atmosphere, and reacted at a stirring speed of 200-300r / min for 2-4h to obtain a polyurethane prepolymer. S2. Modification and component mixing: The organosilicon modifier and silane coupling agent are added sequentially to the polyurethane prepolymer, and the temperature is maintained at 50-70℃ while stirring for 1-2 hours; then the high-temperature resistant filler and antioxidant are added, and the temperature is maintained at 55-65℃ while stirring for 1-1.5 hours; then the solvent is added and stirred until the system is uniformly dispersed to obtain a mixed slurry; S3. Curing agent compounding and post-treatment: Cool the mixed slurry to 30-40℃, add the isocyanate curing agent, and mix at a stirring speed of 150-250r / min for 0.5-1h to obtain a modified polyurethane adhesive with high bonding strength and high temperature resistance.

[0016] Furthermore, after adding the high-temperature resistant filler in S2, ultrasonic-assisted dispersion is used during the stirring process, with an ultrasonic power of 100-150W and an ultrasonic time of 15-30min.

[0017] Furthermore, after the curing agent is added and the stirring is completed in S3, a vacuum degassing treatment is required. The treatment conditions are a vacuum degree of -0.08MPa to -0.1MPa, a temperature of 30-40℃, and a duration of 10-20 minutes.

[0018] A modified polyurethane adhesive with high bonding strength and high temperature resistance is disclosed for use as a dedicated adhesive for thermoplastic polyolefin waterproof membranes. Thermoplastic polyolefin waterproof membranes have low surface energy and strong chemical inertness, making it difficult for conventional adhesives to achieve long-term reliable bonding. The modified polyurethane adhesive of this invention, by introducing organosilicon modifiers and silane coupling agents, effectively improves the wettability and interfacial compatibility of the adhesive with low surface energy polyolefin materials, enhancing physical adsorption and interfacial bonding to the membrane surface. Simultaneously, the polyurethane system itself possesses excellent flexibility and bonding strength, adapting to the thermal expansion and contraction and deformation requirements of the waterproof membrane during use. The synergistic effect of high-temperature resistant fillers, specific structural antioxidants, and isocyanate curing agents enables the adhesive to maintain stable mechanical and bonding properties under high temperature, UV, and long-term aging environments, thus meeting the application requirements of thermoplastic polyolefin waterproof membranes as a dedicated adhesive in roofing and high-temperature conditions.

[0019] The antioxidant molecules described in this invention contain active hydrogen donor groups such as phenolic hydroxyl groups. Their core function is to capture active free radicals generated during the oxidation of polyurethane molecular chains. Under high-temperature conditions, the molecular chains of polyurethane adhesives are prone to breakage, generating a large number of free radicals, which in turn trigger a chain oxidation reaction, leading to colloid degradation and decreased adhesive strength. The antioxidant, by providing its own active hydrogen atoms, combines with these free radicals, converting highly reactive free radicals into stable molecules or less reactive free radicals, terminating the chain oxidation reaction and inhibiting the spread of oxidative aging from the source. The antioxidant works synergistically with high-temperature resistant fillers and organosilicon modifiers. The fillers provide physical barriers and thermal stability, the organosilicon improves molecular chain flexibility and thermal stability, and the antioxidant inhibits oxidation reactions at a chemical level, collectively improving overall high-temperature resistance. The large conjugated system and electron-donating groups in the antioxidant molecules enhance electron delocalization ability, improving free radical capture efficiency and thermal stability. Through mechanisms such as chemical free radical termination and physical synergistic protection, the antioxidant significantly improves the anti-oxidative aging performance of the adhesive under high-temperature conditions, thereby maintaining its adhesive strength and durability.

[0020] Polyether polyols and diisocyanates, as the main structural basis of polyurethane prepolymers, react to form the main chain structure of polyurethane, providing the basic mechanical properties and bonding strength of the adhesive. Polyether polyols impart good flexibility and mobility to the molecular chains, while diisocyanates provide rigid segments and crosslinking points, jointly ensuring the adhesive's basic toughness, strength, and wettability and adhesion to various substrates. The silicone modifier's molecular chains contain silicon-oxygen bonds with high bond energy and excellent thermal stability. During the modification process, silicone segments are chemically integrated into the polyurethane main chain, significantly improving overall heat resistance and inhibiting high-temperature softening and decomposition. Simultaneously, the silicone component also improves the flexibility and hydrophobicity of the adhesive layer, reducing the damage to the bonding interface caused by high-temperature and high-humidity environments. High-temperature resistant fillers act as physical supports and thermal barriers at high temperatures. The endothermic decomposition of aluminum hydroxide can delay the temperature rise of the colloid, synergistically with the silicone modifier to maintain or even enhance bonding strength while improving heat resistance, preventing deformation or failure of the adhesive layer due to high temperatures. Silane coupling agents, as key interfacial bridging components, react with the surface of inorganic fillers at one end and bind to organic polyurethane molecules at the other, significantly improving the compatibility and bonding strength between fillers and the resin matrix, avoiding performance inhomogeneity caused by filler agglomeration. Simultaneously, they enhance the chemical bond between the adhesive and the substrate (such as metals and ceramics), thereby significantly improving adhesion durability at high temperatures. Antioxidants maintain the long-term thermal stability and mechanical properties of the adhesive layer, synergistically forming a thermo-oxidative degradation barrier with high-temperature resistant fillers and silicone modifiers, significantly extending the service life of the adhesive under high-temperature conditions. Isocyanate curing agents provide additional crosslinking points, further enhancing the three-dimensional network density of the entire adhesive system, improving bond strength, heat distortion temperature, and overall heat resistance. Solvents adjust the system viscosity, ensuring uniform mixing of components, improving processability, making the adhesive easy to apply and fully wet the bonded surface, providing a good application foundation for achieving high bond strength.

[0021] Compared with the prior art, the beneficial effects of the present invention are: (1) Significantly improved high temperature resistance: By introducing inorganic fillers and organosilicon modification, this invention effectively solves the problem of traditional adhesives being easy to soften and decompose in high temperature environments, and greatly enhances the stability of adhesives under high temperature conditions.

[0022] (2) Significantly enhanced antioxidant capacity: With the help of specially designed antioxidants, the present invention can effectively inhibit the oxidation reaction of polyurethane molecular chains, significantly extend the service life of adhesives, and improve their antioxidant aging performance.

[0023] (3) Significantly improved high-temperature bonding strength retention: Through high-temperature resistant fillers, silane coupling agents and optimized formulation design, the present invention can still maintain excellent bonding strength in high-temperature environments, ensuring reliable adhesion of the adhesive to a variety of substrates. Attached Figure Description

[0024] Figure 1 This is the NMR spectrum of antioxidant 1 described in this invention.

[0025] Figure 2 This is the NMR spectrum of antioxidant 3 described in this invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely 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.

[0027] Synthesis example 1 Synthesis of Antioxidant 1: first step: ; Under a nitrogen atmosphere, 20.00 g of compound 1, 17.95 g of compound 2, 15.86 g of triethylamine, 0.07 g of palladium on carbon, 0.79 g of tri-tert-butylphosphine, and 300 mL of toluene solution were added to the reaction system. The mixture was stirred until homogeneous, heated to 120 °C, and refluxed for 12 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through diatomaceous earth to remove salts and catalyst. The filtrate was cooled to room temperature, washed three times with water, and the organic phase was retained. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried over anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was evaporated to dryness, and column chromatography was performed, eluting with a mixture of petroleum ether and ethyl acetate. The eluent was evaporated to dryness to obtain 26.02 g of compound 3. Mass spectrometry M / Z: 404 [MS+1].

[0028] Step Two: ; 26.02 g of compound 3, 19.96 g of compound 4, 1.27 g of concentrated sulfuric acid, and 250 ml of toluene solution were added to the reaction system, and the mixture was heated under reflux at 75 °C for 1 h. After the reaction was completed, the mixture was cooled to room temperature. After cooling, the reactants were transferred to a separatory funnel, and saturated sodium carbonate aqueous solution was added. The mixture was shaken, separated, and the lower aqueous phase was discarded. The upper organic phase was extracted successively with saturated sodium chloride aqueous solution, saturated calcium chloride aqueous solution, and water, and separated. The organic phase was transferred to an Erlenmeyer flask, dried with anhydrous magnesium sulfate, filtered, evaporated to dryness, and subjected to silica gel column chromatography with a mixture of petroleum ether and ethyl acetate as the eluent. Evaporation was carried out to dryness, yielding 26.91 g of antioxidant 1. Mass spectrometry M / Z: 592 [MS+1], NMR results are shown below. Figure 1 .

[0029] Synthesis Example 2-Synthesis Example 4 In Synthesis Examples 2-4, antioxidants 2-4 were synthesized sequentially, following the same synthesis method as in Synthesis Example 1, except that compound 2 was replaced. The rest remained the same as in Synthesis Example 1. See Table 1 for details.

[0030] Table 1.

[0031] Example 1 A method for preparing a modified polyurethane adhesive with high bonding strength and high temperature resistance: a. Raw material mass ratio: 52 parts of polyether polyol, selected from: polypropylene glycol, purchased from: Wuhan Xinyang Ruihe Chemical Technology Co., Ltd.; 18 parts of diisocyanate, selected from hexamethylene diisocyanate, purchased from Shandong Tonglan Chemical Co., Ltd.; 12 parts of organosilicon modifier, selected from hydroxyl-terminated polydimethylsiloxane, purchased from Shanghai E. En Chemical Technology Co., Ltd. Seven parts of isocyanate curing agent, selected from: blocked isocyanate curing agent DXB-3375E, purchased from: Dongsen Synthetic Materials Co., Ltd.; 10 parts of high-temperature resistant filler, selected from aluminum hydroxide, purchased from Yangzhou Zhongtianli New Material Co., Ltd. Two parts of silane coupling agent, selected from KH-560, purchased from Shanghai Yuanye Biotechnology Co., Ltd. One part of antioxidant, selected from: antioxidant 1 synthesized in Synthesis Example 1; The solvent, 17 parts, was selected from ethyl acetate and purchased from Shandong Jinyueyuan New Materials Co., Ltd.

[0032] b. Preparation method: S1. Preparation of prepolymer: 52 parts of polyether polyol and 18 parts of diisocyanate were added to a reaction vessel, heated to 80°C under a nitrogen atmosphere, and reacted at a stirring speed of 250 r / min for 3 h to obtain polyurethane prepolymer. S2. Modification and Component Mixing: 12 parts of organosilicon modifier and 2 parts of silane coupling agent were added sequentially to the obtained polyurethane prepolymer, and the mixture was stirred at 60°C for 1.5 hours. Then, 10 parts of high-temperature resistant filler and 1 part of antioxidant were added, and the mixture was stirred at 60°C for another hour. Ultrasonic-assisted dispersion was used with an ultrasonic power of 120W for 20 minutes. Finally, 17 parts of solvent were added and stirred until the system was uniformly dispersed to obtain a mixed slurry. S3. Curing agent compounding and post-treatment: The obtained mixed slurry was cooled to 35°C, and 7 parts of isocyanate curing agent were added. The mixture was stirred at 200 r / min for 0.5 h. Then, vacuum degassing treatment was performed at a vacuum degree of -0.09 MPa, a temperature of 35°C, and a duration of 15 min to obtain a modified polyurethane adhesive with high bonding strength and high temperature resistance.

[0033] Examples 2-4 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is carried out by referring to the preparation method of Example 1, except that the antioxidant is replaced in sequence with antioxidant 2-antioxidant 4 prepared in Synthesis Examples 2-4, and the rest is the same as in Example 1.

[0034] Comparative Example 1 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is carried out by referring to the preparation method of Example 1, except that antioxidant 1 is replaced with antioxidant 1010 (CAS: 6683-19-8), and the rest is the same as in Example 1.

[0035] Comparative Example 2 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is carried out by referring to the preparation method of Example 1, except that antioxidant 1 is replaced with antioxidant 168 (CAS: 31570-04-4), and the rest is the same as in Example 1.

[0036] Comparative Example 3 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is the same as in Example 1, except that the antioxidant is not added.

[0037] Comparative Example 4 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is the same as in Example 1, except that the silicone modifier is not added.

[0038] Comparative Example 5 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is the same as in Example 1, except that the isocyanate curing agent is not added.

[0039] Comparative Example 6 The preparation of a modified polyurethane adhesive with high bonding strength and high temperature resistance is the same as in Example 1, except that the high temperature resistant filler is not added.

[0040] Performance testing 1. Shear strength: The modified polyurethane adhesive with high bonding strength and high temperature resistance prepared in the examples and comparative examples was used as a sample. Its shear strength was tested according to GB / T7124-2008 standard. The results are shown in Table 2.

[0041] 2. Peel strength: The modified polyurethane adhesive with high bonding strength and high temperature resistance prepared in the examples and comparative examples was used as a sample. The T-type peel strength test was carried out in accordance with GB / T 2791-1995 standard. The test speed was 100 mm / min. The results are shown in Table 2.

[0042] 3. Peel strength retention rate after aging: A modified polyurethane adhesive with high bonding strength and high temperature resistance prepared in the examples and comparative examples was placed in an aging test chamber and exposed for 2500 hours. Then, its peel strength was tested according to GB / T2791-1995, and the peel strength retention rate was calculated. The results are shown in Table 1.

[0043] Aging conditions: Radiation intensity: 0.35W / m2 (at 340nm wavelength); Temperature cycling: 60℃ (light stage) to 40℃ (dark stage), 8 hours of light + 4 hours of condensation (simulated rain) per cycle; Relative humidity: 50% (light stage), 95% (condensation stage).

[0044] 4. Limiting Oxygen Index: The modified polyurethane adhesive with high bonding strength and high temperature resistance prepared in the examples and comparative examples was used as a sample. The limiting oxygen index of the material was tested using a limiting oxygen index tester in accordance with GB / T2406.2-2009 standard. The results are shown in Table 2.

[0045] Table 2.

[0046] As shown in Table 2, the performance test results of the various examples and the comparative examples exhibit significant trend differences in shear strength, peel strength, peel strength retention rate after aging, and limiting oxygen index. The example group (containing the specific structure antioxidant and complete components) generally showed excellent comprehensive performance, especially in bond strength, peel strength retention rate after aging, and flame retardancy, all of which were superior to the comparative examples. In the comparative example group, samples lacking antioxidants, silicone modifiers, curing agents, or high-temperature fillers all showed a decline in performance, indicating that these components play a crucial role in improving the bond strength and thermal stability of the adhesive. Furthermore, while samples using conventional antioxidants showed certain performance, they were still inferior to the effect of the specific structure antioxidant described in this invention, demonstrating that the aforementioned key components are essential to the integrity and effectiveness of the technical solution of this invention.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modified polyurethane adhesive with high bonding strength and high temperature resistance, characterized in that, It is made from the following components in parts by weight: 45-60 parts polyether polyol, 15-20 parts diisocyanate, 7-15 parts organosilicon modifier, 5-10 parts isocyanate curing agent, 8-12 parts high-temperature resistant filler, 1-3 parts silane coupling agent, 0.5-2 parts antioxidant, and 10-20 parts solvent. The antioxidant is a compound represented by Formula 1 below: Formula 1: ; R1 in Formula 1 is a substituent selected from methyl, hydroxyl, amino, and phenyl.

2. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The polyether polyol is at least one of polypropylene glycol or polytetrahydrofuran glycol; The diisocyanate is at least one of toluene diisocyanate or hexamethylene diisocyanate.

3. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The organosilicon modifier is at least one of hydroxyl-terminated polydimethylsiloxane or aminopropyl-terminated polydimethylsiloxane.

4. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The isocyanate curing agent is at least one of the blocked isocyanate curing agent DXB-3375E or blocked isocyanate curing agent DXB-3360A.

5. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The high-temperature resistant filler is at least one of aluminum hydroxide or silicon dioxide.

6. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The silane coupling agent is at least one of KH-560 or KH-550.

7. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The antioxidant is one or more of the compounds shown in the following structures: ； 。 8. The modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 1, characterized in that, The solvent is at least one of ethyl acetate or toluene.

9. A method for preparing a modified polyurethane adhesive with high bonding strength and high temperature resistance according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Preparation of prepolymer: The polyether polyol and diisocyanate are added to a reaction vessel, heated to 75-85℃ under a nitrogen inert atmosphere, and reacted at a stirring speed of 200-300r / min for 2-4h to obtain a polyurethane prepolymer. S2. Modification and component mixing: The organosilicon modifier and silane coupling agent are added sequentially to the polyurethane prepolymer, and the temperature is maintained at 50-70℃ while stirring for 1-2 hours; then the high-temperature resistant filler and antioxidant are added, and the temperature is maintained at 55-65℃ while stirring for 1-1.5 hours; then the solvent is added and stirred until the system is uniformly dispersed to obtain a mixed slurry; S3. Curing agent compounding and post-treatment: Cool the mixed slurry to 30-40℃, add the isocyanate curing agent, and mix at a stirring speed of 150-250r / min for 0.5-1h to obtain a modified polyurethane adhesive with high bonding strength and high temperature resistance.

10. A method for preparing a modified polyurethane adhesive with high bonding strength and high temperature resistance according to claim 9, characterized in that, After adding the high-temperature resistant filler to S2, ultrasonic-assisted dispersion is used during the stirring process. The ultrasonic power is 100-150W and the ultrasonic time is 15-30min. After the curing agent in S3 is added and stirred, vacuum degassing treatment is required. The treatment conditions are vacuum degree of -0.08MPa to -0.1MPa, temperature of 30-40℃, and duration of 10-20min.

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