Environment-friendly adhesive, preparation method and application thereof

Abstract

The application belongs to the technical field of adhesives, and particularly relates to an environment-friendly adhesive as well as a preparation method and application thereof. The preparation method of the environment-friendly adhesive comprises the following steps: S1. Under the protection of inert gas, polybutylene adipate glycol, modified carbon nanotubes and isophorone diisocyanate are mixed, and then reacted after being heated; then, dimethylol propionic acid and dibutyltin dilaurate are added for continuous reaction; after being cooled, pH is adjusted; then, acetone is added for stirring; finally, bacteriostatic agent and deionized water are added; after emulsification, the acetone is removed, and a water-based carbon nanotube / polyurethane composite emulsion is obtained; S2. The water-based carbon nanotube / polyurethane composite emulsion is mixed with a defoaming agent, a dispersing agent and a leveling agent, and then stirred, and the environment-friendly adhesive is obtained. The adhesive prepared by the method has low water absorption, excellent bonding performance and antibacterial and mildew-proof performance.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to an environmentally friendly adhesive, its preparation method, and its application. Background Technology

[0002] With the increasing global advocacy for environmentally friendly materials and the growing awareness of environmental protection, waterborne polyurethane (WPU) adhesives, using water as the dispersion medium, are gradually replacing traditional solvent-based polyurethane adhesives and becoming the mainstream direction of industry development. Waterborne polyurethane adhesives exhibit excellent bonding performance to substrates such as plastics, metals, and wood. Furthermore, by using water instead of organic solvents, these adhesives emit no toxic or harmful volatile organic compounds during use, making them environmentally friendly, non-toxic, and pollution-free, meeting the requirements of modern green manufacturing.

[0003] Cinnamaldehyde is a naturally sourced antibacterial agent with broad-spectrum antibacterial activity, particularly effective against molds and some bacteria. However, cinnamaldehyde is highly volatile and poorly soluble in water. Direct addition to aqueous systems can easily lead to precipitation, migration, or volatilization, making it difficult to maintain its antibacterial effect for an extended period and significantly limiting its application.

[0004] Waterborne polyurethane materials maintain excellent weather resistance and elasticity without significantly altering the original manufacturing process, leading to their widespread application in adhesives, coatings, and leather finishing. However, while the introduction of hydrophilic groups into traditional waterborne polyurethane adhesives helps improve emulsion stability, it also causes the cured film to easily absorb water and swell in humid environments, resulting in decreased peel strength. This limits the widespread adoption of waterborne polyurethane adhesives in applications requiring high mechanical strength.

[0005] Therefore, in order to broaden the application range of waterborne polyurethane materials, it is urgent to perform functional modification on them, so as to systematically improve their antibacterial and antifungal properties and interfacial bonding strength while maintaining their environmentally friendly characteristics. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a method for preparing an environmentally friendly adhesive that is simple to operate.

[0007] The second objective of this invention is to provide an environmentally friendly adhesive with low water absorption, excellent bonding performance, and antibacterial and antifungal properties.

[0008] The third objective of this invention is to provide an application of an environmentally friendly adhesive with broad application prospects.

[0009] The objective of this invention is achieved through the following technical solution: A method for preparing an environmentally friendly adhesive includes the following steps: S1. Under inert gas protection, polybutylene adipate diol, modified carbon nanotubes and isophorone diisocyanate are mixed, heated and reacted, then dimethylolpropionic acid and dibutyltin dilaurate are added to continue the reaction, the pH is adjusted after cooling, acetone is added and stirred, then antibacterial agent and deionized water are added, emulsified and acetone is removed to obtain an aqueous carbon nanotube / polyurethane composite emulsion; The structural formula of the antibacterial agent is: S2. The aqueous carbon nanotube / polyurethane composite emulsion is mixed with defoamer, dispersant, and leveling agent, and stirred to obtain the final product.

[0010] Preferably, in step S1, the mass ratio of polybutylene adipate diol, modified carbon nanotubes, isophorone diisocyanate, dimethylolpropionic acid, dibutyltin dilaurate, acetone, and antibacterial agent is 1:(0.04~0.06):(0.4~0.45):(0.03~0.06):(0.0025~0.0035):(0.3~0.5):(0.01~0.03); the temperature is raised to 80~90℃, and the reaction time is 2~4h; the reaction continues for 1~2h; the temperature is lowered to 40~45℃, and the pH is adjusted to 7~8; the stirring time is 30~60min.

[0011] Preferably, the modified carbon nanotubes are prepared by: (1) Under an inert atmosphere, hydroxymethyldioxacyclopentanone, benzotriazole and triphenylphosphine were added to anhydrous tetrahydrofuran, followed by the addition of diisopropyl azodicarbonate. After the reaction, the mixture was purified to obtain the modifier. The structural formula of the modifier is: (2) Aminated multi-walled carbon nanotubes were added to anhydrous ethanol, then potassium hydroxide was added, and after stirring, a modifier was added. The mixture was refluxed and purified to obtain the modified carbon nanotubes.

[0012] This invention prepares a modifier by a nucleophilic substitution reaction between the hydroxyl group of methyldioxapentane and the secondary amine of benzotriazole; subsequently, the ethylene carbonate group on the modifier undergoes a ring-opening nucleophilic substitution reaction with the primary amine group on the surface of the amino carbon nanotube to obtain modified carbon nanotubes.

[0013] Preferably, in step (1), the molar ratio of hydroxymethyldioxacyclopentanone, benzotriazole, triphenylphosphine, and diisopropyl azodicarbonate is 1:(1~1.3):(1~1.3):(1~1.3); the reaction time is 5~8h; in step (2), the mass ratio of aminated multi-walled carbon nanotubes, potassium hydroxide, and modifier is 1:(0.06~0.12):(0.14~0.2); the reflux reaction time is 5~8h.

[0014] Preferably, the antibacterial agent is prepared as follows: (a) 5-fluoro-2-hydroxyacetophenone and cinnamaldehyde were added to anhydrous ethanol, followed by the addition of sodium hydroxide solution. After the reaction, the mixture was purified to obtain intermediate 1. The structural formula of intermediate 1 is: (b) Intermediate 1 and N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine were added to tetrahydrofuran, followed by the addition of triphenylphosphine and di-tert-butyl azodicarbonate. After the reaction, the mixture was purified to obtain intermediate 2. The structural formula of intermediate 2 is as follows: (c) The intermediate 2 is added to tetrahydrofuran, followed by the addition of iodomethane. After the reaction, the mixture is subjected to ion exchange and purification to obtain the antibacterial agent.

[0015] This invention utilizes the Claisen-Schmidt condensation reaction of the aldehyde group of cinnamaldehyde and the methyl ketone of 5-fluoro-2-hydroxyacetophenone to prepare intermediate 1; the phenolic hydroxyl group of intermediate 1 undergoes a nucleophilic substitution reaction with the hydroxyl group of N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine to prepare intermediate 2; intermediate 2 is methylated to obtain an antibacterial agent.

[0016] Preferably, in step (a), the molar ratio of 5-fluoro-2-hydroxyacetophenone, cinnamaldehyde, and sodium hydroxide is 1:(1~1.2):(1~1.2); the mass fraction of the sodium hydroxide solution is 9~11wt%; and the reaction time is 12~24h.

[0017] Preferably, in step (b), the molar ratio of intermediate 1, N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine, triphenylphosphine, and di-tert-butyl azodicarbonate is 1:(1.1~1.3):(1.1~1.3):(1.1~1.3); the reaction temperature is 50~70℃ and the time is 12~16h; in step (c), the molar ratio of intermediate 2 and iodomethane is 1:(2~3); the reaction time is 5~10h.

[0018] Preferably, in step S2, the mass ratio of the aqueous carbon nanotube / polyurethane composite emulsion, defoamer, dispersant, and leveling agent is 1:(0.004~0.006):(0.003~0.005):(0.005~0.01); the stirring time is 30~50 min; the defoamer is BYK-022; the dispersant is BYK-190; and the leveling agent is BYK-307.

[0019] An environmentally friendly adhesive is prepared using the above-described preparation method.

[0020] The above-mentioned environmentally friendly adhesives are used to bond polyethylene substrates, polyethylene terephthalate substrates, polyamide substrates, or aluminum foil substrates.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a method for preparing an environmentally friendly adhesive. The method is simple to operate and has mild reaction conditions. Modified carbon nanotubes and antibacterial agents with specific structures are introduced into an aqueous polyurethane system through in-situ polymerization. No complicated equipment is required, making it suitable for industrial production.

[0022] 2. This invention provides an environmentally friendly adhesive with low water absorption, excellent bonding performance, and antibacterial and antifungal properties.

[0023] 3. This invention improves the adhesive's bonding performance and antibacterial and antifungal properties while reducing water absorption by introducing an antibacterial agent. The quaternary ammonium salt cationic head group of this antibacterial agent can electrostatically bind to the fungal cell membrane, while the hydrophobic tail group inserts into the membrane, causing membrane rupture. Simultaneously, the cinnamaldehyde skeleton inhibits protein polymerization and blocks cell division, resulting in a synergistic effect from this dual antibacterial mechanism. The long-chain alkyl group of the antibacterial agent entangles with the polymer chain, enhancing cohesion. Its cationic properties enhance adsorption on negatively charged surfaces, thereby improving peel strength. The introduction of fluorine atoms improves hydrophobicity, and together with modified carbon nanotubes, significantly reduces water absorption.

[0024] 4. This invention improves the adhesive's bonding performance and antibacterial and antifungal properties while reducing water absorption by introducing modified carbon nanotubes. The benzotriazole on the surface of the modified carbon nanotubes inhibits microbial metabolism by chelating metal ions in the system. Simultaneously, its triazole rings have membrane-disrupting and genetic material-interfering effects, synergistically enhancing antifungal performance with antibacterial agents. The urethane bonds (-O-CO-NH-) on the nanotubes can form hydrogen bonds with hydroxyl and carboxyl groups on the matrix and substrate surface, strengthening interfacial bonding and improving peel strength. The labyrinth effect of the hydrophobic graphite framework extends the water molecule penetration path, reducing water absorption. Attached Figure Description

[0025] Figure 1These are the infrared spectra of the aminated multi-walled carbon nanotubes and modified carbon nanotubes prepared in Example 1 of this invention; wherein, curve 1 represents the aminated multi-walled carbon nanotubes, and curve 2 represents the modified carbon nanotubes prepared in Example 1. Detailed Implementation

[0026] The present invention will be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Specific conditions not specified in the embodiments are based on conventional conditions or product instructions. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0027] In this embodiment of the invention, the molecular weight of polybutylene adipate diol is 1000.

[0028] Preparation Example 1 A modified carbon nanotube, prepared by the following method: (1) Under an inert atmosphere, hydroxymethyldioxane (10 mmol), benzotriazole (11 mmol), and triphenylphosphine (11 mmol) were added to anhydrous tetrahydrofuran (30 mL), followed by the dropwise addition of diisopropyl azodicarbonate (11 mmol). The reaction was allowed to proceed at room temperature for 6 h. The reaction was quenched with water, and the aqueous phase was extracted with ethyl acetate. The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The residue was then subjected to silica gel column chromatography (V... 石油醚 V 乙酸乙酯 =2:1), to obtain the modifier; the NMR and mass spectrometry results of the modifier are as follows: 1 HNMR (C 10 H9N3O3,400MHz,DMSO-d6)δ8.08(dd,1H),7.97(dd,1H),7.58(dt,1H),7.35(dt,1H),4.27-3.83(m,5H);LC-MSm / z:220.06[M+H] + .

[0029] The above reaction process is as follows: (2) Add 5g of aminated multi-walled carbon nanotubes (outer diameter 8~15nm, amino content 0.45wt%) to anhydrous ethanol (100mL), then add potassium hydroxide (0.4g), stir evenly at 40℃, then add modifier (0.8g), and reflux for 7h; concentrate to remove solvent, wash the concentrate with deionized water, and dry the solid to obtain modified carbon nanotubes.

[0030] Preparation Example 2 A modified carbon nanotube, prepared by the following method: (1) Under an inert atmosphere, hydroxymethyldioxane (10 mmol), benzotriazole (10 mmol), and triphenylphosphine (10 mmol) were added to anhydrous tetrahydrofuran (30 mL), followed by the dropwise addition of diisopropyl azodicarbonate (10 mmol). The reaction was allowed to proceed at room temperature for 5 h. The reaction was quenched with water, and the aqueous phase was extracted with ethyl acetate. The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The residue was then subjected to silica gel column chromatography (V... 石油醚 V 乙酸乙酯 The modifier was obtained by a ratio of 2:1; the NMR and mass spectrometry results of the modifier were consistent with those of Preparation Example 1.

[0031] (2) Add 5g of aminated multi-walled carbon nanotubes to anhydrous ethanol (100mL), then add potassium hydroxide (0.3g), stir evenly at 40℃, then add modifier (0.7g), and reflux for 5h; concentrate to remove solvent, wash the concentrate with deionized water, and dry the solid to obtain modified carbon nanotubes.

[0032] Preparation Example 3 A modified carbon nanotube, prepared by the following method: (1) Under an inert atmosphere, hydroxymethyldioxane (10 mmol), benzotriazole (13 mmol), and triphenylphosphine (13 mmol) were added to anhydrous tetrahydrofuran (30 mL), followed by the dropwise addition of diisopropyl azodicarbonate (13 mmol). The reaction was allowed to proceed at room temperature for 8 h. The reaction was quenched with water, and the aqueous phase was extracted with ethyl acetate. The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The residue was then subjected to silica gel column chromatography (V... 石油醚 V 乙酸乙酯 The modifier was obtained by a ratio of 2:1; the NMR and mass spectrometry results of the modifier were consistent with those of Preparation Example 1.

[0033] (2) Add 5g of aminated multi-walled carbon nanotubes to 100mL of anhydrous ethanol, then add 0.6g of potassium hydroxide, stir evenly at 40℃, add 1g of modifier, and reflux for 8h; concentrate to remove solvent, wash the concentrate with deionized water, and dry the solid to obtain modified carbon nanotubes.

[0034] Preparation Example 4 An antibacterial agent, prepared by the following method: (a) Dissolve 5-fluoro-2-hydroxyacetophenone (10 mmol) and cinnamaldehyde (11 mmol) in anhydrous ethanol, add 10 wt% sodium hydroxide solution (11 mmol), and react at room temperature for 18 h; filter the reaction solution, washing the filter cake with water during filtration, and then using a mixed solvent (V乙醇 V 水 The mixture of 5:1 was pulped to obtain intermediate 1; the NMR and mass spectrometry results of intermediate 1 are as follows: 1 HNMR (C 17 H 13 FO2, 400MHz, DMSO- d6 )δ15.47(s,1H),7.78(d,1H),7.45-6.99(m,10H),6.72(d,1H);LC-MSm / z:269.09[M+H] + .

[0035] (b) Intermediate 1 (10 mmol) and N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine (12 mmol) were added to tetrahydrofuran (30 mL), stirred until homogeneous, and then triphenylphosphine (12 mmol) and di-tert-butyl azodicarbonate (12 mmol) were added. The mixture was reacted at 60 °C for 14 h. The mixture was concentrated under reduced pressure, and the residue was subjected to column chromatography (V) 庚烷 V 乙酸乙酯 The mixture was purified by a ratio of 4:1 to obtain intermediate 2. The NMR and mass spectrometry results of intermediate 2 are as follows: 1 HNMR (C 24 H 29 FN2O2, 400MHz, DMSO- d6 )δ7.78(d,1H),7.47-7.33(m,7H),7.22(d,1H),7.13(dd,1H),7.03(d,1H),6.72(d,1H), 4.07(t,2H),2.76(t,2H),2.37(s,4H),2.21(s,6H),2.18(s,3H);LC-MSm / z:397.22[M+H] + .

[0036] (c) Intermediate 2 (10 mmol) was added to tetrahydrofuran (30 mL), followed by iodomethane (25 mmol), and the reaction was carried out at room temperature for 7 h. The solvent and excess iodomethane were evaporated from the reaction solution under reduced pressure, and the solution was converted to chloride by counterion exchange and then freeze-dried to obtain the antibacterial agent. The NMR and mass spectrometry results of the antibacterial agent are as follows: 1 HNMR (C 26 H 35 FN2O2 2+ 400MHz, DMSO- d6)δ7.78(d,1H),7.47-7.33(m,7H),7.22(d,1H),7.13(dd,1H),7.03(d,1H),6.7 2(d,1H),4.37(t,2H),3.69-3.67(m,6H),3.35(s,15H);LC-MSm / z:427.27[M+H] + .

[0037] Preparation Example 5 An antibacterial agent, prepared by the following method: (a) Dissolve 5-fluoro-2-hydroxyacetophenone (10 mmol) and cinnamaldehyde (11 mmol) in anhydrous ethanol, add 11 wt% sodium hydroxide solution (11 mmol), and react at room temperature for 12 h; filter the reaction solution, washing the filter cake with water during filtration, and then using a mixed solvent (V 乙醇 V 水 =5:1) pulping to obtain intermediate 1; the NMR and mass spectra of intermediate 1 are consistent with those of preparation example 4.

[0038] (b) Intermediate 1 (10 mmol) and N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine (11 mmol) were added to tetrahydrofuran (30 mL), stirred until homogeneous, and then triphenylphosphine (11 mmol) and di-tert-butyl azodicarbonate (11 mmol) were added. The mixture was reacted at 50 °C for 16 h. The mixture was concentrated under reduced pressure, and the residue was subjected to column chromatography (V) 庚烷 V 乙酸乙酯 The mixture was purified by a ratio of 4:1 to obtain intermediate 2; the NMR and mass spectrometry results of intermediate 2 were consistent with those of preparation example 4.

[0039] (c) Intermediate 2 (10 mmol) was added to tetrahydrofuran (30 mL), followed by iodomethane (20 mmol), and the reaction was carried out at room temperature for 5 h. The solvent and excess iodomethane were evaporated from the reaction solution under reduced pressure, and the solution was converted to chloride by counterion exchange and then freeze-dried to obtain the antibacterial agent. The NMR and mass spectrometry results of the antibacterial agent were consistent with those of Preparation Example 4.

[0040] Preparation Example 6 An antibacterial agent, prepared by the following method: (a) Dissolve 5-fluoro-2-hydroxyacetophenone (10 mmol) and cinnamaldehyde (12 mmol) in anhydrous ethanol, add 9 wt% sodium hydroxide solution (12 mmol), and react at room temperature for 24 h; filter the reaction solution, washing the filter cake with water during filtration, and then using a mixed solvent (V 乙醇 V 水 =5:1) pulping to obtain intermediate 1; the NMR and mass spectra of intermediate 1 are consistent with those of preparation example 4.

[0041] (b) Intermediate 1 (10 mmol) and N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine (13 mmol) were added to tetrahydrofuran (30 mL), stirred until homogeneous, and then triphenylphosphine (13 mmol) and di-tert-butyl azodicarbonate (13 mmol) were added. The mixture was reacted at 70 °C for 12 h. The mixture was concentrated under reduced pressure, and the residue was subjected to column chromatography (V) 庚烷 V 乙酸乙酯 The mixture was purified by a ratio of 4:1 to obtain intermediate 2; the NMR and mass spectrometry results of intermediate 2 were consistent with those of preparation example 4.

[0042] (c) Intermediate 2 (10 mmol) was added to tetrahydrofuran (30 mL), followed by iodomethane (30 mmol), and the reaction was carried out at room temperature for 10 h. The solvent and excess iodomethane were evaporated from the reaction solution under reduced pressure, and the solution was converted to chloride by counterion exchange and then freeze-dried to obtain the antibacterial agent. The NMR and mass spectrometry results of the antibacterial agent were consistent with those of Preparation Example 4.

[0043] Example 1 A method for preparing an environmentally friendly adhesive includes the following steps: S1. Under nitrogen atmosphere, the mass ratio of polybutylene adipate diol, modified carbon nanotubes, isophorone diisocyanate, dimethylolpropionic acid, dibutyltin dilaurate, acetone, and antibacterial agent was 100:5:42:4:0.3:30:2. Polybutylene adipate diol was mixed with the modified carbon nanotubes and isophorone diisocyanate from Preparation Example 1. After stirring evenly, the mixture was reacted at 85°C for 3 hours. Then, dimethylolpropionic acid and dibutyltin dilaurate were added, and the reaction was continued for 1.5 hours. The temperature was lowered to 42°C, and triethylamine was added to adjust the pH to 7.5. Acetone was added, and the mixture was stirred for 45 minutes. Finally, the antibacterial agent from Preparation Example 4 and deionized water were added to emulsify the mixture. The acetone was then concentrated to remove the emulsion, resulting in an aqueous carbon nanotube / polyurethane composite emulsion. S2. Mix the aqueous carbon nanotube / polyurethane composite emulsion, BYK-022, BYK-190, and BYK-307 in a mass ratio of 100:0.5:0.4:0.7, and stir for 40 minutes to obtain the final product.

[0044] An environmentally friendly adhesive is prepared using the above-described preparation method.

[0045] Example 2 A method for preparing an environmentally friendly adhesive includes the following steps: S1. Under nitrogen atmosphere, the mass ratio of polybutylene adipate diol, modified carbon nanotubes, isophorone diisocyanate, dimethylolpropionic acid, dibutyltin dilaurate, acetone, and antibacterial agent was 100:4:40:3:0.25:30:1. Polybutylene adipate diol was mixed with the modified carbon nanotubes and isophorone diisocyanate from Preparation Example 2. After stirring evenly, the mixture was reacted at 80°C for 4 hours. Then, dimethylolpropionic acid and dibutyltin dilaurate were added, and the reaction was continued for 2 hours. The temperature was lowered to 40°C, triethylamine was added to adjust the pH to 7, acetone was added, and the mixture was stirred for 30 minutes. Finally, the antibacterial agent from Preparation Example 5 and deionized water were added to emulsify the mixture. The acetone was then concentrated to remove the emulsion, resulting in an aqueous carbon nanotube / polyurethane composite emulsion. S2. Mix the aqueous carbon nanotube / polyurethane composite emulsion, BYK-022, BYK-190, and BYK-307 in a mass ratio of 100:0.4:0.3:0.5, and stir for 30 minutes to obtain the final product.

[0046] An environmentally friendly adhesive is prepared using the above-described preparation method.

[0047] Example 3 A method for preparing an environmentally friendly adhesive includes the following steps: S1. Under nitrogen conditions, the mass ratio of polybutylene adipate diol, modified carbon nanotubes, isophorone diisocyanate, dimethylolpropionic acid, dibutyltin dilaurate, acetone, and antibacterial agent was 100:6:45:6:0.35:50:3. Polybutylene adipate diol was mixed with the modified carbon nanotubes and isophorone diisocyanate of Preparation Example 3. After stirring evenly, the mixture was reacted at 90°C for 2 hours. Then, dimethylolpropionic acid and dibutyltin dilaurate were added, and the reaction was continued for 1 hour. The temperature was lowered to 45°C, triethylamine was added to adjust the pH to 8, acetone was added, and the mixture was stirred for 60 minutes. Finally, the antibacterial agent of Preparation Example 6 and deionized water were added to emulsify the mixture. The acetone was then concentrated to remove the emulsion, resulting in an aqueous carbon nanotube / polyurethane composite emulsion. S2. With the mass ratio of aqueous carbon nanotube / polyurethane composite emulsion, BYK-022, BYK-190, and BYK307 being 100:0.6:0.5:1, mix the aqueous carbon nanotube / polyurethane composite emulsion with BYK-022, BYK-190, and BYK-307, and stir for 50 minutes to obtain the final product.

[0048] An environmentally friendly adhesive is prepared using the above-described preparation method.

[0049] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the modified carbon nanotubes in Preparation Example 1 were replaced with aminated multi-walled carbon nanotubes.

[0050] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the antibacterial agent in Preparation Example 4 was replaced with cinnamaldehyde.

[0051] Experimental Example 1 The modified carbon nanotubes prepared in Example 1 were analyzed by Fourier transform infrared spectroscopy (FT-IR), and the results are as follows: Figure 1 As shown.

[0052] Figure 1 These are the infrared spectra of the modified carbon nanotubes prepared in Example 1 of this invention, where curve 1 is the infrared spectrum of the aminated multi-walled carbon nanotubes, and curve 2 is the infrared spectrum of the modified carbon nanotubes prepared in Example 1. (Observation) Figure 1 It is known that, compared to aminated multi-walled carbon nanotubes, modified carbon nanotubes have a higher growth rate at 1725 cm⁻¹. -1 The strong absorption peak at 1610 cm⁻¹ is due to the stretching vibration of the C=O bond in the urethane group. -1 and 1580cm -1 The absorption peaks at the positions correspond to the C=N stretching vibration, C=C skeletal vibration of the benzotriazole ring, and the C=C stretching vibration of the benzylbenzene ring, respectively, confirming the retention of the benzotriazole ring and benzyl structure; the above information indicates that the modifier was successfully grafted onto the aminated carbon nanotubes.

[0053] Experimental Example 2 The antibacterial properties of the adhesive were tested according to GB / T 21866-2008, using Escherichia coli and Staphylococcus aureus as test strains. The specific procedure is as follows: Add the activated bacterial culture to the test tube and dilute until the total bacterial count is 1×10⁻⁶. 6 CFU / mL, the adhesive was added to the bacterial suspension, and the mixture was placed in a constant temperature incubator and cultured with shaking at 37℃ for 24 h. 50 μL of the bacterial suspension was then coated onto agar medium and placed in a constant temperature incubator for another 24 h at 37℃. The number of colonies in each culture dish was observed, and the inhibition rate was calculated using the following formula: Inhibition rate = (S0 - S1) / S0 × 100%, where S0 is the number of colonies without adhesive and S1 is the number of colonies with adhesive. The results are shown in Table 1.

[0054] Table 1 According to the experimental results in Table 1, the environmentally friendly adhesives prepared in Examples 1-3 of this invention exhibit excellent antibacterial properties against *Escherichia coli* and *Staphylococcus aureus*, with inhibition rates exceeding 98%. In contrast, the inhibition rate decreased in Comparative Example 1 after replacing the modified carbon nanotubes with ordinary aminated carbon nanotubes, and the inhibition rate significantly decreased in Comparative Example 2 after replacing the antibacterial agent with cinnamaldehyde. These results indicate that the synergistic effect of the modified carbon nanotubes and the antibacterial agent with a specific structure is key to achieving highly efficient antibacterial activity in this invention.

[0055] Experimental Example 3 The anti-mold performance was tested according to GB / T 1741-2020 "Determination of Anti-mold Resistance of Paint Films". The adhesive was coated to a thickness of 120 μm and incubated at (28±1)℃ for 28 days. The sample was then removed, and the area covered by mold growth (i.e., the area covered by mold growth) was observed and recorded. The tested fungal species was *Aspergillus niger* (…). Aspergillus niger ) and Aspergillus terreus ( Aspergillus terreus ).

[0056] Table 2 According to the experimental results in Table 2, the environmentally friendly adhesives prepared in Examples 1-3 of this invention, after 28 days of cultivation, showed excellent anti-mold performance with 0% growth coverage of Aspergillus niger and Aspergillus terreus. Comparative Examples 1 and 2 showed increased mold growth coverage, with Comparative Example 2 showing a particularly significant increase. These results indicate that there is a significant synergistic anti-mold effect between the benzotriazole grafted onto the modified carbon nanotube surface and the specific structure antibacterial agent in this invention; only through their combined action can the complete inhibition of mold growth be achieved.

[0057] Test Example 4 Water absorption rate: The adhesives of the examples or comparative examples were poured into polytetrafluoroethylene molds, cured, demolded, and weighed as m1. The samples were then soaked in deionized water for 72 hours and removed. The surface moisture was absorbed with filter paper, and the mass after water absorption was immediately weighed as m2. The water absorption rate was calculated according to the following formula: Water absorption rate = (m2-m1) / m1×100%. The results are shown in Table 3.

[0058] Peel strength: The peel strength of each adhesive was tested on a PET substrate in accordance with GB / T 2792-2014. The results are shown in Table 3.

[0059] Table 3 According to the experimental results in Table 3, the environmentally friendly adhesives prepared in Examples 1-3 of this invention have low water absorption and high peel strength. Comparative Example 1 shows increased water absorption and decreased peel strength, indicating that the benzotriazole on the modified carbon nanotube surface and its covalent grafting with the polyurethane matrix are crucial for improving the adhesive's water resistance and interfacial bonding strength. Comparative Example 2 shows significantly increased water absorption and significantly decreased peel strength, indicating that the fluorine atoms introduced into the antibacterial agent are indispensable for enhancing interfacial bonding and hydrophobic properties. These results fully demonstrate that the synergistic effect of the modified carbon nanotubes and the antibacterial agent with a specific structure in this invention is the key technical feature for achieving low water absorption and high peel strength in the adhesive.

[0060] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing an environmentally friendly adhesive, characterized in that, Includes the following steps: S1. Under inert gas protection, polybutylene adipate diol, modified carbon nanotubes and isophorone diisocyanate are mixed, heated and reacted, then dimethylolpropionic acid and dibutyltin dilaurate are added to continue the reaction, the pH is adjusted after cooling, acetone is added and stirred, then antibacterial agent and deionized water are added, emulsified and acetone is removed to obtain an aqueous carbon nanotube / polyurethane composite emulsion; The structural formula of the antibacterial agent is: S2. The aqueous carbon nanotube / polyurethane composite emulsion is mixed with defoamer, dispersant, and leveling agent, and stirred to obtain the final product; The method for preparing the modified carbon nanotubes in step S1 is as follows: (1) Under an inert atmosphere, hydroxymethyldioxacyclopentanone, benzotriazole and triphenylphosphine were added to anhydrous tetrahydrofuran, followed by the addition of diisopropyl azodicarbonate. After the reaction, the mixture was purified to obtain the modifier. The structural formula of the modifier is: (2) Aminated multi-walled carbon nanotubes were added to anhydrous ethanol, then potassium hydroxide was added, and after stirring, the modifier was added. After reflux reaction, the mixture was purified to obtain the modified carbon nanotubes.

2. The method for preparing the environmentally friendly adhesive according to claim 1, characterized in that, In step S1, the mass ratio of polybutylene adipate diol, modified carbon nanotubes, isophorone diisocyanate, dimethylolpropionic acid, dibutyltin dilaurate, acetone, and antibacterial agent is 1:(0.04~0.06):(0.4~0.45):(0.03~0.06):(0.0025~0.0035):(0.3~0.5):(0.01~0.03); the temperature is raised to 80~90℃, and the reaction time is 2~4h; the reaction continues for 1~2h; the temperature is lowered to 40~45℃, and the pH is adjusted to 7~8; the stirring time is 30~60min.

3. The method for preparing the environmentally friendly adhesive according to claim 1, characterized in that, In step (1), the molar ratio of hydroxymethyldioxacyclopentanone, benzotriazole, triphenylphosphine, and diisopropyl azodicarbonate is 1:(1~1.3):(1~1.3):(1~1.3); the reaction time is 5~8h; in step (2), the mass ratio of aminated multi-walled carbon nanotubes, potassium hydroxide, and modifier is 1:(0.06~0.12):(0.14~0.2); the reflux reaction time is 5~8h.

4. The method for preparing the environmentally friendly adhesive according to claim 1, characterized in that, The method for preparing the antibacterial agent is as follows: (a) 5-fluoro-2-hydroxyacetophenone and cinnamaldehyde were added to anhydrous ethanol, followed by the addition of sodium hydroxide solution. After the reaction, the mixture was purified to obtain intermediate 1. The structural formula of intermediate 1 is: (b) Intermediate 1 and N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine were added to tetrahydrofuran, followed by the addition of triphenylphosphine and di-tert-butyl azodicarbonate. After the reaction, the mixture was purified to obtain intermediate 2. The structural formula of intermediate 2 is as follows: (c) The intermediate 2 is added to tetrahydrofuran, followed by the addition of iodomethane. After the reaction, the mixture is subjected to ion exchange and purification to obtain the antibacterial agent.

5. The method for preparing the environmentally friendly adhesive according to claim 4, characterized in that, In step (a), the molar ratio of 5-fluoro-2-hydroxyacetophenone, cinnamaldehyde, and sodium hydroxide is 1:(1~1.2):(1~1.2); the mass fraction of the sodium hydroxide solution is 9~11wt%; and the reaction time is 12~24h.

6. The method for preparing the environmentally friendly adhesive according to claim 4, characterized in that, In step (b), the molar ratio of intermediate 1, N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine, triphenylphosphine, and di-tert-butyl azodicarbonate is 1:(1.1~1.3):(1.1~1.3):(1.1~1.3); the reaction temperature is 50~70℃ and the time is 12~16h; in step (c), the molar ratio of intermediate 2 and iodomethane is 1:(2~3); the reaction time is 5~10h.

7. The method for preparing the environmentally friendly adhesive according to claim 1, characterized in that, In step S2, the mass ratio of the aqueous carbon nanotube / polyurethane composite emulsion, defoamer, dispersant, and leveling agent is 1:(0.004~0.006):(0.003~0.005):(0.005~0.01); the stirring time is 30~50 min; the defoamer is BYK-022; the dispersant is BYK-190; and the leveling agent is BYK-307.

8. An environmentally friendly adhesive, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. An application of the environmentally friendly adhesive according to claim 8, characterized in that, Used for bonding polyethylene substrates, polyethylene terephthalate substrates, polyamide substrates, or aluminum foil substrates.

Images