Antibacterial-non-yellowing composite structural adhesive based on novel titanium dioxide nanotube encapsulated zinc oxide quantum dot filler and preparation method of antibacterial-non-yellowing composite structural adhesive

Abstract

The invention discloses an antibacterial-non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube encapsulated zinc oxide quantum dot filler and a preparation method of the antibacterial-non-yellowing composite structural adhesive. The preparation method comprises the following steps: 1) preparing 8-12nm zinc oxide quantum dots by combining a sol-gel process; 2) jointly dispersing the zinc oxide quantum dots and the hollow titanium dioxide nanotubes in ethanol, sequentially carrying out ultrasonic treatment and 0.22 mu m water system filtering membrane assisted filtration to increase the loading capacity of the quantum dots in the nanotubes, and carrying out primary calcination treatment on the filler after the loading capacity is increased; (3) dipping the nanotube loaded with the quantum dots in tetraethoxysilane, forming a silicon dioxide coating layer on the surface of the nanotube through a sol-gel method, and then carrying out secondary calcination; and 4) modifying the prepared functional filler with a silane coupling agent, and uniformly mixing the modified functional filler with the structural adhesive pre-solution to obtain the composite structural adhesive material. The structural adhesive has the functions of long-acting antibiosis, yellowing resistance and high strength, and can meet the complex use requirements under the humid condition.

Description

Technical Field

[0001] The present invention relates to a preparation technology of an antibacterial structural adhesive, and in particular to an antibacterial-non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler and a preparation method thereof. Background Art

[0002] Structural adhesives, as an indispensable high-performance adhesive material in modern industry, have been widely used in building curtain walls, automobile manufacturing, electronic packaging, home decoration and other fields. When used in humid environments (such as bathrooms, kitchens, basements, etc.), the mold and blackening will greatly affect the aesthetics of the building. Therefore, the current society is increasingly pursuing the antibacterial and anti-yellowing properties of structural adhesives. Currently, the antibacterial structural adhesives on the market mostly use silver ions or organic antibacterial agents, which have problems such as easy precipitation and poor durability. If materials such as nanosilver are used, the appearance and mechanical properties of the structure will be greatly affected due to problems such as easy oxidation and easy agglomeration of the materials. Therefore, there is an urgent need to develop an innovative structural adhesive material that has antibacterial, anti-yellowing and mechanical enhancement functions.

[0003] To address these issues, the present invention proposes a composite structural adhesive based on a multi-level nanofiller structure. Its core innovation lies in preparing 8-12 nm ZnO QDs via a sol-gel method and loading them into the "nanocavity" structure of TiO2NTs. The surface layer is then double-modified to introduce silica and a silane coupling agent structure layer. This design offers multiple advantages: 1) The quantum size effect of ZnO QDs imparts high antibacterial properties, enabling destruction of microbial cell membranes; 2) The hollow structure of TiO2NTs not only increases the loading capacity of ZnO QDs, but also synergistically enhances the antibacterial effect through their inherent photocatalytic activity; 3) The secondary SiO2 coating effectively inhibits the photocatalytic oxidation of ZnO QDs, preventing yellowing caused by degradation of the colloidal substrate; and 4) Surface modification of the filler with a silane coupling agent significantly improves its interfacial compatibility with organic colloids. This multi-level structural design not only addresses the problem of nanoparticle agglomeration but also achieves the integrated antibacterial, anti-yellowing, and enhancement functions through the synergistic composition of the components.

[0004] When these functional fillers are combined with a structural adhesive matrix, the resulting material exhibits exceptional overall performance, making it particularly suitable for use in medical facilities, food processing plants, marine engineering, and other locations with stringent requirements for hygiene and durability. This technology not only provides new insights for upgrading the performance of structural adhesives but also offers a reference for the multifunctional design of other polymer materials, promising broad market prospects and socioeconomic benefits. Summary of the Invention

[0005] The purpose of the present invention is to provide an antibacterial-non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler and a preparation method thereof in order to address the problem that traditional structural adhesives do not have antibacterial ability.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] The specific preparation steps of the antibacterial and non-yellowing composite structural adhesive based on the novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler are as follows:

[0008] 1) Preparation of 8-12nm ZnO QDs by combining sol-gel process;

[0009] 2) ZnO QDs and hollow TiO2NTs were co-dispersed in ethanol, and filtered sequentially through ultrasound and a 0.22 μm water filter membrane to increase the loading of quantum dots in the nanotubes. After completion, the filler was calcined once;

[0010] 3) immersing the quantum dot-loaded nanotubes in ethyl orthosilicate to form a SiO2 coating layer on their surface by a sol-gel method, followed by secondary calcination to obtain TiO2NTs / ZnO QDs / SiO2 functional filler;

[0011] 4) The functional filler prepared above is modified with a silane coupling agent and then uniformly mixed into the structural adhesive pre-solution to obtain the desired composite structural adhesive material.

[0012] In the above technical scheme, further, the preparation process of ZnO QDs in the step 1) is: using a zinc acetate / ethanol solution with a concentration of 0.75-1.1wt% as a precursor, vigorously stirring at a rate of 800-1250r / min in a 0-4°C ice water bath and a nitrogen protection atmosphere, slowly adding a sodium hydroxide / ethanol solution with a concentration of 0.25-0.7wt% as a precipitant, and introducing 0.45-1.1wt% oleylamine or 0.25-0.65wt% CTAB as a surfactant, maintaining the solution pH at 10-12, stirring for 60-145min to form a sol, and then heating the solution temperature to 60-80°C for aging treatment for 100-140min to promote gelation, and finally collecting the precipitate by centrifugation at 10000-12000rpm, and washing with ethanol or acetone 3-5 times to obtain ZnO QDs with a particle size of 8-12nm, which are dispersed in n-hexane and stored.

[0013] Furthermore, the process parameters for ultrasonic dispersion in step 2) are as follows: preparing an anhydrous ethanol solution with a concentration of 0.05–0.1 wt% of ZnO QDs and a concentration of 0.5–1.0 wt% of TiO2NTs (pore size 80-100 nm), and ultrasonically treating the solution for 30–75 min using an ultrasonic instrument with a power of 200–300 W. The process parameters for 0.22 μm aqueous filter membrane-assisted filtration are as follows: vacuum filtration is assisted by a 0.22 μm aqueous filter membrane, utilizing the membrane adsorption effect to enhance the loading of ZnO QDs within the TiO2NTs tube, and the precipitate is collected by centrifugation at 10,000–12,000 rpm and dried at 60–80°C for 80–140 min. The process parameters of the primary calcination treatment are: under a nitrogen or argon protective atmosphere, raise the temperature in the calcination furnace to 300-400°C at a heating rate of 2-4°C / min, calcine for 100-160 minutes, cool to room temperature with the furnace, and stand for 2-4 hours.

[0014] Furthermore, the sol-gel process parameters for preparing the silica layer in step 3) are as follows: immersing TiO2NTs adsorbed with ZnO QDs at a concentration of 0.1-0.5wt% in an ethanol solution containing 5-10wt% tetraethyl orthosilicate (TEOS), adding 0.1-0.5wt% ammonia water to adjust the pH of the solution to 8-9, slowly stirring at 25-35°C for 2-4h to hydrolyze and polycondense the TEOS to form a uniform SiO2 sol layer on the surface of the TiO2NTs, then centrifugally washing with anhydrous ethanol three times to remove unreacted materials, and vacuum drying at 60°C for 6h to solidify the sol layer. The secondary calcination treatment process parameters are as follows: under a nitrogen or argon protective atmosphere, raising the temperature in the calcination furnace to 400-600°C at a heating rate of 1-2°C / min, calcining for 120-180min, cooling to room temperature with the furnace, and standing for 2-4h.

[0015] Furthermore, the silane coupling agent modification process parameters in step 4) are as follows: immersing a ZnO QDs / TiO2NTs@SiO2 filler with a concentration of 0.5-1.0wt% in an ethanol aqueous solution containing 2-5wt% of a silane coupling agent, adjusting the pH to 4-5 with acetic acid, and stirring at 60-70°C for 4-6h to hydrolyze the silane and graft it to the SiO2 surface; wherein the silane coupling agent is one of KH-550 and KH-570, and the volume ratio of ethanol to water is 8:2 to 9:1.

[0016] Furthermore, the process step of uniformly mixing the mixture into the structural adhesive in step 4) is as follows: adding 1-2 kg of structural adhesive resin, 1-2 kg of toughening agent, 150-300 g of curing agent, 100-200 g of curing accelerator, 50-100 g of molecular sieve, 10-20 g of adhesion promoter, 50-100 g of thixotropic agent, 10-20 g of dispersant, and 50-100 g of silane coupling agent-modified ZnOQDs / TiO2NTs@SiO2 functional filler into a planetary mixer. After lowering the dispersion disk of the planetary mixer, two-stage stirring is started: the first stage stirring revolution speed is 200-300 rpm, the dispersion speed is 10-20 rpm, and the stirring time is 15-30 min; the second stage stirring revolution speed is 200-300 rpm, the dispersion speed is 10-20 rpm, and the vacuum stirring time is 120-180 min. The structural adhesive resin is one of E51 bisphenol A epoxy resin, E44 bisphenol A epoxy resin, E54 bisphenol A epoxy resin, and 170 bisphenol F epoxy resin; the toughening agent is one of MX-154, EZ-120, and LSE-103-30; the curing agent is one of 100S, PN23J, and PN25J; the curing accelerator is one of UR300, UR500, and UR700; the molecular sieve is 3A (potassium A type), 4A (sodium A type), 5A (calcium A type), 10Z (calcium Z type); the adhesion promoter is one of BYK-4511, TTOPP-38, and KH-570; the thixotropic agent is one of Cabot-5M, Cabot-TS-720, and R202; the dispersant is one of BYK-9076, BYK-111, and Disperbyk; the stirring temperature must be maintained below 60°C at all times and can be cooled by condensed water if necessary.

[0017] An antibacterial and non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler is obtained by using any of the above-mentioned preparation methods.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1) The present invention uses zinc acetate, TiO2NTs, CTAB, TEOS, silane coupling agent and the like as raw materials, and simultaneously adopts a combination of gel-sol process, ultrasonic loading, filtration-assisted loading, multiple calcinations, hydrothermal method, coupling reaction and nanocomposite process to prepare an antibacterial-non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler and a preparation method thereof. The above raw material selection and process combination are original to the present invention.

[0020] 2) The functional nanofiller in the present invention has a multi-level composite structure: from the inside to the outside, there are four-level structures of ZnO QDs, TiO2NTs, SiO2 and silane coupling agent layers. Among them, ZnO QDs are the main bactericidal components and are located inside the nanotubes. The coating of ZnO QDs by TiO2NTs can, on the one hand, prolong the release cycle of zinc ions and achieve long-term antibacterial effects, and on the other hand, prevent the agglomeration of quantum dots. Secondly, it can also prevent the quantum dots from entering the human body and causing harm to the human body. At the same time, after TiO2NTs wrap ZnO QDs, it can avoid the generation of reactive oxygen species (ROS) by ZnO QDs after illumination, which causes the structural adhesive matrix to turn yellow, and can also enhance the mechanical properties of the structural adhesive through nanocomposites. The presence of the third SiO2 layer can seal the through holes at both ends of the TiO2NTs, achieving the purpose of Zn 2+ The physical buffering of the release rate also prevents direct contact between the internal ZnO QDs and the substrate, thereby avoiding yellowing and discoloration of the structural adhesive matrix; it can also be used to prevent the agglomeration of TiO2NTs. The construction of the outermost silane coupling agent layer is to enhance the compatibility between the functional nanofillers and the structural adhesive matrix, making them more evenly dispersed in the structural adhesive matrix, and avoiding the degradation of the mechanical properties of the structural adhesive due to poor compatibility between the fillers and the matrix.

[0021] 3) The functional nanofiller in the present invention is prepared by using a combination of processes such as gel-sol process, ultrasonic loading, filtration-assisted loading, multiple calcinations, hydrothermal method, and coupling reaction. First, the gel-sol process is used to realize the synthesis of ZnOQDs, and its particle size is successfully controlled to be maintained at 8-12nm, so that it has high antibacterial activity; secondly, ultrasonic loading, filtration-assisted loading, and a single calcination process are used to realize the efficient loading and stable loading of ZnO QDs in TiO2NTs hollow nanotubes; then, the hydrothermal method and the secondary calcination process are used to realize the controllable construction of the third SiO2 layer on the filler surface, realizing the perfect encapsulation of TiO2NTs and ensuring the stable bonding between SiO2 and TiO2NTs; finally, the coupling reaction is used to realize the silane coupling agent modification of the nanofiller surface, thereby improving the compatibility between the filler and the structural adhesive matrix. The functional nanofiller designed in this invention features a complex and novel structure, powerful functionality, and stability. It avoids typical issues associated with traditional fillers, such as uneven dispersion, unstable / permanent antibacterial properties, discoloration of the structural adhesive matrix, and poor compatibility between the filler and the structural adhesive. These advantages stem from the filler's structure, which is achieved through the organic synergy between the aforementioned combined processes. While the aforementioned single processes may have been reported in certain fields, the present invention achieves a synergistic and innovative application of existing processes, demonstrating significant innovation.

[0022] 4) In order to improve the loading efficiency of ZnO QDs in the TiO2 NTs hollow nanotubes in the application, an ultrasonic loading and filtration assisted loading double combination process is designed. Firstly, the particle size of ZnO QDs is controlled to be 8-12 nm, and the pore size of TiO2 NTs is 80-100 nm, so that the quantum dots can be loaded in the nanotubes; secondly, the ultrasonic loading makes the ZnO QDs enter the nanotube cavity through ultrasonic disturbance, preventing the quantum dots from blocking the tube opening; finally, the filtration assisted loading is combined to force the ZnO QDs to be embedded in the TiO2 NTs by pressure driving. In this process, the nanotubes act as "molecular sieves", and the quantum dots are trapped in the tube cavity or the tube wall pores, while the solvent and small molecular impurities are discharged through a 0.22 μm water filtration membrane. The process is simple and convenient, and can make the loading rate increase by more than 20-30%. At the same time, the filtration process can also help to remove the solvent remaining in the nanotubes due to capillary effect. The above technology is designed according to the actual needs of the preparation of nanofiller.

[0023] 5) In the application, the functional nanofiller is developed ingeniously to solve the application problems of easy mold and easy bacteria growth of structural adhesive in ultrasonic environment, and is compounded in the structural adhesive to give the structural adhesive long-acting antibacterial, non-yellowing, high strength and high weather resistance, etc. The above-mentioned functional nanofiller can be applied to various structural adhesives, and has broad-spectrum use. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Preparation process schematic diagram of antibacterial-non-yellowing composite structural adhesive based on new type of titanium dioxide nanotube encapsulated zinc oxide quantum dot filler;

[0025] Figure 2 Zinc oxide quantum dot TEM diagram of one embodiment of the application;

[0026] Figure 3 Antibacterial-non-yellowing composite structural adhesive based on new type of titanium dioxide nanotube encapsulated zinc oxide quantum dot filler. DETAILED DESCRIPTION

[0027] The application will be further described below with reference to specific examples.

[0028] Comparative Example 1:

[0029] 1) Add 2kg E51 bisphenol A epoxy resin, 1.5kg MX-154 toughening agent, 150g 100S curing agent, 150g UR500 curing accelerator, 80g 3A (potassium A type) molecular sieve, 12g BYK-4511 adhesion promoter, 75g Cabot-5M thixotropic agent, and 13g BYK-9076 dispersant to a planetary mixer. Lower the planetary mixer's dispersing disc and start a two-stage mixing cycle: first, at an orbital speed of 200 rpm and a dispersion speed of 10 rpm for 30 minutes; second, at an orbital speed of 300 rpm and a dispersion speed of 20 rpm, stirring under vacuum for 150 minutes. Maintain the stirring temperature below 60°C at all times. Cool with condensed water if necessary.

[0030] 2) The tensile bonding strength of the structural adhesive prepared in this comparative example is 56 MPa, and it has almost no antibacterial ability against mold. The yellowing aging test (the sample is irradiated with a filtered xenon arc lamp in a controlled environment, and its spectrum is adjusted to be similar to surface sunlight through a daylight filter, and the irradiance is stably controlled at 0.65 W / m 2 @340nm, the blackboard temperature was maintained at 70°C, the air temperature in the box was set to 40°C, and the relative humidity was controlled at 65%; the test adopted a cyclic mode, with each cycle lasting 120 minutes, including 102 minutes of light exposure and 18 minutes of water spraying) The color difference value was 8.9 after 1000 hours, and after the structural adhesive was placed in normal bathroom conditions for actual use testing, it was found that mildew spots occurred within 1 month.

[0031] Example 1:

[0032] 1) A 0.8wt% zinc acetate / ethanol solution was used as a precursor and stirred vigorously at a rate of 1000r / min in a 4°C ice-water bath and nitrogen atmosphere. A 0.4wt% sodium hydroxide / ethanol solution was slowly added dropwise as a precipitant, and 0.5wt% CTAB was introduced as a surfactant. The pH of the solution was maintained at 10–12. After stirring for 100min, a sol was formed. The solution temperature was then raised to 70°C and aged for 120min to promote gelation. Finally, the precipitate was collected by centrifugation at 12000rpm and washed five times with acetone to obtain ZnO QDs with a particle size of 8-10nm, which were dispersed in n-hexane for storage.

[0033] 2) Prepare an anhydrous ethanol solution of 0.075wt% ZnO QDs and 0.8wt% TiO2NTs (pore size 80-100nm), and use a 250W ultrasonic instrument to ultrasonicate the solution for 30 minutes. Use a 0.22μm water filter membrane to assist vacuum filtration, and use the membrane adsorption effect to enhance the load of ZnO QDs in the TiO2NTs tube. Collect the precipitate by centrifugation at 11000rpm, and dry the precipitate at 60°C for 100min. Transfer the dried precipitate to a calcining furnace, and under an argon protective atmosphere, raise the temperature in the calcining furnace to 400°C at a heating rate of 2°C / min, calcining for 120min, cooling to room temperature with the furnace, and standing for 2h to complete a calcination treatment.

[0034] 3) TiO2NTs with ZnO QDs adsorbed at a concentration of 0.25 wt% were immersed in an ethanol solution containing 6 wt% TEOS. 0.4 wt% ammonia was added to adjust the solution's pH to 8-9. The solution was slowly stirred at 30°C for 2 h to hydrolyze and polycondense the TEOS, forming a uniform SiO2 sol layer on the TiO2NTs' surface. The unreacted products were then centrifuged and washed three times with anhydrous ethanol. The sol layer was then solidified by vacuum drying at 60°C for 6 h. The product was transferred to a calcining furnace and, under an argon atmosphere, the temperature was increased to 600°C at a rate of 2°C / min. The product was calcined for 150 min, cooled to room temperature, and allowed to stand for 2 h, completing the secondary calcination process.

[0035] 4) A 0.7 wt% ZnO QDs / TiO2NTs@SiO2 filler was immersed in a 4 wt% KH-550 silane coupling agent ethanol aqueous solution (the volume ratio of ethanol to water was 8:2). The pH was adjusted to 4-5 with acetic acid. The mixture was stirred at 60°C for 4 h to hydrolyze the silane and graft it to the SiO2 surface. The desired filler was obtained after washing and drying.

[0036] 5) Add 2kg E51 bisphenol A epoxy resin, 1.5kg MX-154 toughening agent, 150g 100S curing agent, 150g UR500 curing accelerator, 80g 3A (potassium A type) molecular sieve, 12g BYK-4511 adhesion promoter, 75g Cabot-5M thixotropic agent, 13g BYK-9076 dispersant, and 100g silane coupling agent-modified ZnO QDs / TiO2NTs@SiO2 functional filler to a planetary mixer. Lower the planetary mixer's dispersing disc and start a two-stage mixing cycle: the first stage is at an orbital speed of 200 rpm, a dispersion speed of 10 rpm, and a mixing time of 30 minutes; the second stage is at an orbital speed of 300 rpm, a dispersion speed of 20 rpm, and vacuum stirring for 150 minutes. The stirring temperature must be maintained below 60°C at all times. Cool with condensed water if necessary.

[0037] 6) The tensile bonding strength of the structural adhesive prepared in this embodiment is 67 MPa, the antibacterial rate against mold is greater than 99%, the color difference value after 1000 hours of yellowing aging test is 1.2, and after the structural adhesive is placed in a normal bathroom under actual use test, it is found that basically no mold spots and yellowing phenomena occur within one year.

[0038] Example 2:

[0039] 1) A 0.8wt% zinc acetate / ethanol solution was used as a precursor and stirred vigorously at a rate of 1000r / min in a 4°C ice-water bath and nitrogen atmosphere. A 0.4wt% sodium hydroxide / ethanol solution was slowly added dropwise as a precipitant, and 0.5wt% CTAB was introduced as a surfactant. The pH of the solution was maintained at 10–12. After stirring for 100min, a sol was formed. The solution temperature was then raised to 70°C and aged for 120min to promote gelation. Finally, the precipitate was collected by centrifugation at 12000rpm and washed five times with acetone to obtain ZnO QDs with a particle size of 8-10nm, which were dispersed in n-hexane for storage.

[0040] 2) Prepare an anhydrous ethanol solution of 0.075wt% ZnO QDs and 0.8wt% TiO2NTs (pore size 80-100nm), and use a 250W ultrasonic instrument to ultrasonicate the solution for 30 minutes. Use a 0.22μm water filter membrane to assist vacuum filtration, and use the membrane adsorption effect to enhance the load of ZnO QDs in the TiO2NTs tube. Collect the precipitate by centrifugation at 11000rpm, and dry the precipitate at 60°C for 100min. Transfer the dried precipitate to a calcining furnace, and under an argon protective atmosphere, raise the temperature in the calcining furnace to 400°C at a heating rate of 2°C / min, calcining for 120min, cooling to room temperature with the furnace, and standing for 2h to complete a calcination treatment.

[0041] 3) TiO2NTs with ZnO QDs adsorbed at a concentration of 0.25 wt% were immersed in an ethanol solution containing 6 wt% TEOS. 0.4 wt% ammonia was added to adjust the solution's pH to 8-9. The solution was slowly stirred at 30°C for 2 h to hydrolyze and polycondense the TEOS, forming a uniform SiO2 sol layer on the TiO2NTs' surface. The unreacted products were then centrifuged and washed three times with anhydrous ethanol. The sol layer was then solidified by vacuum drying at 60°C for 6 h. The product was transferred to a calcining furnace and, under an argon atmosphere, the temperature was increased to 600°C at a rate of 2°C / min. The product was calcined for 150 min, cooled to room temperature, and allowed to stand for 2 h, completing the secondary calcination process.

[0042] 4) The ZnO QDs / TiO2NTs@SiO2filler with a concentration of 0.7wt% was immersed in an aqueous solution of 4wt% KH-550 silane coupling agent in ethanol (volume ratio of ethanol to water is 8:2), and the pH was adjusted to 4-5 with acetic acid. The solution was stirred at 60°C for 4h to hydrolyze and graft the silane onto the surface of SiO2. After washing and drying, the desired filler was obtained.

[0043] 5) In a planetary mixer, 2kg of E51 bisphenol A epoxy resin, 1.5kg of MX-154 toughening agent, 150g of 100S curing agent, 150g of UR500 curing accelerator, 80g of 3A (potassium A type) molecular sieve, 12g of BYK-4511 adhesion promoter, 75g of Cabot-5M thixotropic agent, 13g of BYK-9076 dispersant, and 50g of silane coupling agent modified ZnO QDs / TiO2NTs@SiO2 functional filler were added. After the dispersing disc of the planetary mixer was lowered, two-stage stirring was started: the first stage was stirring at a revolution speed of 200rpm and a dispersion speed of 10rpm for 30min; the second stage was stirring at a revolution speed of 300rpm and a dispersion speed of 20rpm for 150min under vacuum, and the stirring temperature was maintained below 60°C. If necessary, cooling water was used to lower the temperature.

[0044] 6) Compared to Example 1, the amount of silane coupling agent modified ZnO QDs / TiO2NTs@SiO2 functional filler was reduced in this example. The structural adhesive prepared had a tensile bonding strength of 62MPa, an antibacterial rate against mold of greater than 90%, a color difference value of 2.5 after 1000 hours of yellowing resistance aging test, and no mold and yellowing phenomena occurred within one year after real use test under normal bathroom conditions.

[0045] Example 3:

[0046] 1) A zinc acetate / ethanol solution with a concentration of 0.8wt% was used as a precursor, and a sodium hydroxide / ethanol solution with a concentration of 0.4wt% was added dropwise as a precipitant under the protection of nitrogen atmosphere and an ice water bath at 4°C with vigorous stirring at a speed of 1000r / min. A 0.5wt% CTAB was introduced as a surfactant, and the pH of the solution was maintained at 10-12. After stirring for 100min, a sol was formed, and the solution was heated to 70°C for aging treatment for 120min to promote gelation. Finally, the precipitate was collected by centrifugation at 12000rpm and washed with acetone for 5 times to obtain ZnO QDs with a particle size of 8-10nm, which were stored in n-hexane.

[0047] 2) Prepare an anhydrous ethanol solution of 0.075wt% ZnO QDs and 0.8wt% TiO2NTs (pore size 80-100nm), and use a 250W ultrasonic instrument to ultrasonicate the solution for 30 minutes. Use a 0.22μm water filter membrane to assist vacuum filtration, and use the membrane adsorption effect to enhance the load of ZnO QDs in the TiO2NTs tube. Collect the precipitate by centrifugation at 11000rpm, and dry the precipitate at 60°C for 100min. Transfer the dried precipitate to a calcining furnace, and under an argon protective atmosphere, raise the temperature in the calcining furnace to 400°C at a heating rate of 2°C / min, calcining for 120min, cooling to room temperature with the furnace, and standing for 2h to complete a calcination treatment.

[0048] 3) TiO2NTs with ZnO QDs adsorbed at a concentration of 0.25 wt% were immersed in an ethanol solution containing 6 wt% TEOS. 0.4 wt% ammonia was added to adjust the solution's pH to 8-9. The solution was slowly stirred at 30°C for 2 h to hydrolyze and polycondense the TEOS, forming a uniform SiO2 sol layer on the TiO2NTs' surface. The unreacted products were then centrifuged and washed three times with anhydrous ethanol. The sol layer was then solidified by vacuum drying at 60°C for 6 h. The product was transferred to a calcining furnace and, under an argon atmosphere, the temperature was increased to 600°C at a rate of 2°C / min. The product was calcined for 150 min, cooled to room temperature, and allowed to stand for 2 h, completing the secondary calcination process.

[0049] 4) Add 2kg E51 bisphenol A epoxy resin, 1.5kg MX-154 toughening agent, 150g 100S curing agent, 150g UR500 curing accelerator, 80g 3A (potassium A type) molecular sieve, 12g BYK-4511 adhesion promoter, 75g Cabot-5M thixotropic agent, 13g BYK-9076 dispersant, and 100g ZnO QDs / TiO2NTs@SiO2 functional filler to a planetary mixer. Place the dispersing disc in place and start a two-stage mixing process: the first stage is at an orbital speed of 200 rpm, a dispersion speed of 10 rpm, and a mixing time of 30 minutes; the second stage is at an orbital speed of 300 rpm, a dispersion speed of 20 rpm, and vacuum stirring for 150 minutes. The stirring temperature must be maintained below 60°C at all times. Cool with condensed water if necessary.

[0050] 5) Compared with Example 1, the ZnO QDs / TiO2NTs@SiO2 functional filler was not modified with a silane coupling agent in this embodiment. The tensile bonding strength of the prepared structural adhesive was 43 MPa, the antibacterial rate against mold was greater than 90%, the color difference value after 1000 hours of yellowing aging test was 2.7, and after the structural adhesive was subjected to actual use testing under normal bathroom conditions, it was found that basically no mold spots or yellowing occurred within one year.

Claims

1. A method for preparing an antibacterial and non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler, characterized by: 1) Preparation of ZnO QDs by sol-gel process; 2) ZnO QDs and hollow titanium dioxide nanotubes (TiO2 NTs) were co-dispersed in ethanol, and the mixture was filtered through ultrasound and a 0.22 μm water filter membrane to increase the loading of quantum dots in the nanotubes. The mixture was then calcined to obtain quantum dot-loaded nanotubes. 3) immersing the nanotubes loaded with quantum dots in ethyl orthosilicate to form a silicon dioxide (SiO2) coating layer on their surface by a sol-gel method, and then performing secondary calcination to obtain ZnO QDs / TiO2 NTs@SiO2 functional filler; 4) The functional filler is modified with a silane coupling agent and then uniformly mixed with a structural adhesive pre-solution to obtain an antibacterial and non-yellowing composite structural adhesive material with titanium dioxide nanotubes encapsulating zinc oxide quantum dots as filler.

2. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotubes encapsulating zinc oxide quantum dots as claimed in claim 1, characterized in that: The preparation process of ZnO QDs in step 1) is: A zinc acetate / ethanol solution with a concentration of 0.75-1.1wt% is used as a precursor, stirred in an ice-water bath and a nitrogen protection atmosphere, a sodium hydroxide / ethanol solution with a concentration of 0.25-0.7wt% is added dropwise as a precipitant, and a surfactant is introduced. The pH of the solution is maintained at 10-12. After stirring, a sol is formed, and the solution temperature is then raised to 60-80°C for aging treatment to promote gelation. Finally, the precipitate is collected by centrifugation and washed several times with ethanol or acetone to obtain ZnOQDs with a particle size of 8-12nm.

3. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotubes encapsulating zinc oxide quantum dots as claimed in claim 1, characterized in that: The process parameters of ultrasonic dispersion in step 2) are: An anhydrous ethanol solution containing ZnO QDs and TiO2 NTs is prepared and the solution is ultrasonically treated; the concentration of the ZnO QDs is 0.05-0.1 wt%; the concentration of the TiO2 NTs is 0.5-1.0 wt% and the pore size is 80-100 nm; The process parameters of 0.22μm water filter membrane assisted filtration are: The loading of ZnO QDs in the TiO2NTs tube was enhanced by vacuum filtration assisted by a 0.22 μm water filter membrane using the membrane adsorption effect, and the precipitate was collected by centrifugation and dried.

4. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler according to claim 1, characterized in that: In step 3), the nanotubes loaded with quantum dots are immersed in ethyl orthosilicate to form a silicon dioxide SiO2 coating layer on their surface by a sol-gel method. The parameters are: TiO2 NTs adsorbed with ZnO QDs at a concentration of 0.1-0.5wt% were immersed in an ethanol solution containing 5-10wt% tetraethyl orthosilicate (TEOS). 0.1-0.5wt% ammonia water was added to adjust the pH of the solution to 8-9. The solution was stirred at 25-35°C for 2-4h to hydrolyze and condense the TEOS to form a uniform SiO2 sol layer on the surface of the TiO2 NTs. The unreacted products were then removed by centrifugation and the sol layer was solidified by vacuum drying.

5. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler according to claim 1, characterized in that: The silane coupling agent modification process parameters in step 4) are: The ZnO QDs / TiO2 NTs@SiO2 filler with a concentration of 0.5-1.0 wt% was immersed in an ethanol aqueous solution containing 2-5 wt% of a silane coupling agent. The pH was adjusted to 4-5 with acetic acid, and the mixture was stirred at 60-70°C to hydrolyze the silane and graft it onto the SiO2 surface. The silane coupling agent is one of KH-550 and KH-570, and the volume ratio of ethanol to water is 8:2 to 9:

1.

6. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler according to claim 1, characterized in that: The process steps for uniformly mixing the pre-solution of the structural adhesive in step 4) are as follows: Structural adhesive resin, toughening agent, curing agent, curing accelerator, molecular sieve, adhesion promoter, thixotropic agent, dispersant and silane coupling agent-modified ZnO QDs / TiO2 NTs@SiO2 functional filler were added into a planetary mixer; After lowering the dispersing disk of the planetary mixer, start two-stage stirring: the first stage stirring revolution speed is 200-300rpm, the dispersing speed is 10-20rpm, and the stirring time is 15-30min; the second stage stirring revolution speed is 200-300rpm, the dispersing speed is 10-20rpm, and the vacuum stirring time is 120-180min; The stirring temperature was maintained below 60°C.

7. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler according to claim 6, characterized in that: The structural adhesive resin is selected from one of E51 bisphenol A epoxy resin, E44 bisphenol A epoxy resin, E54 bisphenol A epoxy resin, and 170 bisphenol F epoxy resin; The toughening agent is selected from one of MX-154, EZ-120, and LSE-103-30; The curing agent is selected from one of 100S, PN23J, and PN25J; The curing accelerator is selected from one of UR300, UR500 and UR700; The molecular screening uses one of 3A (potassium A type), 4A (sodium A type), 5A (calcium A type), and 10Z (calcium Z type); The adhesion promoter is selected from one of BYK-4511, TTOPP-38, and KH-570; The thixotropic agent is selected from one of Cabot-5M, Cabot-TS-720, and R202; The dispersant is selected from one of BYK-9076, BYK-111 and Disperbyk.

8. The method for preparing the novel antibacterial and non-yellowing composite structural adhesive based on titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler according to claim 1, characterized in that: The process parameters of the primary calcination treatment are as follows: the dried precipitate is placed in a calcination furnace, and under a nitrogen or argon protective atmosphere, the temperature in the calcination furnace is raised to 300-400°C at a heating rate of 2-4°C / min, calcined for 100-160 minutes, cooled to room temperature with the furnace, and allowed to stand for 2-4 hours; The process parameters of the secondary calcination treatment are as follows: transfer the product to a calcination furnace, raise the temperature in the calcination furnace to 400-600°C at a heating rate of 1-2°C / min under a nitrogen or argon protective atmosphere, calcine for 120-180 minutes, cool to room temperature with the furnace, and stand for 2-4 hours.

9. An antibacterial and non-yellowing composite structural adhesive based on a novel titanium dioxide nanotube-encapsulated zinc oxide quantum dot filler, characterized in that: The method is described in any one of claims 1 to 8.

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