Catalyst for sunlight degradation of polyurethane adhesive as well as preparation method and application of catalyst

Abstract

The invention claims to protect a catalyst for degrading a polyurethane adhesive by sunlight, a preparation method and application, and belongs to novel functional and structural materials. In the preparation process of the catalyst, firstly, C3N4 is subjected to protonation treatment, then MXene nanosheets are subjected to partial oxidation treatment, and then the protonated C3N4 and CNT composite partially oxidized MXene powder are coupled through mechanical mixing and electrostatic interaction, so that agglomeration of the catalyst can be effectively avoided, compounding of photo-induced electrons is prevented, and the photocatalytic reaction activity is improved. The novel catalyst has a surface-to-surface contact heterostructure, the catalytic performance is optimized, the T-type peel strength of the aluminum-plastic composite film is successfully reduced to 2N / 15mm or below, and a polyurethane adhesive in the composite film can be degraded at room temperature under sunlight illumination, so that the recycling of the waste composite film is easier to realize; the method has the characteristics of high efficiency, energy conservation and environmental protection.

Description

Technical Field

[0001] The invention relates to a catalyst for sunlight-degradable polyurethane adhesive, a preparation method and application thereof, and belongs to the technical field of novel functional and structural materials. Background Art

[0002] Aluminum-plastic composite packaging is widely used in high-demand fields such as food and medicine due to its excellent barrier properties and is irreplaceable. However, it is difficult to recycle efficiently after it is discarded, which not only wastes high-value resources but also causes serious environmental pollution, forming a significant contradiction between resources and the environment. In fact, this type of waste contains extremely high resource value: plastic components (such as polyethylene, polypropylene, and polyethylene terephthalate) account for more than 12% of global petroleum-based plastic consumption, and metal aluminum accounts for more than 20% (second only to steel). Data shows that recycling 1 ton of waste plastic can save 2.3 tons of crude oil and reduce 3.14 tons of The green recycling and high-value reuse of aluminum-plastic composite packaging are of great significance to the control of plastic pollution and the development of a low-carbon circular economy.

[0003] Currently, the main separation and recycling methods for discarded aluminum-plastic composite packaging include chemical solvent separation, high-temperature cracking separation, and physical-mechanical separation, but all have significant drawbacks. Chemical solvent separation requires large amounts of solvent and faces challenges such as high cost, difficulty in solvent recovery, deterioration of plastic properties, and secondary pollution. High-temperature cracking separation equipment requires large investment and requires high exhaust gas treatment, which limits its engineering application. Physical-mechanical separation suffers from incomplete separation of aluminum and plastic and low added value of recycled materials. These methods all suffer from poor economic efficiency, incomplete separation, and secondary pollution, and are unable to effectively address the recycling and utilization of discarded aluminum-plastic composite packaging. Developing recycling technologies and theoretical systems that facilitate separation, and developing high-performance, high-value-added products, are key directions to overcome current limitations.

[0004] The research team discovered that using sunlight to degrade polyurethane adhesives in aluminum-plastic composites can reduce the T-peel strength to below 2N / 15mm, making the aluminum and plastics easier to separate and recycle. The key to using sunlight to degrade polyurethane adhesives lies in the preparation of efficient catalysts. Currently, the catalysts reported for degrading polyurethane adhesives in composite films are primarily carbon nitride (C3N4) and its modifications. Research has shown that combining C3N4 with MXene catalysts is an effective way to improve their photocatalytic efficiency. However, MXene sheets are prone to self-stacking, which results in the loss of a large number of reactive sites and reduced ion transport channels.

[0005] In view of the above reasons, how to improve the reaction activity of photocatalysts, degrade polyurethane adhesives under sunlight, facilitate the recycling and reuse of flexible packaging composite films, and achieve room temperature separation of aluminum-plastic packaging is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] To address the deficiencies in the prior art, the present invention aims to provide a catalyst for preparing an efficient and environmentally friendly solar-degradable polyurethane adhesive using carbon nanotubes, MXene nanosheets, and nano-C3N4 powder as raw materials, and to disclose its preparation method and application to achieve room-temperature separation of aluminum-plastic packaging under sunlight.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] The present invention first discloses a method for preparing a catalyst for sunlight-degradable polyurethane adhesive, comprising the following steps:

[0009] S1. Preparation of protonated nano-C3N4 powder:

[0010] Nano-C3N4 powder is added to a strongly acidic aqueous solution, ultrasonically treated, and then stirred to protonate it; then, the protonated C3N4 is centrifugally washed with deionized water until it is neutral to remove the strong acid in the solution; finally, protonated nano-C3N4 powder is obtained by freeze-drying. Protonation can enhance its electrostatic interaction with other components and avoid agglomeration.

[0011] S2. Preparation of CNT composite partially oxidized MXene powder:

[0012] First, CNT powder is dispersed in a deoxycholate aqueous solution to obtain a uniformly dispersed CNT dispersion;

[0013] Then, the MXene nanosheets were placed in a tube furnace, heated to 200-300°C, kept warm for 1-3 hours, and cooled to room temperature to obtain partially oxidized MXene, which was added to the above-mentioned CNT dispersion;

[0014] Then, the mixture was ultrasonically stirred and freeze-dried to obtain CNT-composite partially oxidized MXene powder.

[0015] S3. Preparation of target catalyst:

[0016] The protonated nano-C3N4 powder obtained in the above step S1 is dispersed in deionized water, and the CNT composite partially oxidized MXene powder obtained in the above step S2 is added. After magnetic stirring, the CNT composite partially oxidized MXene coupled C3N4 catalyst is obtained by freeze drying, which is the target catalyst.

[0017] Preferably, the aforementioned MXene nanosheets are Ti3C2Tx-MXene or Ti2CTx-MXene.

[0018] MXene (Ti3C2Tx-MXene or Ti2CTx-MXene) is chemically unstable and gradually oxidizes to TiO2 when exposed to air, losing its co-catalyst function. However, the metal oxides formed by MXene oxidation can form heterojunctions with other semiconductors, further facilitating photocatalytic reactions.

[0019] The present invention first partially oxidizes MXene at 200-300 °C to obtain Ti3C2T x The MXene@TiO2 composite material not only maintains the original layered structure of the MXene but also creates a Schottky junction. Therefore, the partially oxidized MXene in this invention not only retains the excellent conductivity of MXene, making it suitable as a catalyst support, but also has surface functional groups that provide active sites. Partial oxidation of the MXene surface forms an oxide film, which passivates the edges and surface of the MXene to a certain extent, preventing oxidative degradation of the MXene's internal structure and improving its stability.

[0020] During the preparation process, by partially oxidizing the MXene nanosheets and then tightly adsorbing C3N4 and CNT on the partially oxidized MXene nanosheets through mechanical mixing and electrostatic action, the agglomeration of the catalyst can be effectively avoided and its specific surface area can be increased. The MXene nanosheets act as a charge transfer interface to prevent the recombination of photogenerated electrons. At the same time, the nano-titanium dioxide (TiO2) produced by the partial oxidation of the MXene nanosheets further improves the photocatalytic reaction activity.

[0021] Preferably, the mass ratio of the aforementioned nano-C3N4 powder to the strongly acidic aqueous solution is (1-3): (10-30), the concentration of the strongly acidic aqueous solution is 0.4-0.6M, and the strong acid is one of hydrochloric acid, sulfuric acid, and nitric acid.

[0022] More preferably, the mass ratio of the CNT powder to the deoxycholate aqueous solution is 2-4:10-30, and the mass ratio of the CNT powder to the MXene nanosheets is 2-4:1.

[0023] More preferably, the aforementioned deoxycholate is selected from one of sodium taurodeoxycholate, potassium taurodeoxycholate, sodium ursodeoxycholate, potassium ursodeoxycholate, sodium chenodeoxycholate or potassium chenodeoxycholate, and the mass percentage concentration of the deoxycholate aqueous solution is 5-10%.

[0024] Further preferably, in the aforementioned step S2, the method for preparing the partially oxidized MXene nanosheets is: heating the MXene nanosheets to 20,000° C., keeping the temperature for 2 hours, and cooling to room temperature.

[0025] More preferably, in the aforementioned step S3, 1 to 3 parts by mass of the protonated nano-C3N4 powder obtained in step S1 is dispersed in deionized water, and the CNT composite partially oxidized MXene powder obtained in step S2 is added at a mass ratio of nano-C3N4 powder to MXene nanosheets of 100:1 to 3.

[0026] The present invention also claims a catalyst for sunlight-degradable polyurethane adhesive prepared according to the above method.

[0027] The present invention further claims protection for the use of a catalyst for sunlight-degradable polyurethane adhesive as described above in degrading a composite film polyurethane adhesive to achieve aluminum-plastic separation and recovery. The specific method is as follows: the catalyst is added to the polyurethane adhesive, mixed evenly, and then coated on a PET plastic film, dried, hot-pressed and laminated with aluminum foil, and aged at 40-60°C for 36-72 hours to obtain a PET / Al composite film; the PET / Al composite film is exposed to sunlight for 60 days, and its T-peel strength is tested.

[0028] Preferably, in the aforementioned application, the mass ratio of the catalyst to the polyurethane adhesive is 1-3:30-90.

[0029] The present invention is beneficial in that:

[0030] (1) The present invention uses carbon nanotubes (CNTs), MXene nanosheets, and nanocarbon nitride (C3N4) powder as raw materials to prepare a catalyst for the degradation of polyurethane adhesives by sunlight. CNTs are one-dimensional tubular structures with high conductivity and a high aspect ratio. They are tightly compounded on two-dimensional MXene nanosheets, which can inhibit MXene self-stacking, increase active sites, and help form a conductive network structure. Furthermore, CNTs are compounded with partially oxidized MXene nanosheets and coupled to bulk C3N4. The tight interface connection is conducive to the rapid transfer of electrons, improving the ability to transport photogenerated electrons and reducing the photogenerated electron-hole recombination rate. At the same time, nano-titanium dioxide (TiO2) produced by the partial oxidation of MXene nanosheets improves the photocatalytic reaction activity, thereby synergistically improving the photocatalytic effect.

[0031] (2) The preparation method of the present invention is easy to implement and is efficient and environmentally friendly. By protonating C3N4 and then partially oxidizing the MXene nanosheets, the protonated C3N4 and the CNT composite partially oxidized MXene powder are coupled through mechanical mixing and electrostatic action. This can effectively avoid the agglomeration of the catalyst, increase its specific surface area, and have a relatively large pore volume and pore size. Example 1 is the best, with a specific surface area of ​​92.82 m² / g and a pore volume of 0.58 cm³ / g, providing sufficient active sites for the catalytic degradation reaction.

[0032] (3) The catalyst with a novel composite structure prepared by the present invention solves the problem of reduced charge transfer efficiency caused by point-to-point contact and point-to-surface contact of traditional catalysts. Its surface-to-surface contact heterogeneous structure optimizes the catalytic performance, greatly expands the absorption and utilization rate of sunlight, and has excellent outdoor implementation possibilities for photocatalysis. It can degrade the polyurethane adhesive in the composite film under sunlight, reducing the T-peel strength of the PET / Al composite film to below 2N / 15mm (the lowest in Examples 1-3 is 1.63N / 15mm), and can be easily peeled off at room temperature, making the discarded composite film easy to recycle and realize high-value utilization. It has the characteristics of high efficiency, energy saving, and environmental protection, and is of great significance to the control of plastic pollution and the promotion of "carbon neutrality". BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is Ti3C2T in Example 1 of the present invention x -Comparison of infrared spectra of MXene nanosheets before and after partial oxidation;

[0034] Figure 2 This is the infrared spectrum of the catalyst prepared in Example 1 of the present invention;

[0035] Figure 3 This is the infrared spectrum of the catalyst prepared in Comparative Example 1 of the present invention;

[0036] Figure 4 is Ti3C2T in Example 1 of the present invention x -XRD comparison of MXene nanosheets before and after partial oxidation;

[0037] Figure 5 is the XRD pattern of the catalyst prepared in Example 1 of the present invention;

[0038] Figure 6 is the XRD pattern of the catalyst prepared in Comparative Example 1 of the present invention;

[0039] Figure 7 is the XRD pattern of the catalyst prepared in Comparative Example 3 of the present invention;

[0040] Figure 8 is a scanning electron microscope image of the catalyst prepared in Example 1 of the present invention;

[0041] Figure 9 is a scanning electron microscope image of the catalyst prepared in Comparative Example 1 of the present invention;

[0042] Figure 10 is a scanning electron microscope image of the catalyst prepared in Comparative Example 2 of the present invention;

[0043] Figure 11is a scanning electron microscope image of the catalyst prepared in Comparative Example 3 of the present invention;

[0044] Figure 12 1 is the XPS spectrum of the O element on the surface of the aluminum film before and after catalytic degradation of the catalysts prepared in Example 1 and Comparative Example 1 of the present invention;

[0045] Figure 13 This is a T-peel strength test curve of the catalyst prepared in Example 1 of the present invention after 0 days of illumination;

[0046] Figure 14 This is a T-peel strength test curve of the catalyst prepared in Example 1 of the present invention after 60 days of illumination;

[0047] Figure 15 This is a T-peel strength test curve of the catalyst prepared in Comparative Example 1 of the present invention after 0 days of illumination;

[0048] Figure 16 This is a T-peel strength test curve of the catalyst prepared in Comparative Example 1 of the present invention after 60 days of light exposure;

[0049] Figure 17 This is a T-peel strength test curve of the catalyst prepared in Comparative Example 3 of the present invention after 0 days of illumination;

[0050] Figure 18 This is a T-peel strength test curve of the catalyst prepared in Comparative Example 3 of the present invention after 60 days of illumination. DETAILED DESCRIPTION

[0051] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Unless otherwise specified in the present invention, all raw materials used are commercially available. The preferred commercial sources are shown in Table 1 below:

[0053]

[0054] Table 1 Preferred commercial sources of various raw materials

[0055] Example 1

[0056] In this example, the target catalyst was successfully prepared: CNT composite partially oxidized MXene coupled C3N4 catalyst. The preparation process is as follows:

[0057] S1. Preparation of protonated nano-C3N4 powder:

[0058] 1 part by mass of nano-C3N4 powder was added to 10 parts by mass of a 0.4M hydrochloric acid aqueous solution, ultrasonically treated for 30 minutes, and stirred for 2 hours to protonate it; then, the protonated C3N4 was centrifugally washed with deionized water until it was neutral to remove the hydrochloric acid in the solution; finally, the protonated nano-C3N4 powder was obtained by freeze drying.

[0059] S2. Preparation of CNT composite partially oxidized MXene powder:

[0060] First, 2 parts by mass of CNT powder were dispersed in 10 parts by mass of a 5% sodium taurodeoxycholate aqueous solution to obtain a CNT dispersion; then, 1 part by mass of Ti3C2T x -MXene nanosheets were heated to 250°C, kept warm for 2 hours, and cooled to room temperature to obtain partially oxidized MXene, which was added to the above-mentioned CNT dispersion. Subsequently, ultrasonic stirring was performed and freeze-dried to obtain CNT composite partially oxidized MXene powder.

[0061] S3. Preparation of target catalyst:

[0062] 1 part by mass of the protonated nano-C3N4 powder obtained in the above step S1 was dispersed in 10 parts by mass of deionized water, and then 0.03 parts by mass of the CNT composite partially oxidized MXene powder obtained in the above step S2 was added. After magnetic stirring for 2 hours, the CNT composite partially oxidized MXene coupled C3N4 catalyst was obtained by freeze drying.

[0063] Example 2

[0064] The preparation process of this embodiment is basically similar to that of Example 1:

[0065] S1. Preparation of protonated nano-C3N4 powder:

[0066] 2 parts by mass of nano-C3N4 powder were added to 20 parts by mass of a 0.5M sulfuric acid aqueous solution, ultrasonically treated for 45 minutes, and stirred for 3 hours to protonate it; then, the protonated C3N4 was centrifugally washed with deionized water until neutral to remove hydrochloric acid in the solution; finally, the protonated nano-C3N4 powder was obtained by freeze drying.

[0067] S2. Preparation of CNT composite partially oxidized MXene powder:

[0068] First, 3 parts by mass of CNT powder were dispersed in 20 parts by mass of a 7% aqueous solution of potassium ursodeoxycholate to obtain a CNT dispersion; then, 1 part by mass of Ti3CT x-MXene nanosheets were heated to 300°C, kept warm for 1 hour, and cooled to room temperature to obtain partially oxidized MXene, which was added to the above-mentioned CNT dispersion. Subsequently, ultrasonic stirring was performed and freeze-dried to obtain CNT composite partially oxidized MXene powder.

[0069] S3. Preparation of target catalyst:

[0070] 2 parts by mass of the protonated nano-C3N4 powder obtained in the above step S1 was dispersed in 20 parts by mass of deionized water, and then 0.08 parts by mass of the CNT composite partially oxidized MXene powder obtained in the above step S2 was added. After magnetic stirring for 3 hours, the CNT composite partially oxidized MXene coupled C3N4 catalyst was obtained by freeze drying.

[0071] Example 3

[0072] The preparation process of this embodiment is basically similar to that of Example 1:

[0073] S1. Preparation of protonated nano-C3N4 powder:

[0074] 3 parts by mass of nano-C3N4 powder was added to 30 parts by mass of a 0.6M nitric acid aqueous solution, ultrasonically treated for 60 minutes, and stirred for 5 hours to protonate it; then, the protonated C3N4 was centrifugally washed with deionized water until it was neutral to remove hydrochloric acid in the solution; finally, the protonated nano-C3N4 powder was obtained by freeze drying.

[0075] S2. Preparation of CNT composite partially oxidized MXene powder:

[0076] First, 4 parts by mass of CNT powder were dispersed in 30 parts by mass of a 10% aqueous solution of potassium ursodeoxycholate to obtain a CNT dispersion. Then, 1 part by mass of Ti3C2T x -MXene nanosheets were heated to 200°C, kept warm for 3 hours, and cooled to room temperature to obtain partially oxidized MXene, which was added to the above-mentioned CNT dispersion. Subsequently, ultrasonic stirring was performed and freeze-dried to obtain CNT composite partially oxidized MXene powder.

[0077] S3. Preparation of target catalyst:

[0078] 3 parts by mass of the protonated nano-C3N4 powder obtained in the above step S1 was dispersed in 30 parts by mass of deionized water, and then 0.15 parts by mass of the CNT composite partially oxidized MXene powder obtained in the above step S2 was added. After magnetic stirring for 2 to 4 hours, the CNT composite partially oxidized MXene coupled C3N4 catalyst was obtained by freeze drying.

[0079] Comparative Example 1

[0080] The catalyst prepared in this comparative example is a CNT composite partially oxidized MXene coupled with a conventional C3N4 catalyst. Compared with Example 1, the C3N4 is not protonated. The preparation process is as follows:

[0081] S1. Preparation of CNT composite partially oxidized MXene powder:

[0082] First, 2 parts by mass of CNT powder were dispersed in 10 parts by mass of a 5% sodium ursodeoxycholate aqueous solution to obtain a CNT dispersion; then, 1 part by mass of Ti3CT x -MXene nanosheets were heated to 300°C, kept warm for 1 hour, and cooled to room temperature to obtain partially oxidized MXene, which was added to the above-mentioned CNT dispersion. Subsequently, ultrasonic stirring was performed and freeze-dried to obtain CNT composite partially oxidized MXene powder.

[0083] S2. Preparation of catalyst

[0084] 1 part by mass of nano-C3N4 powder was dispersed in 10 parts by mass of deionized water, and then 0.03 parts by mass of the CNT composite partially oxidized MXene powder obtained in S1 was added. After magnetic stirring for 2 hours, the CNT composite partially oxidized MXene coupled with conventional C3N4 catalyst was obtained by freeze drying.

[0085] Comparative Example 2

[0086] The catalyst prepared in this comparative example is a partially oxidized MXene coupled with a conventional C3N4 catalyst. Compared with Example 1, no CNT was added. The preparation process is as follows:

[0087] S1. Preparation of protonated nano-C3N4 powder:

[0088] 1 part by mass of nano-C3N4 powder was added to 10 parts by mass of a 0.4M hydrochloric acid aqueous solution, ultrasonically treated for 30 minutes, and stirred for 2 hours to protonate it; then, the protonated C3N4 was centrifugally washed with deionized water to neutrality to remove the hydrochloric acid in the solution; finally, the protonated nano-C3N4 powder was obtained by freeze-drying the C3N4.

[0089] S2. Preparation of partially oxidized MXene powder:

[0090] 1 mass part of Ti3CT x -MXene nanosheets were heated to 300 °C, kept at this temperature for 1 h, and cooled to room temperature to obtain partially oxidized MXene powder.

[0091] S3. Preparation of catalyst:

[0092] 1 part by mass of the protonated nano-C3N4 powder obtained in the above step S1 was dispersed in 10 parts by mass of deionized water, and then 0.01 parts by mass of the partially oxidized MXene powder obtained in the above step S2 was added. After magnetic stirring for 2 hours, the partially oxidized MXene coupled C3N4 catalyst was obtained by freeze drying.

[0093] Comparative Example 3

[0094] The catalyst prepared in this comparative example is CNT@MXene coupled with C3N4. Compared with Example 1, the MXene powder was not partially oxidized. The preparation process is as follows:

[0095] S1. Preparation of protonated nano-C3N4 powder:

[0096] 3 parts by mass of nano-C3N4 powder was added to 30 parts by mass of a 0.6M nitric acid aqueous solution, ultrasonically treated for 60 minutes, and stirred for 5 hours to protonate it; then, the protonated C3N4 was centrifugally washed with deionized water until it was neutral to remove hydrochloric acid in the solution; finally, the protonated nano-C3N4 powder was obtained by freeze drying.

[0097] S2. Preparation of CNT@MXene powder:

[0098] First, 4 parts by mass of CNT powder were dispersed in 30 parts by mass of a 10% aqueous solution of potassium ursodeoxycholate to obtain a CNT dispersion. Then, 1 part by mass of Ti3C2T x -MXene nanosheets were added to the above CNT dispersion, followed by ultrasonic stirring and freeze-drying to obtain CNT@MXene powder.

[0099] S3. Preparation of catalyst:

[0100] 3 parts by mass of the protonated nano-C3N4 powder obtained in step S1 above were dispersed in 30 parts by mass of deionized water, and then 0.15 parts by mass of the CNT@MXene powder obtained in step S2 above were added. After magnetic stirring for 2-4 hours, the CNT@MXene coupled C3N4 catalyst was obtained by freeze drying.

[0101] Structural characterization and performance testing

[0102] (1) Infrared spectroscopy

[0103] The molecular structure of the catalyst product was characterized by infrared spectroscopy.

[0104] Figure 1 is Ti3C2T in Example 1 x -Comparison of infrared spectra of MXene nanosheets before and after partial oxidation. It can be seen from the figure that: 3420 cm -1and 1386 cm -1 The vibration peaks at 1627 cm-1 belong to the -OH bond adsorbed on the Ti atom and the free -OH bond; -1 The peak at 550 cm corresponds to the C=O bond on the surface. After partial oxidation treatment, the Fourier transform infrared spectrum can be seen at 550 cm -1 The stretching vibration peak of O-Ti-O bond in titanium dioxide was observed at x MXene is oxidized to form TiO2.

[0105] Figure 2 This is the infrared spectrum of the catalyst prepared in Example 1. It can be seen from the figure that the stretching vibration peaks of the C–N bond and the C=N bond in the aromatic CN heterocyclic compound are located at 1000 cm -1 to 1700 cm -1 , 3000-3500 cm -1 The broad peak at 808 cm represents the free amino and hydroxyl groups adsorbed on the sample surface. -1 The characteristic peak at 3 corresponds to the tri-s-triazine unit. The infrared detection results show that the partially oxidized MXene nanosheets are evenly dispersed in the CNT matrix, and the introduction of CNT composite partially oxidized MXene powder does not destroy the basic bond structure of the carbon nitride skeleton.

[0106] Figure 3 The infrared spectrum of the catalyst prepared in Comparative Example 1 is shown in the figure. As can be seen from the figure, since Comparative Example 1 does not contain amino groups, the -1 There is only a hydroxyl peak at 1000~1300 cm -1 Within this range, stretching vibrations of COC and bending vibrations of CH and CC appear, which mainly correspond to the infrared characteristic peaks of MXene.

[0107] (2) X-ray diffraction (XRD) analysis

[0108] Figure 4 is Ti3C2T in Example 1 x -Comparison of XRD patterns of MXene nanosheets before and after partial oxidation. It can be seen from the figure that: Ti3C2T x The characteristic peaks of MXene are (002) plane at 7.5° and (110) at 60.5°. x MXene not only retains the (002) characteristic peak and (110) characteristic peak, but also shows the (101) crystal plane characteristic peak of TiO2 at 25°, which is consistent with the above infrared spectrum. This shows that the method of the present invention makes Ti3C2T xThe surface of MXene is partially oxidized to form an oxide film, which passivates the edge and surface of MXene to a certain extent, thereby preventing the oxidative degradation of the internal structure of MXene and improving the stability of MXene.

[0109] Figure 5 、 Figure 6 and Figure 7 They are respectively the XRD patterns of Example 1, Comparative Example 1 and Comparative Example 3. It can be seen from the figure that: compared with Figure 6 , Figure 5 The XRD pattern of the product shows two diffraction peaks at 13.0° and 27.3°, which are attributed to the planar arrangement (100) plane of the repeating tri-s-triazine units and the stacking (002) plane of the oriented aromatic structure, respectively.

[0110] in addition, Figure 5 and Figure 6 In comparison, the (002) peak shifted from 27.3° to 27.65°, which indicates that the interlayer spacing of the crystal plane is decreasing. The reduced interlayer spacing is beneficial to charge transfer because it reduces the distance of charge transfer, which will help promote the migration of photogenerated electrons, thereby enhancing photocatalytic activity and improving its photocatalytic performance. In addition, Figure 5 Contains the characteristic peak of TiO2 (101) crystal plane at 25.12°, and Figure 6 The characteristic peak of (101) is not shown, which may overlap with the broad peak of (002); Figure 7 (Comparative Example 3) Figure 5 Compared with Ti3C2T x -The characteristic peak of the (101) crystal plane of TiO2 formed by partial oxidation of MXene nanosheets.

[0111] (3) Scanning electron microscopy (SEM)

[0112] The surface microstructure of the prepared catalyst product was characterized by SEM.

[0113] Figure 8 The SEM image of the catalyst prepared in Example 1 shows that the carbon nanotubes (CNTs) are tightly bound to the partially oxidized MXene nanosheets, and after protonation, they interact with the negatively charged Ti3C2T x -The interface connection of the nanosheets is tighter, forming surface coupling.

[0114] Figure 9 This is the SEM image of the catalyst prepared in Example 1. The nano-C3N4 in the raw material is not protonated, but it is x -MXene nanosheets also form surface coupling, but have certain pores, loose structure and obvious agglomeration.

[0115] Figure 10 This is the SEM image of the catalyst prepared in Comparative Example 2. No carbon nanotubes were added to the raw materials, and the protonated nano-C3N4 was loaded on the Ti3C2T x -MXene nanosheets, the interface bonding is not tight.

[0116] Figure 11 This is the SEM image of the catalyst prepared in Comparative Example 3. x -MXene nanosheets are partially oxidized due to the protonation of nano-C3N4 and Ti3C2T x -MXene nanosheets have low adhesion and large particle size, so the interface bonding is loose.

[0117] (4) Specific surface area test

[0118] The test results of specific surface area, pore volume and pore diameter of each embodiment of the present invention and the comparative example are shown in Table 2. It can be seen that the specific surface area of ​​the six groups of samples is not much different. However, further analysis of the pore volume and pore diameter data shows that Example 1 is the optimal embodiment, with the largest pore volume and pore diameter, reaching 0.58 cm³ g -1 and 28.01 nm, indicating that the composite of CNT and partially oxidized MXene expands the pore volume and pore size, which will provide more active sites for the photocatalytic reaction and is beneficial to improving the photocatalytic performance of the material.

[0119]

[0120] Table 2 Specific surface area, pore volume and pore diameter of each catalyst sample

[0121] (5) XPS and functional group quantitative analysis

[0122] Furthermore, X-ray photoelectron spectroscopy (XPS) was used to study the state of oxygen in the PET / Al composite film bonded with polyurethane adhesive. Figure 12 As shown, the O 1s spectrum shows that at day 0, there are two characteristic peaks at 531.9 eV and 533.6 eV, corresponding to HN-C=O (carbamate) and After 60 days of degradation, an additional peak appeared at 532.6 eV, which was assigned to the formation of C-O-C (ether) groups.

[0123] Quantitative analysis of the spectral changes in Example 1 and Comparative Example 1 is detailed in Tables 3 and 4. It shows a gradual decrease in the carbamate (HN-C=O) content, while a corresponding increase in ether (C-O-C) groups is observed. The results in Tables 3 and 4 indicate that when a PET / Al composite film bonded with a polyurethane adhesive ages under sunlight, chain scission primarily occurs at the carbamate (HN-C=O) groups, resulting in a decrease in the carbamate content and a gradual formation of ether (C-O-C) groups. When the catalyst prepared in Example 1 was applied to a polyurethane adhesive, the HN-C=O group content decreased by 82.83% after 60 days of sunlight degradation, while in Comparative Example 1, the decrease was only 17.79%. This demonstrates that the CNT composite partially oxidized MXene coupled to C3N4 catalyst prepared in this invention can effectively promote the degradation of polyurethane adhesives.

[0124]

[0125] Table 3 Quantitative analysis of functional groups in the polyester / aluminum composite film of Example 1

[0126]

[0127] Table 4 Quantitative analysis of functional groups in the polyester / aluminum composite film of Comparative Example 1

[0128] (6) T-type peel strength test

[0129] The catalyst of the present invention is applied in the following specific method: the catalyst obtained in each embodiment or comparative example is added to a polyurethane adhesive with a mass ratio of the catalyst to the polyurethane adhesive of 1-3:30-90, mixed evenly, coated on a PET plastic film, dried, hot-pressed and laminated with aluminum foil, and aged at 40-60° C. for 36-72 hours, preferably at 45° C. for 48 hours, to obtain a PET / Al composite film, which is placed in sunlight for 60 days, and the T peel strength of the PET / Al composite film before and after degradation is tested at room temperature using a universal testing machine.

[0130] in, Figure 13 This is a T-peel strength test curve of Example 1 of the present invention after 0 days of illumination. Figure 14 This is a T-peel strength test curve of Example 1 of the present invention after 60 days of illumination; Figure 15 This is a T-peel strength test curve of Comparative Example 1 of the present invention after 0 days of illumination. Figure 16 This is a T-peel strength test curve of Comparative Example 1 of the present invention after 60 days of illumination; Figure 17 This is a T-peel strength test curve of Comparative Example 3 of the present invention after 0 days of illumination. Figure 18 This is a T-peel strength test curve of Comparative Example 3 of the present invention after 60 days of illumination.

[0131] The specific test results are shown in Table 5.

[0132]

[0133] Table 5 T-peel strength of each embodiment / comparative example applied to the composite film after 0 day / 60 day illumination

[0134] As can be seen from Table 5, the T-peel strength of the composite films prepared from the catalyst products of each Example and the Comparative Example before solar photocatalytic degradation was similar. However, after 60 days of degradation, the T-peel strength of the composite films of the catalysts of Examples 1 to 3 dropped to below 2N / 15mm, and they were easily peeled at room temperature. This indicates that the catalysts prepared from each Example of the present invention accelerated the destruction of the polyurethane adhesive cross-linked network within the composite film system under sunlight, resulting in a weakening of the intermolecular forces and a significant reduction in T-peel strength. However, after 60 days of degradation, the T-peel strength of the composite films of Comparative Examples 1, 2, and 3 remained above 3N / 15mm and was not easily peeled at room temperature, indicating that the catalytic activity of the catalysts prepared in each Comparative Example was low and they were unable to effectively degrade the polyurethane adhesive in the short term.

[0135] In summary, the present invention has produced a catalyst for the degradation of polyurethane adhesives by sunlight. This novel catalyst composite structure solves the defect of reduced charge transfer efficiency caused by point-to-point contact and point-to-surface contact of catalysts in traditional technologies. Its surface-to-surface contact heterogeneous structure greatly expands the absorption and utilization rate of sunlight, has excellent outdoor photocatalytic implementation possibilities, and can degrade composite film polyurethane adhesives in a short period of time (within 60 days) under sunlight. It has the characteristics of high efficiency, energy saving, and environmental protection, and has good application prospects in sewage treatment, waste gas treatment, green recycling and other fields.

[0136] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for sunlight-degradable polyurethane adhesive, characterized in that: The steps include: S1. Preparation of protonated nano-C3N4 powder: The nano-C3N4 powder is added to a strongly acidic aqueous solution, ultrasonically treated and then stirred to protonate it, the strong acid in the solution is removed by washing, and the protonated nano-C3N4 powder is obtained by freeze-drying. S2. Preparation of CNT composite partially oxidized MXene powder: dispersing CNT powder in a deoxycholate aqueous solution to obtain a CNT dispersion; The MXene nanosheets were placed in a tube furnace, heated to 200-300°C, kept warm for 1-3 hours, and cooled to room temperature to obtain partially oxidized MXene, which was then added to the above-mentioned CNT dispersion, ultrasonically stirred, and freeze-dried to obtain CNT composite partially oxidized MXene powder; S3. Preparation of target catalyst: The protonated nano-C3N4 powder obtained in the above step S1 is dispersed in deionized water, and the CNT composite partially oxidized MXene powder obtained in the above step S2 is added. After magnetic stirring, the CNT composite partially oxidized MXene coupled C3N4 catalyst is obtained by freeze drying, which is the target catalyst.

2. The method for preparing a catalyst for sunlight-degradable polyurethane adhesive according to claim 1, characterized in that: The MXene nanosheet is Ti3C2Tx-MXene or Ti2CTx-MXene.

3. The method for preparing a catalyst for sunlight-degradable polyurethane adhesive according to claim 1, characterized in that: The mass ratio of the nano-C3N4 powder to the strong acidic aqueous solution is (1-3): (10-30), the concentration of the strong acidic aqueous solution is 0.4-0.6M, and the strong acid is one of hydrochloric acid, sulfuric acid, and nitric acid.

4. The method for preparing a catalyst for sunlight-degradable polyurethane adhesive according to claim 1, characterized in that: The mass ratio of the CNT powder to the deoxycholate aqueous solution is 2-4:10-30, and the mass ratio of the CNT powder to the MXene nanosheets is 2-4:

1.

5. The method for preparing a catalyst for sunlight-degradable polyurethane adhesive according to claim 1, characterized in that: The deoxycholate is selected from one of sodium taurodeoxycholate, potassium taurodeoxycholate, sodium ursodeoxycholate, potassium ursodeoxycholate, sodium chenodeoxycholate or potassium chenodeoxycholate, and the mass percentage concentration of the deoxycholate aqueous solution is 5% to 10%.

6. The method for preparing a catalyst for sunlight-degradable polyurethane adhesive according to claim 1, characterized in that: The method for preparing the partially oxidized MXene nanosheets in step S2 is as follows: placing the MXene nanosheets in a tube furnace, heating to 250° C., keeping the temperature for 2 hours, and cooling to room temperature to obtain the partially oxidized MXene nanosheets.

7. The method for preparing a catalyst for sunlight-degradable polyurethane adhesive according to claim 1, characterized in that: In step S3, 1-3 parts by mass of the protonated nano-C3N4 powder obtained in step S1 is dispersed in deionized water, and the CNT composite partially oxidized MXene powder obtained in step S2 is added at a mass ratio of nano-C3N4 powder to MXene nanosheets of 100:1-3.

8. A catalyst for sunlight-degradable polyurethane adhesive, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a catalyst for sunlight-degradable polyurethane adhesive according to claim 8 in degrading polyurethane adhesive of composite films to achieve aluminum-plastic separation and recovery, characterized in that: The method is as follows: the catalyst is added to a polyurethane adhesive, mixed evenly, and then coated on a PET plastic film, dried, hot-pressed with aluminum foil, and aged at 40-60°C for 36-72 hours to obtain a PET / Al composite film; the PET / Al composite film is exposed to sunlight for 60 days, and its T-peel strength is tested.

10. The use according to claim 9, characterized in that The mass ratio of the catalyst to the polyurethane adhesive is 1-3:30-90.

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