COFs (covalent organic frameworks) waterborne polyurethane composite material as well as preparation method and application thereof

Abstract

The invention discloses a COFs waterborne polyurethane composite material and a preparation method and application thereof.According to the composite material, water serves as a main dispersion medium, the content of volatile organic compounds (VOC) of the composite material meets the European Union REACH regulations and the GB / T 27630 standard, and the composite material has excellent mechanical properties and corrosion resistance, can be applied to scenes with strict requirements for health, environmental protection and high performance and has good application prospects. Such as automotive upholstery, functional protective coatings, water-based adhesives, environment-friendly elastomer products and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular, to a COFs waterborne polyurethane composite material, its preparation method, and its application. Background Technology

[0002] Polyurethane (PU) materials are widely used in coatings, adhesives, foams, and elastomers due to their excellent comprehensive properties. Traditional solvent-based polyurethanes release large amounts of volatile organic compounds (VOCs) during use, posing a threat to the environment and human health. Waterborne polyurethane (WPU), using water as the primary dispersion medium, significantly reduces VOC content at the source, meeting increasingly stringent environmental regulations such as the EU REACH regulation and China's GB / T 27630 "Guidelines for Air Quality Assessment in Passenger Cars." Therefore, it has broad application prospects in automotive interiors, furniture, and leather finishing, effectively reducing in-vehicle air pollution and meeting consumers' demands for a healthy driving environment.

[0003] However, traditional waterborne polyurethane coatings still lag behind solvent-based polyurethanes in terms of mechanical strength, water resistance, and corrosion resistance, limiting their application in high-performance applications. To improve the performance of waterborne polyurethanes, researchers have explored various modification methods, among which the introduction of nanofillers is an effective approach.

[0004] Covalent organic frameworks (COFs) are a class of porous crystalline polymers formed by covalently linking organic structural units. COFs possess regular pore structures, high specific surface areas, low densities, and excellent chemical and thermal stability, showing great potential in fields such as gas adsorption and separation, catalysis, sensing, and energy storage. In recent years, incorporating COFs as functional fillers into polymer matrices to prepare high-performance composite materials has become a research hotspot.

[0005] Patent application CN116875199A discloses a low-odor, ultra-pure moisture-curing PUR composition for automotive interiors and its preparation method. It also mentions using an organic framework containing reactive groups (such as COF materials) to bond with isocyanate into the polyurethane chain to lock in small molecule volatiles and solve the high-temperature odor problem of PUR adhesives. However, this patent application mainly targets moisture-curing polyurethane hot melt adhesives (PUR), and its system and curing mechanism differ significantly from the waterborne polyurethane system of this invention. Furthermore, its primary purpose is to reduce odor and lock in VOCs, without delving into the systematic improvement of the mechanical and corrosion-resistant properties of WPU through various COF materials.

[0006] Although existing research and patents have demonstrated the application potential of COFs in polyurethane materials, there is still a lack of a systematic solution for preparing various COFs with different structures through a solvothermal method and applying them to waterborne polyurethane systems to achieve extremely low VOC emissions while significantly improving the overall performance of materials (especially mechanical strength and corrosion resistance), especially in applications such as automotive interiors where there are strict requirements for health, environmental protection and high performance. Summary of the Invention

[0007] The purpose of this invention is to provide a COFs waterborne polyurethane composite material, its preparation method and application, in order to solve the technical problems of difficulty in simultaneously achieving low VOC emissions and improving the overall performance of the material.

[0008] To achieve the above objectives, this invention provides a COFs-based waterborne polyurethane composite material, which is obtained by uniformly dispersing covalent organic framework materials (COFs) in a waterborne polyurethane (WPU) matrix. The COFs are selected from any one or more of TP-PDA, TB-PDA, TB-OH, and TB-COOH. TP-PDA is prepared from 1,3,5-tricarboxymethylresorcinol and p-phenylenediamine; TB-PDA is prepared from 1,3,5-tricarboxyphenyl and p-phenylenediamine; TB-OH is prepared from 1,3,5-tricarboxyphenyl and 2,5-diaminophenol; and TB-COOH is prepared from 1,3,5-tricarboxyphenyl and 2,5-diaminobenzoic acid.

[0009] As one of the preferred technical solutions, the mass fraction of COFs in the WPU matrix is ​​0.1-10%, more preferably 1-5%, and even more preferably 4%.

[0010] As one of the preferred technical solutions, COFs are prepared by a solvothermal method.

[0011] This invention also provides a method for preparing the aforementioned COFs waterborne polyurethane composite material, the specific steps of which are as follows: (1) COFs were prepared by selecting organic monomers using a solvothermal method; (2) Add at least one COFs to waterborne polyurethane WPU and disperse it evenly to obtain a COFs-WPU composite emulsion; (3) Coating or molding the COFs-WPU composite emulsion, drying and curing it, yields the final product.

[0012] As one of the preferred technical solutions, the specific method of step (1) is as follows: first, the organic structural monomer is dissolved in a mixed solution of 1,4-dioxane and mesitylene, then an aqueous solution of acetic acid is added, ultrasonic treatment is performed, the mixture is transferred to an ampoule, liquid nitrogen is used for quick freezing, freezing-vacuuming-thawing cycle is performed, the ampoule is sealed, heated, cooled to room temperature, centrifuged to collect the precipitate, washed, and vacuum dried.

[0013] As a further preferred technical solution, the organic structural monomer includes an amino-containing monomer and an aldehyde-containing monomer, wherein the ratio of the amino-containing monomer, the aldehyde-containing monomer, 1,4-dioxane, mesitylene, and the aqueous acetic acid solution is 0.45 mmol: 0.3 mmol: 1.5 mL: 1.5 mL: 0.5 mL, and the aqueous acetic acid solution has a concentration of 3 mol / L.

[0014] As a further preferred technical solution, the organic structural monomers are 1,3,5-tricarboxymethylresorcinol and p-phenylenediamine, with a molar ratio of 1:1.5; The organic monomers are 1,3,5-tricarboxymethylbenzene and p-phenylenediamine, with a molar ratio of 1:1.5. The organic monomers are 1,3,5-tricarboxyphenyl and 2,5-diaminophenol, with a molar ratio of 1:1.5. The organic monomers are 1,3,5-tricarboxyphenyl and 2,5-diaminobenzoic acid, with a molar ratio of 1:1.5.

[0015] As one of the further preferred technical solutions, the ultrasonic treatment time is 10 minutes.

[0016] As one of the further preferred technical solutions, the heating conditions are: heating at 120℃ for 72 hours.

[0017] As one of the further preferred technical solutions, the vacuum drying conditions are: vacuum drying at 80℃ for 12 hours.

[0018] As one of the preferred technical solutions, in step (1), the organic structural monomers are 1,3,5-tricarboxymethylresorcinol and p-phenylenediamine, and the COFs prepared are TP-PDA; The organic monomers are 1,3,5-tricarboxymethylbenzene and p-phenylenediamine, and the resulting COFs are TB-PDA; The organic monomers are 1,3,5-tricarboxyphenyl and 2,5-diaminophenol, and the prepared COFs are TB-OH; The organic monomers are 1,3,5-tricarboxyphenyl and 2,5-diaminobenzoic acid, and the prepared COFs are TB-COOH.

[0019] As one of the preferred technical solutions, in step (2), the method of uniform dispersion is as follows: pre-disperse at high speed of 1000 rpm for 30 minutes, and then perform ultrasonic treatment by an ultrasonic cell disruptor. The ultrasonic treatment conditions are: power 400W, working time 5 seconds, intermittent time 5 seconds, and total ultrasonic time 30 minutes.

[0020] As one of the preferred technical solutions, in step (3), the coating and molding method is: uniformly scrape the composite emulsion onto the surface of the substrate; correspondingly, the drying and curing conditions are: drying at room temperature for 24 hours, or drying at 50°C for 24 hours.

[0021] As a further preferred technical solution, the substrate is a Q235 steel sheet, which is pretreated before coating. The specific methods are: sanding, degreasing with acetone, washing with deionized water, and drying.

[0022] As one of the preferred technical solutions, in step (3), the molding method is: pour the composite emulsion into the mold and level it into a film at room temperature; correspondingly, the drying and curing conditions are: let it stand and dry for 24 hours, and then dry it at 50°C for 24 hours.

[0023] The present invention also provides the application of the aforementioned COFs waterborne polyurethane composite material in automotive interior parts, functional protective coatings, waterborne adhesives or environmentally friendly elastomer products.

[0024] The present invention has the following beneficial effects: This invention provides a COFs waterborne polyurethane composite material, its preparation method, and its application. The composite material uses water as the main dispersion medium, and its volatile organic compound (VOC) content complies with the EU REACH regulation and GB / T 27630 standard. Furthermore, it has excellent mechanical properties and corrosion resistance, and can be applied in scenarios with strict requirements for health, environmental protection, and high performance, such as automotive interior parts, functional protective coatings, waterborne adhesives, and environmentally friendly elastomer products.

[0025] This invention prepares a variety of COFs with different structures by a solvothermal method, and then uniformly disperses at least one COF in waterborne polyurethane (WPU) to achieve extremely low volatile organic compound (VOC) emissions while significantly improving the overall performance of the material, especially the mechanical strength and corrosion resistance.

[0026] Taking TP-PDA (synthesized from 1,3,5-tricarboxymethylresorcinol and p-phenylenediamine) as an example, it has a unique flower-like morphology. When added as a nanofiller to WPU, the water absorption rate of the composite coating significantly decreased from 26.7% to 12.1%. When the mass fraction of TP-PDA is 4%, the compressive strength of the composite film can reach 26.8 MPa. After immersing a 2% TP-PDA / WPU composite coating in 0.1 MKOH solution for 3 days, the low-frequency impedance value can reach 5.6 × 10⁻⁶. 8 Ω·cm 2 The performance is an order of magnitude higher than that of pure WPU coatings, exhibiting superior mechanical and corrosion resistance. This invention provides an effective method for preparing high-performance, environmentally friendly waterborne polyurethane composite materials, with promising applications in fields such as automotive interiors.

[0027] The specific advantages of this invention are as follows: 1. Environmentally friendly with extremely low VOC content: The composite material of this invention uses water as the dispersion medium, which fundamentally reduces the use of organic solvents. The VOC content is extremely low, which complies with EU REACH regulations, GB / T 27630 and other environmental protection standards. It helps to reduce air pollution in enclosed spaces such as vehicles and meets consumers' demand for a healthy driving environment.

[0028] 2. Significantly Improved Mechanical Properties: The mechanical properties of the WPU matrix are effectively enhanced by introducing COF nanofillers with specific structures and morphologies. For example, when the mass fraction of Tp-PDA is 4%, the compressive strength of the composite film can reach 26.8 MPa, which is much higher than that of pure WPU.

[0029] 3. Excellent corrosion resistance: The addition of COF nanofillers improves the density of the coating and hinders the penetration of corrosive media. For example, after immersing a 4% TP-PDA / WPU composite coating in 0.1 M KOH for 3 days, its low-frequency impedance value is an order of magnitude higher than that of the pure WPU coating, reaching 5.6 × 10⁻⁶. 8 Ω·cm 2 It exhibits excellent corrosion resistance.

[0030] 4. Diversity and Controllability of Preparation Methods: This invention prepares a variety of different COFs materials using a solvothermal method, providing greater flexibility and possibilities for controlling the properties of composite materials according to different application requirements. The solvothermal method itself is also a mature and controllable COFs preparation technology.

[0031] 5. Broad application prospects: Given its environmentally friendly characteristics and excellent comprehensive performance, the composite material of this invention is particularly suitable for fields with high requirements for both environmental protection and performance, such as automotive interiors, functional protective coatings, and water-based adhesives.

[0032] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Here is the chemical structure diagram of COF nanomaterials; Figure 2 SEM images of four COF nanomaterials; Figure 3 Infrared spectra of four COF nanomaterials; Figure 4 This is an impedance diagram of a composite material; the diameter of the semicircle reflects the AC frequency impedance, and the larger the semicircle, the greater the impedance and the better the corrosion resistance. Figure 5 The diagram shows the compressive strength and low-frequency impedance of the composite material. Detailed Implementation

[0034] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0035] Raw materials and experimental equipment required for this invention: Waterborne polyurethane (WPU) emulsion: purchased from Wanhua Chemical. COF monomer solvents and other reagents: such as mesitylene, 1,4-dioxane, acetic acid, tetrahydrofuran, etc., were all of analytical grade.

[0036] Instruments and equipment: ultrasonic cleaner, high-speed disperser, vacuum drying oven, scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), electronic universal testing machine, electrochemical workstation.

[0037] Example 1 TP-PDA / WPU composite material Preparation of TP-PDA COFs 63 mg (0.3 mmol) of TP and 48 mg (0.45 mmol) of PDA were dissolved in a mixed solution containing 1.5 mL of 1,4-dioxane and 1.5 mL of mesitylene, followed by the addition of 0.5 mL of a 3 mol / L aqueous acetic acid solution. The mixture was sonicated for 10 minutes and then transferred to 10 mL ampoules. The ampoules were quenched with liquid nitrogen, and after three freeze-vacuum-thaw cycles, the ampoules were sealed with a flame torch. The sealed ampoules were then heated in an oven at 120 °C for 72 hours. After the reaction mixture cooled to room temperature, the red precipitate was collected by centrifugation and washed three times with tetrahydrofuran. The collected red precipitate was dried under vacuum at 80 °C for 12 hours to obtain a dark red powder, named TP-PDA. The reaction formula is shown below. Figure 1 .

[0038] The powder's crystalline structure and chemical bonding were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM images of the product are shown below. Figure 2 Infrared spectrum Figure 3 .

[0039] Preparation method of TP-PDA / WPU composite material (1) Preparation of composite emulsion: Weigh TP-PDA powder and make its final mass fraction in WPU emulsion (solid content about 30-40%) 5%. Slowly add TP-PDA powder to WPU emulsion and pre-disperse it for 30 minutes under high-speed stirring (e.g., 1000 rpm). Then, use an ultrasonic cell disruptor to sonicate it (e.g., power 400W, working for 5 seconds, intermittent for 5 seconds, total time 30 minutes) to obtain a uniform and stable TP-PDA / WPU composite emulsion.

[0040] Composite film / coating preparation: (2) Film preparation: The above composite emulsion was poured into a polytetrafluoroethylene mold, leveled at room temperature to form a film, dried for 24 hours, and then dried in a 50°C oven for 24 hours until constant weight was obtained to obtain a composite film with a thickness of about 0.5 mm.

[0041] Coating preparation: The Q235 steel sheet was sanded, degreased with acetone, washed with deionized water, and dried. The composite emulsion was evenly coated onto the treated Q235 steel sheet, controlling the wet film thickness. After drying at room temperature for 24 hours, it was then dried in a 50℃ oven for 4 hours. The dry film thickness was controlled at (80±5) μm.

[0042] Example 2 TB-PDA / WPU composite material (1) Preparation of TB-PDA COFs The preparation of TB-PDA COFs was achieved by a solvothermal method.

[0043] Consistent with the method in Example 1, 48.6 mg of 1,3,5-tricarboxyphenyl (TB) and 48 mg of 1,4-phenylenediamine (PDA) were dissolved in a mixed solution containing 1.5 mL of 1,4-dioxane and 1.5 mL of mesitylene, followed by the addition of 0.5 mL of a 3 mol / L aqueous acetic acid solution. The mixture was sonicated for 10 minutes and then transferred to 10 mL ampoules. The ampoules were quenched with liquid nitrogen, and after three freeze-vacuum-thaw cycles, the ampoules were sealed with a flame gun. The sealed ampoules were then heated in an oven at 120°C for 72 hours. After the reaction mixture cooled to room temperature, the red precipitate was collected by centrifugation and washed three times with tetrahydrofuran. The collected red precipitate was then vacuum-dried at 80°C for 12 hours to obtain a dark brown TB-PDA powder.

[0044] See product SEM image Figure 2 Infrared spectrum Figure 3 .

[0045] Example 3 Preparation and testing of OH / WPU composite materials 48.6 mg of 1,3,5-tricarboxyphenyl (TB) and 55.2 mg of 2,5-diaminophenol (OH) were dissolved in a mixed solution containing 1.5 mL of 1,4-dioxane and 1.5 mL of mesitylene, followed by the addition of 0.5 mL of a 3 mol / L aqueous acetic acid solution. The mixture was sonicated for 10 minutes and then transferred to 10 mL ampoules. The ampoules were quenched with liquid nitrogen, and after three freeze-vacuum-thaw cycles, the ampoules were sealed with a flame gun. The sealed ampoules were then heated in an oven at 120 °C for 72 hours. After the reaction mixture cooled to room temperature, the red precipitate was collected by centrifugation and washed three times with tetrahydrofuran. The collected red precipitate was dried under vacuum at 80 °C for 12 hours to obtain a brownish-red powder, TB-OH.

[0046] See product SEM image Figure 2 Infrared spectrum Figure 3 .

[0047] Example 4 Preparation and Testing of COOH / WPU Composite Materials 48.6 mg of 1,3,5-tricarboxymethylbenzene (TB) and 67.8 mg of 2,5-diaminobenzoic acid (COOH) were dissolved in a mixed solution containing 1.5 mL of 1,4-dioxane and 1.5 mL of mesitylene, followed by the addition of 0.5 mL of a 3 mol / L aqueous acetic acid solution. The mixture was sonicated for 10 minutes and then transferred to 10 mL ampoules. The ampoules were quenched with liquid nitrogen, and after three freeze-vacuum-thaw cycles, the ampoules were sealed with a flame gun. The sealed ampoules were then heated in an oven at 120 °C for 72 hours. After the reaction mixture cooled to room temperature, the red precipitate was collected by centrifugation and washed three times with tetrahydrofuran. The collected red precipitate was dried under vacuum at 80 °C for 12 hours to obtain a brownish-yellow powder, TB-COOH.

[0048] See product SEM image Figure 2 Infrared spectrum Figure 3 .

[0049] Comparative Example 1 A method for preparing a pure WPU coating (1) Ultrasonic treatment was performed using a cell disruptor (power 400W, working time 5 seconds, intermittent time 5 seconds, total time 30 minutes) to obtain a uniform and stable WPU emulsion.

[0050] (2) Preparation of composite films / coatings: Film preparation: The above composite emulsion was poured into a polytetrafluoroethylene mold, leveled at room temperature to form a film, allowed to stand and dry for 24 hours, and then placed in a 50°C oven to dry for 24 hours until constant weight, to obtain a film with a thickness of about 0.5 mm.

[0051] Coating preparation: The Q235 steel sheet was sanded, degreased with acetone, washed with deionized water, and dried. The emulsion was evenly coated onto the treated Q235 steel sheet, controlling the wet film thickness. After drying at room temperature for 24 hours, it was then dried in a 50℃ oven for 4 hours. The dry film thickness was controlled at (80±5) μm.

[0052] The performance of the composite materials obtained in Examples 1-4 and the comparative examples was tested respectively.

[0053] 1. Mechanical property testing: The compressive strength and elongation at break of the composite film were tested using an electronic universal testing machine according to GB / T 1040-2006 standard, with a tensile rate of 50 mm / min. The results are shown below. Figure 5 Yellow area.

[0054] 2. Low-frequency impedance test: The composite emulsion from step (1) was dispersed evenly, and 5 μL was measured and applied to a surface with a cross-sectional area of ​​0.2475 cm². 2On a glassy carbon electrode (coating thickness approximately 200 μm), at room temperature in 0.1 M KOH electrolyte. Using an electrochemical three-electrode system, under open-circuit voltage, and via a Chenhua CHI660 electrochemical workstation, the test frequency was 0.01-10. 6 The EIS electrochemical impedance value at Hz. Results are shown in [reference needed]. Figure 4 and Figure 5 Medium green bar chart.

[0055] 3. Corrosion Resistance Test: Following GB / T 1771-2007, electrochemical impedance spectroscopy (EIS) was performed on the glassy carbon electrode coated with the composite coating using an electrochemical workstation (coating thickness 200 μm). The test was conducted in 0.1 M KOH solution for 3 days (corrosion resistance durability). The test frequency range was 10... 6 Hz to 10 -2 The AC disturbance signal amplitude is 10 mV at Hz. Performance test results are attached. Figure 5 The green section shows no significant decrease in resistance during the durability test; refer to the impedance information obtained in step 2.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A COFs waterborne polyurethane composite material, characterized in that, It is obtained by uniformly dispersing covalent organic framework materials (COFs) in an aqueous polyurethane (WPU) matrix. The COFs are selected from any one or more of TP-PDA, TB-PDA, TB-OH, and TB-COOH. TP-PDA is prepared from 1,3,5-tricarboxymethylresorcinol and p-phenylenediamine. TB-PDA is prepared from 1,3,5-tricarboxyphenyl and p-phenylenediamine. TB-OH is prepared from 1,3,5-tricarboxyphenyl and 2,5-diaminophenol. TB-COOH is prepared from 1,3,5-tricarboxyphenyl and 2,5-diaminobenzoic acid.

2. The COFs waterborne polyurethane composite material according to claim 1, characterized in that, The mass fraction of COFs in the WPU matrix is ​​0.1% to 10%.

3. The COFs waterborne polyurethane composite material according to claim 1, characterized in that, COFs were prepared by a solvothermal method.

4. A method for preparing a COFs waterborne polyurethane composite material according to any one of claims 1 to 3, characterized in that, The specific steps are as follows: (1) COFs were prepared by selecting organic monomers using a solvothermal method; (2) Add at least one COFs to waterborne polyurethane WPU and disperse it evenly to obtain a COFs-WPU composite emulsion; (3) Coating or molding the COFs-WPU composite emulsion, drying and curing it, yields the final product.

5. The preparation method according to claim 4, characterized in that, The specific method of step (1) is as follows: First, dissolve the organic monomer in a mixed solution of 1,4-dioxane and mesitylene, then add an aqueous solution of acetic acid, sonicate, transfer to an ampoule, freeze with liquid nitrogen, cycle through freezing-vacuuming-thawing, seal the ampoule, heat, cool to room temperature, centrifuge to collect the precipitate, wash, and vacuum dry.

6. The preparation method according to claim 4, characterized in that, In step (1), the organic structural monomers are 1,3,5-tricarboxymethylresorcinol and p-phenylenediamine, and the COFs prepared are TP-PDA; The organic monomers are 1,3,5-tricarboxymethylbenzene and p-phenylenediamine, and the resulting COFs are TB-PDA; The organic monomers are 1,3,5-tricarboxyphenyl and 2,5-diaminophenol, and the prepared COFs are TB-OH; The organic monomers are 1,3,5-tricarboxyphenyl and 2,5-diaminobenzoic acid, and the prepared COFs are TB-COOH.

7. The application of a COFs waterborne polyurethane composite material according to any one of claims 1 to 3 in automotive interior parts, functional protective coatings, waterborne adhesives or environmentally friendly elastomer products.

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