Visible light repairing type waterborne polyurethane emulsion and preparation method thereof

Abstract

The invention relates to the field of high polymer materials, and discloses a visible light repairing type waterborne polyurethane emulsion and a preparation method thereof.The preparation method comprises the following steps that polytetrahydrofuran, isophorone diisocyanate, 2, 2-dimethylolpropionic acid and butyltin dilaurate are taken and placed in a reactor, pre-polymerization chain extension is conducted at the temperature of 60-90 DEG C, and a polyurethane prepolymer is obtained; the preparation method comprises the following steps: firstly, adding ASB-PEG2000-ASB, carrying out chain extension at 40-60 DEG C, then adding butanediol and carbohydrazide, continuously carrying out chain extension, then adding glucose, carrying out crosslinking at 40-60 DEG C, finally cooling to 25-50 DEG C, adding triethylamine, carrying out stirring to form a salt, adding deionized water, carrying out stirring dispersion, and carrying out emulsification so as to prepare the visible light repairing type waterborne polyurethane emulsion. The water-based polyurethane emulsion has the advantages that the water-based polyurethane emulsion has wide absorption in the visible light wave band, the self-repairing efficiency is high, the water-based polyurethane emulsion and polytetrahydrofuran are simultaneously used as soft segments to be introduced into water-based polyurethane, and the prepared water-based polyurethane emulsion has high mechanical performance and a visible light induced self-repairing function.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a visible light repairable waterborne polyurethane emulsion and a preparation method thereof. Background Art

[0002] Waterborne polyurethane is a new type of polyurethane system that uses water instead of organic solvents as a dispersion medium. It has the advantages of being pollution-free, safe and reliable, having excellent mechanical properties, good biocompatibility, and easy to modify. In recent years, it has become an environmentally friendly material that meets high performance requirements. However, waterborne polyurethane materials will inevitably be mechanically damaged in daily use, which usually greatly affects their performance and service life. Therefore, giving waterborne polyurethane self-healing properties is an effective strategy to improve its durability and reduce its maintenance costs.

[0003] Visible light is a mild, green, and easily accessible natural resource. Self-healing materials induced by visible light are effective candidate materials for achieving green and sustainable development chemistry. Compounds containing aromatic Schiff base bonds absorb visible light, and they undergo rapid imine metathesis and exchange under visible light irradiation. In the prior art, compounds containing aromatic Schiff base bonds are usually introduced into waterborne polyurethane in the form of chain extenders, and the hydroxyl groups of the synthesized aromatic Schiff base small molecules are reacted with the isocyanate groups of the polyurethane chain segments to increase the molecular weight while introducing visible light self-healing properties. However, the synthesized aromatic Schiff base small molecules usually have a narrow absorption in the visible light band, low visible light utilization, and the self-healing properties generally cannot reach the best.

[0004] In addition, there is a certain contradiction between the fast and easy-to-achieve self-healing performance of existing self-healing polyurethane elastomers and their high mechanical strength. When weaker interactions are involved in the polymer network, it exhibits highly dynamic characteristics and can achieve faster self-healing, but at the same time it exhibits soft and viscoelastic properties and has poor mechanical properties. Summary of the invention

[0005] In order to solve the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a visible light repair type aqueous polyurethane emulsion and a preparation method thereof, and to prepare a new compound ASB-PEG containing an aromatic Schiff base bond 2000 -ASB, which has a wide absorption in the visible light band and high self-repair efficiency, and ASB-PEG 2000 -ASB and polytetrahydrofuran are simultaneously introduced as soft segments into the waterborne polyurethane structure chain, and the prepared waterborne polyurethane emulsion has both high mechanical properties and visible light induced self-healing function.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps: placing polytetrahydrofuran, isophorone diisocyanate, 2,2-dihydroxymethyl propionic acid and butyltin dilaurate in a reactor, placing the reactor at 60-90° C. for prepolymerization and chain extension for 2-4 hours, and then adding ASB-PEG 2000 -ASB is placed at 40-60°C for chain extension for 2-4h, then butanediol and carbohydrazide are added to continue chain extension for 2-3h, then glucose is added and stirred, and placed at 40-60°C for cross-linking reaction for 2-5h, and finally cooled to 25-50°C, triethylamine is added and stirred for salt formation for 1-2h, and after the reaction is completed, deionized water is added and stirred vigorously to fully disperse, and a visible light repairable waterborne polyurethane emulsion is prepared after emulsification;

[0008] The ASB-PEG 2000 The structural formula of -ASB is as follows:

[0009]

[0010] Preferably, the ASB-PEG 2000 The mass ratio of ASB to polytetrahydrofuran mixture, isophorone diisocyanate, 2,2-dihydroxymethylpropionic acid, butanediol, carbohydrazide, glucose and triethylamine is 20-27:7-9:1-1.5:0.2-0.4:0.2-0.4:0.3-0.5:1.

[0011] Preferably, the stirring rate during the reaction is 150-300 rpm, and the stirring rate during the dispersion is 1000-1500 rpm.

[0012] Preferably, the ASB-PEG 2000 The synthetic route of ASB is as follows:

[0013]

[0014] The preparation method specifically comprises the following steps:

[0015] (1) Take PEG 2000 , triethylamine was dissolved in anhydrous dichloromethane, placed in an ice water bath and stirred to mix, and under nitrogen protection, a mixed solution of p-toluenesulfonyl chloride and dichloromethane was slowly added dropwise, and the reaction was stirred for 30 to 40 minutes after the addition was completed, and then moved to room temperature and continued to stir and react for 42 to 48 hours. After the reaction was completed, the suspension was filtered, the filtrate was concentrated and precipitated in ether for multiple times, centrifuged and dried to prepare OTs-PEG 2000 -OTs;

[0016] (2) Take OTs-PEG 2000-OTs and sodium azide are dissolved in N,N-dimethylformamide, and reacted at 60-80°C for 24-48 hours in a nitrogen atmosphere. After the reaction is completed, the solvent is removed by vacuum distillation, the product is dissolved in toluene, and the unreacted sodium azide is removed by suction filtration. The filtrate is vacuum distilled to dry the solvent and then dissolved in dichloromethane, precipitated in ether for multiple times, centrifuged and dried to prepare N3-PEG 2000 -N3;

[0017] (3) dissolving propargyl bromide and anhydrous potassium carbonate in acetone, raising the temperature to 60-80° C. under nitrogen protection, slowly dropping a mixed solution of p-hydroxybenzaldehyde and toluene solution, and reacting for 24-28 hours. After the reaction is completed, removing the solvent by distillation under reduced pressure, dissolving the product with dichloromethane, washing with deionized water, drying with anhydrous sodium sulfate, concentrating, and separating and purifying with silica gel column chromatography to prepare POBA;

[0018] (4) Take N3-PEG 2000 -N3, POBA and catalyst pentamethyldiethylenetriamine were dissolved in chloroform, and after freeze degassing and dehydration and deoxygenation under nitrogen, cuprous bromide was further added under nitrogen atmosphere, and the mixture was reacted at 40-50°C for 42-48 hours. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was dissolved in tetrahydrofuran, and the copper salt was removed by alkaline alumina chromatography column. After concentration, the mixture was precipitated with ether, centrifuged and dried to prepare CHO-PEG. 2000 -CHO;

[0019] (5) Take CHO-PEG 2000 -CHO and p-aminophenol were dissolved in ethanol and refluxed at 50-85°C for 24-48 hours in a nitrogen atmosphere. After the reaction was completed, the solvent was removed by distillation under reduced pressure, the product was dissolved in dichloromethane, and precipitated in isopropanol. After centrifugation, the solid was further washed with ether to remove isopropanol and dried to prepare ASB-PEG 2000 -ASB.

[0020] Preferably, in step (1), PEG 2000 , p-toluenesulfonyl chloride and triethylamine in a molar ratio of 1:5-10:4-8.

[0021] Preferably, in step (2), OTs-PEG 2000 The molar ratio of -OTs to sodium azide is 1:5-10.

[0022] Preferably, in step (3), the molar ratio of propyne bromide, p-hydroxybenzaldehyde and anhydrous potassium carbonate is 1:1-1.5:1-1.5.

[0023] Preferably, in step (4), N3-PEG 2000The molar ratio of -N3, POBA, cuprous bromide and pentamethyldiethylenetriamine is 1:5-10:0.25-3:1-3.

[0024] Preferably, in step (5), CHO-PEG 2000 The molar ratio of -CHO to p-aminophenol is 1:5-10.

[0025] A visible light repairable waterborne polyurethane emulsion is prepared by the above-mentioned preparation method.

[0026] Beneficial effects of the present invention:

[0027] The present invention utilizes p-toluenesulfonyl chloride to convert PEG 2000 The hydroxyl groups on both sides were modified to p-toluenesulfonyl groups, and then sodium azide was used to replace the p-toluenesulfonyl groups with azide groups. Then, the aromatic aldehyde groups were introduced by the click reaction between the carbon-carbon triple bond and the azide groups. Finally, the aromatic Schiff base bond-containing compound ASB-PEG was synthesized by the Schiff base reaction between the aromatic aldehyde groups and the amino groups. 2000 -ASB, which has a wide absorption in the visible light band, and the self-healing performance is based on the imine exchange of aromatic Schiff base compounds induced by visible light between chain segments, so the utilization rate of visible light is high and the self-healing efficiency is higher. The present invention uses polytetrahydrofuran diol, 2,2-dihydroxymethyl propionic acid and isophorone diisocyanate to prepolymerize and extend the chain under the catalysis of butyltin dilaurate, and then adds the prepared ASB-PEG 2000 -ASB for chain extension, further adding butanediol and carbohydrazide to continue chain extension reaction, followed by adding glucose for cross-linking, and finally adding triethylamine for salt formation, adding deionized water for vigorous stirring, fully dispersing and emulsifying, to prepare a visible light induced self-healing waterborne polyurethane emulsion, in which ASB-PEG 2000 -ASB and polytetrahydrofuran were simultaneously introduced into the waterborne polyurethane structure chain as soft segments, which greatly improved the flexibility and mobility of the polyurethane segments and increased the exchange rate between the polyurethane segments, which was beneficial to the self-healing performance induced by imine exchange. 2000 The introduction of -ASB reduces the glass transition temperature of polyurethane, endows polyurethane with stable performance at low temperature, and at the same time enables the aqueous polyurethane emulsion prepared by the present invention to have both high mechanical properties and visible light induced self-repairing function. Each step of the reaction is safe and reliable, the conversion rate is high, and the operation is simple, thereby broadening its application field. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 ASB-PEG prepared in Example 1 of the present invention 2000 - ASB H NMR spectrum;

[0030] Figure 2 ASB-PEG prepared in Example 1 of the present invention 2000 - FT-IR spectrum of ASB;

[0031] Figure 3 ASB-PEG prepared in Example 1 of the present invention 2000 -UV-Vis spectrum of ASB;

[0032] Figure 4 The present invention verifies ASB-PEG 2000 -NMR comparison of the imine exchange process between ASB and small molecule aromatic Schiff base monomer in deuterated dimethyl sulfoxide under visible light irradiation;

[0033] Figure 5 The invention provides a preparation route for the visible light repairable waterborne polyurethane emulsion;

[0034] Figure 6 FT-IR spectrum of the visible light repairable waterborne polyurethane emulsion H-WPU2 film of the present invention;

[0035] Figure 7 The particle size distribution spectrum of the visible light repairable waterborne polyurethane emulsion prepared in the examples and comparative examples of the present invention;

[0036] Figure 8 The stress-strain curves of the films prepared from the visible light repairable waterborne polyurethane emulsions in the embodiments of the present invention and the comparative examples;

[0037] Fig. 9 The ultraviolet-visible light absorption diagram of the film prepared from the visible light repairable waterborne polyurethane emulsion in the examples and comparative examples of the present invention;

[0038] Fig.10 The thermogravimetric graphs of films prepared from visible light repairable waterborne polyurethane emulsions in the examples and comparative examples of the present invention;

[0039] Fig.11 This is a graph showing the test results of the puncture repair performance of the film prepared by the visible light repairable waterborne polyurethane emulsion in Examples 3 and 5 of the present invention and Comparative Example 2;

[0040] Fig.12 The graph is a test result of film fracture-healing performance of films prepared by visible light repairable waterborne polyurethane emulsions in the examples and comparative examples of the present invention;

[0041] Fig.13 The relationship between the repair rate and time of the H-WPU2 film in the preparation of the visible light repairable waterborne polyurethane emulsion in the embodiment of the present invention and the stress-strain curve of the film at different repair times;

[0042] Fig.14 The dynamic thermomechanical analysis diagrams of different groups of films in the preparation of visible light repairable waterborne polyurethane emulsions in Examples of the present invention and Comparative Example 2. DETAILED DESCRIPTION

[0043] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1 ASB-PEG 2000 The preparation method of ASB comprises the following steps:

[0045] (1) Take 20g PEG 2000 , 7.6 g of triethylamine was dissolved in 40 mL of anhydrous dichloromethane, placed in a 0°C ice-water bath and stirred to mix, and under nitrogen protection, a mixed solution of 16.2 g of p-toluenesulfonyl chloride dissolved in 20 mL of dichloromethane was slowly added dropwise, and the mixture was stirred for 30 minutes after the addition was completed, and then moved to room temperature and continued to stir and react for 48 hours. After the reaction was completed, the suspension was filtered, the filtrate was concentrated and precipitated in ether for 2 to 3 times, centrifuged and dried to prepare OTs-PEG 2000 -OTs;

[0046] (2) Take 10g OTs-PEG 2000 -OTs, 2.11g sodium azide were dissolved in 20mL N, N-dimethylformamide, and reacted at 80°C for 48h in a nitrogen atmosphere. After the reaction was completed, the solvent was removed by vacuum distillation, the product was dissolved in toluene, and the unreacted sodium azide was removed by suction filtration. The filtrate was vacuum distilled and the solvent was dried, then dissolved in dichloromethane, precipitated in ether 2-3 times, centrifuged and dried to prepare N3-PEG 2000 -N3;

[0047] (3) 18 g of propyne bromide and 27.16 g of anhydrous potassium carbonate were dissolved in 80 mL of acetone, and the temperature was raised to 70° C. under nitrogen protection, and a mixed solution of 18.69 g of p-hydroxybenzaldehyde dissolved in 20 mL of toluene solution was slowly added dropwise, and the reaction was continued for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was dissolved in dichloromethane, washed with deionized water, and dried with anhydrous sodium sulfate. After concentration, a mixed solvent of ethyl acetate and petroleum ether in a volume ratio of 1:1 was used as an eluent, and POBA was separated and purified by silica gel column chromatography to prepare POBA;

[0048] (4) Take 12g N3-PEG 2000 -N3, 6.9g POBA and 3.09g catalyst pentamethyldiethylenetriamine were dissolved in chloroform, and after freeze degassing and dehydration and oxygen removal under nitrogen, 1.18g cuprous bromide was further added under nitrogen atmosphere, and the mixture was reacted at 40°C for 48h. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was dissolved in tetrahydrofuran, and the copper salt was removed by alkaline alumina chromatography column. After concentration, the mixture was precipitated with ether, centrifuged and dried to prepare CHO-PEG. 2000 -CHO;

[0049] (5) Take 10g CHO-PEG 2000 -CHO, 2 g p-aminophenol were dissolved in 20 mL ethanol, and refluxed at 85 ° C for 48 h in a nitrogen atmosphere. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was dissolved in dichloromethane and precipitated in isopropanol. After centrifugation, the solid was further washed with ether to remove isopropanol and dried to prepare ASB-PEG 2000 -ASB.

[0050] See also Figure 1-4 , Figure 1 ASB-PEG of the present invention 2000 -ASB's H NMR spectrum shows that the product ASB-PEG is confirmed by the appearance of the newly generated benzene ring (δ=7.83, 7.15, 6.77 ppm) and Schiff base hydrogen (δ=8.52) peaks in the H NMR of deuterated dimethyl sulfoxide (DMSO-d6) after the reaction. 2000 -The successful synthesis of ASB.

[0051] Figure 2 ASB-PEG of the present invention 2000 - FT-IR spectrum of ASB, at 1597 cm -1 The newly appeared carbon-nitrogen double bond absorption peak at 2000 -The successful synthesis of ASB.

[0052] Figure 3 ASB-PEG of the present invention 2000 -ASB at 2.5×10 -5mol / L ethanol solution (left), 5×10 -4 The UV-visible spectrum of 1.5 mol / L ethanol solution (right) has a wide absorption band in the visible light band (characteristic absorption is 570 nm), which can utilize light energy with higher efficiency.

[0053] Figure 4 ASB-PEG is verified for the present invention 2000 - ASB and small molecule aromatic Schiff base monomers in deuterated dimethyl sulfoxide under visible light irradiation in the presence of imine exchange NMR comparison diagram. 2000 -ASB1 at δ = 8.51ppm and ASB1 at δ = 8.62ppm Schiff base hydrogen (Ⅰ and Ⅱ) are mixed and irradiated with visible light at room temperature to produce a new Schiff base compound ASB-PEG 2000 -ASB2 (Ⅲ at δ = 8.52ppm) and ASB2 (Ⅳ at δ = 8.61ppm), proving that ASB-PEG 2000 Imine exchange of -ASB with small molecule aromatic Schiff base monomers.

[0054] Embodiment 2 A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps:

[0055] 15 g of polytetrahydrofuran, 8 g of isophorone diisocyanate, 1.34 g of 2,2-dihydroxymethylpropionic acid, and 0.1 wt% of catalyst butyltin dilaurate were placed in a reactor and prepolymerized and extended at 70 ° C for 3 h, and then 6.42 g of ASB-PEG prepared in Example 1 was added. 2000 -ASB was placed at 50°C for chain extension for 2h, followed by the addition of 0.3g butanediol and 0.3g carbohydrazide for further chain extension for 2h, followed by the addition of 0.4g glucose and stirring, placed at 50°C for cross-linking reaction for 2h, and finally cooled to 30°C, and 1g triethylamine was added and stirred for 1h to form a salt. After the reaction was completed, deionized water was added and stirred vigorously to fully disperse, and the visible light repairable waterborne polyurethane emulsion H-WPU1 was prepared after emulsification.

[0056] Embodiment 3 A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps:

[0057] 10 g of polytetrahydrofuran, 8 g of isophorone diisocyanate, 1.34 g of 2,2-dihydroxymethylpropionic acid, and 0.1 wt% of catalyst butyltin dilaurate were placed in a reactor and prepolymerized and extended at 70 ° C for 3 h, and then 12.83 g of ASB-PEG prepared in Example 1 was added. 2000-ASB was placed at 50°C for chain extension for 2h, followed by the addition of 0.3g butanediol and 0.3g carbohydrazide for further chain extension for 2h, followed by the addition of 0.4g glucose and stirring, placed at 50°C for cross-linking reaction for 2h, and finally cooled to 30°C, and 1g triethylamine was added and stirred for 1h to form salt. After the reaction was completed, deionized water was added and stirred vigorously to fully disperse, and the visible light repairable waterborne polyurethane emulsion H-WPU2 was prepared after emulsification.

[0058] Embodiment 4 A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps:

[0059] 5 g of polytetrahydrofuran, 8 g of isophorone diisocyanate, 1.34 g of 2,2-dihydroxymethylpropionic acid, and 0.1 wt% of catalyst butyltin dilaurate were placed in a reactor and prepolymerized and chain extended at 70 ° C for 3 h, and then 19.25 g of ASB-PEG prepared in Example 1 was added. 2000 -ASB was placed at 50°C for chain extension for 2h, followed by the addition of 0.3g butanediol and 0.3g carbohydrazide for further chain extension for 2h, followed by the addition of 0.4g glucose and stirring, placed at 50°C for cross-linking reaction for 2h, and finally cooled to 30°C, and 1g triethylamine was added and stirred for 1h to form salt. After the reaction was completed, deionized water was added and stirred vigorously to fully disperse, and the visible light repairable waterborne polyurethane emulsion H-WPU3 was prepared after emulsification.

[0060] Embodiment 5 A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps:

[0061] 8 g of isophorone diisocyanate, 1.34 g of 2,2-dimethylol propionic acid, and 0.1 wt% of catalyst butyltin dilaurate were placed in a reactor and prepolymerized and extended at 70°C for 3 h. Then, 25.66 g of ASB-PEG prepared in Example 1 was added. 2000 -ASB was placed at 50°C for chain extension for 2h, followed by the addition of 0.3g butanediol and 0.3g carbohydrazide for further chain extension for 2h, followed by the addition of 0.4g glucose and stirring, placed at 50°C for cross-linking reaction for 2h, and finally cooled to 30°C, and 1g triethylamine was added and stirred for 1h to form a salt. After the reaction was completed, deionized water was added and stirred vigorously to fully disperse, and the visible light repairable waterborne polyurethane emulsion H-WPU4 was prepared after emulsification.

[0062] Comparative Example 1 A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps:

[0063] Take 25.66g of polytetrahydrofuran, 8g of isophorone diisocyanate, 1.34g of 2,2-dihydroxymethylpropionic acid, and 0.1wt% of catalyst butyltin dilaurate in a reactor, place it at 70°C for pre-polymerization and chain extension for 3h, then add 0.3g of butanediol to continue chain extension for 2h, then add 0.4g of glucose and stir to mix, place it at 50°C for cross-linking reaction for 2h, finally cool to 30°C, add 1g of triethylamine and stir to form salt for 1h, after the reaction is completed, add deionized water and stir vigorously to fully disperse, and prepare visible light repairable waterborne polyurethane emulsion WPU0 after emulsification.

[0064] Comparative Example 2 A method for preparing a visible light repairable waterborne polyurethane emulsion comprises the following steps:

[0065] Take 25.66g of polytetrahydrofuran, 8g of isophorone diisocyanate, 1.34g of 2,2-dihydroxymethylpropionic acid, and 0.1wt% of catalyst butyltin dilaurate in a reactor, place it at 70°C for pre-polymerization and chain extension for 3h, then add 0.3g of butanediol and 0.3g of carbohydrazide and place it at 50°C for chain extension for 2h, then add 0.4g of glucose and stir to mix, place it at 50°C for cross-linking reaction for 2h, finally cool to 30°C, add 1g of triethylamine and stir to form salt for 1h, after the reaction is completed, add deionized water and stir vigorously to fully disperse, and prepare the visible light repairable waterborne polyurethane emulsion H-WPU0 after emulsification.

[0066] See also Figure 5-12 , Figure 5 The preparation route of the visible light repairable waterborne polyurethane emulsion of the present invention is to use ASB-PEG 2000 -ASB is introduced into waterborne polyurethane as a macromolecular chain extender and also as a soft segment.

[0067] Figure 6 The FT-IR spectrum of the visible light repairable waterborne polyurethane emulsion H-WPU2 film of the present invention is shown at 2273 cm -1 The absorption peak of -NCO at 3330cm-1 has almost disappeared, proving that -NCO in polyurethane has almost completely reacted with -OH and -NH2. -1 、1240cm -1 and 1098cm -1 The urethane absorption peak proves the successful synthesis of polyurethane.

[0068] Figure 7 This is the particle size distribution spectrum of the visible light repairable aqueous polyurethane emulsion prepared in Examples 2-5 of the present invention and Comparative Examples 1-2. The narrow particle size distribution peak proves that the aqueous polyurethane emulsion is well dispersed.

[0069] Figure 8The stress-strain curves of the films prepared with the visible light repairable waterborne polyurethane emulsions in Examples 2-5 of the present invention and Comparative Examples 1-2 prove that the films prepared with the visible light repairable waterborne polyurethane emulsions in Examples 2-5 have basic mechanical properties for practical applications.

[0070] Fig. 9 The ultraviolet-visible light absorption diagram of the film prepared with the visible light-repairing waterborne polyurethane emulsion in Examples 2-5 of the present invention and Comparative Examples 1-2 proves that the film prepared with the visible light-repairing waterborne polyurethane emulsion in Examples 2-5 has absorption in the visible light band and has good transparency, and can be well applied in various daily life scenes.

[0071] Fig.10 The thermal gravimetric analysis (TGA) diagrams of the films prepared with the visible light repairable waterborne polyurethane emulsions in Examples 2-5 of the present invention and Comparative Examples 1-2 demonstrate that the films prepared with the visible light repairable waterborne polyurethane emulsions in Examples 2-5 have good thermal stability, the temperature for 5% weight loss is above 200°C, and the temperature for complete decomposition is around 430°C.

[0072] Fig.11 The puncture repair performance of the film prepared by the visible light repairable waterborne polyurethane emulsion in Comparative Example 2 and Examples 3 and 5 of the present invention was tested. A 80 μm wide blade was used to pierce a film with a thickness of about 1 mm. The film was heated at 300 mW / cm 2 The film was irradiated for 3 minutes at a distance of 20 mm under a xenon lamp (wavelength 400-800 nm), and the surface temperature of the film was observed by an infrared thermal imager, and the healing performance of the film was observed using an optical microscope. By comparing with the blank group (temperature 59.17 ° C, crack repair rate 7.5%), the photothermal effect of the aromatic Schiff base (ASB) group (temperature up to 101 ° C) and the self-healing performance of visible light-induced imine exchange were demonstrated.

[0073] Fig.12 Film fracture-healing performance test of films prepared by visible light repairable waterborne polyurethane emulsions in Examples 2-5 of the present invention and Comparative Examples 1-2. Use scissors to cut the original film sample (30×10×1 mm 3 ) was cut into two pieces, which were then tightly reconnected and exposed to a wavelength range of 400-800nm ​​at a distance of 20mm and a power of 300mW / cm 2 The samples were then exposed to a xenon light source to achieve self-repair, and then tested at a tensile rate of 20 mm / min, with each sample tested three times. Calculate the self-repair efficiency (η): η = σ t / σ0×100%, where σ t is the tensile strength after repair, σ0 is the original tensile strength, which proves that with the increase of ASB-PEG 2000-The increase of ASB monomer content leads to higher self-repair rate.

[0074] Fig.13 The relationship between the repair rate and time of the H-WPU2 group film in the preparation of the visible light repairable waterborne polyurethane emulsion in the embodiment of the present invention and the stress-strain curve of the film at different repair times proves that the self-repair efficiency increases with time and reaches a maximum value of 91.7% after 35 minutes of xenon lamp irradiation.

[0075] Fig.14 The dynamic thermomechanical analysis of different groups of films prepared by the visible light repairable aqueous polyurethane emulsion in Comparative Example 2 and Examples 2-5 of the present invention proves that when ASB-PEG 2000 -When the ASB content is half of the total soft segment, it has a lower glass transition temperature (-65°C) and more stable performance at low temperatures.

[0076] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0077] 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 present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a visible light repairable waterborne polyurethane emulsion, characterized in that: The following steps are involved: Polytetrahydrofuran, isophorone diisocyanate, 2,2-dihydroxymethyl propionic acid and butyltin dilaurate were placed in a reactor and prepolymerized and chain extended at 60-90°C for 2-4 hours, and then ASB-PEG was added. 2000 -ASB is placed at 40-60°C for chain extension for 2-4h, then butanediol and carbohydrazide are added to continue chain extension for 2-3h, then glucose is added and stirred, and placed at 40-60°C for cross-linking reaction for 2-5h, and finally cooled to 25-50°C, triethylamine is added and stirred for salt formation for 1-2h, and after the reaction is completed, deionized water is added and stirred vigorously to fully disperse, and a visible light repairable waterborne polyurethane emulsion is prepared after emulsification; The ASB-PEG 2000 The structural formula of -ASB is as follows:

2. The method for preparing the visible light repairable aqueous polyurethane emulsion according to claim 1, characterized in that: The ASB-PEG 2000 The mass ratio of ASB to polytetrahydrofuran mixture, isophorone diisocyanate, 2,2-dihydroxymethylpropionic acid, butanediol, carbohydrazide, glucose and triethylamine is 20-27:7-9:1-1.5:0.2-0.4:0.2-0.4:0.3-0.5:

1.

3. The method for preparing the visible light repairable aqueous polyurethane emulsion according to claim 1, characterized in that: The stirring rate of the cross-linking reaction at 40-60° C. for 2-5 hours is 150-300 rpm. After the reaction is completed, deionized water is added and stirred vigorously for full dispersion at a stirring rate of 1000-1500 rpm.

4. The method for preparing the visible light repairable aqueous polyurethane emulsion according to claim 1, characterized in that: The ASB-PEG 2000 The synthetic route of ASB is as follows: The preparation method specifically comprises the following steps: (1) Take PEG 2000 , triethylamine was dissolved in anhydrous dichloromethane, placed in an ice water bath and stirred to mix, and under nitrogen protection, a mixed solution of p-toluenesulfonyl chloride and dichloromethane was slowly added dropwise, and the reaction was stirred for 30 to 40 minutes after the addition was completed, and then moved to room temperature and continued to stir and react for 42 to 48 hours. After the reaction was completed, the suspension was filtered, the filtrate was concentrated and precipitated in ether for multiple times, centrifuged and dried to prepare OTs-PEG 2000 -OTs; (2) Take OTs-PEG 2000 -OTs and sodium azide are dissolved in N,N-dimethylformamide, and reacted at 60-80°C for 24-48 hours in a nitrogen atmosphere. After the reaction is completed, the solvent is removed by vacuum distillation, the product is dissolved in toluene, and the unreacted sodium azide is removed by suction filtration. The filtrate is vacuum distilled to dry the solvent and then dissolved in dichloromethane, precipitated in ether for multiple times, centrifuged and dried to prepare N3-PEG 2000 -N3; (3) dissolving propargyl bromide and anhydrous potassium carbonate in acetone, raising the temperature to 60-80° C. under nitrogen protection, slowly dropping a mixed solution of p-hydroxybenzaldehyde and toluene solution, and reacting for 24-28 hours. After the reaction is completed, removing the solvent by distillation under reduced pressure, dissolving the product with dichloromethane, washing with deionized water, drying with anhydrous sodium sulfate, concentrating, and separating and purifying with silica gel column chromatography to prepare POBA; (4) Take N3-PEG 2000 -N3, POBA and catalyst pentamethyldiethylenetriamine were dissolved in chloroform, and after freeze degassing and dehydration and deoxygenation under nitrogen, cuprous bromide was further added under nitrogen atmosphere, and the mixture was reacted at 40-50°C for 42-48 hours. After the reaction was completed, the solvent was removed by vacuum distillation, and the product was dissolved in tetrahydrofuran, and the copper salt was removed by alkaline alumina chromatography column. After concentration, the mixture was precipitated with ether, centrifuged and dried to prepare CHO-PEG. 2000 -CHO; (5) Take CHO-PEG 2000 -CHO and p-aminophenol were dissolved in ethanol and refluxed at 50-85°C for 24-48 hours in a nitrogen atmosphere. After the reaction was completed, the solvent was removed by distillation under reduced pressure, the product was dissolved in dichloromethane, and precipitated in isopropanol. After centrifugation, the solid was further washed with ether to remove isopropanol and dried to prepare ASB-PEG 2000 -ASB.

5. The method for preparing the visible light repairable aqueous polyurethane emulsion according to claim 4, characterized in that: In the step (1), PEG 2000 , p-toluenesulfonyl chloride and triethylamine in a molar ratio of 1:5-10:4-8.

6. The method for preparing the visible light repairable waterborne polyurethane emulsion according to claim 4, characterized in that: In the step (2), OTs-PEG 2000 The molar ratio of -OTs to sodium azide is 1:5-10.

7. The method for preparing the visible light repairable waterborne polyurethane emulsion according to claim 4, characterized in that: In the step (3), the molar ratio of propyne bromide, p-hydroxybenzaldehyde and anhydrous potassium carbonate is 1:1-1.5:1-1.

5.

8. The method for preparing the visible light repairable waterborne polyurethane emulsion according to claim 4, characterized in that: In step (4), N3-PEG 2000 The molar ratio of -N3, POBA, cuprous bromide and pentamethyldiethylenetriamine is 1:5-10:0.25-3:1-3.

9. The method for preparing the visible light repairable waterborne polyurethane emulsion according to claim 4, characterized in that: In the step (5), CHO-PEG 2000 The molar ratio of -CHO to p-aminophenol is 1:5-10.

10. A visible light repairable waterborne polyurethane emulsion, characterized in that: The method is prepared according to any one of claims 1 to 9.

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