Self-repairing paper-based paint, preparation method and application

Abstract

The invention provides a self-repairing paper-based coating, a preparation method and application, and the self-repairing paper-based coating is prepared by taking an isocyanate-terminated polyurethane prepolymer generated by diisocyanate and dihydroxyl-terminated polyol as a branch chain and introducing hyperbranched polyester serving as a core and polysulfide rubber serving as a cross-linking agent. By controlling the adding proportion of the diisocyanate, the dihydroxyl-terminated polyhydric alcohol, the hyperbranched polyester and the polysulfide rubber, part of unreacted isocyanate groups are remained at the tail end of the self-repairing paper-based paint. When the surface of a paper-based material containing cellulose is coated with the self-repairing paper-based paint, residual isocyanate group-NCO reacts with hydroxyl group-OH in the cellulose to form a binary polymer blending system with an interlocking network structure. The binary polymer blending system not only realizes firm bonding of the self-repairing paper-based paint and the paper-based material, but also realizes self-repairing of the paper-based material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer coating and relates to a self-repairing paper-based coating, a preparation method and application. BACKGROUND

[0002] Cellulose is a green renewable natural bio-based material, and its green and efficient utilization can be realized through functionalization. For example, self-repairing cellulose-based materials have the advantages of prolonging the service life of materials, reducing resource consumption and reducing environmental pollution, and are widely used in the fields of sensors, wound dressings, coatings, tissue repair materials and the like.

[0003] At present, the self-repairing cellulose-based material can be prepared into a paper-based edge strip used in a decorative particle board, a decorative fiber board and the like, so as to replace plastic products such as PVC, ABS, PP and PMMA, and achieve the purposes of biodegradability and environmental protection. The paper-based edge strip is usually a disposable product. When the paper-based edge strip is scratched or worn to produce scratches, it is often impossible to repair or replace alone, and only the entire board can be replaced, which not only leads to waste of material resources, but also increases the use cost of maintenance and replacement. Based on this, a self-repairing paper-based coating is provided, which is an environmentally friendly material that can be reused, and can significantly improve the recycling rate of paper and prolong the service life.

[0004] Generally, two conditions need to be met to realize the self-repairing performance of the material: (1) the dynamic reversible groups on both sides of the material fracture surface can undergo dissociation-association reaction under external conditions, and the cracks are sutured. (2) After the material is broken, the polymer molecular chains on both sides of the fracture surface have strong flowability, which drives the two sides of the fracture interface to approach each other to provide driving force for the mutual contact of the dynamic reversible bonds. For cellulose-based materials, cellulose is a linear homopolymer composed of beta-D-glucose connected by beta-1, 4 glycosidic bonds. The intermolecular hydrogen bonding and the interaction between cellulose layers make cellulose have a certain rigid structure, which limits the movement of cellulose molecular chains and makes it difficult to meet the self-repairing conditions of the material. SUMMARY

[0005] The purpose of the present application is to provide a self-repairing paper-based coating, a preparation method and application, so as to solve the problems of insufficient self-repairing performance of cellulose-based paper-based materials and low use efficiency.

[0006] To achieve the above-mentioned purpose, the following technical solutions are adopted in the present application: The present application provides a self-repairing paper-based coating, and the preparation raw materials thereof include diisocyanate, end dihydroxyl polyol, hyperbranched polyester, polysulfide rubber and catalyst.

[0007] The hyperbranched polyester is a core component of the self-repairing paper-based coating in the present application, which is a highly branched, three-dimensional conformation and non-entangled polymer. Unlike linear or simply branched polymers, the unique structural characteristics of hyperbranched polyester make it have more terminal groups and larger molecular volume, which in turn endow the polymer material with excellent molecular chain fluidity. When subjected to external stress, this characteristic enables hyperbranched polyester to effectively guide and disperse stress, inhibit the formation and expansion of micro-cracks, thereby significantly improving the toughness of the polymer and enhancing its impact resistance.

[0008] In the present application, the terminal of the hyperbranched polyester is hydroxyl or amine group, and the number of the hydroxyl or amine group is 8-24; the molecular weight of the hyperbranched polyester is 600-5000 g / mol.

[0009] The main chain of polysulfide rubber contains -S-S- bond, which is a synthetic rubber. Polysulfide rubber has excellent weather resistance and chemical resistance, and can effectively resist the erosion of environmental factors such as ultraviolet light, ozone, oxygen, rainwater and high and low temperature, and is not prone to cracking, powdering, discoloration and other aging phenomena. At the same time, it also shows good resistance to various oils such as machine oil, gasoline, diesel oil, organic solvents such as benzene, toluene, xylene, and chemical reagents such as acid, base, and salt solution.

[0010] The disulfide bond in polysulfide rubber is a dynamic covalent bond in the form of R1-S-S-R2, which can undergo dynamic reversible exchange reaction under the stimulation of various external conditions such as sunlight, temperature and alkaline environment, and introduce a dynamic reversible exchange group for the self-repairing paper-based coating. When the self-repairing paper-based coating is damaged, the cross-reaction of the broken interface sulfur free radicals can promote the recombination of the molecular chains on both sides of the fracture, realizing the self-repairing performance of the self-repairing paper-based coating.

[0011] In the present application, the terminal isocyanate group polyurethane prepolymer generated by diisocyanate and terminal dihydroxyl polyol is branched, introducing the core hyperbranched polyester and the crosslinking agent polysulfide rubber to prepare the self-repairing paper-based coating. The mechanism of the self-repairing performance of the self-repairing paper-based coating is: (1) By controlling the addition ratio of the diisocyanate, the end dihydroxyl polyol, the hyperbranched polyester, and the polysulfide rubber, the residual unreacted isocyanate groups in the self-repairing paper-based coating are ensured. When the self-repairing paper-based coating is coated on the surface of the paper-based material containing cellulose, the residual isocyanate groups -NCO react with the hydroxyl groups -OH in the cellulose, so that the rigid network of the cellulose and the flexible network of the polymer in the self-repairing paper-based coating are combined and interpenetrated through the chemical bonds between the molecular chains, forming a binary polymer blend system with an interlocking network structure. This system "forces" the two originally incompatible phases to be compatible, and builds a uniform and stable rigid-flexible interlocking network structure material, realizing firm bonding between the self-repairing paper-based coating and the paper-based material.

[0012] (2) When the paper-based material is damaged to generate cracks or scratches, the rigid-flexible interlocking network structure material realizes the self-repairing function of the cellulose paper-based material through the action mechanism of "rigid-flexible interlocking and flexible driving rigid", the flexible molecular chains of the polymer guide the rigid molecular chains of the cellulose to the crack section, shorten the crack distance, and promote the mutual contact of the disulfide bonds on both sides of the crack. At the same time, under heating or sunlight irradiation, the dynamic reversible exchange reaction of the disulfide bonds on both sides of the crack occurs, re-forming chemical bonds, and then combining the crack section and repairing the crack, thereby prolonging the service life of the material, reducing resource consumption, and endowing the coating with the ability to resist external mechanical impact and other damages.

[0013] In the present application, the molar ratio of the isocyanate groups in the diisocyanate, the hydroxyl groups in the end dihydroxyl polyol, the hydroxyl groups or amine groups in the hyperbranched polyester, and the mercapto groups in the polysulfide rubber is 8:4:2:1, and the residual isocyanate groups in the self-repairing paper-based coating are 1 / 8 of the molar amount of the residual diisocyanate.

[0014] In the present application, the diisocyanate includes one or more of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexyl methane diisocyanate.

[0015] In the present application, the end dihydroxyl polyol includes polyethylene glycol and / or polytetrahydrofuran, and the molecular weight of the end dihydroxyl polyol is 800-5000 g / mol.

[0016] In the present application, the catalyst is dibutyl tin dilaurate.

[0017] The self-repairing paper-based coating in the present application is used for preparing a self-repairing paper-based material, such as a paper-based edge strip.

[0018] The present application also provides a preparation method of the self-repairing paper-based coating, which comprises: S01: after dissolving the diisocyanate, the end dihydroxyl polyol and the catalyst in N,N-dimethylformamide, mixing, condensation reaction between the isocyanate group in the diisocyanate and the hydroxyl group in the end dihydroxyl polyol occurs at 50-80℃ for 3-8h, forming the end isocyanate group polyurethane prepolymer; S02: after dissolving the hyperbranched polyester in N,N-dimethylformamide, slowly adding to the end isocyanate group polyurethane prepolymer, condensation reaction between the hydroxyl group or amine group in the hyperbranched polyester and the isocyanate group in the end isocyanate group polyurethane prepolymer occurs at 40-60℃ for 3-6h, forming the hyperbranched polyurethane; S03: after dissolving the polysulfide rubber in N,N-dimethylformamide, slowly adding to the hyperbranched polyurethane, condensation reaction between the mercapto group in the polysulfide rubber and the isocyanate group in the hyperbranched polyurethane occurs at 40-60℃ for 1-5h, forming the self-repairing paper-based coating.

[0019] When the self-repairing paper-based coating is coated on the surface of the paper-based material and a scratch is drawn on the surface of the paper-based material, under the condition of sunlight or heating, the residual isocyanate group in the self-repairing paper-based coating and the hydroxyl group of cellulose in the paper-based material occur polymerization reaction, realizing self-repairing of the scratch on the surface of the paper-based material.

[0020] The present application has the following beneficial effects: (1) In the present application, the end isocyanate group polyurethane prepolymer generated by the diisocyanate and the end dihydroxyl polyol is branched, introducing the hyperbranched polyester as the core and the polysulfide rubber as the crosslinking agent, to prepare the self-repairing paper-based coating.

[0021] (2) By controlling the addition proportion of the diisocyanate, the end dihydroxyl polyol, the hyperbranched polyester and the polysulfide rubber, the residual unreacted isocyanate group at the end of the self-repairing paper-based coating is ensured. When the self-repairing paper-based coating is coated on the surface of the paper-based material containing cellulose, the residual isocyanate group-NCO and the hydroxyl group-OH in the cellulose occur reaction, so that the rigid network of the cellulose and the flexible network of the polymer in the self-repairing paper-based coating are combined and interpenetrated through the chemical bond between the molecular chains, forming a binary polymer blend system with interlocking network structure. This system "forces" the originally incompatible two phases to be compatible, constructing a uniform and stable rigid-flexible interlocking network structure material, realizing firm bonding between the self-repairing paper-based coating and the paper-based material.

[0022] (3) When the paper-based material is damaged to generate cracks or scratches, the rigid-flexible interlocking network structure material realizes the self-repairing function of the cellulose paper-based material through the mechanism of rigid-flexible interlocking and flexible driving rigid, the flexible molecular chain of the polymer leads the rigid molecular chain of the cellulose to the crack section, shortens the crack distance, and promotes the mutual contact of the disulfide bonds on both sides of the crack. At the same time, under the heating or sunlight irradiation, the dynamic reversible exchange reaction of the disulfide bonds on both sides of the crack occurs, the chemical bonds are reformed, and then the crack section is combined to repair the crack, thereby prolonging the service life of the material, reducing the resource consumption, and endowing the coating with the ability to resist external mechanical collision and other damages.

[0023] (4) The self-repairing paper-based coating in the application is used for preparing a self-repairing paper-based material, such as a paper-based edge strip. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The synthesis route map of the self-repairing paper-based coating prepared for Example 1; Figure 2 The rheological property analysis map of the self-repairing paper-based coating prepared for Example 1 and Comparative Example 1; Figure 3 The recycling performance analysis map of the self-repairing paper-based coating prepared for Example 1 and Comparative Example 1; Figure 4 The FT-IR (Fourier-Transform Infrared Spectroscopy) map of the self-repairing paper-based coating prepared for Example 1 after the reaction with cellulose; Figure 5 The rheological property analysis map of the self-repairing paper-based coating prepared for Example 1 after the reaction with cellulose; Figure 6 The self-repairing performance analysis map of the self-repairing paper-based coating prepared for Example 1 and Comparative Example 1 on the surface of paper. DETAILED DESCRIPTION

[0025] The technical solutions of the application will be further explained and described below through specific examples.

[0026] Example 1 The application example provides a self-repairing paper-based coating, and a synthesis route map of the coating is shown in the accompanying drawings. Figure 1 The preparation method of the coating comprises the following steps: S101: 10 g of polytetrahydrofuran with a molecular weight of 2000 g / mol is dried in a 120°C oven for 12 h, and after removing the water, it is placed in a four-necked flask. 20 mL of N, N-dimethylformamide is added to the four-necked flask, and mechanical stirring is carried out at a rotation speed of 200 r / min. 2.22 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate are accurately weighed, dissolved in 30 mL of DMF, and then placed in a constant-pressure dropping funnel. The polytetrahydrofuran solution is slowly added under the protection of nitrogen, and after stirring and mixing uniformly, the reaction is carried out at 60°C for 6 h to obtain a polyurethane prepolymer PU. In the reaction process, the molar ratio of -OH in polytetrahydrofuran to -NCO in isophorone diisocyanate is 1:2.

[0027] S102: 0.50 g of hyperbranched polyester with a molecular weight of 1200 g / mol and 12 -OH groups at the end is accurately weighed and added to 20 mL of DMF and dissolved under the action of ultrasonic waves. The dissolved hyperbranched polyester is slowly added to the polyurethane prepolymer solution, and after reacting at 40°C for 4 h, a hyperbranched polyurethane prepolymer HPU is obtained. In the reaction process, the molar ratio of -OH in the hyperbranched polyester to -NCO in the isophorone diisocyanate is 1:4.

[0028] S103: 0.83 g of poly-sulfur rubber with a molecular weight of 1000 g / mol is dissolved in 20 mL of DMF and slowly added to the HPU solution, and after reacting at 40°C for 3 h, a crosslinked self-repairing paper-based coating is obtained. In the reaction process, the molar ratio of -SH in the poly-sulfur rubber to -NCO in the isophorone diisocyanate is 1:8.

[0029] Example 2 The self-repairing paper-based coating provided by the embodiments of the present application has the following preparation method: S201: 25 g of polytetrahydrofuran with a molecular weight of 5000 g / mol is dried in a 120°C oven for 12 h, and after removing the water, it is placed in a four-necked flask. 20 mL of N, N-dimethylformamide is added to the four-necked flask, and mechanical stirring is carried out at a rotation speed of 200 r / min. 2.22 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate are accurately weighed, dissolved in 30 mL of DMF, and then placed in a constant-pressure dropping funnel. The polytetrahydrofuran solution is slowly added under the protection of nitrogen, and after stirring and mixing uniformly, the reaction is carried out at 80°C for 3 h to obtain a polyurethane prepolymer PU. In the reaction process, the molar ratio of -OH in polytetrahydrofuran to -NCO in isophorone diisocyanate is 1:2.

[0030] S202: accurately weigh the hyperbranched polyester with a molecular weight of 5000 g / mol, a mass of 0.52 g, and 48 -OH groups at the end, add it to 20 mL of DMF, and dissolve it under the action of ultrasonic waves. Slowly add the dissolved hyperbranched polyester to the polyurethane prepolymer solution, and after 6 h of reaction at 40°C, a hyperbranched polyurethane prepolymer HPU is obtained. In this reaction process, the molar ratio of -OH in the hyperbranched polyester to -NCO in the isophorone diisocyanate is 1:4.

[0031] S203: dissolve the polysulfide rubber with a molecular weight of 1000 g / mol and a mass of 0.83 g in 20 mL of DMF, slowly add it to the HPU solution, and after 1 h of reaction at 60°C, a crosslinked self-repairing paper-based coating is obtained. In this reaction process, the molar ratio of -SH in the polysulfide rubber to -NCO in the isophorone diisocyanate is 1:8.

[0032] Example 3 The self-repairing paper-based coating provided by the embodiments of the present application has the following preparation method: S301: place the polyethylene glycol with a molecular weight of 3000 g / mol and a mass of 15 g in a 120°C oven for drying for 12 h, and after removing the water, place it in a four-necked flask. Add 20 mL of N,N-dimethylformamide to the four-necked flask and mechanically stir at a speed of 200 r / min. Accurately weigh 1.68 g of hexamethylene diisocyanate and 0.1 g of dibutyltin dilaurate, dissolve them in 30 mL of DMF, and then place them in a constant-pressure dropping funnel. Slowly add the polyethylene glycol solution to the constant-pressure dropping funnel under the protection of nitrogen, stir and mix uniformly, and then react at 50°C for 8 h to obtain a polyurethane prepolymer PU. In this reaction process, the molar ratio of -OH in the polyethylene glycol to -NCO in the hexamethylene diisocyanate is 1:2.

[0033] S302: accurately weigh the hyperbranched polyester with a molecular weight of 2400 g / mol, a mass of 0.50 g, and 24 -OH groups at the end, add it to 20 mL of DMF, and dissolve it under the action of ultrasonic waves. Slowly add the dissolved hyperbranched polyester to the polyurethane prepolymer solution, and after 3 h of reaction at 60°C, a hyperbranched polyurethane prepolymer HPU is obtained. In this reaction process, the molar ratio of -OH in the hyperbranched polyester to -NCO in the hexamethylene diisocyanate is 1:4.

[0034] S303: dissolve the polysulfide rubber with a molecular weight of 1000 g / mol and a mass of 0.83 g in 20 mL of DMF, slowly add it to the HPU solution, and after 5 h of reaction at 40°C, a crosslinked self-repairing paper-based coating is obtained. In this reaction process, the molar ratio of -SH in the polysulfide rubber to -NCO in the hexamethylene diisocyanate is 1:8.

[0035] Example 4 The example of the present application provides a self-repairing paper-based coating, and a preparation method thereof comprises the following steps: S401: polyethylene glycol with a molecular weight of 800 g / mol and a mass of 8 g is placed in a 120°C oven for drying for 12 h, and after removing the water, it is placed in a four-necked flask. 20 mL of N, N-dimethylformamide is added to the four-necked flask, and mechanical stirring is carried out at a speed of 200 r / min. 2.62 g of dicyclohexyl methane diisocyanate and 0.1 g of dibutyltin dilaurate are accurately weighed, dissolved in 30 mL of DMF, and then placed in a constant pressure dropping funnel, slowly added to the polyethylene glycol solution under the protection of nitrogen, and after stirring and mixing uniformly, reacted at 50°C for 8 h to obtain a polyurethane prepolymer PU. In the reaction process, the molar ratio of -OH in polyethylene glycol to -NCO in dicyclohexyl methane diisocyanate is 1:2.

[0036] S402: accurately weigh the hyperbranched polyester with a molecular weight of 500 g / mol, a mass of 0.42 g, and 6 -OH at the end, add it to 20 mL of DMF, and dissolve it under the action of ultrasonic waves. The dissolved hyperbranched polyester is slowly added to the polyurethane prepolymer solution, and after reacting at 50°C for 3 h, a hyperbranched polyurethane prepolymer HPU is obtained. In the reaction process, the molar ratio of -OH in the hyperbranched polyester to -NCO in the dicyclohexyl methane diisocyanate is 1:4.

[0037] S403: polythioprene with a molecular weight of 1000 g / mol and a mass of 0.83 g is dissolved in 20 mL of DMF, slowly added to the HPU solution, and after reacting at 50°C for 3 h, a cross-linked self-repairing paper-based coating is obtained. In the reaction process, the molar ratio of -SH in the polythioprene to -NCO in the dicyclohexyl methane diisocyanate is 1:8.

[0038] Comparative Example 1 The comparative example of the present application provides a self-repairing paper-based coating, and a preparation method thereof is the same as that of Example 1, except that it does not contain polythioprene.

[0039] Comparative Example 2 The comparative example of the present application provides a self-repairing paper-based coating, and a preparation method thereof is the same as that of Example 2, except that it does not contain polythioprene.

[0040] Comparative Example 3 The comparative example of the present application provides a self-repairing paper-based coating, and a preparation method thereof is the same as that of Example 3, except that it does not contain polythioprene.

[0041] Comparative Example 4 The comparative embodiments of this application provide a self-healing paper-based coating, which is prepared in the same way as in Embodiment 4, except that it does not contain polysulfide rubber.

[0042] Comparative Example 5 This application provides a self-healing paper-based coating in a comparative embodiment. The preparation method is the same as in Example 1, except that the polysulfide rubber with a molecular weight of 1000 g / mol and a mass of 0.83 g is replaced with 2,2'-dithiodiethanol with a mass of 0.19 g.

[0043] To verify that the self-healing paper-based coating prepared in this application meets the self-healing conditions, the self-healing paper-based coatings prepared in Example 1 and Comparative Example 1 were ground in polytetrafluoroethylene abrasive molds, dried in an 80°C oven, and solvent removed to obtain polymer films. The rheological behavior of the two materials in Example 1 and Comparative Example 1 was studied using a high-efficiency rotational rheometer system, and the results were obtained. Figure 2 .

[0044] From the appendix Figure 2 As can be seen, the polymer film in Comparative Example 1 exhibits the characteristic of G′>G″ at 30℃, 60℃, and 80℃, displaying typical solid-like behavior, indicating that its structure is stable and primarily relies on elastic energy storage. The polymer film in Example 1 also shows the elastic-dominant characteristic of G′>G″ at 30℃ and 60℃, but when the temperature rises to 80℃, as the frequency decreases, G′ and G″ intersect, i.e., G′=G″. This indicates that the polymer film in Example 1 transforms from elastic-dominant solid behavior to viscous-dominant liquid behavior. This transformation confirms that the dynamic exchange capacity of the SS bonds in polysulfide rubber is significantly enhanced under heating conditions, thereby promoting the transition of the polymer to a viscous flow state, and further demonstrating that the self-healing paper-based coating prepared in this application meets the conditions for self-healing.

[0045] Based on the above mechanism, this application prepares the self-healing paper-based coatings prepared in Example 1 and Comparative Example 1 into polymer films, then pulverizes them, and then re-prepares them into sheet materials under hot pressing at 120°C to obtain the attached... Figure 3 .

[0046] From the appendix Figure 3 As can be seen, after hot pressing under the same conditions, the self-healing paper-based coating in Example 1, once prepared into a polymer film, can form a uniform recycled film after pulverization, while this is not the case in Comparative Example 1. This indicates that during the recycling process, the interface of the pulverized self-healing paper-based coating can achieve effective recombination through the dynamic exchange of SS bonds in the polysulfide rubber. In contrast, due to the lack of reversible exchange of dynamic SS bonds, the polymer film prepared from the self-healing paper-based coating in Comparative Example 1 does not achieve good recycling performance.

[0047] To demonstrate the reaction between the self-healing paper-based coating prepared in the embodiments of this application and cellulose, the self-healing paper-based coating prepared in Example 1 was mixed with cellulose at a mass ratio of 9:1. Then, FT-IR comparative analysis and rheological property analysis of each monomer and the final product were performed using an infrared spectrometer to obtain the results. Figure 4 , 5 .

[0048] From the appendix Figure 4 It can be seen that isophorone diisocyanate at 2250 cm -1 The -NCO characteristic peak at 1730 cm⁻¹ completely disappeared, while the peak at 1730 cm⁻¹ disappeared at 1730 cm⁻¹. -1 A strong absorption band appears at this point, corresponding to the stretching vibration of C=O in urethane, thus confirming the formation of the polyurethane backbone. Furthermore, reactant analysis shows that polytetrahydrofuran, hyperbranched polyester, and cellulose exhibit strong absorption at 3200-3400 cm⁻¹. -1 The intensity of the hydroxyl characteristic peak decreased significantly, indicating that -OH participated in the reaction. Polysulfide rubber showed a significant decrease in intensity at 2550 cm⁻¹. -1 The -SH characteristic peak disappears, and the 600-700 cm⁻¹ peak also disappears. -1 The presence of CS bond vibration signals at 1100 cm⁻¹ demonstrates that thiol groups selectively participate in the construction of thiocarbamates. Polytetrahydrofuran at 1100 cm⁻¹... -1 The presence of COC characteristic absorption at the site confirms the integrity of the polyether segment structure. In summary, the synthesis of HPU-PSO-HEC was achieved through a stepwise addition reaction of -OH in polytetrahydrofuran, hyperbranched polyester, and cellulose with -SH in polysulfide rubber and -NCO in isophorone diisocyanate. Each reaction site exhibited high selectivity, successfully constructing the expected polymer structure.

[0049] From the appendix Figure 5 It is evident that the addition of cellulose to the self-healing paper-based coating does indeed hinder molecular chain movement due to the rigid structure of cellulose in the interlocking network, resulting in a decrease in the G′=G″ transition frequency. However, the transition from the elastic state to the viscous flow state can still be achieved in the end. This dynamic transition behavior provides an important foundation for the self-healing properties of the material.

[0050] To quantify the mechanical and self-healing properties of the self-healing paper-based coatings prepared in Examples 1-4 and Comparative Examples 1-5 of this application, the self-healing paper-based coatings prepared in Examples 1-4 and Comparative Examples 1-5 were respectively prepared into films and cut into dumbbell-shaped strips of 4×50cm. These strips were then cut and rejoined. The joined films were placed in an 80℃ oven for 1 hour for repair. By comparing the mechanical strength of the strips before and after repair, the repair efficiency was calculated, as shown in Table 1. The formula for calculating the self-healing efficiency is as follows: Self-healing efficiency (%) = Tensile strength of the repaired coating (MPa) / Tensile strength of the original coating (MPa) × 100% Table 1: Mechanical strength and self-healing efficiency of self-healing paper-based coatings prepared in Examples 1-4 and Comparative Examples 1-5 As shown in Table 1, the self-healing paper-based coatings prepared in Examples 1-4 all exhibit high self-healing efficiencies, with the highest reaching 105.0%. In contrast, the self-healing efficiency of the self-healing paper-based coatings prepared in Examples 1-4 is only 24.0%. This indicates that the dynamic disulfide bonds in the polysulfide rubber play a crucial role in the polymer's self-healing process. In Table 1, the self-healing paper-based coating prepared in Example 1 demonstrates a repair efficiency >100%, which is attributed to the dynamic exchange of SS after material fracture, which promotes the reconstruction of the molecular chain network, thereby generating an enhanced mechanical property effect.

[0051] Furthermore, when a linear 2,2'-dithiodiethanol with a smaller molecular weight was used instead of polysulfide rubber to prepare the self-healing paper-based coating in Comparative Example 5, the self-healing efficiency of the coating was only 67.1%. This indicates that the structural characteristics of branched polysulfide rubber and the number of disulfide bonds in the polysulfide rubber molecule have significant advantages in improving the dynamic exchange capacity and self-healing performance of the polymer molecular chain.

[0052] Furthermore, to demonstrate that the self-healing paper-based coating prepared in this application has self-healing capabilities after being applied to the paper surface, the self-healing paper-based coatings prepared in Example 1 and Comparative Example 1 were applied at a concentration of 10 g / m³. 2 The appropriate amount of each agent was applied to the paper surface, and then a 5-10µm scratch was made. The surface was then left to heal at 80℃ for 0.5 hours. After the healing process, the changes in the scratch on the material surface were examined using a super-depth-of-field microscope to obtain the results. Figure 6 .

[0053] From the appendix Figure 6 As can be seen, the paper coated with the self-healing paper-based coating in Example 1 had no obvious scratches after repair, while the paper coated with the self-healing paper-based coating in Comparative Example 1 still had obvious scratches after repair. This shows that polysulfide rubber plays an important role in the self-healing process of the self-healing paper-based coating.

[0054] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A self-repairing paper-based coating, characterized by, The raw materials include diisocyanate, end dihydroxyl polyol, hyperbranched polyester, polysulfide rubber and catalyst.

2. The self-repairing paper-based coating according to claim 1, characterized in that, The molar ratio of isocyanate groups in the diisocyanate, hydroxyl groups in the end dihydroxyl polyol, hydroxyl groups or amine groups in the hyperbranched polyester, and mercapto groups in the polysulfide rubber is 8:4:2:1, and the self-repairing paper-based coating contains 1 / 8 of the molar amount of isocyanate groups of the diisocyanate.

3. The self-repairing paper-based coating according to claim 1, characterized in that, The diisocyanate includes one or more of isophorone diisocyanate, hexamethylene diisocyanate and dicyclohexyl methane diisocyanate.

4. The self-repairing paper-based coating according to claim 1, characterized in that, The end dihydroxyl polyol includes polyethylene glycol and / or polytetrahydrofuran, and the molecular weight of the end dihydroxyl polyol is 800-5000 g / mol.

5. The self-repairing paper-based coating according to claim 1, characterized in that, The hyperbranched polyester has hydroxyl groups or amine groups at the ends, and the number of the hydroxyl groups or amine groups is 8-24; the molecular weight of the hyperbranched polyester is 600-5000 g / mol.

6. The self-repairing paper-based coating according to claim 1, characterized in that, The catalyst is dibutyl tin dilaurate.

7. The method for preparing a self-repairing paper-based coating according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S01: the diisocyanate and the end dihydroxyl polyol are dissolved in a solvent and mixed, and a condensation reaction occurs under the action of a catalyst to form an end isocyanate group-containing polyurethane prepolymer; S02: the hyperbranched polyester is dissolved in a solvent, and the end isocyanate group-containing polyurethane prepolymer is slowly added to generate a hyperbranched polyurethane through a condensation reaction; S03: the polysulfide rubber is dissolved in a solvent, and the hyperbranched polyurethane is slowly added to generate a self-repairing paper-based coating through a condensation reaction.

8. The method for preparing the self-healing paper-based coating according to claim 7, characterized in that, The reaction temperature in S01 is 50-80°C, and the reaction time is 3-8 h; the reaction temperature in S02 is 40-60°C, and the reaction time is 3-6 h; the reaction temperature in S03 is 40-60°C, and the reaction time is 1-5 h.

9. The method for preparing the self-healing paper-based coating according to claim 7, characterized in that, The solvent is N,N-dimethylformamide.

10. The self-repairing paper-based coating according to any one of claims 1-6 is used to prepare a self-repairing paper-based material.

Images