Polyacrylate modified polyurethane emulsion, self-repairing polyurethane coating, preparation method and application

Abstract

The invention relates to the technical field of polyurethane materials, in particular to a polyacrylate modified polyurethane emulsion, a self-repairing polyurethane coating, a preparation method and application. The preparation method comprises the following steps: firstly, preparing an isocyanate-terminated prepolymer, then reacting the isocyanate-terminated prepolymer with a dihydroxy disulfide compound, introducing a disulfide bond into a polyurethane structure, and adding a diisocyanate tripolymer to continuously react to form a polyurethane prepolymer with a network structure; the preparation method comprises the following steps: firstly, preparing a polyurethane prepolymer emulsion, then adding an acrylate emulsion into the polyurethane prepolymer emulsion to pre-disperse acrylate molecules among a polyurethane network structure, then adding a chain extender to carry out chain extension on polyurethane, and then adding an auxiliary initiator to initiate acrylate polymerization so as to generate linear polyacrylate; the linear polyacrylate is interspersed in a cross-linked polyurethane network structure to form a polyacrylate modified polyurethane emulsion with a semi-interpenetrating network structure; and then light conversion particle polypyrrole is added, so that the self-repairing performance of the material is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane materials, and in particular to a polyacrylate modified polyurethane emulsion, a self-repairing polyurethane coating, and a preparation method and application thereof. Background Art

[0002] Waterborne polyurethane is a polymer material synthesized by the reaction of isocyanate, hydroxyl polyol and small molecule chain extender with water as dispersion medium. It contains little or no organic solvent and has the characteristics of environmental protection, non-flammability, low cost and easy cleaning. It is widely used in coatings, fabric finishing agents, leather and adhesives. At the same time, waterborne polyurethane also has the characteristics of wear resistance, flexibility and low temperature resistance of traditional solvent-based polyurethane. However, waterborne polyurethane is easily affected by external factors and produces microcracks during long-term use, which destroys the integrity of the material matrix and reduces the service life of the material. Since White et al. first synthesized self-healing materials in 2001, self-healing materials have been booming. Self-healing materials can be triggered by external stimuli such as heat, light, electricity and magnetism. According to the repair mechanism, self-healing materials can be divided into two categories: exogenous type and intrinsic type. Among them, exogenous type self-healing materials usually add repairing substances inside to self-heal, while intrinsic type self-healing materials mainly achieve self-repair of cracks through dynamic reversible covalent bonds or dynamic non-reversible covalent bonds.

[0003] Most of the self-healing waterborne polyurethane materials reported so far have problems such as poor water resistance, high repair temperature, long repair time, low repair efficiency, low mechanical strength, and inability to achieve precise positioning repair. Therefore, it is necessary to provide a self-healing polyurethane that takes into account both room temperature self-healing performance and mechanical properties and can achieve precise positioning repair of damaged parts. Summary of the invention

[0004] In view of the problems that most of the existing self-repairing water-based polyurethane materials have poor water resistance, high repair temperature, long repair time, low repair efficiency, low mechanical strength, and cannot achieve precise positioning repair, the present invention provides a polyacrylate modified polyurethane emulsion, a self-repairing polyurethane coating, a preparation method and an application.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] A method for preparing a polyacrylate modified polyurethane emulsion comprises the following steps:

[0007] The diisocyanate, the hydrophilic compound and the diol are reacted to obtain an isocyanate-terminated prepolymer; after the isocyanate-terminated prepolymer is reacted with the dihydroxy disulfide, a diisocyanate trimer is added to continue the reaction to obtain a polyurethane prepolymer emulsion;

[0008] After the polyurethane prepolymer emulsion, acrylate emulsion and initiator are emulsified, a chain extender is added to carry out a polyurethane chain extension reaction. After the chain extension is completed, a co-initiator is added to initiate acrylate polymerization to obtain a polyacrylate modified polyurethane emulsion.

[0009] Relative to the prior art, the preparation method of the polyacrylate modified polyurethane emulsion provided by the present invention first prepares an isocyanate-terminated prepolymer, then reacts the isocyanate-terminated prepolymer with a dihydroxy disulfide compound, introduces a disulfide bond in the polyurethane structure, and adds a diisocyanate trimer to continue the reaction to form a polyurethane prepolymer with a network structure; then, an acrylate emulsion is added to the polyurethane prepolymer emulsion, so that the acrylate molecules are pre-dispersed between the polyurethane network structure, and then a chain extender is added to extend the polyurethane chain, and then an auxiliary initiator is added to initiate acrylate polymerization to generate a linear polyacrylate, which is interspersed in the cross-linked polyurethane network structure to form a polyacrylate modified polyurethane emulsion with a semi-interpenetrating network structure. The disulfide bond is introduced into the polyacrylate modified polyurethane structure of the semi-interpenetrating network structure, giving the material excellent self-healing ability, and the polyacrylate is introduced through the semi-interpenetrating network structure, which enhances the strength and toughness of the material, solves the defect that the existing material cannot take into account both self-healing and mechanical properties, and provides a polyurethane composite material with excellent performance for self-healing materials.

[0010] The characteristic of the polyacrylate-modified polyurethane emulsion prepared by the above method is that the polyacrylate penetrates into the network structure of the polyurethane on a molecular scale, but the two polymers are not chemically combined, which not only increases the compatibility of the polyacrylate and the polyurethane, but also retains the advantages of the two materials, which is conducive to giving full play to the advantages of both, forming a composite material with better performance, and improving the comprehensive performance of the material.

[0011] Furthermore, the preparation method of the polyacrylate modified polyurethane emulsion specifically comprises the following steps:

[0012] S1, adding diisocyanate, hydrophilic compound, diol and catalyst into solvent, reacting at 40°C to 50°C for 1h to 3h, then heating to 70°C to 80°C for 2h to 4h, then adding diol and continuing to react at 70°C to 90°C for 2h to 4h, then cooling to 60°C to 70°C, adding dihydroxy disulfide, reacting for 5h to 7h, finally adding diisocyanate trimer, continuing to react for 0.5h to 1h, to obtain polyurethane prepolymer emulsion;

[0013] S2, after neutralizing the polyurethane prepolymer emulsion, add initiator, acrylate emulsion, emulsifier and water, after emulsification, add chain extender, react at 20°C to 40°C for 0.5h to 1h, then add co-initiator under inert atmosphere, react at 20°C to 40°C for 4h to 6h, to obtain polyacrylate modified polyurethane emulsion.

[0014] Furthermore, the diisocyanate is isophorone diisocyanate (IPDI).

[0015] Furthermore, the hydrophilic compound is 2,2-dihydroxymethylpropionic acid.

[0016] Furthermore, the diol is a polyether polyol having a hydroxyl content of 54.5 mgKOH / g to 57.5 mgKOH / g, a molecular weight of 2000, and a functionality of 2.

[0017] Specifically, the diol is DL-2000D.

[0018] Furthermore, the catalyst is dibutyltin dilaurate.

[0019] Furthermore, the dihydroxy disulfide is bis(2-hydroxyethyl) disulfide.

[0020] Furthermore, the diisocyanate trimer is isophorone diisocyanate trimer.

[0021] Furthermore, in S1, the molar ratio of the diisocyanate, the hydrophilic compound and the dihydroxy disulfide is 50-60:20-25:1.

[0022] Furthermore, in S1, the molar ratio of the diol added for the first time to the dihydroxy disulfide is 4 to 6:1; and the molar ratio of the diol added for the second time to the dihydroxy disulfide is 3 to 5:1.

[0023] Furthermore, in S1, the solvent is N,N-dimethylformamide, and the mass ratio of the solvent to the hydrophilic compound is 1 to 1.5:1.

[0024] Furthermore, in S1, the amount of the diisocyanate trimer added is 5% to 7% of the total mass of the diisocyanate, diol, hydrophilic compound, dihydroxy disulfide and solvent; the amount of the catalyst added is 0.04% to 0.1% of the total mass of the diisocyanate, diol, hydrophilic compound, dihydroxy disulfide and solvent.

[0025] As a specific embodiment of the present invention, in S2, triethylamine is used to neutralize the polyurethane prepolymer emulsion.

[0026] Furthermore, the initiator is benzoyl peroxide.

[0027] Furthermore, the acrylic ester emulsion includes methyl acrylate and butyl acrylate.

[0028] Furthermore, the mass ratio of methyl acrylate to butyl acrylate is 0.8-1.2:1.

[0029] Furthermore, the co-initiator is N,N-dimethylaniline.

[0030] Furthermore, the emulsifier is DCA-8620.

[0031] Furthermore, the molar ratio of the chain extender in S2 to the diisocyanate in S1 is 1-1.5:2-3.

[0032] Furthermore, in S2, the mass ratio of the acrylic emulsion, the initiator, the emulsifier, the co-initiator and the polyurethane prepolymer emulsion is 50-60:0.3-0.5:1.5-2:0.2-0.5:100.

[0033] Furthermore, in S2, the amount of water added is 150% to 160% of the mass of all reaction materials in S2.

[0034] The inert gas described in the present invention is a conventional inert gas in the art, such as nitrogen, argon, etc.

[0035] Exemplarily, the method for preparing polypyrrole comprises the following steps:

[0036] Dissolve polyvinyl alcohol in water, add ferric chloride to dissolve, let stand for 1h to 2h, then add pyrrole at -5℃ to 5℃, stir and polymerize for 3h to 5h, then centrifuge at high speed, wash, and freeze-dry to obtain polypyrrole.

[0037] Furthermore, the mass ratio of the polyvinyl alcohol to water is 1-2:90-100. The ferric chloride is ferric chloride hexahydrate, and the mass ratio of the ferric chloride to polyvinyl alcohol is 5-7:1-2. The mass ratio of the pyrrole to polyvinyl alcohol is 3-4:1-2.

[0038] The polypyrrole prepared by the method has good thermal stability and high electrical conductivity and can be uniformly dispersed in polyacrylate-modified polyurethane emulsion.

[0039] The structural formula (I) of the chain extender is shown as follows:

[0040]

[0041] As a specific embodiment of the present invention, the preparation method of the above chain extender comprises the following steps:

[0042] At 20-30° C., slowly drop 1 mol of hexamethylenediamine into 2-2.5 mol of diethyl maleate, and stir magnetically for 9.5-10 hours to obtain a chain extender.

[0043] In a second aspect, the present invention further provides a polyacrylate-modified polyurethane emulsion, which is prepared by any of the above-mentioned methods for preparing the polyacrylate-modified polyurethane emulsion.

[0044] The polyacrylate modified polyurethane emulsion provided by the present invention has a semi-interpenetrating network structure. Through the design of the semi-interpenetrating network structure, the self-healing of the polyurethane material is realized, and the prepared emulsion has both the excellent mechanical properties of polyurethane and the excellent properties of acrylic resin such as good weather resistance, water resistance, solvent resistance, etc., giving full play to the advantages of both, and providing a polyurethane material with excellent performance for self-healing materials.

[0045] In a third aspect, the present invention also provides a self-repairing polyurethane coating, comprising the polyacrylate-modified polyurethane emulsion.

[0046] Furthermore, the self-repairing polyurethane coating comprises the polyacrylate-modified polyurethane emulsion and polypyrrole.

[0047] By introducing reversible dynamic disulfide bonds into waterborne polyurethane, the material is endowed with higher mechanical properties and excellent self-repairing ability, and by adding light-converting particles polypyrrole, the self-repairing performance of the material is further improved, and high-efficiency self-repairing under room temperature lighting conditions is achieved. Therefore, the self-repairing polyurethane provided by the present invention does not need to be heated at high temperature to achieve self-repair, thus saving energy and having high repair efficiency. A repair rate of more than 89% can be achieved by irradiating with near-infrared light for only 40 minutes, which is conducive to timely repairing damaged parts and avoiding crack expansion, thereby significantly improving the service life of the material.

[0048] Furthermore, the mass ratio of the polyacrylate modified polyurethane emulsion to polypyrrole is 200:(0.01-0.02).

[0049] The preparation method of the above self-repairing polyurethane material comprises the following steps:

[0050] The polypyrrole is added into an organic solvent to dissolve, and then the polyacrylate modified polyurethane emulsion is added and mixed evenly to obtain a self-repairing polyurethane material.

[0051] Furthermore, the organic solvent is N,N-dimethylformamide.

[0052] In a fourth aspect, the present invention further provides a self-healing polyurethane coating formed by any of the self-healing polyurethane coatings described above.

[0053] The self-healing polyurethane coating provided by the present invention can achieve self-healing through light irradiation. After irradiation with 808nm near-infrared light for 40 minutes, the self-healing efficiency is 89.25%. The initial tensile strength of the self-healing polyurethane coating is 12-13MPa, and the elongation at break can reach more than 610%. After repair, the tensile strength can reach 11-12MPa, and the elongation at break can reach more than 440%. It has both good self-healing performance and mechanical properties, and can be self-healed under light at room temperature, and has broad application prospects.

[0054] The present invention also provides a method for forming a self-repairing polyurethane coating, comprising the following steps:

[0055] The self-repairing polyurethane material is coated on a substrate, and a self-repairing polyurethane coating is obtained after curing.

[0056] In a fifth aspect, the present invention also provides a method for repairing a self-healing polyurethane coating, comprising the following steps: irradiating the self-healing polyurethane coating under near-infrared light of 805nm to 810nm for 30min to 50min to complete the self-repair process of the coating.

[0057] In a sixth aspect, the present invention further provides a product, comprising a substrate and the above-mentioned self-healing polyurethane coating disposed on the substrate.

[0058] During the construction and use of the coating, the inside and surface of the material will inevitably be damaged. However, some damage is difficult to detect with instruments, which makes it impossible to effectively guarantee the stability and mechanical strength of the coating, thereby failing to protect the substrate and bringing unpredictable serious consequences to the substrate material. The self-repairing polyurethane coating provided by the present invention has both good mechanical properties and self-repairing properties. Using it as a protective layer can effectively increase the service life of the product and reduce its maintenance cost.

[0059] Furthermore, the product includes leather, household appliances, wood products, architectural decorations, plastics or industrial equipment.

[0060] Waterborne polyurethane has the advantages of being non-toxic and environmentally friendly, and is a green polymer material. By giving the waterborne polyurethane material a self-repairing function, the service life of the material can be extended, the waste of resources can be reduced, and the application field of the material can be further expanded. The self-repairing polyurethane material provided by the present invention is applied to leather finishing materials, which can not only protect the leather material from external damage, but also increase the service life of the leather, thereby reducing the damage to the environment caused by waste materials. At the same time, the self-repairing polyurethane material provided by the present invention can also be applied to the fields of home appliances, wood products, construction, plastics, industrial anti-corrosion, etc., and has huge development potential and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1The reaction mechanism diagram of preparing polyacrylate modified polyurethane emulsion in the embodiment of the present invention;

[0062] Figure 2 The SEM images of polypyrrole prepared in the embodiment of the present invention at different magnifications;

[0063] Figure 3 The SEM images of the SWPUA-1 specimens prepared in Example 1 of the present invention repaired at 75°C for different times;

[0064] Figure 4 Schematic diagram of the self-healing mechanism of the SWPUA-1 polyacrylate modified polyurethane emulsion prepared in Example 1 of the present invention;

[0065] Figure 5 The infrared spectra of polypyrrole, SWPUA-1 prepared in Example 1, SWPUA / PPy-1 prepared in Example 4, and SWPUA / PPy-2 prepared in Example 5; wherein (a) is polypyrrole, and (b) is Example 1, Example 4, and Example 5;

[0066] Figure 6 Optical microscope images of SWPUA-1 prepared in Example 1, SWPUA / PPy-1 prepared in Example 4, and SWPUA / PPy-2 prepared in Example 5 repaired at different times under near-infrared light irradiation, wherein (a) Example 1, (b) Example 4, and (c) Example 5;

[0067] Figure 7 The SEM images of SWPUA / PPy-1 prepared in Example 4 repaired at different times under near-infrared light irradiation;

[0068] Figure 8 The graphs show the change in tensile strength and elongation at break of SWPUA-1 prepared in Example 1, SWPUA / PPy-1 prepared in Example 4, and SWPUA / PPy-2 prepared in Example 5 after repair at different times under near-infrared light irradiation; wherein, (a) Example 1, (b) Example 4, and (c) Example 5. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0070] In order to better illustrate the present invention, further examples are given below.

[0071] The polyether diol DL-2000D used in the following examples is from Bluestar Dongda, and the emulsifier DCA-8620 is from Guangzhou Ruiju.

[0072] The preparation method of polypyrrole used in the following examples is as follows:

[0073] 1.01g of polyvinyl alcohol was added to 100mL of water, dissolved at 100℃, and cooled to room temperature to obtain a polyvinyl alcohol solution; then, 6.25g of ferric chloride hexahydrate was added to the polyvinyl alcohol solution, and the solution was allowed to stand for 1h. The solution was transferred to an ice bath environment. After the ice bath temperature stabilized, 3.02g of pyrrole was added, and the mixture was stirred for 4h for polymerization. Then, the mixture was centrifuged at 10000r / min for 1h. The obtained solid was washed with hot water for several times, and freeze-dried to obtain polypyrrole. The SEM image of the prepared polypyrrole is shown in FIG. Figure 2 As shown in the figure, it can be seen that the prepared polypyrrole is nanoparticles with a particle size of 70 to 80 nm.

[0074] Other reaction conditions defined in the present invention may also be used to prepare polypyrrole. As long as they are within the scope defined in the present invention, they can achieve the same technical effect as the polypyrrole prepared by the above method.

[0075] The preparation method of the chain extender in the following examples is as follows:

[0076] At 20-30°C, slowly add 1 mol of hexamethylenediamine to 2-2.5 mol of diethyl maleate and stir magnetically for 9.5-10 hours to obtain a chain extender with the structure shown below:

[0077] The structure of the chain extender is shown in formula (I):

[0078]

[0079] Example 1

[0080] This embodiment provides a method for preparing a polyacrylate modified polyurethane emulsion, comprising the following steps:

[0081] S1, 33.3g (0.15mol) of isophorone diisocyanate, 6.7g (0.05mol) of dimethylol propionic acid, 25g (0.0125mol) of polyether diol (DL-2000D), 6.7g N,N-dimethylformamide and 60 mg of dibutyltin dilaurate were added to a three-necked flask equipped with a stirrer, a condenser and a thermometer, and reacted at 45°C for 2 hours, then heated to 80°C and continued to react for 2 hours, and then 20 g (0.01 mol) of polyether diol (DL-2000D) was added, and the reaction was continued at 85°C for 2 hours, and then the temperature was lowered to 65°C, and 0.3865 g (0.0025 mol) of bis (2-hydroxyethyl) disulfide was added to the solution, and the reaction was continued with stirring for 6 hours, and then 4.6043 g of isophorone diisocyanate trimer was added, and the reaction was continued with stirring for 0.5 hours to obtain a polyurethane prepolymer emulsion;

[0082] S2, the polyurethane prepolymer emulsion was cooled to 40°C, and 5.1g (0.05mol) of triethylamine was added for neutralization; 0.2901g of benzoyl peroxide, 24.1725g of methyl acrylate and 24.1725g of ethyl acrylate were mixed evenly, and then added to the neutralized polyurethane prepolymer emulsion, and then 1.4503g of emulsifier (DCA-8620) and 269.5755g of deionized water were added for emulsification. After emulsification, 27.6g (0.06mol) of chain extender was added for chain extension reaction. After reacting for 1h, 0.2417g of N,N-dimethylaniline was added under nitrogen atmosphere, and the reaction was continued for 4.5h to obtain a polyacrylate modified polyurethane emulsion, which was recorded as SWPUA-1.

[0083] The reaction mechanism diagram of preparing polyacrylate modified polyurethane emulsion in this embodiment is as follows: Figure 1 shown.

[0084] Example 2

[0085] This embodiment provides a method for preparing a polyacrylate modified polyurethane emulsion, comprising the following steps:

[0086] S1, 27.9g (0.126mol) of isophorone diisocyanate, 8.3g (0.062mol) of dimethylol propionic acid, 21g (0.01mol) of polyether diol (DL-2000D), 12.4g N,N-dimethylformamide and 40 mg of dibutyltin dilaurate were added to a three-necked flask equipped with a stirrer, a condenser and a thermometer, and reacted at 50°C for 1 hour, then heated to 70°C and continued to react for 4 hours, and then 16.5 g (0.008 mol) of polyether diol (DL-2000D) was added, and the reaction was continued at 75°C for 4 hours, and then cooled to 65°C, 0.3865 g (0.0025 mol) of bis (2-hydroxyethyl) disulfide was added to the solution, and the reaction was continued with stirring for 6 hours, and then 5.1941 g of isophorone diisocyanate trimer was added, and the reaction was continued with stirring for 0.5 hours to obtain a polyurethane prepolymer emulsion;

[0087] S2, the polyurethane prepolymer emulsion was cooled to 40°C, and 6.37g (0.063mol) of triethylamine was added for neutralization; 0.4324g of benzoyl peroxide, 24.1725g of methyl acrylate and 24.1725g of ethyl acrylate were mixed evenly, and then added to the neutralized polyurethane prepolymer emulsion, and then 1.5214g of emulsifier (DCA-8620) and 252.6099g of deionized water were added for emulsification. After emulsification, 19.6g (0.043mol) of chain extender was added for chain extension reaction. After reacting for 1h, 0.4572g of N,N-dimethylaniline was added under nitrogen atmosphere, and the reaction was continued for 6h to obtain a polyacrylate modified polyurethane emulsion, which was recorded as SWPUA-2.

[0088] Example 3

[0089] This embodiment provides a method for preparing a polyacrylate modified polyurethane emulsion, comprising the following steps:

[0090] S1, 31.3g (0.14mol) of isophorone diisocyanate, 7.6g (0.057mol) of dimethylol propionic acid, 30.5g (0.015mol) of polyether diol (DL-2000D), 10g N,N-dimethylformamide and 100 mg of dibutyltin dilaurate were added to a three-necked flask equipped with a stirrer, a condenser and a thermometer, and reacted at 40°C for 3 hours, then heated to 75°C and continued to react for 3 hours, and then 24 g (0.012 mol) of polyether diol (DL-2000D) was added, and the reaction was continued at 80°C for 3 hours, and then cooled to 65°C, 0.3865 g (0.0025 mol) of bis (2-hydroxyethyl) disulfide was added to the solution, and the reaction was continued with stirring for 6 hours, and then 7.2685 g of isophorone diisocyanate trimer was added, and the reaction was continued with stirring for 0.5 hours to obtain a polyurethane prepolymer emulsion;

[0091] S2, the polyurethane prepolymer emulsion was cooled to 40°C, and 5.7g (0.056mol) of triethylamine was added for neutralization; 0.5651g of benzoyl peroxide, 33.607g of methyl acrylate and 33.607g of ethyl acrylate were mixed evenly, and then added to the neutralized polyurethane prepolymer emulsion, and then 2.2832g of emulsifier (DCA-8620) and 349.9191g of deionized water were added for emulsification. After emulsification, 46g (0.1mol) of chain extender was added for chain extension reaction. After reacting for 1h, 0.3621N,N-dimethylaniline was added under nitrogen atmosphere, and the reaction was continued for 5h to obtain a polyacrylate modified polyurethane emulsion, which was recorded as SWPUA-3.

[0092] Example 4

[0093] This embodiment provides a self-healing polyurethane material, including 200 parts of polyacrylate modified polyurethane emulsion and 0.01 parts of polypyrrole.

[0094] The preparation method of the above self-repairing polyurethane material comprises the following steps:

[0095] 2 mg of polypyrrole was added to 20 g of N,N-dimethylformamide, and the polypyrrole was dissolved by a cell crusher and ultrasonic dispersion. Then, the obtained polypyrrole solution was added to 40 g of the polyacrylate-modified polyurethane emulsion prepared in Example 1, and magnetic stirring was performed for 1 hour to obtain a self-healing polyurethane material, which was recorded as SWPUA / PPy-1.

[0096] Example 5

[0097] This embodiment provides a self-healing polyurethane material, including 200 parts of polyacrylate modified polyurethane emulsion and 0.016 parts of polypyrrole.

[0098] The preparation method of the above self-repairing polyurethane material comprises the following steps:

[0099] 3.2 mg of polypyrrole was added to 32 g of N,N-dimethylformamide, and the polypyrrole was dissolved by a cell crusher and ultrasonic dispersion. Then, the obtained polypyrrole solution was added to 40 g of the polyacrylate-modified polyurethane emulsion prepared in Example 2, and magnetic stirring was performed for 1 hour to obtain a self-healing polyurethane material, which was recorded as SWPUA / PPy-2.

[0100] Example 6

[0101] This embodiment provides a self-healing polyurethane material, including 200 parts of polyacrylate modified polyurethane emulsion and 0.02 parts of polypyrrole.

[0102] The preparation method of the above self-repairing polyurethane material comprises the following steps:

[0103] 4 mg of polypyrrole was added to 40 g of N,N-dimethylformamide, and the polypyrrole was dissolved by a cell crusher and ultrasonic dispersion. Then, the obtained polypyrrole solution was added to 40 g of the polyacrylate-modified polyurethane emulsion prepared in Example 3, and magnetic stirring was performed for 1 hour to obtain a self-healing polyurethane material, which was recorded as SWPUA / PPy-3.

[0104] Test example

[0105] The SWPUA-1 polyacrylate modified polyurethane emulsion prepared in Example 1, the SWPUA / PPy-1 self-healing polyurethane material prepared in Example 4, and the SWPUA / PPy-2 self-healing polyurethane material prepared in Example 5 were poured into a silicone mold, defoamed in a vacuum drying oven for 0.5 h, dried at room temperature for 48 h, and then dried in a 40°C forced air drying oven for 48 h to obtain a film with a thickness of about 1 mm. The samples were cut into dumbbell-shaped specimens using a dumbbell-shaped type 3 cutter that complies with ISO 37:2005.

[0106] The SWPUA-1 film, SWPUA / PPy-1 film and SWPUA / PPy-2 film were cut into dumbbell-shaped specimens with microcracks of 300 μm in depth using a micrometer scratch tester.

[0107] The prepared SWPUA-1 specimens were repaired at 75℃ for different time periods, and the morphology of the film fracture was observed using an S-4800 scanning electron microscope analyzer. Figure 3 As shown in the figure, it can be seen that compared with the unrepaired specimen, the scratches on the specimen after repair at 75°C for 1 hour are significantly thinner and lighter. At the same time, after repairing at 75°C for 3 hours, the scratches on the specimen basically completely disappear, proving that the SWPUA-1 prepared in the embodiment of the present invention has excellent repair performance at 75°C.

[0108] Figure 4 Schematic diagram of the self-healing mechanism of SWPUA-1 polyacrylate modified polyurethane emulsion prepared in Example 1 of the present invention. The self-healing process can be simply divided into two stages. The first stage is the diffusion of molecular chains on both sides of the crack and the exchange reaction of disulfide bonds, and the second stage is the random movement of molecular chains. Figure 4It can be seen that the self-healing mechanism is mainly achieved through the breakage and recombination of disulfide bonds in the first stage. When the two sides of the microcrack are close enough to favorable temperature conditions, the exchange reaction of disulfide bonds will occur. At the same time, affected by external factors such as the number of disulfide bonds, microstructure and temperature, the polymer can achieve mutual conversion of two equilibrium states and realize self-repair. However, in the process of molecular chain breakage and recombination, some new structures such as physical entanglement and chain links are inevitably generated, which is the randomized movement of molecular chains. After repair, physical entanglement may cause entanglement of molecular fragments, and chain links may capture acrylate fragments. Both of these situations can serve as cross-linking points, resulting in increased material strength, even exceeding the original strength. However, the molecular flexibility is reduced, resulting in the inability of the elongation at break to return to the original value. According to the self-healing mechanism analysis, SWPUA-1 has excellent self-healing properties.

[0109] Figure 5 Fourier infrared chromatograms of the polypyrrole prepared in the present invention (a), the SWPUA-1 polyacrylate modified polyurethane emulsion prepared in Example 1, the SWPUA / PPy-1 self-healing polyurethane material prepared in Example 4, and the SWPUA / PPy-2 self-healing polyurethane material prepared in Example 5 (b). As can be seen from the figure, compared with SWPUA-1, the stretching vibration peaks of -COC- and -C=O of the SWPUA / PPy-1 composite material and the stretching vibration and bending vibration of -NH of the carbamate group have not changed. At the same time, the peak at 2270cm -1 The -NCO characteristic peak near 3540cm -1 The -OH characteristic peak nearby did not appear, indicating that the introduction of polypyrrole PPy had little effect on the chemical structure of SWPUA / PPy-1 nanocomposites. This may be because the content of added PPy was too low, resulting in the infrared characteristic peak of PPy being blocked by the infrared characteristic peak of SWPUA, thus having little effect on the chemical structure of SWPUA / PPy composites.

[0110] The thin film samples of the self-healing polyurethane materials SWPUA-1 prepared in Example 1, SWPUA / PPy-1 prepared in Example 4, and SWPUA / PPy-2 prepared in Example 5 were irradiated with a HEX8081000 / 2000L90 infrared line laser. The laser was a near-infrared light with a wavelength of 808nm. At the same time, the repair effect of different irradiation times was detected. A WV-CP300 / CH optical microscope was used to observe the self-healing changes of microcracks. The self-healing process of the microcracks on SWPUA / PPy-1 for 40 minutes can be seen through an optical microscope. Recording was done every 10 minutes. The results are as follows: Figure 6 The SEM images of the repair process of SWPUA / PPy-1 are shown in Figure 7As shown in the figure, it can be seen that SWPUA-1 has no self-healing effect. After 30 minutes of light repair, SWPUA / PPy-1 only leaves a faint trace on the film surface, proving that SWPUA / PPy-1 has excellent self-healing performance. SWPUA / PPy-2 has a higher PPy content, which may be due to the problem of dispersion uniformity, resulting in a lower repair efficiency than SWPUA / PPy-1.

[0111] The SWPUA-1 prepared in Example 1, the SWPUA / PPy-1 prepared in Example 4, and the SWPUA / PPy-2 sample films prepared in Example 5 were subjected to tensile tests using an ETM104C universal testing machine. The size of the dumbbell-shaped samples was 50 mm*4 mm*1 mm. The tensile strength (σ m ) and elongation at break (ε m ), and the results of five measurements were averaged. The dumbbell-shaped samples were divided into two groups, the first group was 300μm deep scratch samples, and the second group was non-scratched samples as reference. The cut dumbbell-shaped specimens were kept at room temperature for 12 hours to eliminate internal stress, and then the specimens were scratched and repaired, and tensile tests were performed at a tensile rate of 100mm / min to measure their tensile strength and elongation at break. Finally, the self-healing efficiency was calculated using the following tensile strength formula. The results are shown in Figure 8 shown.

[0112] Self-repair efficiency SH=σ 修复后 / σ 原始 ×100%

[0113] Among them, σ 修复后 is the tensile strength of the repaired sample, MPa;

[0114] σ 原始 is the tensile strength of the original sample, MPa.

[0115] As can be seen from the figure, the tensile strength and elongation at break of the SWPUA-1 sample are almost not recovered, which indicates that SWPUA-1 without PPy has no self-healing ability under the irradiation of near-infrared light. SWPUA / PPy-1 exhibits the best self-healing performance, with a tensile strength self-healing rate of 89.25% after 40 minutes of repair.

[0116] Table 1

[0117]

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a polyacrylate modified polyurethane emulsion, characterized in that: The steps include: The diisocyanate, the hydrophilic compound and the diol are reacted to obtain an isocyanate-terminated prepolymer; after the isocyanate-terminated prepolymer is reacted with the dihydroxy disulfide, a diisocyanate trimer is added to continue the reaction to obtain a polyurethane prepolymer emulsion; After the polyurethane prepolymer emulsion, acrylate emulsion and initiator are emulsified, a chain extender is added to carry out a polyurethane chain extension reaction. After the chain extension is completed, a co-initiator is added to initiate acrylate polymerization to obtain a polyacrylate modified polyurethane emulsion.

2. The method for preparing the polyacrylate-modified polyurethane emulsion according to claim 1, characterized in that: The specific steps include: S1, adding diisocyanate, hydrophilic compound, diol and catalyst into solvent, reacting at 40°C to 50°C for 1h to 3h, then heating to 70°C to 80°C for 2h to 4h, then adding diol and continuing to react at 70°C to 90°C for 2h to 4h, then cooling to 60°C to 70°C, adding dihydroxy disulfide, reacting for 5h to 7h, finally adding diisocyanate trimer, continuing to react for 0.5h to 1h, to obtain polyurethane prepolymer emulsion; S2, after neutralizing the polyurethane prepolymer emulsion, add initiator, acrylate emulsion, emulsifier and water, after emulsification, add chain extender, react at 20°C to 40°C for 0.5h to 1h, then add co-initiator under inert atmosphere, react at 20°C to 40°C for 4h to 6h, to obtain polyacrylate modified polyurethane emulsion.

3. The method for preparing the polyacrylate-modified polyurethane emulsion according to claim 1 or 2, characterized in that: The diisocyanate is isophorone diisocyanate; and / or The hydrophilic compound is 2,2-dimethylolpropionic acid; and / or The diol is a polyether polyol having a hydroxyl content of 54.5 mgKOH / g to 57.5 mgKOH / g, a molecular weight of 2000, and a functionality of 2; and / or The catalyst is dibutyltin dilaurate; and / or The dihydroxy disulfide is bis(2-hydroxyethyl) disulfide; and / or The diisocyanate trimer is isophorone diisocyanate trimer; and / or The initiator is benzoyl peroxide; and / or The acrylic ester emulsion comprises methyl acrylate and butyl acrylate; and / or The co-initiator is N,N-dimethylaniline; and / or The structure of the chain extender is shown in formula (I):

4. A polyacrylate modified polyurethane emulsion, characterized in that: The polyacrylate-modified polyurethane emulsion is prepared by the preparation method of the polyacrylate-modified polyurethane emulsion according to any one of claims 1 to 3.

5. A self-repairing polyurethane coating, characterized in that: The invention comprises the polyacrylate modified polyurethane emulsion as claimed in claim 4.

6. The self-repairing polyurethane coating according to claim 5, characterized in that: The invention comprises the polyacrylate modified polyurethane emulsion and polypyrrole.

7. The self-repairing polyurethane coating according to claim 6, characterized in that: The mass ratio of the polyacrylate modified polyurethane emulsion to polypyrrole is 200:(0.01-0.02).

8. A self-repairing polyurethane coating, characterized in that: The self-repairing polyurethane coating is formed from the self-repairing polyurethane coating according to any one of claims 5 to 7.

9. A product, characterized in that The invention comprises a substrate and the self-healing polyurethane coating according to claim 8 disposed on the substrate.

10. The method for repairing the self-repairing polyurethane coating according to claim 8, characterized in that: The method comprises the following steps: irradiating the self-repairing polyurethane coating under 805nm-810nm near-infrared light for 30min-50min to complete the self-repairing of the coating.

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