Preparation method of self-repairing waterborne polyurethane leather coating material containing polyurethane colloid capsule

Abstract

The invention provides a preparation method of a self-repairing waterborne polyurethane leather coating material containing a polyurethane colloid capsule, which comprises the following steps: firstly, preparing an O / W type Pickering emulsion by taking modified SiO2 nanoparticles as a stabilizer and a polyurethane solution as an oil phase; the preparation method comprises the following steps: firstly, taking the polyurethane colloid capsule as a template, forming the colloid capsule capable of being dispersed in a water system through a sol-gel reaction, and finally, uniformly dispersing the colloid capsule into a waterborne polyurethane leather finishing emulsion to prepare the waterborne polyurethane leather self-repairing coating material containing the polyurethane colloid capsule. According to the invention, the polyurethane healing agent is used as a core material, and the modified SiO2 nanoparticles are used as a shell wall, so that the prepared spherical colloid capsule is high in encapsulation efficiency and strong in stability. According to the preparation method provided by the invention, the problems of poor self-repairing performance and mechanical property caused by low compatibility of a healing agent and a polyurethane matrix for leather finishing and easy agglomeration of a traditional microcapsule in a waterborne polyurethane emulsion in a traditional external aid type self-repairing polyurethane coating are solved; and the wear resistance of the leather polyurethane coating is remarkably improved by introducing SiO2.

Description

Technical Field

[0003] The present invention relates to the field of preparation of polyurethane colloidal capsule self - repairing coatings, and specifically relates to a method for a self - repairing aqueous polyurethane leather coating material containing polyurethane colloidal capsules, aiming to use Pickering solid particles SiO2 nanoparticles as the shell wall and polyurethane healing agent as the core material to achieve the goal of external repair of polyurethane leather coatings by polyurethane colloidal capsules. Background Art

[0004] Polyurethane (PU) is a polymer containing urethane repeating units, mainly formed by the addition polymerization of polyisocyanates and macromolecular polyols in the presence of chain extenders. Macromolecular polyols (such as polyether diols, polyester diols, etc.) are usually referred to as soft segments, while isocyanates (aromatic or aliphatic) and chain extenders (small diols or diamines) are usually referred to as hard segments. The hard phase formed by the self - assembly of isocyanates and chain extenders through hydrogen bonds of urethane groups is dispersed in the soft phase composed of flexible polymer chains, resulting in microphase separation. The hard phase serves as physical cross - link points, giving PU good mechanical strength. At the same time, the flexible polymer chains endow polyurethane with elasticity and flexibility. Therefore, by selecting different raw materials and the relative proportions of hard and soft segments, it is easy to adjust the phase separation structure, thereby changing the properties of polyurethane, which is widely used in fields such as coatings, leather, and flexible electronics. However, mechanical damages such as abrasion will inevitably occur during the use of leather coating materials, and endowing them with self - repairing functions is of great significance for extending the service life of materials and reducing maintenance costs.

[0005] Microcapsule-based self-healing polymer composites were first invented by White et al. in 2001. During the crack formation process, the microcapsules rupture, releasing the encapsulated healing agent, which comes into contact with the damaged area and initiates a polymerization reaction through a catalyst to repair the crack surface and restore mechanical integrity. Exogenous microcapsule self-healing does not require external factor stimulation and can achieve damage repair through the healing agent at room temperature. For example, Chinese Patent CN202310075157.X prepares microcapsules with TFXPUA, 1,6-hexanediol diacrylate, and 2-hydroxy-2-methyl-1-phenyl-1-propanone as the core material and polyurethane as the wall material, and then mixes them evenly with an aqueous polyurethane emulsion to obtain an MTFXPUA / WPU composite coating film with high self-healing efficiency. There have been many reports on the strategy of using microcapsules for self-healing. In practical applications, the compatibility between the microcapsule healing agent and the coating matrix is a key factor determining the self-healing performance. Poor interaction between the healing agent and the matrix may lead to the loss of the healing agent or its damage or decomposition by the coating material before release. This will significantly reduce the effectiveness of the healing agent and the self-healing performance of the coating, and will reduce the strength, durability of the coating or cause the coating surface to be uneven. This not only affects the functionality of the coating, but may also affect its appearance and aesthetics. However, there are few reports on solving the poor compatibility between the healing agent and the coating matrix.

[0006] The most commonly used finishing agent in the field of leather finishing is aqueous polyurethane. The existing reported self-healing aqueous polyurethane materials have problems such as poor compatibility between traditional microcapsule healing agents and polyurethane matrices and easy agglomeration in aqueous systems, which ultimately lead to poor mechanical properties and self-healing properties of the coating materials. The present invention innovatively proposes to use polyurethane as the core material of the healing agent to prepare colloidal capsules that can be dispersed in water to solve the above problems. The present invention provides a method for preparing a self-healing aqueous polyurethane leather coating material containing polyurethane colloidal capsules. First, modify SiO2 nanoparticles into Pickering solid particles, use a solvent-based polyurethane solution as the oil phase, and prepare an O / W type Pickering emulsion stabilized by SiO2 nanoparticles through high-speed emulsification; then use the Pickering emulsion as a template for synthesizing colloidal capsules, add active silane to form colloidal capsules that can be dispersed in the water system through a sol-gel reaction at the oil / water interface, and finally uniformly disperse the colloidal capsules into the aqueous polyurethane leather finishing emulsion to obtain a self-healing aqueous polyurethane leather coating material containing polyurethane colloidal capsules. The present invention uses polyurethane healing agent as the core material to prepare colloidal capsules that can be dispersed in water, with high encapsulation efficiency, large loading capacity, and strong stability; the prepared colloidal capsules are spherical and have a colloidal shell wall structure formed by one or more layers of modified SiO2 nanoparticles. The preparation method provided by the present invention solves the problems of poor self-healing performance and mechanical properties of traditional external self-healing polyurethane coatings due to low compatibility between the healing agent and the polyurethane matrix used for leather finishing and easy agglomeration of traditional microcapsules in the aqueous polyurethane emulsion solution, and endows it with good self-healing performance while taking into account the mechanical properties of the material. In addition, the SiO2 introduced by the preparation method of the present invention can also significantly improve the wear resistance of the leather polyurethane coating. This method has not been reported in the literature and patents. Therefore, carrying out research on polyurethane colloidal capsules with self-healing functions can improve the practical application of polyurethane colloidal capsule aqueous polyurethane self-healing materials in leather coatings. Summary of the Invention

[0007] The present invention provides a method for preparing a self-healing aqueous polyurethane leather coating material containing polyurethane colloidal capsules, which is characterized in that first, the SiO2 nanoparticles are surface-hydrophobically modified, and then a polyurethane solution is used as the oil phase to form an O / W type Pickering emulsion stabilized by SiO2 nanoparticles at the two-phase interface; then active silane is added to crosslink and fix through a sol-gel reaction at the oil / water interface to form colloidal capsules containing polyurethane, and finally the colloidal capsules containing polyurethane are uniformly dispersed into a special leather aqueous polyurethane finishing emulsion to prepare a self-healing aqueous polyurethane leather coating material containing polyurethane colloidal capsules. The specific preparation method is as follows:

[0008] (1) Preparation of modified SiO2 nanoparticles: Hydrophobic modification of hydrophilic fumed SiO2 nanoparticles was carried out using organosilane. Weigh a certain amount of SiO2 into a reactor, add anhydrous ethanol, stir and heat up to 30 - 70 °C, then add organosilane with a mass ratio of (5 - 1):1 to SiO2 and appropriate amount of deionized water to make the solid content of the system 20% - 50%, and stir and react for 1 - 8 h; after the reaction, centrifuge the mixture for 5 - 10 min at a centrifuge speed of 5000 - 8000 r / min; then redisperse the precipitate obtained by centrifugation in anhydrous ethanol, repeat the above centrifugation operation 3 - 6 times, and finally dry the precipitate at 40 - 60 °C for 24 - 48 h to obtain modified SiO2 nanoparticles.

[0009] (2) Preparation of modified SiO2 nanoparticle dispersion: Weigh a certain amount of modified SiO2 nanoparticles into a certain amount of deionized water to make the concentration of the system 1 wt% - 5 wt%, and ultrasonically disperse for 10 - 120 min to obtain modified SiO2 nanoparticle dispersion.

[0010] (3) Preparation of polyurethane solution: Add a certain amount of macromolecular diol into a reactor, and vacuum dry and dehydrate at 90 - 120 °C for 2 - 5 h. After drying, cool down to 60 - 80 °C and protect with inert gas, then add diisocyanate, where the molar ratio of diisocyanate to macromolecular diol is (4 - 10):1, stir at a speed of 500 - 3000 rpm, and stir and react for 0.5 - 2 h; then add small molecule chain extender and catalyst into the reactor, where the molar ratio of small molecule chain extender to macromolecular diol is (3 - 9):1, and control the solid content of the reaction solution at 20% - 50% by adding appropriate solvent, control the reaction temperature at 10 - 90 °C, stir at a speed of 200 - 2000 rpm, and continue to react for 0.5 - 4 h to obtain polyurethane solution.

[0011] (4) Mix the polyurethane solution obtained in step (3) and the modified SiO2 nanoparticle dispersion obtained in step (2), control the oil - water mass ratio of the system at (2 - 5):10, and control the dosage of modified SiO2 nanoparticles at 1.0 wt% of the dry weight of polyurethane; then emulsify the mixture with a homogenizing emulsifier at a rotation speed of 10000 - 15000 rpm for 10 - 70 s, filter with a 50 - 100 mesh sieve, and then remove the solvent by vacuum distillation to obtain an O / W - type Pickering emulsion stabilized by SiO2 nanoparticles.

[0012] (5) Preparation of pre - hydrolyzed active silane: Mix active silane, deionized water and anhydrous ethanol according to the mass ratio of (1 - 9):15:30, stir for 30 min at a stirring speed of 200 - 2000 rpm and a temperature of 10 - 50 °C to obtain pre - hydrolyzed active silane.

[0013] (6) Mix the O / W Pickering emulsion prepared in step (4) with the pre-hydrolyzed active silane obtained in step (5), control the dry weight ratio of the active silane to the polyurethane to be 1:1, and react at 35 - 70 °C for 1 - 72 h to obtain a colloidal capsule dispersible in water.

[0014] (7) Ultrasonically disperse a certain amount of the colloidal capsule for 30 s - 5 min, then add it to the waterborne polyurethane finishing emulsion for leather, and uniformly disperse it through a homogenizing emulsifier for 5 - 30 min to obtain a self-healing waterborne polyurethane leather coating material containing polyurethane colloidal capsules.

[0015] The colloidal capsule is a spherical colloidal capsule with a polyurethane core, a silica nanoparticle shell, and a diameter of 10 - 60 μm.

[0016] The organosilane is one or a mixture of several of dimethyldichlorosilane, vinyltrimethoxysilane, propyltrimethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane, octadecyltrichlorosilane, hexadecyltrichlorosilane, octyltrichlorosilane, and their modified products.

[0017] The diisocyanate is one or a mixture of several of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), and dicyclohexylmethane diisocyanate (HMDI).

[0018] The macromolecular diol is one or a mixture of several of polycaprolactone diol (PCL), polybutylene adipate diol (PBAG), polytetrahydrofuran diol (PTMG), polypropylene glycol (PPG), and polycarbonate diol (PCDL).

[0019] The small molecule chain extender is one or a mixture of several of 2,2-bis(hydroxymethyl)propionic acid (DMPA), ethylenediamine (EDA), 1,4-butanediol (BDO), diethylene glycol (DEG), and 1,6-hexanediol (HDO).

[0020] The preparation method of a self-healing waterborne polyurethane leather coating material containing polyurethane colloidal capsules is characterized in that the solvent is one or a mixture of several of ethyl acetate, acetone, dimethylformamide, N-methylpyrrolidone, dichloromethane, and isopropyl ether.

[0021] The active silane described above is one or a mixture of several of triethoxymethylsilane (MTES), tetraethoxysilane (TEOS), γ-aminopropyltriethoxysilane (APTES), and tripropoxymethylsilane (MTMS).

[0022] The addition amount (dry weight) of the polyurethane-containing colloidal capsule described above is 5-30 wt%.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The polyurethane colloidal capsule of the present invention has a homogeneous repair function: the healing agent in the colloidal capsule is polyurethane, which has excellent chemical compatibility with the aqueous polyurethane matrix. After repair, the interfacial bonding is firm, avoiding the performance weakening caused by heterogeneous materials. After repair, the problem of hard segment / soft segment microphase separation will not be introduced, maintaining the flexibility of the coating, improving wear resistance and tensile strength, and being very suitable for applications in industrial fields such as leather.

[0025] (2) The polyurethane-containing colloidal capsule of the present invention is formed in an aqueous system and can be stably dispersed in the aqueous system. Therefore, it can be stably dispersed in the aqueous polyurethane finishing emulsion, solving the problem that traditional self-healing microcapsules are prone to agglomeration in aqueous media.

[0026] (3) In addition, the present invention innovatively proposes to use the colloidal capsule to develop a self-healing aqueous polyurethane leather coating material; this kind of colloidal capsule is different from the traditional microcapsules used for self-healing. There is a certain pore structure on the surface of the colloidal capsule, and it can achieve on-demand repair through external stimuli (such as mechanical rupture by stress, etc.), which is superior to the "one-time release" of traditional "microcapsules". Description of the Drawings

[0027] Appendix Figure 1 : Infrared spectrum diagram of modified silica nanoparticles.

[0028] Appendix Figure 2 : (a) Optical microscope image of Pickering emulsion containing polyurethane; (b) Optical microscope image of polyurethane-containing colloidal capsule.

[0029] Appendix Figure 3 : Scanning electron microscope image of polyurethane-containing colloidal capsule.

[0030] Appendix Figure 4 : Optical microscope images of self-healing aqueous polyurethane leather coating material containing polyurethane colloidal capsule: (a) Before repair; (b) After repair.

[0031] Appendix Figure 5 : Appearance images of samples after wear resistance test of leather coated with traditional aqueous polyurethane (SWPU), traditional polyurethane (SPU), and aqueous polyurethane (PWPU-5) containing polyurethane colloidal capsule. Detailed Embodiments

[0032] The following are three embodiments of the present invention to specifically illustrate a method for a self-healing aqueous polyurethane leather coating material containing polyurethane colloidal capsules.

[0033] Example 1

[0034] Weigh 3.00 g of SiO2 into a three-necked flask, add 59.25 g of absolute ethanol, heat it to 65 °C while stirring, then add 1.50 g of propyltrimethoxysilane and 0.75 g of deionized water respectively, and stir and react for 8 h; after the reaction is completed, centrifuge the mixed solution for 10 min at a centrifuge speed of 8000 r / min, and redisperse the precipitate in absolute ethanol, repeat the above centrifugation operation 3 times, and finally place the precipitate in a vacuum drying oven at 70 °C and dry it overnight to obtain modified SiO2 nanoparticles. Weigh 0.05 g of modified SiO2 nanoparticles and add them to 4.95 g of deionized water, and ultrasonically disperse for 20 min to obtain a modified SiO2 nanoparticle dispersion, which is reserved for later use.

[0035] Weigh 20.00 g (10 mmol) of polycaprolactone diol (Mn ~ 2000) into a three-necked flask, and vacuum dry and dehydrate it at 120 °C for 2 h. After drying, cool it down to 80 °C and protect it with nitrogen, then add 13.32 g (60 mmol) of isophorone diisocyanate, and react for 1 h under magnetic stirring. After the reaction is completed, cool it down to 70 °C, add 4.50 g (50 mmol) of 1,4-butanediol and two drops of the catalyst dibutyltin dilaurate, and at the same time add the anhydrous solvent ethyl acetate and react for 2 h. After the reaction is completed, a polyurethane solution with a solid content of 40% is obtained.

[0036] Weigh 5.00 g of the polyurethane solution and 5.00 g of the SiO2 nanoparticle dispersion and mix them, and use an emulsifier to emulsify them at a high speed for 5 min under the condition of a stirring speed of 15000 rpm, and filter them through a 200-mesh sieve. The obtained filtrate is a Pickering emulsion stabilized by nano-SiO2. Finally, carry out vacuum distillation on the prepared Pickering emulsion stabilized by SiO2 nanoparticles to remove ethyl acetate, and obtain a polyurethane emulsion stabilized by SiO2 nanoparticles.

[0037] Add 0.5 g of tetraethoxysilane to 15 g of absolute ethanol and 7.5 g of water, stir for 30 min under the condition of a stirring speed of 200 rpm, and then add it to the polyurethane emulsion stabilized by SiO2 nanoparticles, and react at 35 °C for 72 h to form colloidal capsules. Mix 10 g of polyurethane colloidal capsules with a solid content of 20% and 100 g of aqueous polyurethane with a solid content of 20%, and ultrasonically disperse for 60 s for use in leather self-healing coatings.

[0038] Example 2

[0039] Weigh 3.00 g of SiO2 into a three-necked flask, add 59.25 g of absolute ethanol, heat up to 65 °C while stirring, then add 1.50 g of vinyltrimethoxysilane and 0.75 g of deionized water respectively, and stir and react for 8 h. After the reaction is completed, centrifuge the mixed solution for 10 min using a refrigerated centrifuge at a speed of 8000 r / min, redisperse the precipitate in absolute ethanol, repeat the above centrifugation operation 3 times, and finally place the precipitate in a vacuum drying oven at 70 °C for drying overnight to obtain modified SiO2 nanoparticles. Weigh 0.06 g of modified SiO2 nanoparticles and add them to 3.94 g of deionized water, and ultrasonically disperse for 20 min to obtain a dispersion of modified SiO2 nanoparticles for standby.

[0040] Weigh 20.00 g (10 mmol) of polytetrahydrofuran ether glycol (Mn ~ 2000) into a three-necked flask, and vacuum dry and dehydrate at 120 °C for 2 h. After drying, cool down to 80 °C and pass nitrogen for protection, then add 13.32 g (60 mmol) of isophorone diisocyanate thereto, and react under magnetic stirring for 1 h. After the reaction is completed, cool down to 70 °C, add 6.71 g (50 mmol) of 2,2-bis(hydroxymethyl)propionic acid and two drops of catalyst dibutyltin dilaurate, and at the same time add anhydrous solvent acetone and react for 2 h. After the reaction is completed, a polyurethane solution with a solid content of 40% is obtained.

[0041] Weigh 6.00 g of the polyurethane solution and 4.00 g of the SiO2 nanoparticle dispersion and mix them, and high-speed emulsify at a stirring speed of 15000 rpm for 5 min using an emulsifier, and filter through a 200-mesh sieve. The obtained filtrate is a Pickering emulsion stabilized by nano-SiO2. Finally, carry out vacuum distillation on the prepared Pickering emulsion stabilized by SiO2 nanoparticles to remove acetone, and obtain a polyurethane emulsion stabilized by SiO2 nanoparticles.

[0042] Add 0.1 g of triethoxymethylsilane to 3 g of absolute ethanol and 1.5 g of water, stir for 30 min under the condition of a stirring speed of 200 rpm, then add it to the polyurethane emulsion stabilized by SiO2 nanoparticles, and react at 35 °C for 72 h to form colloidal capsules. Mix 15 g of the polyurethane colloidal capsules with a solid content of 20% and 100 g of the aqueous polyurethane with a solid content of 20%, and ultrasonically disperse for 60 s for use in leather self-repair coatings.

[0043] Example 3

[0044] Weigh 3.00 g of SiO2 into a three-necked flask, add 59.25 g of absolute ethanol, heat it to 65 °C while stirring, then add 3.50 g of dimethyldichlorosilane and 0.75 g of deionized water respectively, and stir and react for 8 h. After the reaction is completed, centrifuge the mixed solution with a refrigerated centrifuge for 10 min at a centrifugation speed of 8000 r / min, redisperse the precipitate in absolute ethanol, repeat the above centrifugation operation 3 times, and finally dry the precipitate in a vacuum drying oven at 70 °C overnight to obtain modified SiO2 nanoparticles. Weigh 0.07 g of modified SiO2 nanoparticles and add them to 2.93 g of deionized water, and ultrasonically disperse for 20 min to obtain a dispersion of modified SiO2 nanoparticles for standby.

[0045] Weigh 20.00 g (10 mmol) of polycarbonate diol (Mn ~ 2000) into a three-necked flask and vacuum dry and dehydrate it at 120 °C for 2 h. After drying, cool it to 80 °C and protect it with nitrogen, then add 13.32 g (60 mmol) of isophorone diisocyanate to it, and react for 1 h under magnetic stirring. After the reaction is completed, cool it to 70 °C, add 6.71 g (50 mmol) of 2,2-bis(hydroxymethyl)propionic acid and two drops of catalyst dibutyltin dilaurate, and at the same time add anhydrous solvent dimethylformamide and react for 2 h. After the reaction is completed, a polyurethane solution with a solid content of 40% is obtained.

[0046] Weigh 7.00 g of the polyurethane solution and 3.00 g of the SiO2 nanoparticle dispersion and mix them, and then high-speed emulsify them with an emulsifier at a stirring speed of 15000 rpm for 5 min, and filter them through a 200-mesh sieve. The obtained filtrate is a Pickering emulsion stabilized by nano-SiO2. Finally, the prepared Pickering emulsion stabilized by SiO2 nanoparticles is subjected to vacuum distillation to remove dimethylformamide to obtain a polyurethane emulsion stabilized by SiO2 nanoparticles.

[0047] Add 3.5 g of γ-aminopropyltriethoxysilane to 10.5 g of absolute ethanol and 5.25 g of water, stir for 30 min at a stirring speed of 200 rpm, then add it to the polyurethane emulsion stabilized by SiO2 nanoparticles, and react at 35 °C for 72 h to form colloidal capsules. Mix 20 g of the polyurethane colloidal capsule with a solid content of 20% and 100 g of the aqueous polyurethane with a solid content of 20%, and ultrasonically disperse for 60 s for use in the leather self-repair coating.

Claims

1. The present invention provides a preparation method of a self-repairing aqueous polyurethane leather coating material containing a polyurethane colloid capsule, which is characterized in that First, the SiO2 nanoparticles are surface-hydrophobically modified. Then, using a polyurethane solution as the oil phase, an O / W type Pickering emulsion stabilized by SiO2 nanoparticles at the two-phase interface is formed. Next, active silane is added to crosslink and fix at the oil / water interface through a sol-gel reaction to form a colloidal capsule containing polyurethane. Finally, the colloidal capsule containing polyurethane is uniformly dispersed into a waterborne polyurethane finishing emulsion for leather to prepare a self-healing waterborne polyurethane leather coating material containing polyurethane colloidal capsules. The specific preparation method is as follows: (1) Preparation of modified SiO2 nanoparticles: Hydrophobically modify hydrophilic fumed SiO2 nanoparticles using organosilane. Weigh a certain amount of SiO2 into a reactor, add absolute ethanol, stir and heat up to 30 - 70 °C, then add organosilane with a mass ratio of (5 - 1):1 to SiO2 and an appropriate amount of deionized water to make the solid content of the system 20% - 50%, and stir and react for 1 - 8 h. After the reaction, centrifuge the mixture for 5 - 10 min at a centrifugation speed of 5000 - 8000 r / min. Then redisperse the precipitate obtained by centrifugation in absolute ethanol, repeat the above centrifugation operation 3 - 6 times, and finally dry the precipitate at 40 - 60 °C for 24 - 48 h to obtain modified SiO2 nanoparticles; (2) Preparation of modified SiO2 nanoparticle dispersion: Weigh a certain amount of modified SiO2 nanoparticles into a certain amount of deionized water to make the concentration of the system 1 wt% - 5 wt%, and ultrasonically disperse for 10 - 120 min to obtain a modified SiO2 nanoparticle dispersion; (3) Preparation of polyurethane solution: Add a certain amount of macromolecular diol into a reactor and vacuum dry and dehydrate at 90 - 120 °C for 2 - 5 h. After drying, cool down to 60 - 80 °C and protect with inert gas, then add diisocyanate, where the molar ratio of diisocyanate to macromolecular diol is (4 - 10):1, stir at a speed of 500 - 3000 rpm, and stir and react for 0.5 - 2 h. Then add a small molecule chain extender and a catalyst into the reactor, where the molar ratio of the small molecule chain extender to the macromolecular diol is (3 - 9):1, and control the solid content of the reaction solution at 20% - 50% by adding an appropriate amount of solvent, control the reaction temperature at 10 - 90 °C, stir at a speed of 200 - 2000 rpm, and continue to react for 0.5 - 4 h to obtain a polyurethane solution; (4) Mix the polyurethane solution obtained in step (3) and the modified SiO2 nanoparticle dispersion obtained in step (2), control the oil / water mass ratio of the system at (2 - 5):10, and control the dosage of modified SiO2 nanoparticles at 1.0 wt% of the dry weight of polyurethane. Then emulsify the mixture with a homogenizing emulsifier at a rotation speed of 10000 - 15000 rpm for 10 - 70 s, filter with a 50 - 100 mesh sieve, and then remove the solvent by vacuum distillation to obtain an O / W type Pickering emulsion stabilized by SiO2 nanoparticles; (5) Preparation of pre-hydrolyzed active silane: Mix the active silane, deionized water and absolute ethanol according to the mass ratio of (1-9):15:30, stir for 30 min, with the stirring speed of 200-2000 rpm and the temperature of 10-50 °C to obtain the pre-hydrolyzed active silane; (6) Mix the O / W Pickering emulsion prepared in step (4) and the pre-hydrolyzed active silane obtained in step (5), control the dry weight ratio of the active silane to the polyurethane to be 1:1, and react at 35-70 °C for 1-72 h to prepare the colloidal capsule dispersible in water; (7) Ultrasonically disperse a certain amount of the colloidal capsule for 30 s - 5 min, then add it to the waterborne polyurethane finishing emulsion for leather, and uniformly disperse it through a homogenizing emulsifier for 5-30 min to prepare the self-healing waterborne polyurethane leather coating material containing polyurethane colloidal capsules.

2. The preparation method of a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The colloidal capsule is a spherical colloidal capsule with polyurethane as the core material, silica nanoparticles as the shell layer and a diameter of 10-60 μm.

3. The preparation method of a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The organosilane is one or a mixture of several of dimethyldichlorosilane, vinyltrimethoxysilane, propyltrimethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane, octadecyltrichlorosilane, hexadecyltrichlorosilane, octyltrichlorosilane and their modified products.

4. The preparation method of a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The diisocyanate is one or a mixture of several of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI) and dicyclohexylmethane diisocyanate (HMDI).

5. The method for a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The macromolecular diol is one or a mixture of several of polycaprolactone diol (PCL), polybutylene adipate diol (PBAG), polytetrahydrofuran diol (PTMG), polypropylene glycol (PPG) and polycarbonate diol (PCDL).

6. The preparation method of a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The small molecule chain extender is one or a mixture of several of 2,2-bis(hydroxymethyl)propionic acid (DMPA), ethylenediamine (EDA), 1,4-butanediol (BDO), diethylene glycol (DEG) and 1,6-hexanediol (HDO).

7. The preparation method of a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The solvent is one or a mixture of several of ethyl acetate, acetone, dimethylformamide, N-methylpyrrolidone, dichloromethane and isopropyl ether.

8. The preparation method of a self-healing aqueous polyurethane leather coating material containing a polyurethane colloid capsule according to claim 1, characterized in that The active silane is one or a mixture of several of trimethoxymethylsilane (MTES), tetraethoxysilane (TEOS), γ-aminopropyltriethoxysilane (APTES) and trimethoxymethylsilane (MTMS).

9. A method for preparing a self-healing waterborne polyurethane leather coating material containing a polyurethane colloid capsule as described in claim 1, characterized in that The addition amount (dry weight) of the polyurethane colloidal capsule-containing material is 5-30 wt%.

Images