Waterborne polyurethane dispersoid for finishing high-gloss leather and preparation method of waterborne polyurethane dispersoid

Abstract

The invention discloses a water-based polyurethane dispersoid for finishing high-gloss leather and a preparation method of the water-based polyurethane dispersoid. The preparation method comprises the following steps: adding a composition of an isocyanate trimer cross-linking agent, a polyol monomer, dicyclohexylmethane diisocyanate and isophorone diisocyanate into dehydrated oligomer dihydric alcohol; then adding a hydrophilic chain extender and a micromolecular dihydric alcohol chain extender to carry out chain extension reaction, neutralizing and adjusting the reaction liquid by using triethylamine, adding a solvent to reduce the viscosity of the material, adding deionized water, and stirring and dispersing to obtain an emulsion; and removing the solvent under vacuum and reduced pressure, adding the flatting agent and the defoaming agent, and stirring to obtain the waterborne polyurethane dispersion. An isocyanate trimer cross-linking agent is introduced, so that molecules containing unsaturated bonds in the system particularly have a conjugated system structure, and the gloss of the adhesive film is improved; polyol monomers are introduced to form polyurethane resin with a cross-linked structure or an interpenetrating polymer network, so that a coating film is fuller, the smoothness of the surface of the adhesive film is facilitated, and the gloss of the adhesive film is improved.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to an aqueous polyurethane dispersion for high-gloss leather finishing and a preparation method thereof. Background Art

[0002] Leather finishing agents are a general term for a class of leather auxiliaries used for leather surface finishing to protect and beautify leather. They play a very important role in the leather manufacturing industry, can increase the beauty of leather, extend the service life of leather, significantly improve the quality and grade of leather products, and increase commercial value.

[0003] As the main raw material of the leather industry, solvent-based polyurethane leather finishing agents emit a large amount of organic solvents during use, causing environmental pollution. The application of aqueous polyurethane leather finishing agents will greatly reduce the emission of organic solvents. Aqueous polyurethane leather finishing agents are not only non-toxic, pollution-free, non-flammable, environmentally friendly and safe during use, but also the coatings still have the characteristics of high abrasion resistance, high elasticity, high adhesion, water resistance, weather resistance, chemical resistance and good adaptability to various substrates generally possessed by solvent-based polyurethanes. However, their gloss is poor. Therefore, people have been engaged in the research of high-gloss polyurethanes. For example, a high-gloss aqueous polyurethane resin and a preparation method thereof disclosed in the Chinese invention patent with the publication number CN103044652A. The diisocyanate preferably used in this method is one or more of toluene diisocyanate and diphenylmethane diisocyanate, and more preferably toluene diisocyanate. The prepared aqueous polyurethane resin is prone to discoloration and yellowing.

[0004] Currently, the aqueous polyurethane finishing agents used for leather finishing generally have problems such as insufficient brightness of the film and yellowing of the product. Currently, there is no high-gloss aqueous polyurethane applied in the field of leather finishing. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an aqueous polyurethane dispersion for high-gloss leather finishing and a preparation method thereof to improve the gloss of the film.

[0006] To solve the above technical problems, according to one aspect of the present invention, a preparation method of an aqueous polyurethane dispersion for high-gloss leather finishing is provided, including the following steps: Step 1: Add 1-6 parts by weight of an isocyanate trimer crosslinking agent, 1-6 parts by weight of a polyol monomer, 32.5-40 parts by weight of a composition of dicyclohexylmethane diisocyanate (HMDI) and isophorone diisocyanate (IPDI) to 70-85 parts by weight of an oligomeric diol after dehydration, and react at 70-90 °C for 1-2 h, wherein the temperature is preferably 75-88 °C, and further preferably 85 °C, to generate a -NCO terminal prepolymer; Step 2: Add 5 - 10 parts by weight of a hydrophilic chain extender, and conduct a chain extension reaction at 80 - 90 °C for 0.5 - 1 h; Step 3: Add 0.3 - 2 parts by weight of a small molecule diol chain extender, and conduct a chain extension reaction at 70 - 90 °C for 2 - 4 h; Step 4: Neutralize and adjust the pH value of the reaction solution to 6 - 7 with 4.5 - 7 parts by weight of triethylamine, add 10 parts by weight of a solvent, and add 250 - 280 parts by weight of deionized water and stir to disperse into an emulsion; the solvent is preferably acetone; Step 5: Remove the solvent by vacuum decompression; Step 6: Add 0.8 - 2 parts by weight of a leveling agent; Step 7: Add 0.1 - 0.2 parts by weight of an antifoaming agent to obtain the aqueous polyurethane dispersion.

[0007] As a preferred embodiment, in Step 1, the oligomer diol is any proportion mixture of two or more of propylene glycol (PPG), polytetrahydrofuran ether glycol (PTMEG), poly(1,2 - propanediol adipate) polyol (PPA), and polycaprolactone (PCL).

[0008] As a preferred embodiment, heat the oligomer diol to 90 - 120 °C and conduct vacuum dehydration for 60 - 90 min to obtain the dehydrated oligomer diol.

[0009] As a preferred embodiment, in Step 1, the isocyanate trimer cross - linker is a trimer of toluene diisocyanate (TDI), a trimer of isophorone diisocyanate (IPDI), a trimer of hexamethylene diisocyanate (HDI), or a trimer of dicyclohexylmethane diisocyanate (HMDI).

[0010] As a preferred embodiment, in Step 1, the polyol monomer is castor oil, hydrogenated castor oil, trimethylolpropane (TMP), or pentaerythritol.

[0011] As a preferred embodiment, in Step 2, the hydrophilic chain extender is dimethylolpropionic acid, dimethylolbutyric acid, dimethylol half - ester, hydroxyacetic acid, 2 - hydroxypropionic acid, dihydroxybenzoic acid, or dihydroxysuccinic acid.

[0012] As a preferred embodiment, in Step 3, the small molecule diol is 1,4 - butanediol, 1,4 - cyclohexanedimethanol, ethylene glycol, propylene glycol, hexanediol, diethylene glycol, or triethylene glycol.

[0013] As a preferred embodiment, in Step 6, the leveling agent is at least one of polydimethylsiloxane, polyester - modified silicone, polyether - modified polydimethylsiloxane, silicone oil, or silicone - modified polyacrylate.

[0014] As a preferred embodiment, in step seven, the defoamer is at least one of lauryl acetate, polyoxyethylene polyoxypropylene amine ether, polydimethylsiloxane, dimethyl silicone oil, tributyl phosphate, and phenyl ethanol oleate.

[0015] According to another aspect of the present invention, there is provided an aqueous polyurethane dispersion for high-gloss leather finishing, which is obtained by the above-described preparation method.

[0016] The beneficial effects of the present invention are as follows: 1) The introduction of an isocyanate trimer crosslinking agent enables molecules containing unsaturated bonds, especially those with a conjugated system structure, in the system, improving the gloss of the film; 2) The introduction of polyol monomers forms a polyurethane resin with a crosslinked structure or an interpenetrating polymer network, making the coating film more plump, facilitating the flatness of the film surface, and improving the gloss of the film. The above double modification of the aqueous polyurethane solves the problem of insufficient film brightness when the aqueous polyurethane is applied to the field of leather finishing.

[0017] The film of the aqueous polyurethane dispersion for high-gloss leather finishing prepared by the method of the present invention is measured by a BYK4446 glossmeter. Its gloss at a 20° angle (GZ) is greater than 130. It is suitable for the finishing of PU, PVC, and genuine leather products, such as the leather finishing of clothing series, leather bags, sofas, and car seat covers. It is also suitable for the exterior and edge finishing of leather and leather products such as clothing, belts, handbags, and seats, as well as the finishing of surfaces such as signs. It meets the product quality indicators required by users in terms of environmental protection, yellowing resistance, etc. Specific Embodiments

[0018] The following are some examples to further illustrate the technical solutions claimed in the present invention. However, the examples and comparative examples are used to explain the embodiments of the present invention and do not exceed the scope of the subject matter of the present invention. The protection scope of the present invention is not limited by the described examples. Unless otherwise specifically stated, the materials and reagents used in the present invention can be obtained from commercial products in the art. Example 1

[0019] Add 60 g of propylene glycol (PPG), 10 g of polytetrahydrofuran ether diol (PTMEG), and 10 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 120 °C for 1 h to dehydrate, and cool to 60 °C after stopping the vacuum; then, add 1 g of hexamethylene diisocyanate (HDI) trimer, 1 g of trimethylolpropane (TMP), add a composition of 20 g of dicyclohexylmethane diisocyanate (HMDI) and 16 g of isophorone diisocyanate (IPDI), react at 85 °C for 1.5 h to form an -NCO-terminated prepolymer; then, add 5 g of dimethylolpropionic acid and carry out chain extension reaction at 88 °C for 0.5 h, add 2 g of 1,4-butanediol and carry out chain extension reaction at 70 °C for 3.5 h; cool to 50 °C and carry out neutralization reaction with 5.5 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 6; use 10 g of acetone to reduce the viscosity of the material, add 260 g of deionized water and stir for 4 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, then add 0.8 g of polyester-modified silicone and 0.1 g of polyoxyethylene polyoxypropylene amine ether and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 2

[0020] Add 55 g of propylene glycol (PPG), 15 g of polytetrahydrofuran ether diol (PTMEG), and 5 g of 1,2-propylene glycol adipate polyol (PPA) into a 500 mL four-necked flask, heat to melt, evacuate at 90 °C for 1.5 h to dehydrate, and cool to 60 °C after stopping the vacuum; then, add a composition of 28 g of dicyclohexylmethane diisocyanate (HMDI) and 7 g of isophorone diisocyanate (IPDI), 4 g of castor oil, 1.5 g of isophorone diisocyanate (IPDI) trimer, react at 82 °C for 1.5 h to form an -NCO-terminated prepolymer; then, add 7 g of dimethylolbutyric acid and carry out chain extension reaction at 82 °C for 1 h, add 1 g of diethylene glycol and carry out chain extension reaction at 85 °C for 3 h; cool to 50 °C and carry out neutralization reaction with 5 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 7; use 10 g of acetone to reduce the viscosity of the material, add 270 g of deionized water and stir at room temperature for 10 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 1.5 g of polyether-modified polydimethylsiloxane and 0.2 g of dimethyl silicone oil and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 3

[0021] Add 50 g of propylene glycol (PPG), 20 g of polytetrahydrofuran ether glycol (PTMEG), and 5 g of poly(1,2-propylene adipate) polyol (PPA) into a 500 mL four-necked flask, heat to melt, evacuate at 115 °C for 1.5 h, and cool down to 50 °C after stopping the vacuum; then, add a composition of 23.5 g of dicyclohexylmethane diisocyanate (HMDI) and 9 g of isophorone diisocyanate (IPDI), 1.5 g of hexamethylene diisocyanate (HDI) trimer, 2 g of hydrogenated castor oil, and react at 86 °C for 1.5 h to form an -NCO terminated prepolymer; then, add 7 g of dimethylolpropionic acid and carry out chain extension reaction at 90 °C for 0.5 h, add 0.5 g of triethylene glycol and carry out chain extension reaction at 90 °C for 2 h; cool down to 50 °C and carry out neutralization reaction with 4.5 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 6.5; use 10 g of acetone to reduce the viscosity of the material, add 250 g of deionized water and stir at room temperature for 5 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 1 g of polyester modified silicone and 0.2 g of polydimethylsiloxane and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 4

[0022] Add 50 g of propylene glycol (PPG), 10 g of polytetrahydrofuran ether glycol (PTMEG), and 15 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 120 °C for 1.5 h, and cool down to 50 °C after stopping the vacuum; then, add a composition of 30 g of dicyclohexylmethane diisocyanate (HMDI) and 10 g of isophorone diisocyanate (IPDI), 6 g of castor oil, 2 g of dicyclohexylmethane diisocyanate (HMDI) trimer, and react at 88 °C for 1 h to form an -NCO terminated prepolymer; then, add 10 g of dimethylolpropionic acid and carry out chain extension reaction at 88 °C for 1 h, add 0.3 g of 1,4-butanediol and carry out chain extension reaction at 85 °C for 2 h; cool down to 50 °C and carry out neutralization reaction with 6 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 6; use 10 g of acetone to reduce the viscosity of the material, add 280 g of deionized water and stir at room temperature for 6 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 2 g of polyether modified polydimethylsiloxane and 0.2 g of polydimethylsiloxane and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 5

[0023] Add 40 g of propylene glycol (PPG), 15 g of polytetrahydrofuran ether glycol (PTMEG), and 15 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 100 °C for 1.5 h, and cool to 50 °C after stopping the vacuum; then, add a composition of 28 g of dicyclohexylmethane diisocyanate (HMDI) and 10 g of isophorone diisocyanate (IPDI), 4 g of hexamethylene diisocyanate (HDI) trimer, 1 g of trimethylolpropane (TMP), and react at 82 °C for 1.5 h to form an -NCO terminated prepolymer; then, add 8 g of dimethylolpropionic acid and carry out chain extension reaction at 80 °C for 1 h, add 0.9 g of 1,4-butanediol and carry out chain extension reaction at 82 °C for 3 h; cool to 50 °C and carry out neutralization reaction with 7 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 7; use 10 g of acetone to reduce the viscosity of the material, add 265 g of deionized water and stir at room temperature for 8 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 1 g of polyester modified silicone and 0.2 g of polyoxyethylene polyoxypropylene amine ether and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 6

[0024] Add 50 g of propylene glycol (PPG), 20 g of polytetrahydrofuran ether glycol (PTMEG), and 5 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 120 °C for 1.5 h, and cool to 50 °C after stopping the vacuum; then, add a composition of 30 g of dicyclohexylmethane diisocyanate (HMDI) and 8 g of isophorone diisocyanate (IPDI), 6 g of hexamethylene diisocyanate (HDI) trimer, 2 g of hydrogenated castor oil, and react at 85 °C for 1.5 h to form an -NCO terminated prepolymer; then, add 8 g of dimethylolpropionic acid and carry out chain extension reaction at 80 °C for 1 h, add 2 g of 1,4-cyclohexanedimethanol and carry out chain extension reaction at 90 °C for 2 h; cool to 50 °C and carry out neutralization reaction with 6 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 6.5; use 10 g of acetone to reduce the viscosity of the material, add 280 g of deionized water and stir at room temperature for 10 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 2 g of polyether modified polydimethylsiloxane and 0.2 g of polyoxyethylene polyoxypropylene amine ether and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 7

[0025] Add 40 g of propylene glycol (PPG), 20 g of polytetrahydrofuran ether glycol (PTMEG), and 10 g of poly(1,2-propylene adipate) polyol (PPA) into a 500 mL four-necked flask, heat to melt, evacuate at 90 °C for 1.5 h, and cool to 50 °C after stopping the vacuum; add a composition of 25 g of dicyclohexylmethane diisocyanate (HMDI) and 12 g of isophorone diisocyanate (IPDI), 5 g of castor oil, and 2 g of isophorone diisocyanate (IPDI) trimer, and react at 78 °C for 1.5 h to form an -NCO-terminated prepolymer; then, add 7 g of dimethylolpropionic acid and carry out a chain extension reaction at 82 °C for 0.5 h, add 0.5 g of 1,4-butanediol and carry out a chain extension reaction at 80 °C for 3 h, cool to 50 °C and carry out a neutralization reaction with 5.5 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 6.5; use 10 g of acetone to reduce the viscosity of the material, add 270 g of deionized water and stir at room temperature for 8 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 1.5 g of silicone oil and 0.2 g of polydimethylsiloxane and stir to obtain an aqueous polyurethane dispersion for leather finishing. Example 8

[0026] Add 50 g of propylene glycol (PPG), 20 g of polytetrahydrofuran ether glycol (PTMEG), and 15 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 120 °C for 1.5 h, and cool to 50 °C after stopping the vacuum; then, add a composition of 30 g of dicyclohexylmethane diisocyanate (HMDI) and 10 g of isophorone diisocyanate (IPDI), 6 g of pentaerythritol, and 2 g of an isocyanate trimer crosslinker which is toluene diisocyanate (TDI) trimer, and react at 75 °C for 2 h to form an -NCO-terminated prepolymer; then, add 10 g of 2-hydroxypropanoic acid and carry out a chain extension reaction at 90 °C for 1 h, add 0.3 g of 1,4-butanediol and carry out a chain extension reaction at 85 °C for 2 h; cool to 50 °C and carry out a neutralization reaction with 7 g of triethylamine for 30 min to adjust the pH value of the reaction solution to 6; use 10 g of acetone to reduce the viscosity of the material, add 280 g of deionized water and stir at room temperature for 6 h to disperse into a light blue translucent emulsion, evacuate to remove the solvent acetone, add 2 g of silicone-modified polyacrylate and 0.2 g of phenethyl alcohol oleate and stir to obtain an aqueous polyurethane dispersion for leather finishing.

[0027] Comparative Example 1 Add 50 g of propylene glycol (PPG), 10 g of polytetrahydrofuran ether diol (PTMEG), and 15 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 90 °C for 1.5 h, cool to 50 °C after stopping the vacuum, add 30 g of dicyclohexylmethane diisocyanate (HMDI), 10 g of isophorone diisocyanate (IPDI), and 4.2 g of dicyclohexylmethane diisocyanate (HMDI) trimer and react for 1.5 h. Then add 10 g of dimethylolpropionic acid and react at 80 °C for 1 h, add 0.3 g of 1,4-butanediol and react at 85 °C for 2.5 h, carry out a neutralization reaction with 6 g of triethylamine for 30 min, at the same time reduce the viscosity of the material with 10 g of acetone, add 280 g of deionized water, finally evacuate to remove the solvent acetone, add 2 g of polyether-modified polydimethylsiloxane, add 0.2 g of polydimethylsiloxane and stir to obtain an aqueous polyurethane dispersion for leather finishing.

[0028] Comparative Example 2 Add 50 g of propylene glycol (PPG), 10 g of polytetrahydrofuran ether diol (PTMEG), and 15 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 120 °C for 1.5 h, cool to 50 °C after stopping the vacuum, add 30 g of dicyclohexylmethane diisocyanate (HMDI), 10 g of isophorone diisocyanate (IPDI), and 9 g of castor oil and react for 1.5 h. Then add 10 g of dimethylolpropionic acid and react at 85 °C for 0.5 h, add 0.3 g of 1,4-butanediol and react at 75 °C for 2.5 h, carry out a neutralization reaction with 6 g of triethylamine for 30 min, at the same time reduce the viscosity of the material with 10 g of acetone, add 280 g of deionized water, finally evacuate to remove the solvent acetone, add 2 g of polyether-modified polydimethylsiloxane, add 0.2 g of polydimethylsiloxane and stir to obtain an aqueous polyurethane dispersion for leather finishing.

[0029] Comparative Example 3 Add 50 g of propylene glycol (PPG), 10 g of polytetrahydrofuran ether diol (PTMEG), and 15 g of polycaprolactone (PCL) into a 500 mL four-necked flask, heat to melt, evacuate at 100 °C for 1.5 h, cool to 50 °C after stopping the vacuum, add 30 g of dicyclohexylmethane diisocyanate (HMDI), 10 g of isophorone diisocyanate (IPDI) and react for 1.5 h. Then add 10 g of dimethylolpropionic acid and react at 80 °C for 1 h, add 1.6 g of 1,4-butanediol and react at 80 °C for 2.5 h, carry out a neutralization reaction with 6 g of triethylamine for 30 min, at the same time reduce the viscosity of the material with 10 g of acetone, add 280 g of deionized water, finally evacuate to remove the solvent acetone, add 2 g of polyether-modified polydimethylsiloxane, add 0.2 g of polydimethylsiloxane and stir to obtain an aqueous polyurethane dispersion for leather finishing.

[0030] In Comparative Example 1, no polyol monomer was added; in Comparative Example 2, no isocyanate trimer crosslinking agent was added; and in Comparative Example 3, neither polyol monomer nor isocyanate trimer crosslinking agent was added. Their properties were compared with the aqueous polyurethane dispersions for leather finishing prepared in Examples 1-7 above, and the results are listed in Table 1.

[0031] Glossiness test: GB / T 9754-2007. The glossiness of the film was measured using a digital glossmeter with an incident angle of 20 o . Three different points were measured. When the error between the three measurements and the average value was not more than 5%, the arithmetic mean was taken as the final result.

[0032] Tensile strength and elongation at break test: Using an electronic tensile tester, the samples were tested according to GB / T 1040.3-2006. Each sample was tested three times, and the average value was taken.

[0033] Heat-resistant yellowing test: The film made from the product was kept at a constant temperature of 120°C for 2 hours to observe whether the film changed color.

[0034] Table 1 Comparison of glossiness properties between Examples and Comparative Examples Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength / MPa >18 >17 >18 >18 >20 >20 >18 >15 >20 >14 Heat resistance to yellowing (120 °C, 2 h) No yellowing No yellowing No yellowing No yellowing No yellowing No yellowing No yellowing No yellowing No yellowing No yellowing Elongation at break / % >800 >1000 >900 >900 >800 >1000 >900 >900 >800 >1100 20° angle glossiness (GZ) 139 133 136 146 131 140 134 87 95 71 In summary, the aqueous polyurethane dispersion for leather finishing prepared in the present invention has properties such as high gloss and yellowing resistance, effectively solving the defect of insufficient brightness in the prior art applied to the field of leather finishing.

[0035] The scope of protection claimed in the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention can have various deformations and modifications. Any modification, improvement, and equivalent replacement made within the concept and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A preparation method of an aqueous polyurethane dispersion for high-gloss leather finishing, characterized in that, It includes the following steps: Step 1: Add 1-6 parts by weight of isocyanate trimer crosslinking agent, 1-6 parts by weight of polyol monomer, 32.5-40 parts by weight of a composition of dicyclohexylmethane diisocyanate (HMDI) and isophorone diisocyanate (IPDI) to 70-85 parts by weight of dehydrated oligomeric diol, and react at 70-90 °C for 1-2 h to generate an -NCO terminal prepolymer; Step 2: Add 5-10 parts by weight of hydrophilic chain extender and carry out a chain extension reaction at 80-90 °C for 0.5-1 h; Step 3: Add 0.3-2 parts by weight of small molecule diol chain extender and carry out a chain extension reaction at 70-90 °C for 2-4 h; Step 4: Neutralize and adjust the pH value of the reaction solution to 6-7 with 4.5-7 parts by weight of triethylamine, add 10 parts by weight of solvent, and add 250-280 parts by weight of deionized water and stir to disperse into an emulsion; Step 5: Remove the solvent by vacuum decompression; Step 6: Add 0.8-2 parts by weight of leveling agent; Step 7: Add 0.1-0.2 parts by weight of defoaming agent to obtain the aqueous polyurethane dispersion.

2. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 1, characterized in that, In Step 1, the oligomeric diol is any proportion mixture of two or more of propylene glycol (PPG), polytetrahydrofuran ether glycol (PTMEG), poly(1,2-propylene adipate) diol (PPA), and polycaprolactone (PCL).

3. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 2, characterized in that, Heat the oligomeric diol to 90-120 °C and dehydrate it under vacuum for 60-90 min to obtain the dehydrated oligomeric diol.

4. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 1, 2 or 3, characterized in that, In Step 1, the isocyanate trimer crosslinking agent is toluene diisocyanate (TDI) trimer, isophorone diisocyanate (IPDI) trimer, hexamethylene diisocyanate (HDI) trimer, or dicyclohexylmethane diisocyanate (HMDI) trimer.

5. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 4, characterized in that, In Step 1, the polyol monomer is castor oil, hydrogenated castor oil, trimethylolpropane (TMP), or pentaerythritol.

6. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 1 or 5, characterized in that, In Step 2, the hydrophilic chain extender is dimethylolpropionic acid, dimethylolbutyric acid, dimethylol half ester, hydroxyacetic acid, 2-hydroxypropionic acid, dihydroxybenzoic acid, or dihydroxysuccinic acid.

7. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 6, characterized in that, In Step 3, the small molecule diol is 1,4-butanediol, 1,4-cyclohexanedimethanol, ethylene glycol, propylene glycol, hexanediol, diethylene glycol, or triethylene glycol.

8. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 1 or 7, characterized in that, In Step 6, the leveling agent is at least one of polydimethylsiloxane, polyester modified silicone, polyether modified polydimethylsiloxane, silicone oil, or silicone modified polyacrylate.

9. The preparation method of the aqueous polyurethane dispersion for high-gloss leather finishing according to claim 8, characterized in that, In Step 7, the defoaming agent is at least one of lauryl acetate, polyoxyethylene polyoxypropylene amine ether, polydimethylsiloxane, dimethyl silicone oil, tributyl phosphate, or phenethyl oleate.

10. An aqueous polyurethane dispersion for high-gloss leather finishing, characterized in that, Obtained by the preparation method according to any one of Claims 1-9.