Waterborne polyurethane resin for earphone cover leather and preparation method of waterborne polyurethane resin

Abstract

The invention provides waterborne polyurethane resin for earphone cover leather and a preparation method of the waterborne polyurethane resin. The preparation method mainly comprises the following steps: (1) preparing modified boron nitride nano powder; and (2) preparing the waterborne polyurethane resin. The prepared waterborne polyurethane resin for the earphone cover leather has good mechanical properties, air and moisture permeability, waterproofness and thermal conductivity, and the earphone cover leather prepared by taking the waterborne polyurethane resin as the raw material has an excellent shaping effect and alcohol resistance.

Description

Technical Field

[0001] The present invention relates to the field of aqueous polyurethane resins, and particularly to an aqueous polyurethane resin for earphone leatherette and a preparation method thereof. Background Art

[0002] With the rapid economic development, people's living standards have been continuously improved, and the use of earphones has become more and more frequent, and the requirements for earphone leatherette have also become higher and higher. Since aqueous polyurethane resin can endow leather with various trendy aesthetic effects while being environmentally friendly, it has become one of the important materials for preparing earphone leatherette.

[0003] Due to the pursuit of softness and comfort of earphone leatherette, an aqueous polyurethane resin with a certain elasticity is required as the raw material for the synthetic leather surface layer. One method is to reduce the chemical cross-linking density of the aqueous polyurethane resin by reducing the molar ratio of isocyanide to hydroxyl participating in the reaction. However, the alcohol resistance of lightly cross-linked aqueous polyurethane resin is poor, and when it is in long-term contact with alcohol-containing cosmetics as the surface layer material of earphone leatherette, swelling, discoloration or hardening of the texture will occur, thus affecting the comfort and aesthetics of the earphone. In addition, hot pressing and shaping is a necessary process for preparing earphone leather, which requires that the aqueous polyurethane for earphone leather has a certain shaping effect and resilience. A good shaping effect generally requires that the aqueous polyurethane has a certain hardness to maintain a specific shape after hot pressing, but the improvement of hardness may affect the resilience of the leather.

[0004] Aiming at the above problems, the present invention provides an aqueous polyurethane resin for earphone leatherette and a preparation method thereof. The earphone leatherette prepared with it as the raw material has good alcohol resistance and shaping effect at the same time. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides an aqueous polyurethane resin for earphone leatherette and a preparation method thereof. The earphone leatherette prepared with it as the raw material has good alcohol resistance and shaping effect at the same time.

[0006] To achieve the above object, the present invention adopts the following technical solutions: An aqueous polyurethane resin for earphone leatherette and a preparation method thereof. The preparation method of the aqueous polyurethane resin includes the following steps: (1) Preparation of modified boron nitride nanopowder: Add hexagonal boron nitride nanopowder and amino silane compound into a tris aminomethane buffer solution with a pH value of 8-9, stir at 22-28 °C for 10-20 min, add dopamine, and then stir at room temperature for 22-26 h. Centrifuge with ethanol for 8-12 min, and dry to constant weight at 55-65 °C to obtain the modified boron nitride nanopowder; (2)Preparation of aqueous polyurethane resin: Add polyol and 2,2-dimethylolpropionic acid into a four-necked flask, stir at 35-45 °C under a nitrogen-protected environment, add acetone and dibutyltin dilaurate, add isocyanate after heating to 55-65 °C and react for 3-5 h, then slowly add trimethylolpropane within 0.5-1 h, stir for 1-2 h, stir and add triethylamine and continue to react for 1-2 h, then add a dispersant and the modified boron nitride nanopowder prepared in step (1) at 25-35 °C, add deionized water at 3-7 °C after reacting for 3-5 h, and finally remove acetone by rotary evaporation under reduced pressure in a rotary evaporator at 25-35 °C for 20-30 min to obtain the aqueous polyurethane resin.

[0007] Preferably, in step (1), the mass ratio of trisaminomethane buffer solution, hexagonal boron nitride nanopowder, aminosilane compound, and dopamine is 1∶(0.3-0.5)∶(0.2-0.3)∶(0.1-0.2).

[0008] Preferably, the aminosilane compound in step (1) is one of 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0009] Preferably, in step (2), the molar ratio of polyol, isocyanate, and trimethylolpropane is 1∶(0.6-0.8)∶(0.03-0.04).

[0010] Preferably, in step (2), the mass ratio of polyol, 2,2-dimethylolpropionic acid, acetone, dibutyltin dilaurate, triethylamine, dispersant, modified boron nitride nanopowder, and deionized water is 1∶(0.05-0.09)∶(0.4-0.5)∶(0.006-0.010)∶(0.03-0.06)∶(0.001-0.006)∶(0.08-0.12)∶(3.5-3.7).

[0011] Preferably, the polyol in step (2) is one of polyethylene glycol, polypropylene glycol, and polybutylene glycol.

[0012] Preferably, the isocyanate in step (2) is one of isophorone diisocyanate, L-lysine diisocyanate, and hexamethylene diisocyanate.

[0013] Preferably, the dispersant in step (2) is a non-ionic organosilicon dispersant.

[0014] Compared with the existing technologies, the beneficial effects of the present application include but are not limited to: The present invention incorporates boron nitride nanopowder into the aqueous polyurethane resin in a limited manner and uses it as the raw material for the earphone sleeve leather, so that the earphone sleeve leather after the hot pressing process has a good shaping effect (Table 1). At the same time, the presence of boron nitride makes the earphone sleeve leather have good alcohol resistance. In the alcohol resistance test results, no fading phenomenon appears on the surface of the finished leather ( Figure 1 ).

[0015] Other advantages, objectives and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The alcohol resistance test results of the synthetic leather of Comparative Example 2 and Example 1, where (a) is Comparative Example 2 and (b) is Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be specifically described below through examples, which are only used for further illustration of the present invention and should not be construed as limiting the protection scope of the present invention. It should be understood that after reading the content of the present invention, those skilled in the art make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0018] Example 1 The preparation steps of the aqueous polyurethane resin for the earphone sleeve leather are as follows: (1) Preparation of modified boron nitride nanopowder: Add 10 parts of hexagonal boron nitride nanopowder and 7 parts of trimethylsilyldiethylamine to 25 parts of tris (hydroxymethyl) aminomethane buffer solution with a pH value of 8.5, stir at 25 °C for 15 min, add 4 parts of dopamine, stir at room temperature for another 24 h, centrifuge with ethanol for 10 min, and dry to constant weight at 60 °C to obtain the modified boron nitride nanopowder.

[0019] (2) Preparation of aqueous polyurethane resin: Add 90 parts of polybutylene glycol and 7 parts of 2,2-dimethylolpropionic acid to a four-necked flask, stir at 35-45 °C under a nitrogen-protected environment, add 43 parts of acetone and 0.7 part of dibutyltin dilaurate, raise the temperature to 60 °C, then add 37 parts of isophorone diisocyanate and react for 4 h. Subsequently, slowly add 5 parts of trimethylolpropane within 1 h, stir for 2 h, add 4 parts of triethylamine and continue to react for 1.5 h. Add 0.1 part of non-ionic silicone dispersant and 9 parts of the modified boron nitride nanopowder prepared in step (1) at 30 °C. After 4 h, add 320 parts of deionized water at 3 °C, and finally remove acetone by vacuum distillation in a rotary evaporator at 30 °C for 25 min to obtain the aqueous polyurethane resin.

[0020] Example 2 Preparation steps of the waterborne polyurethane resin for the earphone leather case: (1)Preparation of modified boron nitride nanopowder: Add 10 parts of hexagonal boron nitride nanopowder and 6 parts of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane to 20 parts of trisaminomethane buffer solution with a pH value of 8, stir at room temperature for 10 min, add 4 parts of dopamine, stir at room temperature for another 22 h, centrifuge with ethanol for 8 min, and dry at 55 °C until constant weight to obtain the modified boron nitride nanopowder.

[0021] (2)Preparation of waterborne polyurethane resin: Add 85 parts of polyethylene glycol and 7 parts of 2,2-dimethylolpropionic acid to a four-necked flask, stir at 35 °C under a nitrogen-protected environment, add 42 parts of acetone and 0.8 part of dibutyltin dilaurate, raise the temperature to 55 °C, add 35 parts of L-lysine diisocyanate and react for 3 h, then slowly add 4 parts of trimethylolpropane within 1 h, stir for 1 h, add 5 parts of triethylamine and continue to react for 1 h, add 0.5 part of non-ionic silicone dispersant and 11 parts of the modified boron nitride nanopowder prepared in step (1) at 30 °C, add 314 parts of deionized water at 5 °C after 3 h, and finally remove acetone by vacuum distillation in a rotary evaporator at 25 °C for 20 min to obtain the waterborne polyurethane resin.

[0022] Example 3 Preparation steps of the waterborne polyurethane resin for the earphone leather case: (1)Preparation of modified boron nitride nanopowder: Add 11 parts of hexagonal boron nitride nanopowder and 7 parts of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane to 35 parts of trisaminomethane buffer solution with a pH value of 9, stir at room temperature for 20 min, add 4 parts of dopamine, stir at room temperature for another 26 h, centrifuge with ethanol for 12 min, and dry at 65 °C until constant weight to obtain the modified boron nitride nanopowder.

[0023] (2)Preparation of waterborne polyurethane resin: Add 95 parts of polypropylene glycol and 5 parts of 2,2-dimethylolpropionic acid to a four-necked flask, stir at 45 °C under a nitrogen-protected environment, add 38 parts of acetone and 0.6 part of dibutyltin dilaurate, raise the temperature to 65 °C, add 27 parts of hexamethylene diisocyanate and react for 5 h, then slowly add 6 parts of trimethylolpropane within 0.5 h, stir for 1 h, add 3 parts of triethylamine and continue to react for 2 h, add 0.1 part of non-ionic silicone dispersant and 8 parts of the modified boron nitride nanopowder prepared in step (1) at 30 °C, add 335 parts by mass of deionized water at 7 °C after 5 h, and finally remove acetone in a rotary evaporator at 35 °C to obtain the waterborne polyurethane resin.

[0024] Comparative Example 1 Preparation steps of the waterborne polyurethane resin for the ordinary earphone leather case: (1) Preparation of modified boron nitride nanometer powder: Add 10 parts of hexagonal boron nitride nanometer powder and 7 parts of trimethylsilyl diethylamine to 25 parts of tris (hydroxymethyl) aminomethane buffer solution with a pH value of 8.5, stir at room temperature for 15 min, add 4 parts of dopamine, stir at room temperature for another 24 h, centrifuge with ethanol for 10 min, and dry at 60 °C until constant weight to obtain the modified boron nitride nanometer powder.

[0025] (2) Preparation of waterborne polyurethane resin: Add 90 parts of polybutylene glycol and 7 parts of 2,2 - dimethylolpropionic acid to a four - necked flask, stir at 35 - 45 °C under a nitrogen - protected environment, add 43 parts of acetone and 0.7 part of dibutyltin dilaurate, raise the temperature to 60 °C, then add 75 parts of isophorone diisocyanate and react for 4 h. Subsequently, slowly add 5 parts of trimethylolpropane within 1 h, stir for 2 h, add 4 parts of triethylamine and continue to react for 1.5 h. Add 0.1 part of non - ionic silicone dispersant and 9 parts of the modified boron nitride nanometer powder prepared in step (1) at 30 °C. After 4 h, add 320 parts of deionized water at 3 °C, and finally remove acetone by rotary evaporation under reduced pressure in a rotary evaporator at 30 °C for 25 min to obtain the waterborne polyurethane resin.

[0026] Comparative Example 2 The preparation steps of the waterborne polyurethane without modified boron nitride nanometer powder are as follows: Preparation of waterborne polyurethane resin: Add 90 parts of polybutylene glycol and 7 parts of 2,2 - dimethylolpropionic acid to a four - necked flask, stir at 35 - 45 °C under a nitrogen - protected environment, add 43 parts of acetone and 0.7 part of dibutyltin dilaurate, raise the temperature to 60 °C, then add 37 parts of isophorone diisocyanate and react for 4 h. Subsequently, slowly add 5 parts of trimethylolpropane within 1 h, stir for 2 h, add 4 parts of triethylamine and continue to react for 1.5 h. After 4 h, add 320 parts of deionized water at 3 °C, and finally remove acetone by rotary evaporation under reduced pressure in a rotary evaporator at 30 °C for 25 min to obtain the waterborne polyurethane resin.

[0027] Comparative Example 3 The preparation steps of the waterborne polyurethane containing unmodified boron nitride nanometer powder and adding a dispersant are as follows: Preparation of aqueous polyurethane resin: Add 90 parts of polybutylene glycol and 7 parts of 2,2-dimethylolpropionic acid into a four-necked flask, stir at 35 - 45 °C under a nitrogen-protected environment, add 43 parts of acetone and 0.7 part of dibutyltin dilaurate, raise the temperature to 60 °C, then add 37 parts of isophorone diisocyanate and react for 4 h. Subsequently, slowly add 5 parts of trimethylolpropane within 1 h, stir for 2 h, add 4 parts of triethylamine and continue to react for 1.5 h. Add 0.1 part of non-ionic silicone dispersant and 9 parts of hexagonal boron nitride nanopowder at 30 °C. After 4 h, add 320 parts of deionized water at 3 °C. Finally, remove acetone by vacuum distillation in a rotary evaporator at 30 °C for 25 min to obtain the aqueous polyurethane resin.

[0028] Comparative Example 4 The preparation steps of the aqueous polyurethane containing unmodified boron nitride nanopowder and without dispersant are as follows: Preparation of aqueous polyurethane resin: Add 90 parts of polybutylene glycol and 7 parts of 2,2-dimethylolpropionic acid into a four-necked flask, stir at 35 - 45 °C under a nitrogen-protected environment, add 43 parts of acetone and 0.7 part of dibutyltin dilaurate, raise the temperature to 60 °C, then add 37 parts of isophorone diisocyanate and react for 4 h. Subsequently, slowly add 5 parts of trimethylolpropane within 1 h, stir for 2 h, add 4 parts of triethylamine and continue to react for 1.5 h. Add 9 parts of hexagonal boron nitride nanopowder at 30 °C. After 4 h, add 320 parts of deionized water at 3 °C. Finally, remove acetone by vacuum distillation in a rotary evaporator at 30 °C for 25 min to obtain the aqueous polyurethane resin.

[0029] Test methods and results The examples and comparative examples were tested. The test methods for mechanical properties, alcohol resistance, air and moisture permeability, water resistance, thermal conductivity, etc. are as follows: Mechanical properties: Use a mold to make the cured aqueous polyurethane into a sample of 10 mm × 70 mm, and test it on an electronic universal material testing machine. Record and calculate the elongation at break and elastic modulus.

[0030] Air and moisture permeability: Set the instrument temperature to 38 °C and the relative humidity to 50%. Then place the specimen on a moisture permeation cup containing 34 mL of distilled water to form a test assembly and place it in the instrument. Weigh the assembly after 1 h, calculate the weight loss of distilled water and obtain the moisture permeability.

[0031] Water resistance: The water absorption rate of the aqueous polyurethane was tested according to the national standard H / GT 3344—1985.

[0032] Thermal conductivity: The thermal conductivity of the waterborne polyurethane was tested using a Hot Disk thermal conductivity meter. The measurement was carried out using the transient plane heat source method (TPS2500S, Hot Disk), in accordance with the ISO22007-2:2015 standard: the test temperature was 25 °C, the sample size was 30 mm × 30 mm, and the average value was taken after 6 tests.

[0033] Heat setting property: A certain amount of curing agent was added to the waterborne polyurethane, stirred evenly, then scraped and coated on the release paper and heated and dried to form a waterborne polyurethane surface layer material. Then, an adhesive was scraped and coated on the surface layer material and directly bonded to the base fabric. After drying, the release paper was peeled off to obtain the waterborne polyurethane synthetic leather. The waterborne polyurethane synthetic leather was heat-set using a headphone sleeve leather heat-setting machine. The heat-setting temperature was 125 °C, and the setting time was set to 1 min. Note: The setting performance is rated from level 1 to level 5, from poor to good. Level 1 is very poor, and the headphone sleeve leather is basically not set; ≥ level 3 is qualified; level 5 is very good, the headphone sleeve leather has a good setting effect, has a certain resilience and does not collapse.

[0034] Alcohol resistance: The waterborne polyurethane resin was scraped and coated on the release paper and heated and dried to form a surface layer material. Then, an adhesive was scraped and coated on the surface layer material and bonded to the foaming layer. After drying, the release paper was peeled off to obtain the waterborne polyurethane synthetic leather. The test was carried out using an alcohol abrasion resistance tester by the drop method. First, the synthetic leather sample A and B plates were fixed with a clamp and the sample surface was kept flat. A medical cotton cloth was used to wrap the test head and it was made to fall vertically on the surface of the sample plate, and the required weights were applied to make it have a certain frictional force. The instrument speed was adjusted to 30 times / min, the frictional stroke range was 0 - 50 mm, and the mass of the applied weight was 500 g. One cycle consisted of 30 times. The start key was pressed to start the test. During the test, anhydrous ethanol was continuously dropped so that there was always anhydrous ethanol for wiping at the interface connection between the cotton cloth and the sample A and B. After wiping 30 times, the test was stopped and the surface of the coating was observed for discoloration. Each sample was tested at least three times.

[0035] The test results are shown in Table 1, Figure 1 as shown below.

[0036] Table 1 Test results of various properties of Examples 1-3 and Comparative Examples 1-3 Table 1 shows the test results of various properties of Examples 1~3 and Comparative Examples 1~3.

[0037] The elongation at break of Examples 1 to 3 (≥450%) was higher than that of Comparative Examples 1 to 4, and the elastic modulus (≤6.5 MPa) was lower than that of Comparative Examples 1 to 4. Specifically, compared with Comparative Example 1, in the preparation of aqueous polyurethane in Examples 1 to 3, the molar ratio of isocyanide groups to hydroxyl groups was reduced, thereby reducing the crosslinking density of the aqueous polyurethane, increasing the elongation at break, and decreasing the elastic modulus. In addition, in Comparative Example 2, boron nitride was not added, while in Comparative Examples 3 to 4, boron nitride was unevenly dispersed, all of which ultimately led to a decrease in the elongation at break and an increase in the elastic modulus, indicating that the modification method and the addition of a dispersant can promote the uniform dispersion of boron nitride powder in aqueous polyurethane, thereby enhancing the mechanical properties of the aqueous polyurethane.

[0038] The water vapor permeability of Examples 1 to 3 (≥3000 g / m 2 ·24 h) was higher than that of Comparative Examples 1 to 4. Specifically, it was higher than that of Comparative Example 1 because the ratio of isocyanide groups to hydroxyl groups in the aqueous polyurethane prepared in Comparative Example 1 was higher, and the chemical crosslinking density was greater, resulting in a reduction in the intermolecular voids and a decrease in the mobility of molecular segments, thereby reducing the water vapor permeability; the reason for being higher than that of Comparative Example 2 was presumably that the modified boron nitride nanopowder added in Examples 1 to 3 constructed a porous network, and a large amount of water vapor and air could freely pass through the network pores, thereby making the prepared aqueous polyurethane have better water vapor permeability. Although boron nitride was added in Comparative Examples 3 and 4, due to the poor dispersibility of boron nitride without dopamine modification, the water vapor permeability of the two groups was significantly lower than that of Examples 1 to 3. In addition, the water vapor permeability of Comparative Example 4 was worse than that of Comparative Example 3, indicating that the dispersant can promote the further dispersion of boron nitride.

[0039] The water absorption rate reflects the waterproof property of the aqueous polyurethane. The lower the water absorption rate, the better the waterproof property of the aqueous polyurethane. The reason for the lower water absorption rate (≤3%) of Examples 1 to 3 compared with Comparative Example 2 was presumably that the modified boron nitride nanopowder added in Examples 1 to 3 had the characteristics of a graphene-like crystal plane structure and a low surface energy, which blocked the water droplets and made them stay on the surface of the polyurethane, thereby making the prepared aqueous polyurethane waterproof; the reason for being lower than that of Comparative Examples 3 and 4 was that the boron nitride nanopowder in Examples 1 to 3 was modified, and the amino-silane compound further reduced its surface energy, making the prepared aqueous polyurethane have stronger waterproof property. At the same time, dopamine synergistically increased the interfacial affinity of the boron nitride nanopowder, making it evenly dispersed. In addition, the waterproof property of Comparative Example 4 was worse than that of Comparative Example 3, indicating that the added dispersant can improve the waterproof property of the aqueous polyurethane to a certain extent.

[0040] Another reason for choosing boron nitride in the present invention is that the earphone leather needs to be heat-pressed and shaped. The heat conductivity of boron nitride enables the synthetic leather to dissipate heat faster, avoiding damage to the performance of the synthetic leather due to excessive local temperature. At the same time, the added amino-silane compound forms Si-OH-Si bonds through thermal decomposition. This chemical bond plays a plasticizing role and plays a shaping role during the preparation of the earphone sleeve leather. From the thermal conductivity data in Table 1, the thermal conductivity of Examples 1-3 is higher than that of Comparative Example 2, indicating that the addition of modified boron nitride nanopowder can improve the thermal conductivity of polyurethane. The thermal conductivity effects of Comparative Examples 3 and 4 are not ideal, probably because the boron nitride powder in Comparative Examples 3 and 4 has uneven distribution.

[0041] From the results of the thermal setting property test of the waterborne polyurethane synthetic leather, it can be seen that Examples 1-3 have better thermal setting effects than Comparative Example 1. It is speculated that the increase in the content of isocyanide groups in Comparative Example 1 increases the content of hard segments in the waterborne polyurethane, thereby increasing the hardness of the waterborne polyurethane. However, excessive hardness will affect the resilience of the material and the final setting effect. The setting effect of Comparative Example 2 is the worst, probably because it has a large elasticity and lacks the filling of boron nitride nanopowder, resulting in insufficient hardness and being difficult to form finally. The boron nitride powder in Comparative Examples 3 and 4 is unevenly dispersed, resulting in worse setting effects than Examples 1-3.

[0042] Figure 1 The results of the alcohol resistance test of the synthetic leather of Comparative Example 2 and Example 1 are shown in the figure, where (a) is Comparative Example 2 and (b) is Example 1. It can be seen from the figure that Comparative Example 2 shows a fading phenomenon after being wiped with alcohol 30 times, while the leather surface of Example 1 remains intact and does not fade, indicating that the modified boron nitride nanopowder in Example 1 can improve the alcohol resistance of the material.

[0043] In summary, the waterborne polyurethane resin for the earphone sleeve leather prepared by the present invention has good mechanical properties, air permeability and moisture permeability, water resistance and thermal conductivity, and the earphone sleeve leather prepared from it has excellent setting effect and alcohol resistance.

[0044] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all covered by the protection scope of the present invention.

Claims

1. A water-based polyurethane resin for earphone cover leather and a preparation method thereof, characterized in that: The preparation comprises the following steps: (1) Preparation of modified boron nitride nanopowder: add hexagonal boron nitride nanopowder and aminosilane compound to triaminomethane buffer solution with a pH value of 8-9, stir at 22-28°C for 10-20 min, add dopamine, stir at room temperature for another 22-26 h, centrifuge with ethanol for 8-12 min, and dry at 55-65°C to constant weight to obtain modified boron nitride nanopowder; (2) Preparation of waterborne polyurethane resin: Add polyol and 2,2-dihydroxymethylpropionic acid to a four-necked flask, stir at 35-45°C under nitrogen protection, add acetone and dibutyltin dilaurate, heat to 55-65°C, add isocyanate and react for 3-5h, then slowly add trimethylolpropane within 0.5-1h, stir for 1-2h, add triethylamine and continue to react for 1-2h, then add dispersant and modified boron nitride nanopowder obtained in step (1) at 25-35°C, react for 3-5h, add deionized water at 3-7°C, and finally remove acetone by reduced pressure distillation in a rotary evaporator at 25-35°C for 20-30min to obtain a waterborne polyurethane resin.

2. The aqueous polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: In step (1), the mass ratio of triaminomethane buffer solution, hexagonal boron nitride nanopowder, aminosilane compound and dopamine is 1: (0.3-0.5): (0.2-0.3): (0.1-0.2).

3. The water-based polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: The amino compound in step (1) is one of 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

4. The water-based polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: In step (2), the molar ratio of polyol, isocyanate and trimethylolpropane is 1: (0.6-0.8): (0.03-0.04).

5. The water-based polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: In step (2), the mass ratio of polyol, 2,2-dihydroxymethylpropionic acid, acetone, dibutyltin dilaurate, triethylamine, dispersant, modified boron nitride nanopowder, and deionized water is 1: (0.05-0.09): (0.4-0.5): (0.006-0.010): (0.03-0.06): (0.001-0.006): (0.08-0.12): (3.5-3.7).

6. The aqueous polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: The polyol in step (2) is one of polyethylene glycol, polypropylene glycol or polybutylene glycol.

7. The water-based polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: The isocyanate in step (2) is one of isophorone diisocyanate, L-lysine diisocyanate and hexamethylene diisocyanate.

8. The water-based polyurethane resin for earphone cover leather and the preparation method thereof according to claim 1, characterized in that: The dispersant in step (2) is a non-ionic silicone dispersant.

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