Delustering waterborne polyurethane coating and preparation method thereof

Abstract

The invention provides a matting waterborne polyurethane coating and a preparation method thereof, and relates to the technical field of waterborne polyurethane, silicon dioxide is treated in a deionized water solution by adopting an amino-terminated coupling agent, drying is not needed after treatment, the matting waterborne polyurethane coating is directly used with the water solution, and the uniformity of the particle size of the silicon dioxide is guaranteed. Amino on the surface of the treated modified silicon dioxide reacts with NCO of a polyurethane molecular chain segment, and then the silicon dioxide is grafted to the polyurethane molecular chain segment, so that the stability of the silicon dioxide in a waterborne polyurethane solution is guaranteed, the silicon dioxide is free of precipitation and layering phenomena after being stored for a long time under very low viscosity, and construction operation is more convenient. The prepared matt waterborne polyurethane coating resin forms a unique grafting structure in the film forming process, and leather coated with the matt waterborne polyurethane coating resin is fine and smooth in hand feeling, obvious in fog feeling, good in matt property, free of color loss, excellent in dry and wet rubbing resistance and excellent in mechanical property.

Description

Technical Field

[0001] The present application belongs to the technical field of waterborne polyurethane, and in particular relates to a matte waterborne polyurethane coating and a preparation method thereof. Background Art

[0002] Waterborne polyurethane is an aqueous solution, dispersion or emulsion of polyurethane in water. It is widely used in decorative coatings for buildings, homes, cars, leather clothing, household appliances, etc. Waterborne polyurethane can be used to prepare matte coatings, which can reduce the gloss of the coating. However, the matte waterborne polyurethane coatings in the prior art are generally obtained by matting agents or self-matting modification, but the prepared polyurethane coatings are not stable and are prone to precipitation and stratification during long-term storage, resulting in poor performance of the polyurethane coatings. Summary of the invention

[0003] The purpose of the present application is to provide a matte waterborne polyurethane coating and a preparation method thereof, aiming to solve the technical problem of poor stability of waterborne polyurethane coatings in the prior art.

[0004] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0005] In a first aspect, the present application provides a method for preparing a matte waterborne polyurethane coating, comprising the following steps:

[0006] (a) treating micron-sized silica with a coupling agent containing terminal amino groups in deionized water to generate modified silica with -NH2 as the terminal group for later use;

[0007] (b) reacting a polyol with a diisocyanate to generate a polyurethane prepolymer with -NCO as the terminal group, adding a hydrophilic chain extender to the prepared polyurethane prepolymer for further reaction, adding triethylamine to adjust the pH to 6.5-7.5 after the reaction, and adding a certain amount of acetone to reduce the viscosity of the material;

[0008] (c) adding the modified silicon dioxide with -NH2 as the terminal group prepared in step (a) to the product obtained in the above step (b) to disperse into a milky white emulsion with a bluish color, and removing the solvent acetone by vacuum distillation to obtain a one-component matte waterborne polyurethane coating.

[0009] According to a preferred embodiment, the mass fraction ratio of the coupling agent to the silicon dioxide is (0.4-0.7):1.

[0010] According to a preferred embodiment, the silicon dioxide is fumed silicon dioxide with an untreated surface and a particle size of 3 to 6 microns;

[0011] The coupling agent is a silane coupling agent, and the silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0012] According to a preferred embodiment, in step (a), it also includes: dispersing micron-sized silica in deionized water, adding a coupling agent containing terminal amino groups, reacting at 40°C for 4 hours to generate modified silica with -NH2 as the terminal group, and cooling to 10-15°C for standby use.

[0013] According to a preferred embodiment, the mass fraction ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the polyol is (0.3-0.45):1;

[0014] The mass fraction ratio of the hydrophilic chain extender to the polyol is (0.08-0.11):1;

[0015] The amount of acetone used is 5-10% by weight of the polyol.

[0016] According to a preferred embodiment, in step (b), it also includes: adding diisocyanate to the dehydrated polyol, reacting at 70-95° C. for 1-2 hours to generate a polyurethane prepolymer with -NCO as the terminal group; adding a hydrophilic chain extender to the prepared polyurethane prepolymer, and performing a chain extension reaction at 75-95° C. for 1.5-2 hours. After the reaction is completed, the pH value of the reaction solution is adjusted to 6.5-7.5 by neutralization with triethylamine, and acetone accounting for 5-10% of the weight of the polyol is added to reduce the viscosity of the material.

[0017] According to a preferred embodiment, the diisocyanate includes a mixture of one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexyl diisocyanate and a hexamethylene diisocyanate trimer.

[0018] According to a preferred embodiment, the polyol includes one or both of polyester polyol and polyether polyol, wherein the polyester polyol includes one or more of polyethylene adipate, polybutylene adipate, polyethylene adipate, polyhexylene adipate, polyneopentyl adipate or polydipropylene adipate; the polyether polyol includes one or more of polyoxypropylene glycol (PPG), polytetramethylene glycol (PTMG) and polyethylene glycol (PEG);

[0019] The hydrophilic chain extender includes one or both of dimethylol propionic acid and dimethylol butyric acid.

[0020] According to a preferred embodiment, in step (c), the modified silica with -NH2 as the end group prepared in step (a) is added to the product obtained in the above step (b) and dispersed into a milky white with blue emulsion, the reaction temperature is 35-40°C, and the reaction time is 6-8h.

[0021] In a second aspect, the present application further provides a matte waterborne polyurethane coating, wherein the matte waterborne polyurethane coating is prepared by the preparation method described in any one of the first aspects.

[0022] Based on the above technical scheme, the matte waterborne polyurethane coating and preparation method thereof of the present application have at least the following technical effects:

[0023] The method for preparing the matt waterborne polyurethane coating of the present invention uses a coupling agent containing terminal amino groups in a deionized water solution to treat silica. After treatment, it does not need to be dried and can be used directly with the aqueous solution, thereby ensuring the uniformity of the silica particle size. The amino groups on the surface of the modified silica after treatment react with the NCO of the polyurethane molecular chain segment, and then the silica is grafted onto the polyurethane molecular chain segment, thereby ensuring the stability of the silica in the aqueous polyurethane solution, allowing it to be stored for a long time at a very low viscosity without precipitation and stratification, and making the construction operation more convenient. The matt waterborne polyurethane coating resin prepared by the present invention forms a unique grafting structure in the film-forming process, and after coating the leather, it has a delicate hand feel, obvious fogging, good matte properties, no color fading, excellent dry and wet rubbing resistance, and excellent mechanical properties. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application 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 application and are not used to limit the present application.

[0025] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0026] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0027] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0029] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0030] The first aspect of the embodiment of the present application provides a method for preparing a matte waterborne polyurethane coating, comprising the following steps:

[0031] (a) Treating micron-sized silica with a coupling agent containing terminal amino groups in deionized water to generate modified silica with -NH2 as the terminal group for later use.

[0032] Specifically: disperse micron-sized silica into deionized water, add a silane coupling agent containing terminal amino groups, react at 40°C for 4 hours to generate modified silica with -NH2 as the terminal group, cool to 10-15°C for standby use, wherein the mass fraction ratio of the coupling agent to silica is (0.4-0.7):1. The silica is fumed silica with an untreated surface and a particle size of 3-6 microns. The silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane (KH-540), 3-aminopropyltriethoxysilane (KH550), N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602), N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (KH-791) or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792).

[0033] (b) reacting polyol and diisocyanate to generate a polyurethane prepolymer with -NCO as the terminal group, adding a hydrophilic chain extender to the prepared polyurethane prepolymer for further reaction, adding triethylamine to adjust the pH to 6.5-7.5 after the reaction, and adding a certain amount of acetone to reduce the viscosity of the material. Specifically: adding diisocyanate to the dehydrated polyol, reacting at 70-95°C for 1-2h to generate a polyurethane prepolymer with -NCO as the terminal group; adding a hydrophilic chain extender to the prepared polyurethane prepolymer, and performing a chain extension reaction at 75-95°C for 1.5-2h, neutralizing with triethylamine after the reaction to adjust the pH value of the reaction solution to 6.5-7.5, and adding acetone accounting for 5-10% of the weight of the polyol to reduce the viscosity of the material.

[0034] The mass fraction ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the polyol is (0.3-0.45):1. The mass fraction ratio of the hydrophilic chain extender to the polyol is (0.08-0.11):1. The amount of acetone used is 5-10% of the weight of the polyol. The diisocyanate includes one or more of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) or dicyclohexyl diisocyanate (HMDI) and a mixture of hexamethylene diisocyanate trimer (HDI trimer). The polyol includes one or both of polyester polyol or polyether polyol, wherein the polyester polyol includes one or more of polyethylene adipate, polybutylene adipate, polydiethylene adipate, polyhexylene adipate, polyneopentyl adipate or polydipropylene adipate; the polyether polyol includes one or more of polyoxypropylene glycol (PPG), polytetramethylene glycol (PTMG) and polyethylene glycol (PEG). The hydrophilic chain extender includes one or both of dimethylol propionic acid or dimethylol butyric acid.

[0035] (c) adding the modified silicon dioxide with -NH2 as the terminal group prepared in step (a) to the product obtained in the above step (b) to disperse into a milky white emulsion with a bluish color, reacting at a temperature of 35 to 40°C for a reaction time of 6 to 8 hours, and removing the solvent acetone by vacuum distillation to obtain a one-component matte waterborne polyurethane coating.

[0036] The preparation method of the present application uses a silane coupling agent containing terminal amino groups to treat micron-sized silica in a deionized water solution. After treatment, it does not need to be dried and can be used directly with the aqueous solution, thereby ensuring the uniformity of the silica particle size. Then, the amino groups on the surface of the modified silica after treatment react with the NCO of the polyurethane molecular chain segment, thereby grafting the silica onto the polyurethane molecular chain segment, thereby ensuring the stability of the silica in the aqueous polyurethane solution, allowing it to be stored for a long time at a very low viscosity without precipitation and stratification, and making the construction operation more convenient.

[0037] The following describes the invention in conjunction with specific embodiments.

[0038] Example 1

[0039] Step a: Add 580g of deionized water and 14g of KH792 silane coupling agent into a four-necked flask, then slowly add 35g of silica and quickly disperse for 10-15min, wherein the solid content of silica is 6%, reduce the stirring speed, heat to 40°C and react for 4h, then cool to between 10-15°C for the next step.

[0040] Step b: This step is performed while step a is being performed. 100g of polyneopentyl adipate and 50g of polyoxypropylene glycol are added to a four-necked flask, heated to melt, vacuumed at 105°C for 1.5h, cooled to 60°C, 50g of IPDI and 6g of HDI trimer are added to react at 85°C for 2h, 15g of dimethylol propionic acid is added to react for 1.5h, 12g of triethylamine is used for neutralization reaction for 30min, 13g of acetone is used to reduce the viscosity of the material, cooled to 33°C, the aqueous solution of modified silicon dioxide obtained in step a is added for emulsification and dispersion to form a milky white and blue emulsion, reacted at 35-40°C for 6-8h, and the solvent acetone is removed by vacuum decompression to obtain a matte waterborne polyurethane coating.

[0041] After testing, the product viscosity is 195mPa·s -1 , there is no precipitation or stratification after centrifugation at 3000r / min for 45min, the glossiness at 60° is ≤5°, the tensile strength is ≥10Mpa, and the elongation at break is ≥1000%.

[0042] Example 2

[0043] Step a: Add 500g of deionized water and 13g of KH602 silane coupling agent into a four-necked flask, then slowly add 26g of silica and quickly disperse for 10-15min, reduce the stirring speed, heat to 40℃ and react for 4h, then cool to between 10-15℃ for the next step.

[0044] Step b: This step is performed while step a is being performed. Add 100g of polybutylene adipate and 50g of polytetrahydrofuran diol into a four-necked flask, heat and melt, evacuate at 105°C for 1.5h, cool to 60°C, add 39g of HDI and 6g of HDI trimer and react at 85°C for 2h, then add 13g of dimethylol propionic acid and react for 1.5h, neutralize with 10g of triethylamine for 30min, and at the same time use 8g of acetone to reduce the viscosity of the material, cool to 33°C, add the aqueous solution of modified silicon dioxide obtained in step a and emulsify and disperse it into a milky white and blue emulsion, react at 35-40°C for 6-8h, remove the solvent acetone under vacuum to obtain a matte waterborne polyurethane coating.

[0045] After testing, the product viscosity is 180mPa·s -1 , there is no precipitation or stratification after centrifugation at 3000r / min for 45min, the glossiness at 60° is ≤5°, the tensile strength is ≥10Mpa, and the elongation at break is ≥1000%.

[0046] Example 3

[0047] Step a: Add 600g of deionized water and 14g of KH791 silane coupling agent into a four-necked flask, then slowly add 24g of silica and quickly disperse for 10-15min, reduce the stirring speed, heat to 40℃ and react for 4h, then cool to between 10-15℃ for the next step.

[0048] Step b: This step is performed while step a is being performed. 100g of polyethylene glycol adipate and 50g of polyethylene glycol are added to a four-necked flask, heated to melt, vacuumed at 105°C for 1.5h, cooled to 60°C, 59g of HMDI and 6g of HDI trimer are added to react at 80°C for 1.5h, 16g of dimethylol propionic acid is added to react for 1.5h, 14g of triethylamine is used for neutralization reaction for 30min, 13g of acetone is used to reduce the viscosity of the material, cooled to 33°C, the aqueous solution of modified silicon dioxide obtained in step a is added for emulsification and dispersion to form a milky white and blue emulsion, reacted at 35-40°C for 6-8h, and the solvent acetone is removed by vacuum decompression to obtain a matte waterborne polyurethane coating.

[0049] After testing, the product viscosity is 210mPa·s -1 , there is no precipitation or stratification after centrifugation at 3000r / min for 45min, the glossiness at 60° is ≤5°, the tensile strength is ≥10Mpa, and the elongation at break is ≥1000%.

[0050] Example 4

[0051] Step a: Add 530g of deionized water, 8g of KH792 silane coupling agent and 6g of KH550 silane coupling agent into a four-necked flask, then slowly add 20g of silica and quickly disperse for 10-15min, reduce the stirring speed, heat to 40°C and react for 4h, then cool to between 10-15°C for the next step.

[0052] Step b: This step is performed while step a is being performed. Add 100g of polyethylene adipate and 50g of polypropylene adipate into a four-necked flask, heat and melt, evacuate at 105°C for 1.5h, cool to 60°C, add 40g of TDI and 6g of HDI trimer and react at 75°C for 1h, then add 12g of dimethylol propionic acid and react for 1.5h, neutralize with 10.5g of triethylamine for 30min, and at the same time use 15g of acetone to reduce the viscosity of the material, cool to 33°C, add the aqueous solution of modified silicon dioxide obtained in step a and emulsify and disperse it into a milky white and blue emulsion, react at 35-40°C for 6-8h, remove the solvent acetone under vacuum and reduce pressure to obtain a matte waterborne polyurethane coating.

[0053] After testing, the product viscosity is 220mPa·s -1 , there is no precipitation or stratification after centrifugation at 3000r / min for 45min, the glossiness at 60° is ≤5°, the tensile strength is ≥10Mpa, and the elongation at break is ≥1000%.

[0054] Example 5

[0055] Step a: Add 530g of deionized water, 9g of KH602 silane coupling agent and 6g of KH540 silane coupling agent into a four-necked flask, then slowly add 22g of silica and quickly disperse for 10-15min, reduce the stirring speed, heat to 40°C and react for 4h, then cool to between 10-15°C for the next step.

[0056] Step b: This step is performed while step a is being performed. Add 100g polyethylene adipate and 50g polyoxypropylene glycol into a four-necked flask, heat and melt, evacuate at 105°C for 1.5h, cool to 60°C, add 50g IPDI and 6g HDI trimer and react at 85°C for 2h, then add 16g dihydroxymethylbutyric acid and react for 2h, neutralize with 12g triethylamine for 30min, and use 13g acetone to reduce the viscosity of the material, cool to 33°C, add the aqueous solution of modified silicon dioxide obtained in step a and emulsify and disperse it into a milky white and blue emulsion, react at 35-40°C for 6-8h, remove the solvent acetone under vacuum, and obtain a matte waterborne polyurethane coating.

[0057] After testing, the product viscosity is 190mPa·s -1 , there is no precipitation or stratification after centrifugation at 3000r / min for 45min, the glossiness at 60° is ≤5°, the tensile strength is ≥10Mpa, and the elongation at break is ≥1000%.

[0058] Comparative Example 1

[0059] Step a: add 100g of polyneopentyl adipate and 50g of polyoxypropylene glycol into a four-necked flask, heat and melt, evacuate at 105°C for 1.5h, cool to 60°C, add 50g of IPDI and 6g of HDI trimer, react at 85°C for 2h, add 15g of dihydroxymethylpropionic acid for 1.5h, neutralize with 12g of triethylamine for 30min, and reduce the viscosity of the material with 13g of acetone, cool to 33°C, add 542g of deionized water for emulsification and dispersion to obtain an emulsion, react at 35-40°C for 6-8h, remove the solvent acetone under vacuum to obtain a waterborne polyurethane coating.

[0060] Step b: Add 35 g of silicon dioxide with a solid content of 6% to the waterborne polyurethane obtained in step a, and quickly disperse for 30 minutes. Add 0.2% of the total amount of the material, Degao 810 defoamer, to defoam, to obtain a waterborne polyurethane coating.

[0061] After testing, the product viscosity is 495mPa·s -1 , 3000r / min centrifugation for 45min, a small amount of soft precipitation, no stratification phenomenon, glossiness at 60° ≤10°, tensile strength <10Mpa, elongation at break <1000%.

[0062] The product test results of Examples 1 to 5 and Comparative Example 1 are shown in Table 1.

[0063] Table 1 Product performance test results of Examples 1 to 5

[0064]

[0065] From the above results, it can be seen that compared with Comparative Example 1, the waterborne polyurethane coatings prepared in Examples 1 to 5 of the present application have no precipitation and stratification phenomenon at very low viscosity and can be stored for a long time, and the gloss, tensile strength and elongation at break of the waterborne polyurethane coatings prepared in Examples 1 to 5 are better than those in Comparative Example 1.

[0066] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a matte waterborne polyurethane coating, characterized in that: The steps include: (a) treating micron-sized silica with a coupling agent containing terminal amino groups in deionized water to generate modified silica with -NH2 as the terminal group for later use; (b) reacting a polyol with a diisocyanate to generate a polyurethane prepolymer with -NCO as the terminal group, adding a hydrophilic chain extender to the prepared polyurethane prepolymer for further reaction, adding triethylamine to adjust the pH to 6.5-7.5 after the reaction, and adding a certain amount of acetone to reduce the viscosity of the material; (c) adding the modified silicon dioxide with -NH2 as the terminal group prepared in step (a) to the product obtained in the above step (b) to disperse into a milky white emulsion with a bluish color, and removing the solvent acetone by vacuum distillation to obtain a one-component matte waterborne polyurethane coating.

2. The preparation method according to claim 1, characterized in that: The mass fraction ratio of the coupling agent to the silicon dioxide is (0.4-0.7):

1.

3. The preparation method according to claim 1 or 2, characterized in that: The silicon dioxide is fumed silicon dioxide with an untreated surface and a particle size of 3 to 6 microns; The coupling agent is a silane coupling agent, and the silane coupling agent includes one or more of γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

4. The preparation method according to claim 3, characterized in that: In step (a), the process also includes: dispersing micron-sized silica into deionized water, adding a coupling agent containing an amino group, reacting at 40° C. for 4 hours to generate modified silica with -NH2 as the terminal group, and cooling the mixture to 10-15° C. for later use.

5. The preparation method according to claim 1, characterized in that: The mass fraction ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the polyol is (0.3-0.45):1; The mass fraction ratio of the hydrophilic chain extender to the polyol is (0.08-0.11):1; The amount of acetone used is 5-10% by weight of the polyol.

6. The preparation method according to claim 5, characterized in that: In step (b), the method further comprises: adding diisocyanate to the dehydrated polyol, reacting at 70-95° C. for 1-2 hours to generate a polyurethane prepolymer with -NCO as the terminal group; adding a hydrophilic chain extender to the prepared polyurethane prepolymer, carrying out a chain extension reaction at 75-95° C. for 1.5-2 hours, neutralizing with triethylamine after the reaction to adjust the pH value of the reaction solution to 6.5-7.5, and adding acetone accounting for 5-10% of the weight of the polyol to reduce the viscosity of the material.

7. The preparation method according to claim 6, characterized in that: The diisocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexyl diisocyanate and a mixture of hexamethylene diisocyanate trimer.

8. The preparation method according to claim 6, characterized in that: The polyol includes one or both of polyester polyol or polyether polyol, wherein the polyester polyol includes one or more of polyethylene adipate, polybutylene adipate, polydiethylene adipate, polyhexylene adipate, polyneopentyl adipate or polydipropylene adipate; the polyether polyol includes one or more of polyoxypropylene glycol, polytetramethylene glycol and polyethylene glycol; The hydrophilic chain extender includes one or both of dimethylol propionic acid and dimethylol butyric acid.

9. The preparation method according to claim 1, characterized in that: In step (c), the modified silicon dioxide with -NH2 as the terminal group prepared in step (a) is added to the product obtained in the above step (b) to be dispersed into a milky white and blue emulsion. The reaction temperature is 35-40°C and the reaction time is 6-8h.

10. A matte waterborne polyurethane coating, characterized in that: The matte waterborne polyurethane coating is prepared by the preparation method described in any one of claims 1 to 9.

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