A waterborne polyurethane anti-fog coating and its preparation method and application

Abstract

The present invention relates to the technical field of anti-fog coating preparation, and in particular to a waterborne polyurethane anti-fog coating, and its preparation method and application. An isocyanate, a long-chain polyol, and a catalyst are mixed and stirred to obtain a stirred reactant; the stirred reactant is mixed with a hydrophilic chain extender and allowed to react further to obtain a continued reactant; the continued reactant is mixed with a neutralizer and allowed to undergo a neutralization reaction to obtain a neutralized reactant; the neutralized reactant is mixed with water and subjected to shear emulsification to obtain a hydrophilic waterborne polyurethane; the hydrophilic polyurethane is mixed with a surfactant and hydrophilic particles to obtain a waterborne polyurethane anti-fog coating. The waterborne polyurethane anti-fog coating provided by the present invention has low-temperature resistance and super-hydrophilicity, and has a hydrophobic angle of 0°.

Description

Technical Field

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

[0002] At present, the preparation of waterborne polyurethane anti-fog coatings often adopts two strategies: super-hydrophobic and super-hydrophilic modification. Among them, the super-hydrophobic strategy aims to reduce the intermolecular forces between condensed water droplets in the air and the surface of the object, so that the droplets roll off naturally. For example, patent CN118222175A prepares a fluorine-containing hydrophobic anti-fog waterborne polyurethane coating. The coating formed has a low surface energy, which can make water droplets slide off the coating to achieve an anti-fog effect. However, the hydrophobic anti-fog strategy relies too much on gravity to make the water droplets roll off, and the water droplets need to reach a certain size before gravity can play an effect of assisting the water droplets to roll off to achieve an anti-fog effect. Therefore, the use scenarios are limited, and the excessive use of fluorine-based substances will cause serious pollution to the environment. CN111849333A uses a hydrophilic strategy to introduce silica to achieve hydrophilic modification of waterborne polyurethane, so that the coating obtains a hydrophilic effect and realizes the anti-fog function. The introduction of a single hydrophobic particle achieves a limited hydrophobic effect. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a waterborne polyurethane anti-fog coating and a preparation method and application thereof. The waterborne polyurethane anti-fog coating provided by the present invention has low temperature resistance and super hydrophilicity.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a waterborne polyurethane anti-fog coating, comprising the following steps:

[0006] 1) mixing an isocyanate, a long-chain polyol, and a catalyst and performing a stirring reaction to obtain a stirred reactant;

[0007] 2) mixing the stirred reactant obtained in step 1) with a hydrophilic chain extender and continuing the reaction to obtain a continued reactant;

[0008] 3) mixing the continued reactant obtained in step 2) with a neutralizing agent and performing a neutralization reaction to obtain a neutralized reactant;

[0009] 4) mixing the neutralized reactant obtained in step 3) with water, and subjecting the mixture to shear emulsification to obtain a hydrophilic waterborne polyurethane;

[0010] 5) The hydrophilic polyurethane obtained in step 4) is mixed with a surfactant and hydrophilic particles to obtain a waterborne polyurethane anti-fog coating.

[0011] Preferably, the long-chain polyol in step 1) comprises polyester polyol and / or polyether polyol;

[0012] The polyester polyol includes aliphatic polyester polyol or aromatic polyester polyol;

[0013] The polyether polyol includes polytetramethylene glycol or polyethylene glycol;

[0014] The catalyst includes dibutyltin dilaurate;

[0015] The stirring reaction conditions include: temperature of 70-85° C., rotation speed of 150-500 rpm, and time of 1 hour.

[0016] Preferably, the hydrophilic chain extender in step 2) comprises a carboxyl chain extender and / or an ionic chain extender;

[0017] The carboxyl chain extender includes dimethylol propionic acid or dimethylol butyric acid;

[0018] The ionic chain extension includes sodium ethylenediamine ethanesulfonate or sodium 1,4-butanediol-2-sulfonate;

[0019] The conditions for the continued reaction include: temperature of 70-85° C., rotation speed of 150-500 rpm, and time of 2-5 hours.

[0020] Preferably, the neutralizing agent in step 3) comprises triethylamine;

[0021] The neutralization reaction conditions include: temperature of 35-45° C., rotation speed of 150-500 rpm, and time of 0.5 h.

[0022] Preferably, the molar ratio of the isocyanate, the long-chain polyol, the hydrophilic chain extender and the neutralizer is 1.5:0.35-0.85:0.35-0.85:0.03-0.05;

[0023] The amount of the catalyst used is one thousandth of the total mass of the isocyanate and the long-chain polyol.

[0024] Preferably, the mass ratio of the neutralization reactant to water in step 4) is 0.1 to 1.5:1;

[0025] The shear emulsification conditions include: a rotation speed of 1000 to 5000 rpm and a time of 5 to 20 minutes.

[0026] Preferably, in step 5), the mass ratio of the hydrophilic polyurethane to the surfactant and the hydrophilic particles is 100:1-5:1-5;

[0027] The mixing conditions include: a rotation speed of 100 to 600 rpm and a time of 10 to 20 minutes;

[0028] The surfactant includes an ionic surfactant or a nonionic surfactant;

[0029] The ionic surfactant includes sodium lauryl sulfate;

[0030] The nonionic surfactant includes one or more of Tween 20, Tween 80, polyoxyethylene ester and polyglycerol ester;

[0031] The hydrophilic particles include one or more of potassium hydroxide, silicon hydroxide and silicon dioxide.

[0032] The present invention also provides a waterborne polyurethane anti-fog coating prepared by the preparation method described in the above technical solution.

[0033] The present invention also provides the use of the waterborne polyurethane anti-fog coating described in the above technical solution in improving the hydrophilicity of the coating.

[0034] The present invention also provides the use of the waterborne polyurethane anti-fog coating described in the above technical solution in inhibiting water condensation on the surface of a hydrophobic material product.

[0035] The innovation of the present invention is as follows:

[0036] (1) Combining the multi-angle regulation of long-chain polyols and hydrophilic chain extenders, the waterborne polyurethane film is given excellent mechanical properties after film formation and the hydrophilicity is initially improved;

[0037] (2) The synergistic use of multiple and different types of surfactants and hydrophilic particulate matter further enhances the hydrophilicity and gives the waterborne polyurethane coating super-hydrophilicity after film formation, thereby enabling it to obtain excellent anti-fog performance;

[0038] (3) By combining the selection of long-chain polyols, chain extenders, and surfactants, as well as regulating the viscosity of waterborne polyurethane, the toughness and structural stability of the waterborne polyurethane anti-fog coating after film formation can be improved from multiple angles, thereby giving it excellent low-temperature resistance. Compared with conventional anti-fog coatings, it can be used for anti-fogging in low-temperature environments, such as the outer cover of a smoothie ice maker and anti-fogging of glass in low-temperature environments in winter;

[0039] (4) By combining the selection of long-chain polyols, hydrophilic chain extenders, and surfactants, the surface energy of waterborne polyurethane can be synergistically regulated, thereby adjusting the adhesion of waterborne polyurethane anti-fog coatings to achieve uniform and tight adhesion to different material substrates.

[0040] Application scenarios: Smoothie ice maker covers, motorcycle helmets, car glass and window glass, etc.

[0041] Special note: The present invention has a certain targeted design, focusing on the two points of low temperature resistance and anti-fog performance. The obtained water-based polyurethane coating can be used as an anti-fog coating for the outer cover of the ice maker, so that customers can clearly observe the state of the ice inside the ice maker. In addition, the outer cover of the ice maker needs to add a water guide groove structure (such as Figure 1 ) Collect and remove the water droplets that slide down the surface of the super-hydrophilic coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0043] Figure 1 Cover for smoothie ice maker;

[0044] Figure 2 The contact angles of the smoothie maker cover before and after applying a super-hydrophilic water-based polyurethane coating, achieving super-hydrophilicity (hydrophobic angle of 0°);

[0045] Figure 3 The anti-fog effect of a test tube before and after applying a super-hydrophilic water-based polyurethane coating. Before applying the anti-fog coating, the test tube filled with ice water fogged up and became opaque; after application, the surface of the test tube remained transparent.

[0046] Figure 4 After applying low-temperature-resistant and low-temperature-resistant water-based polyurethane coatings to the outer cover of a smoothie ice maker, respectively, the coating's state changes after being placed in a -12°C environment for 6 hours. DETAILED DESCRIPTION

[0047] The present invention provides a method for preparing a waterborne polyurethane anti-fog coating, comprising the following steps:

[0048] 1) mixing an isocyanate, a long-chain polyol, and a catalyst and performing a stirring reaction to obtain a stirred reactant;

[0049] 2) mixing the stirred reactant obtained in step 1) with a hydrophilic chain extender and continuing the reaction to obtain a continued reactant;

[0050] 3) mixing the continued reactant obtained in step 2) with a neutralizing agent and performing a neutralization reaction to obtain a neutralized reactant;

[0051] 4) mixing the neutralized reactant obtained in step 3) with water, and subjecting the mixture to shear emulsification to obtain a hydrophilic waterborne polyurethane;

[0052] 5) The hydrophilic polyurethane obtained in step 4) is mixed with a surfactant and hydrophilic particles to obtain a waterborne polyurethane anti-fog coating.

[0053] In the present invention, an isocyanate, a long-chain polyol, and a catalyst are mixed and stirred to produce a stirred reaction product. In the present invention, the long-chain polyol preferably comprises a polyester polyol and / or a polyether polyol. In the present invention, the polyester polyol preferably comprises an aliphatic polyester polyol or an aromatic polyester polyol. In the present invention, the polyether polyol preferably comprises polytetrahydrofuran polyol or polyethylene glycol. In the present invention, the catalyst preferably comprises dibutyltin dilaurate. In the present invention, the stirring reaction preferably occurs at a temperature of 70 to 85°C, a rotation speed of 150 to 500 rpm, and a reaction time of 1 hour.

[0054] The present invention further comprises mixing the obtained stirred reactant with a hydrophilic chain extender and then continuing the reaction to obtain a continued reactant. In the present invention, the hydrophilic chain extender preferably includes a carboxyl chain extender and / or an ionic chain extender. In the present invention, the carboxyl chain extender preferably includes dimethylol propionic acid or dimethylol butyric acid. In the present invention, the ionic chain extender preferably includes sodium ethylenediamine ethanesulfonate or sodium 1,4-butanediol-2-sulfonate. In the present invention, the conditions for the continued reaction preferably include: a temperature of 70 to 85°C, a rotation speed of 150 to 500 rpm, and a time of 2 to 5 hours.

[0055] The present invention comprises mixing the obtained continued reactant with a neutralizing agent and conducting a neutralization reaction to obtain a neutralized reactant. In the present invention, the neutralizing agent preferably comprises triethylamine. In the present invention, the neutralization reaction conditions preferably include: a temperature of 35 to 45° C., a rotation speed of 150 to 500 rpm, and a time of 0.5 h.

[0056] In the present invention, the molar ratio of the isocyanate, long-chain polyol, hydrophilic chain extender and neutralizer is preferably 1.5:0.35-0.85:0.35-0.85:0.03-0.05. In the present invention, the amount of the catalyst is preferably 1 / 1000 of the total mass of the isocyanate and long-chain polyol.

[0057] The present invention mixes the obtained neutralized reactant with water and performs shear emulsification to obtain a hydrophilic waterborne polyurethane. In the present invention, the mass ratio of the neutralized reactant to water is preferably 0.1 to 1.5:1. In the present invention, the shear emulsification conditions preferably include a rotation speed of 1000 to 5000 rpm and a time of 5 to 20 minutes. In the present invention, the water is preferably deionized water.

[0058] In the present invention, long-chain polyols regulate the mechanical properties, stability, and low-temperature resistance of the waterborne polyurethane film after film formation. The molecular weight of the long-chain polyol is selected within the range of 600-4000 g / mol. The hydrophilic chain extender regulates the hydrophilicity, mechanical properties, stability, and low-temperature resistance of the waterborne polyurethane film after film formation. In the present invention, deionized water is added to adjust the solid content of the waterborne polyurethane to a range of 10-60%. In combination with the use of long-chain polyols and chain extenders of different types and molecular weights, the viscosity of the waterborne polyurethane can be controlled to a range of 50-4000 mPa·s to adjust the film-forming properties, mechanical properties, stability, and low-temperature resistance of the waterborne polyurethane.

[0059] The present invention mixes the obtained hydrophilic polyurethane with a surfactant and hydrophilic particles to obtain a water-based polyurethane anti-fog coating. In the present invention, the mass ratio of the hydrophilic polyurethane to the surfactant and the hydrophilic particles is preferably 100:1-5:1-5. In the present invention, the mixing conditions preferably include: 100-600 rpm for 10-20 minutes. In the present invention, the surfactant preferably includes an ionic surfactant or a non-ionic surfactant. In the present invention, the ionic surfactant preferably includes sodium lauryl sulfate. In the present invention, the non-ionic surfactant preferably includes one or more of Tween 20, Tween 80, polyoxyethylene esters, and polyglycerol esters. In the present invention, the hydrophilic particles preferably include one or more of potassium hydroxide, silicon hydroxide, and silicon dioxide.

[0060] The present invention provides a waterborne polyurethane anti-fog coating prepared by the preparation method described in the above technical solution.

[0061] The present invention also provides the use of the waterborne polyurethane anti-fog coating described in the above technical solution in improving the hydrophilicity of the coating.

[0062] The present invention also provides the use of the waterborne polyurethane anti-fog coating described in the above technical solution to inhibit water condensation on the surface of a hydrophobic material article. In the present invention, the hydrophobic material article is preferably a glass or plastic article. In the present invention, the water on the surface of the hydrophobic material article is preferably water vapor or water droplets.

[0063] In the present invention, the use method of the waterborne polyurethane anti-fog coating preferably includes: (1) brushing, using a brush to dip the anti-fog coating and apply it to the surface of an object; (2) dipping, dipping the object into the anti-fog coating slurry, and then naturally dripping the excess coating to obtain a uniform coating; (3) scraping, dropping the anti-fog coating on the surface of the object and using a scraper to scrape the coating evenly; (4) spraying, using a high-pressure spray gun to spray the anti-fog coating on the surface of the object. After coating, the sample is placed at ambient temperature to dry naturally for 6-12 hours, or placed in an oven at 60°C for 2 hours to obtain a dry and stable anti-fog coating.

[0064] In the present invention, the anti-fog coating is applied by brush coating and oven drying in both the examples and the comparative examples.

[0065] In order to further illustrate the present invention, the present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1

[0067] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0068] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time for 1 hour;

[0069] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the continued reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0070] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0071] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane;

[0072] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolpropionic acid was 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 1 / 1000 of the total mass of isocyanate and polyethylene glycol.

[0073] 5) mixing the hydrophilic polyurethane obtained in step 4) with sodium lauryl sulfate and silica particles (300 rpm for 15 min) to obtain a waterborne polyurethane anti-fog coating; wherein the mass ratio of the hydrophilic polyurethane, sodium lauryl sulfate and silica particles is 92:5:3.

[0074] The hydrophobic angle of waterborne polyurethane anti-fog coating is 0°;

[0075] In addition, Figure 3 As shown, a waterborne polyurethane anti-fog coating is applied 1 mm to the surface of a test tube filled with an ice-water mixture. Compared with the test tube without coating, the test tube has good transparency at ambient temperature, which indicates that its surface is not fogged, while the surface of the uncoated test tube is foggy and opaque.

[0076] Comparative Example 1

[0077] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0078] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time for 1 hour;

[0079] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the conditions for the continued reaction are: temperature 80° C., rotation speed 400 rpm, and time 2 to 5 hours;

[0080] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 0°C, rotation speed 500 rpm, time 0.5 h

[0081] 4) mixing the neutralized reactant obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane, that is, a waterborne polyurethane anti-fog coating;

[0082] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolpropionic acid was 1.5:0.5:0.3; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 0.1% of the total mass of the isocyanate and polyethylene glycol.

[0083] The hydrophobic angle of the waterborne polyurethane anti-fog coating is 53°.

[0084] Comparative Example 2

[0085] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0086] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time for 1 hour;

[0087] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the continued reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0088] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0089] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane, thereby obtaining a waterborne polyurethane anti-fog coating;

[0090] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolpropionic acid was 1.5:0.5:0.4; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 0.1% of the total mass of the isocyanate and polyethylene glycol.

[0091] The hydrophobic angle of waterborne polyurethane anti-fog coating is 47°.

[0092] Comparative Example 3

[0093] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0094] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time for 1 hour;

[0095] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the continued reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0096] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0097] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane, thereby obtaining a waterborne polyurethane anti-fog coating;

[0098] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolpropionic acid was 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 0.1% of the total mass of the isocyanate and polyethylene glycol.

[0099] The hydrophobic angle of the waterborne polyurethane anti-fog coating is 42°.

[0100] Comparative Example 4

[0101] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0102] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time for 1 hour;

[0103] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the continued reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0104] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0105] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane;

[0106] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolpropionic acid was 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 1 / 1000 of the total mass of isocyanate and polyethylene glycol.

[0107] 5) The hydrophilic polyurethane obtained in step 4) was mixed with sodium lauryl sulfate (300 rpm for 15 min) to obtain a waterborne polyurethane anti-fog coating; wherein the ratio of the hydrophilic polyurethane to the sodium lauryl sulfate was 97.5:2.5.

[0108] The hydrophobic angle of the waterborne polyurethane anti-fog coating is 19°.

[0109] Comparative Example 5

[0110] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0111] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time for 1 hour;

[0112] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the continued reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0113] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0114] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane;

[0115] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolpropionic acid was 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 1 / 1000 of the total mass of isocyanate and polyethylene glycol.

[0116] 5) The hydrophilic polyurethane obtained in step 4) was mixed with sodium lauryl sulfate (300 rpm for 15 min) to obtain a waterborne polyurethane anti-fog coating; wherein the ratio of the hydrophilic polyurethane to the sodium lauryl sulfate was 95:5.

[0117] The hydrophobic angle of the waterborne polyurethane anti-fog coating is 12°.

[0118] Comparative Example 6

[0119] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0120] 1) mixing isocyanate, polytetramethylene glycol (molecular weight 1000 Da) and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm;

[0121] 2) mixing the stirred reaction product obtained in step 1) with dimethylolpropionic acid and continuing the reaction to obtain a continued reaction product; the continued reaction conditions are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0122] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0123] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane;

[0124] The molar ratio of isocyanate to the hydroxyl groups in the polytetramethylene glycol and the hydroxyl groups in the dimethylol propionic acid is 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate is fixed at 0.3:1.5. The amount of dibutyltin dilaurate used is 0.1% of the total mass of the isocyanate and polytetramethylene glycol.

[0125] The hydrophobic angle of the waterborne polyurethane anti-fog coating is 63°.

[0126] Comparative Example 7

[0127] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0128] 1) mixing isocyanate, polyethylene glycol (molecular weight 1000 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm;

[0129] 2) mixing the stirred reactant obtained in step 1) with dimethylolbutyric acid and continuing the reaction to obtain a continued reactant; the conditions for the continued reaction are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0130] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0131] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane;

[0132] The molar ratio of isocyanate to the hydroxyl groups in polyethylene glycol and dimethylolbutyric acid was 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 0.1% of the total mass of the isocyanate and polyethylene glycol.

[0133] The hydrophobic angle of the waterborne polyurethane anti-fog coating is 59°.

[0134] Comparative Example 8

[0135] A method for preparing a waterborne polyurethane anti-fog coating comprises the following steps:

[0136] 1) mixing isocyanate, glycerol (molecular weight 92 Da), and dibutyltin dilaurate and stirring to react to obtain a stirred reaction product; the stirring reaction conditions are: temperature 80° C., rotation speed 400 rpm;

[0137] 2) mixing the stirred reactant obtained in step 1) with dimethylolbutyric acid and continuing the reaction to obtain a continued reactant; the conditions for the continued reaction are: temperature 80° C., rotation speed 400 rpm, and time 3 hours;

[0138] 3) The continued reaction product obtained in step 2) was mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the neutralization reaction conditions were: temperature 40°C, rotation speed 500 rpm, and time 0.5 h

[0139] 4) mixing the neutralized reaction product obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a speed of 2000 rpm for 10 minutes to obtain a hydrophilic waterborne polyurethane;

[0140] The molar ratio of isocyanate to the hydroxyl groups in glycerol and dimethylolbutyric acid was 1.5:0.5:0.5; the molar ratio of triethylamine to isocyanate was fixed at 0.3:1.5. The amount of dibutyltin dilaurate used was 1 / 1000 of the total mass of isocyanate and glycerol.

[0141] 5) mixing the hydrophilic polyurethane obtained in step 4) with sodium lauryl sulfate and silica particles (300 rpm for 15 min) to obtain a waterborne polyurethane anti-fog coating; wherein the mass ratio of the hydrophilic polyurethane, sodium lauryl sulfate and silica particles is 92:5:3, to obtain a waterborne polyurethane anti-fog coating.

[0142] The hydrophobic angle of waterborne polyurethane anti-fog coating is 0°.

[0143] In addition, the water-based polyurethane anti-fog coating in the comparative example and the water-based polyurethane anti-fog coating in Example 1 were respectively applied 1 mm on the surface of the outer cover of the smoothie ice maker, and then placed in an environment of -12°C for 6 hours. The coating in the comparative example partially fell off, while the coating in Example 1 remained stable.

[0144] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a waterborne polyurethane anti-fog coating, characterized in that: The following steps are involved: 1) mixing an isocyanate, a long-chain polyol, and a catalyst and reacting the mixture with stirring to obtain a stirred reactant; wherein the long-chain polyol has a molecular weight of 600-4000 g / mol; 2) mixing the stirred reactant obtained in step 1) with a hydrophilic chain extender and continuing the reaction to obtain a continued reactant; 3) mixing the continued reactant obtained in step 2) with a neutralizing agent and performing a neutralization reaction to obtain a neutralized reactant; 4) mixing the neutralized reactant obtained in step 3) with water and emulsifying the mixture by shearing to obtain a hydrophilic waterborne polyurethane; the hydrophilic waterborne polyurethane has a solid content of 10-60% and a viscosity of 50-4000 mPa·s; 5) mixing the hydrophilic polyurethane obtained in step 4) with a surfactant and hydrophilic particles to obtain a waterborne polyurethane anti-fog coating; the mass ratio of the hydrophilic polyurethane to the surfactant and the hydrophilic particles is 100:1-5:1-5; the hydrophilic particles include one or more of potassium hydroxide, silicon hydroxide and silicon dioxide; The molar ratio of the isocyanate, the long-chain polyol, the hydrophilic chain extender and the neutralizer is 1.5:0.35-0.85:0.35-0.85:0.03-0.

05.

2. The preparation method according to claim 1, characterized in that The long-chain polyol in step 1) comprises polyester polyol and / or polyether polyol; The polyester polyol includes aliphatic polyester polyol or aromatic polyester polyol; The polyether polyol includes polytetramethylene glycol or polyethylene glycol; The catalyst includes dibutyltin dilaurate; The stirring reaction conditions include: temperature of 70-85° C., rotation speed of 150-500 rpm, and time of 1 hour.

3. The preparation method according to claim 1, characterized in that Said step 2) hydrophilic chain extender comprises a carboxyl chain extender and / or an ionic chain extender; The carboxyl chain extender includes dimethylol propionic acid or dimethylol butyric acid; The ionic chain extension includes sodium ethylenediamine ethanesulfonate or sodium 1,4-butanediol-2-sulfonate; The conditions for the continued reaction include: temperature of 70-85° C., rotation speed of 150-500 rpm, and time of 2-5 hours.

4. The preparation method according to claim 1, characterized in that The neutralizing agent in step 3) comprises triethylamine; The neutralization reaction conditions include: temperature of 35-45° C., rotation speed of 150-500 rpm, and time of 0.5 h.

5. The preparation method according to claim 1, characterized in that The amount of the catalyst used is one thousandth of the total mass of the isocyanate and the long-chain polyol.

6. The preparation method according to claim 1, characterized in that The mass ratio of the neutralization reactant to water in step 4) is 0.1 to 1.5:1; The shear emulsification conditions include: a rotation speed of 1000 to 5000 rpm and a time of 5 to 20 minutes.

7. The preparation method according to claim 1, characterized in that The mixing conditions in step 5) include: a rotation speed of 100 to 600 rpm and a mixing time of 10 to 20 minutes; The surfactant includes an ionic surfactant or a nonionic surfactant; The ionic surfactant includes sodium lauryl sulfate; The nonionic surfactant includes one or more of Tween 20, Tween 80, polyoxyethylene ester and polyglycerol ester.

8. A waterborne polyurethane anti-fog coating prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the waterborne polyurethane anti-fog coating according to claim 8 in improving the hydrophilicity of a coating.

10. Use of the waterborne polyurethane anti-fog coating according to claim 8 in inhibiting water condensation on the surface of a hydrophobic material product.

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