Waterborne polyurethane antifogging coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of preparation of antifogging coatings, in particular to a waterborne polyurethane antifogging coating as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing isocyanate, long-chain polyol and a catalyst, and carrying out a stirring reaction to obtain a stirring reactant; mixing the stirred reactant with a hydrophilic chain extender, and continuously reacting to obtain a continuous reactant; mixing the continuous reactant with a neutralizer, and carrying out a neutralization reaction to obtain a neutralized reactant; mixing the neutralization reactant with water, shearing and emulsifying to obtain hydrophilic waterborne polyurethane; and mixing the hydrophilic polyurethane with a surfactant and the hydrophilic particles to obtain the waterborne polyurethane anti-fog coating. The waterborne polyurethane antifogging coating provided by the invention has low temperature resistance and super-hydrophilicity, and the hydrophobic angle is 0 degree.

Description

Technical Field

[0001] The invention relates to the technical field of anti-fog coating preparation, and 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 the condensed water droplets in the air and the surface of the article, so that the droplets roll off naturally. For example, a fluorine-containing hydrophobic anti-fog waterborne polyurethane coating is prepared in patent CN118222175A, and the coating formed has a lower 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 gravity effect can only play the effect of assisting the water droplets to roll off after the water droplets reach a certain size to achieve an anti-fog effect. Therefore, the use scenario is limited, and the excessive use of fluorine-based substances will cause serious pollution to the environment. And CN111849333A introduces silica to achieve hydrophilic modification of waterborne polyurethane through a hydrophilic strategy, so that the coating obtains a hydrophilic effect to achieve an 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 isocyanate, long-chain polyol and catalyst and stirring to react 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 comprises polytetrahydrofuran polyol 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 type 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: a temperature of 70 to 85° C., a rotation speed of 150 to 500 rpm, and a time of 2 to 5 hours.

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

[0021] The conditions of the neutralization reaction 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 scheme.

[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 innovative features of the present invention are as follows:

[0036] (1) Combining the multi-angle regulation of long-chain polyols and hydrophilic chain extenders, the waterborne polyurethane 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 can further enhance the hydrophilicity and endow the waterborne polyurethane coating with super hydrophilicity after film formation, thereby achieving excellent anti-fogging 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 machine covers, motorcycle helmets, car glass and window glass, etc.

[0041] Special attention: 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 to be used in the embodiments are briefly introduced below.

[0043] Figure 1 Cover for smoothie ice maker;

[0044] Figure 2 The contact angles before and after applying the super-hydrophilic waterborne polyurethane coating to the outer cover of the smoothie maker achieved super-hydrophilicity (hydrophobic angle of 0°);

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

[0046] Figure 4 After applying non-low-temperature resistant and low-temperature resistant water-based polyurethane coatings to the outer cover of the smoothie ice maker respectively, the coating's state changes after being placed in a -12℃ 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 isocyanate, long-chain polyol and catalyst and stirring to react 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] The present invention mixes isocyanate, long-chain polyol and catalyst and then stirs and reacts to obtain a stirred reactant. In the present invention, the long-chain polyol preferably includes polyester polyol and / or polyether polyol. In the present invention, the polyester polyol preferably includes aliphatic polyester polyol or aromatic polyester polyol. In the present invention, the polyether polyol preferably includes polytetrahydrofuran polyol or polyethylene glycol. In the present invention, the catalyst preferably includes dibutyltin dilaurate. In the present invention, the conditions of the stirring reaction preferably include: temperature of 70 to 85°C, rotation speed of 150 to 500 rpm, and time of 1 hour.

[0054] The present invention continues the reaction after mixing the obtained stirred reactant with a hydrophilic chain extender 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 500rpm, and a time of 2 to 5h.

[0055] The present invention mixes the obtained continued reactant with a neutralizing agent and then conducts a neutralization reaction to obtain a neutralized reactant. In the present invention, the neutralizing agent preferably includes triethylamine. In the present invention, the conditions of the neutralization reaction 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 one thousandth of the total mass of the isocyanate and the long-chain polyol.

[0057] The present invention mixes the obtained neutralization reactant with water and performs shear emulsification to obtain a hydrophilic waterborne polyurethane. In the present invention, the mass ratio of the neutralization 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 waterborne polyurethane after film formation. The molecular weight of the long-chain polyol is selected within the range of 600-4000g / mol. The hydrophilic chain extender regulates the hydrophilicity, mechanical properties, stability and low-temperature resistance of waterborne polyurethane after film formation. In the present invention, deionized water is added to adjust the solid content of waterborne polyurethane within the range of 10-60%, and the viscosity of waterborne polyurethane can be regulated by combining the use of long-chain polyols and chain extenders of different types and molecular weights, so that the viscosity range is controlled within 50-4000mPa·s to adjust the film-forming property, mechanical properties, stability and low-temperature resistance of waterborne polyurethane.

[0059] The present invention mixes the obtained hydrophilic polyurethane with a surfactant and hydrophilic particles to obtain a waterborne 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: 100-600rpm, and the time is 10-20min. 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 dodecyl sulfate. In the present invention, the non-ionic surfactant preferably includes one or more of Tween 20, Tween 80, polyoxyethylene ester and polyglycerol ester. 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 scheme.

[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 in inhibiting water condensation on the surface of a hydrophobic material product. In the present invention, the hydrophobic material product is preferably a glass product or a plastic product. In the present invention, the water on the surface of the hydrophobic material product 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 method, using a brushing tool to dip the anti-fog coating and apply it to the surface of the object; (2) dipping method, dipping the object into the anti-fog coating slurry, and then naturally dripping the excess coating to obtain a uniform coating; (3) scraping film method, dropping the anti-fog coating on the surface of the object, and using a scraper to scrape the coating evenly; (4) spraying method, using a high-pressure spray gun tool 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 brushing and drying in an oven 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 in conjunction with 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, comprising the following steps:

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

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

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

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

[0072] The molar ratio of isocyanate to the hydroxyl group in polyethylene glycol and the hydroxyl group in 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 is 1 / 1000 of the total mass of isocyanate and polyethylene glycol;

[0073] 5) mixing the hydrophilic polyurethane obtained in step 4) with sodium dodecyl 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 dodecyl 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 coated 1 mm on the surface of a test tube filled with an ice-water mixture. Compared with before coating, the test tube has good transparency at ambient temperature, indicating that its surface is not foggy, 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, comprising the following steps:

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

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

[0080] 3) The continued reaction product obtained in step 2) is mixed with triethylamine and subjected to a neutralization reaction to obtain a neutralized reaction product; the conditions for the neutralization reaction are: temperature 0°C, rotation speed 500 rpm, and 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 rotation 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 group in polyethylene glycol and the hydroxyl group in dimethylol propionic acid is 1.5:0.5:0.3; the molar ratio of triethylamine to isocyanate is fixed at 0.3:1.5. The amount of dibutyltin dilaurate used is one thousandth of the total mass of 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, comprising the following steps:

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

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

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

[0089] 4) mixing the neutralized reactant obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a rotation 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 group in polyethylene glycol and the hydroxyl group in dimethylol propionic acid is 1.5:0.5:0.4; the molar ratio of triethylamine to isocyanate is fixed at 0.3:1.5. The amount of dibutyltin dilaurate used is one thousandth of the total mass of 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, comprising the following steps:

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

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

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

[0097] 4) mixing the neutralized reactant obtained in step 3) with water at a mass ratio of 3:7, and shearing and emulsifying at a rotation 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 group in polyethylene glycol and the hydroxyl group in 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 one thousandth of the total mass of isocyanate and polyethylene glycol.

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

[0100] Comparative Example 4

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

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

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

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

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

[0106] The molar ratio of isocyanate to the hydroxyl group in polyethylene glycol and the hydroxyl group in 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 is 1 / 1000 of the total mass of isocyanate and polyethylene glycol;

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

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

[0109] Comparative Example 5

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

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

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

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

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

[0115] The molar ratio of isocyanate to the hydroxyl group in polyethylene glycol and the hydroxyl group in 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 is 1 / 1000 of the total mass of isocyanate and polyethylene glycol;

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

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

[0118] Comparative Example 6

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

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

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

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

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

[0124] The molar ratio of isocyanate to the hydroxyl group in polytetramethylene glycol and the hydroxyl group in 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 is one thousandth of the total mass of 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, comprising the following steps:

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

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

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

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

[0132] The molar ratio of isocyanate to the hydroxyl group in polyethylene glycol and the hydroxyl group in dimethylolbutyric 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 one thousandth of the total mass of 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, comprising the following steps:

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

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

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

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

[0140] The molar ratio of isocyanate to the hydroxyl group in glycerol and the hydroxyl group in dimethylolbutyric 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 is one thousandth of the total mass of isocyanate and glycerol;

[0141] 5) mixing the hydrophilic polyurethane obtained in step 4) with sodium dodecyl 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 dodecyl 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 coated on the surface of the outer cover of the ice smoothie machine 1 mm, 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 describes the present invention in detail, 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 protection scope 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 isocyanate, long-chain polyol and catalyst and stirring to react to obtain a stirred reactant; 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 subjecting the mixture to shear emulsification to obtain a hydrophilic waterborne polyurethane; 5) The hydrophilic polyurethane obtained in step 4) is mixed with a surfactant and hydrophilic particles to obtain a waterborne polyurethane anti-fog coating.

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 comprises polytetrahydrofuran polyol 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: The hydrophilic chain extender in step 2) includes a carboxyl chain extender and / or an ionic chain extender; The carboxyl type 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: a temperature of 70 to 85° C., a rotation speed of 150 to 500 rpm, and a time of 2 to 5 hours.

4. The preparation method according to claim 1, characterized in that: The neutralizing agent in step 3) comprises triethylamine; The conditions of the neutralization reaction 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 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; 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: In step 5), the mass ratio of the hydrophilic polyurethane to the surfactant and the hydrophilic particles is 100:1-5:1-5; The mixing conditions include: a rotation speed of 100 to 600 rpm and a 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; The hydrophilic particles include one or more of potassium hydroxide, silicon hydroxide and silicon dioxide.

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 the 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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