Preparation method and application of hydrophobically modified polyurethane nanocomposite material

Abstract

The present invention relates to the technical field of polyurethane hydrophobic materials, and discloses a preparation method and application of a hydrophobically modified polyurethane nanocomposite material, comprising the following steps: (1) mixing polytetrahydrofuran, polypropylene glycol, and isophorone diisocyanate for reaction; (2) adding dihydroxy-terminated polydimethylsiloxane or glycerol monostearate to the reaction solution for reaction, then adding a chain extender for reaction, and adding triethylamine for neutralization to obtain a modified waterborne polyurethane emulsion; (3) adding SiO2 powder to octadecyltrichlorosilane for reaction to obtain hydrophobic SiO2 powder; (4) adding the hydrophobic SiO2 powder to ethyl acetate to obtain a first mixed solution; adding the modified waterborne polyurethane emulsion to ethyl acetate to obtain a second mixed solution; and adding the first mixed solution to the second mixed solution to obtain a hydrophobically modified polyurethane nanocomposite material. The present invention combines modified waterborne polyurethane with nano-SiO2 to achieve good hydrophobicity and durability.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethane hydrophobic materials, and more particularly relates to a preparation method and application of a hydrophobically modified polyurethane nanocomposite material. Background Art

[0002] With the continuous progress and development of society, people are paying more and more attention to superhydrophobic materials. In nature, the surface of lotus leaves does not contain expensive and complex chemicals, but exhibits long-term and stable superhydrophobic properties. Research has revealed two main reasons for the superhydrophobicity of lotus leaf surfaces: special structure and surface wax. The microstructure of the lotus leaf surface presents orderly distributed papillae with an average diameter of 5 to 9 microns, and each papilla is covered with microvilli with a diameter of 124 nanometers. A large amount of air is stored between these microstructures, making it impossible for water droplets to penetrate and allowing them to roll freely. This property is attributed to the synergistic effect of the air layer, stalactite protrusions and wax layer. By studying the formation mechanism of these natural superhydrophobic surfaces, more design ideas are provided for the development of multifunctional superhydrophobic surfaces.

[0003] Most superhydrophobic surfaces exhibit weak mechanical durability and are easily damaged by slight abrasion (such as hand touch), not to mention mechanical wear and friction, which leads to a significant decrease in contact angle or even a complete loss of superhydrophobicity, which is the main bottleneck for the practical application of superhydrophobic surfaces.

[0004] Therefore, in order to apply super-hydrophobic surface in industry, its mechanical durability must be improved, for example, on polymer fiber or sponge substrate, build micro-nano roughness structure. Conventionally, low surface energy coating is combined with substrate using the method of chemical etching, to form durable super-hydrophobic coating. However, the preparation step of this method is complicated, and cannot be mass-produced, so its application prospects are limited. Therefore, also by selecting the method adopting physical adsorption to manufacture durable super-hydrophobic surface, polymer auxiliary film forming is used, and conventional polymer includes polyurethane, epoxy resin and acrylate resin etc. This method can not only strengthen the combination between micro-nano rough structure and matrix, but also can provide stable bonding between layer and matrix. Summary of the Invention

[0005] The present invention aims to provide a preparation method and application of a hydrophobically modified polyurethane nanocomposite material. The polyether polyol polytetrahydrofuran and polypropylene glycol are used as soft segments. Due to the presence of ether bonds in the molecular chain, the water resistance of the waterborne polyurethane coating can be improved to a certain extent, thereby enhancing its hydrophobicity. Dihydroxy-terminated polydimethylsiloxane or glycerol monostearate is used as a modifier to enhance the hydrophobicity of the waterborne polyurethane and adjust the structure of the soft and hard segments, effectively improving the film-forming properties of the waterborne polyurethane. Furthermore, octadecyltrichlorosilane is used to modify SiO2 powder, enhancing its hydrophobicity while imparting more reactive groups to its surface, enabling a stronger bond with the polyurethane. The modified nano-SiO2 is mixed with the modified waterborne polyurethane to form a micro-nano roughened structure similar to the surface structure of a lotus leaf, thereby achieving a hydrophobic effect of 1+1>2, further enhancing the hydrophobicity of the waterborne polyurethane nanocomposite material.

[0006] In order to achieve the above object, the present invention is achieved through the following technical solution: a method for preparing a hydrophobically modified polyurethane nanocomposite material, comprising the following steps:

[0007] (1) Mix polytetrahydrofuran, polypropylene glycol, and isophorone diisocyanate, add a solvent to reduce the viscosity, control the reaction temperature at 60-80°C under catalyst conditions, and react for 2-4 hours under an inert gas atmosphere;

[0008] (2) adding a modifier to the reaction solution, wherein the modifier is dihydroxy-terminated polydimethylsiloxane and / or glyceryl monostearate, and reacting for 1-2 hours, then adding a chain extender and reacting for 1-2 hours, then cooling to 30-40° C., adding triethylamine for neutralization for 1-2 hours, and finally adding ice water for emulsification, and removing the solvent by rotary evaporation to obtain a modified waterborne polyurethane emulsion;

[0009] (3) dissolving SiO2 powder in methanol, ultrasonically stirring, adding octadecyltrichlorosilane, reacting at room temperature for 6-12 hours, then centrifuging and vacuum drying to obtain hydrophobic SiO2 powder;

[0010] (4) adding hydrophobic SiO2 powder to ethyl acetate, stirring, and then ultrasonically dispersing to obtain a first mixed solution; adding the modified aqueous polyurethane emulsion to ethyl acetate, stirring, and then ultrasonically dispersing to obtain a second mixed solution; adding the first mixed solution to the second mixed solution, stirring, and then ultrasonically dispersing to obtain a hydrophobically modified polyurethane nanocomposite material.

[0011] Further preferably, in step (1), the molar ratio of the polytetrahydrofuran, polypropylene glycol, and isophorone diisocyanate is (2-3):1:(4-7).

[0012] Further preferably, in step (1), the weight average molecular weight of polytetrahydrofuran is 2000, and the weight average molecular weight of polypropylene glycol is 2000. Further preferably, in step (1), the ratio of the amount of the catalyst and the solvent used to the total mass of polytetrahydrofuran, polypropylene glycol, and isophorone diisocyanate is 100-150 μL:20-50 mL:30-45 g; the catalyst is dibutyltin dilaurate; the solvent is acetone, and the amount of the solvent used is.

[0013] Further preferably, in step (2), the molar ratio of isophorone diisocyanate, dihydroxy-terminated polydimethylsiloxane, chain extender and ethylenediamine is 0.03: 0.001-0.003: 0.01-0.02: 0.01-0.02; the molar ratio of isophorone diisocyanate, glyceryl monostearate, chain extender and ethylenediamine is 0.03: 0.003-0.005: 0.01-0.02: 0.01-0.02; and the chain extender is 2,2-dihydroxymethylpropionic acid.

[0014] Silicones rely on the migration of Si-o-si bonds to form micro-nano structures and achieve hydrophobicity. When the silicone content in polyurethane reaches a certain level, the low-surface-energy silicone forms a complete modified layer on the surface of the polyurethane coating. As the silicone content increases, the surface energy of the polyurethane coating no longer changes, so the water contact angle of the coating reaches its maximum. Glyceryl monostearate relies on long-chain alkanes to achieve a hydrophobic effect and form a micro-nano structure. When an appropriate amount of glyceryl monostearate is added, the hydrophobic long-chain alkanes can produce a hydrophobic effect. Too much will cause entanglement and no hydrophobic effect. To ensure that the hydrophobic chain segment is long enough and has enough space to migrate, the chain extender 2,2-dihydroxymethylpropionic acid is added after the modifier.

[0015] Further preferably, in step (2), the weight average molecular weight of the bishydroxy-terminated polydimethylsiloxane is 1000-2000.

[0016] The best effect is achieved when the molecular weight is between 1000 and 2000. This is because when the molecular weight is small, the Si-O-Si bond cannot migrate. When the molecular weight is too large, the Si-O-Si bond migration will become entangled and the hydrophobicity cannot be effectively exerted.

[0017] Further preferably, in step (2), the amount of ice water used is 20-40% of the total mass of the reactants after neutralization; the temperature of the rotary evaporation is 30-60° C., and the time is 30-60 min.

[0018] Further preferably, in step (3), the ratio of the amount of SiO2 powder, methanol and octadecyltrichlorosilane used is 1-5g:20-50mL:1-5mL; the particle size of the SiO2 powder is not more than 100nm; the centrifugal speed is 4000-8000rpm; and the vacuum drying temperature is 60-80℃.

[0019] Further preferably, in step (4), during the preparation of the first mixed solution, the ratio of the amount of hydrophobic SiO2 powder and ethyl acetate used is 1-5g:30-40mL, stirring is 1-2h, and ultrasonic dispersion is carried out for 10-40min.

[0020] Further preferably, in step (4), during the preparation of the second mixed solution, the ratio of the modified aqueous polyurethane emulsion to ethyl acetate is 30-50 mL:20-30 mL, stirring is performed for 1-2 h, and ultrasonic dispersion is performed for 1-2 h.

[0021] The silica particles and modified polyurethane form a complete coating with an obvious micro-nano rough structure on the coating surface. However, as the amount of polyurethane used increases, the coating surface becomes smoother, and many micropores and micro-nano structures formed on the surface are covered by polyurethane. Therefore, the roughness is reduced, and there is no longer a large amount of air cushion under the water droplets, which reduces the water contact angle of the coating.

[0022] Further preferably, in step (4), the first mixed solution is added to the second mixed solution and stirred for 1-2 hours, and ultrasonically dispersed for 1-2 hours.

[0023] The second technical solution of the present invention: an application of the hydrophobically modified polyurethane nanocomposite material obtained by the above preparation method in a coating.

[0024] Further preferably, the coating is obtained by loading the hydrophobically modified polyurethane nanocomposite into a spray gun, spraying it evenly on the surface of the substrate, drying it at room temperature for 12-24 hours, and then vacuum drying it at 40-60° C. for 6-12 hours to completely remove the solvent, and then storing it in a desiccator to avoid moisture.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) Using dihydroxy-terminated polydimethylsiloxane or glycerol monostearate to modify waterborne polyurethane to make it hydrophobic is a chemical modification. Using modified nano-SiO2 mixed with modified waterborne polyurethane, on the one hand, due to the presence of hydrogen bonds between the chain segments, strong hydrogen bonding forces can be generated between the modified nano-SiO2 and the modified waterborne polyurethane molecular chains through hydrogen bonding. On the other hand, due to the presence of certain hydroxyl groups on the surface of modified nano-SiO2, they can react with the terminal isocyanate of the waterborne polyurethane to a certain extent to form cross-linked covalent bonds. This method has both hydrogen bonding and cross-linking reactions and belongs to the physical and chemical method. A synergistic modification method is adopted. Due to the main chain siloxy bond structure (hydroxyl-terminated polydimethylsiloxane as a block component) or the long side chain (glyceryl monostearate as a block structure) structure of the modified waterborne polyurethane, the hydrophobicity of the waterborne polyurethane is improved. At the same time, since the modified nano-silica itself has strong hydrophobicity, the simultaneous use of the two, the curing reaction of the polyurethane and the phase separation effect between the components make the coating have a micro-nano rough structure similar to the surface structure of the lotus leaf, thereby achieving a hydrophobic effect of 1+1>2, which further enhances the hydrophobicity of the waterborne polyurethane nanocomposite material.

[0027] (2) The modified waterborne polyurethane / nano-SiO2 prepared by the method of the present invention uses ethyl acetate as a solvent, which can make the overall composite emulsion evenly dispersed and not easy to agglomerate; by determining the optimal mixing ratio of modified nano-SiO2 and modified waterborne polyurethane, the suspension is dispersed stably and the material is guaranteed to have good durability.

[0028] (3) The modified waterborne polyurethane / nano-SiO2 prepared by the method of the present invention has both hydrophobicity and durability, and the modified waterborne polyurethane acts as a bonding component, which can not only enhance the adhesion between the coating and the substrate, but also ensure that the nano-silica particles can be stably present in the coating and can be stably combined with the substrate without being destroyed. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the infrared spectrum of the modified waterborne polyurethane in Example 1;

[0030] Figure 2 This is the infrared spectrum of the modified nano-silica in Example 1;

[0031] Figure 3 Graphs showing contact angles without sandpaper polishing in Examples 1 and 2. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] Performance characterization:

[0034] (1) Water contact angle test: The test was conducted by Kruss, Germany, with a droplet volume of 5 μL. The contact angle was measured as the average value of five points on the sample.

[0035] (2) Rolling angle test: Use a microsyringe to drop 5 mL of deionized water onto the modified waterborne polyurethane composite coating. Then slowly tilt the sample. When the sample is tilted to a certain corner, the water drop on the coating just rolls down due to gravity. The angle between the sample surface and the horizontal at this time is the rolling angle. The average value is obtained after 5 similar tests.

[0036] (3) Anti-friction performance test: Place 1000-grit sandpaper on the modified waterborne polyurethane composite coating, and make the modified waterborne polyurethane composite coating directly contact the sandpaper. Place a 50g weight on the sandpaper, and then pull the sandpaper in the direction parallel to the film, keeping the coating and sandpaper parallel to each other. After moving 20cm, measure the contact angle of the modified waterborne polyurethane composite coating. This operation is repeated three times, and the average value of the water contact angle and the rolling angle is calculated.

[0037] Example 1

[0038] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0039] (2) Add 2.5 g of dihydroxy-terminated polydimethylsiloxane (weight-average molecular weight of 1000) to the reaction solution and react for 1 h, then add 1.88 g of 2,2-dihydroxymethylpropionic acid and react for 2 h, lower the temperature of the water bath to 40 ° C, add 1.42 g of triethylamine to the three-necked flask for neutralization, and react for 1 h; lower the temperature of the water bath to room temperature, add ice water to the three-necked flask (the amount added is 30% of the total reactant mass after neutralization), stir and emulsify at a speed of 2000 r / min for 40 min; finally, use a rotary evaporator to evaporate at 40 ° C for 40 min until no bubbles are generated to obtain a silicone-modified waterborne polyurethane emulsion.

[0040] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0041] (4) 4 g of hydrophobic SiO2 powder was added to 36 mL of ethyl acetate and stirred for 30 min, followed by ultrasonic dispersion for 1 h to obtain a first mixed solution. 20 g of organosilicon-modified aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0042] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0043] Example 2 (The only difference from Example 1 is that in step (2), the dihydroxy-terminated polydimethylsiloxane is replaced by glyceryl monostearate)

[0044] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0045] (2) 1.43 g of glyceryl monostearate was added to the reaction solution and reacted for 1 h, followed by addition of 1.88 g of 2,2-dihydroxymethylpropionic acid and reaction for 2 h. The temperature of the water bath was lowered to 40° C., and 1.42 g of triethylamine was added to the three-necked flask for neutralization and reaction for 1 h. The temperature of the water bath was lowered to room temperature, and ice water (the amount added was 30% of the total reactant mass after neutralization) was added to the three-necked flask. The mixture was stirred and emulsified at a speed of 2000 r / min for 40 min. Finally, the mixture was subjected to rotary evaporation at 40° C. for 40 min until no bubbles were generated, thereby obtaining a glyceryl monostearate-modified aqueous polyurethane emulsion.

[0046] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0047] (4) 4 g of hydrophobic SiO2 powder was added to 36 mL of ethyl acetate and stirred for 30 min, followed by ultrasonic dispersion for 1 h to obtain a first mixed solution. 20 g of monostearate-modified aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, stirred vigorously for 30 min, followed by ultrasonic dispersion for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0048] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0049] Example 3

[0050] (1) Pre-dissolve polytetrahydrofuran (26.16 g, 0.01308 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 3:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 50°C under nitrogen at a speed of 200 r / min for 2 h.

[0051] (2) Add 2.5 g of dihydroxy-terminated polydimethylsiloxane (weight-average molecular weight of 1000) to the reaction solution and react for 1 h, then add 1.88 g of 2,2-dihydroxymethylpropionic acid and react for 2 h, lower the temperature of the water bath to 40 ° C, add 1.42 g of triethylamine to the three-necked flask for neutralization, and react for 1 h; lower the temperature of the water bath to room temperature, add ice water to the three-necked flask (the amount added is 30% of the total reactant mass after neutralization), stir and emulsify at a speed of 2000 r / min for 40 min; finally, use a rotary evaporator to evaporate at 40 ° C for 40 min until no bubbles are generated to obtain a silicone-modified waterborne polyurethane emulsion.

[0052] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0053] (4) 4 g of hydrophobic SiO2 powder was added to 36 ml of ethyl acetate and stirred for 30 min, followed by ultrasonic dispersion for 1 h to obtain a first mixed solution. 20 g of organosilicon-modified aqueous polyurethane emulsion was added to 30 ml of ethyl acetate, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0054] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0055] Comparative Example 1 (the only difference from Example 1 is that the polyurethane is not modified with silicone)

[0056] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0057] (2) Add 1.88 g of 2,2-dihydroxymethylpropionic acid to the reaction solution and react for 2 h. Lower the temperature of the water bath to 40°C, add 1.42 g of triethylamine to the three-necked flask for neutralization, and react for 1 h. Lower the temperature of the water bath to room temperature, add ice water to the three-necked flask (the amount added is 30% of the total mass of the reactants after neutralization), stir and emulsify at a speed of 2000 r / min for 40 min. Finally, use a rotary evaporator to evaporate at 40°C for 40 min until no bubbles are generated to obtain an aqueous polyurethane emulsion.

[0058] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0059] (4) 4 g of hydrophobic SiO2 powder was added to 36 mL of ethyl acetate, stirred for 30 min, and then ultrasonically dispersed for 1 h to obtain a first mixed solution. 20 g of aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, vigorously stirred for 30 min, and then ultrasonically dispersed for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, vigorously stirred for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0060] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0061] Comparative Example 2 (the only difference from Example 2 is that the polyurethane is not modified with glyceryl monostearate)

[0062] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0063] (2) Add 1.88 g of 2,2-dihydroxymethylpropionic acid to the reaction solution and react for 2 h. Lower the temperature of the water bath to 40°C, add 1.42 g of triethylamine to the three-necked flask for neutralization, and react for 1 h. Lower the temperature of the water bath to room temperature, add ice water to the three-necked flask (the amount added is 30% of the total mass of the reactants after neutralization), stir and emulsify at a speed of 2000 r / min for 40 min. Finally, use a rotary evaporator to evaporate at 40°C for 40 min until no bubbles are generated to obtain an aqueous polyurethane emulsion.

[0064] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0065] (4) 4 g of hydrophobic SiO2 powder was added to 36 mL of ethyl acetate, stirred for 30 min, and then ultrasonically dispersed for 1 h to obtain a first mixed solution. 20 g of aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, vigorously stirred for 30 min, and then ultrasonically dispersed for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, vigorously stirred for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0066] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0067] Comparative Example 3 (the only difference from Example 1 is that the amount of hydrophobic SiO2 powder added in step (4) is too small, exceeding the scope defined in the claims)

[0068] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0069] (2) Add 2.5 g of dihydroxy-terminated polydimethylsiloxane (weight-average molecular weight of 1000) to the reaction solution and react for 1 h, then add 1.88 g of 2,2-dihydroxymethylpropionic acid and react for 2 h, lower the temperature of the water bath to 40 ° C, add 1.42 g of triethylamine to the three-necked flask for neutralization, and react for 1 h; lower the temperature of the water bath to room temperature, add ice water to the three-necked flask (the amount added is 30% of the total reactant mass after neutralization), stir and emulsify at a speed of 2000 r / min for 40 min; finally, use a rotary evaporator to evaporate at 40 ° C for 40 min until no bubbles are generated to obtain a silicone-modified waterborne polyurethane emulsion.

[0070] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0071] (4) 3 g of hydrophobic SiO2 powder was added to 72 mL of ethyl acetate and stirred for 30 min, followed by ultrasonic dispersion for 1 h to obtain a first mixed solution. 20 g of organosilicon-modified aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, vigorously stirred for 30 min, and then ultrasonically dispersed for 1 h to obtain a second mixed solution. One-half the volume of the first mixed solution was added to the second mixed solution, vigorously stirred for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0072] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0073] Comparative Example 4 (the only difference from Example 1 is that the amount of bishydroxy-terminated polydimethylsiloxane added in step (2) is too much and exceeds the scope defined in the claims)

[0074] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0075] (2) 3.6 g of dihydroxy-terminated polydimethylsiloxane (weight-average molecular weight of 1000) was added to the reaction solution and reacted for 1 h. Then, 1.88 g of 2,2-dihydroxymethylpropionic acid was added and reacted for 2 h. The temperature of the water bath was lowered to 40 ° C. 1.42 g of triethylamine was added to the three-necked flask for neutralization and reacted for 1 h. The temperature of the water bath was lowered to room temperature. Ice water (the amount added was 30% of the total reactant mass after neutralization) was added to the three-necked flask and stirred at 2000 r / min for emulsification for 40 min. Finally, the mixture was subjected to rotary evaporation at 40 ° C for 40 min until no bubbles were generated to obtain a silicone-modified waterborne polyurethane emulsion.

[0076] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0077] (4) 4 g of hydrophobic SiO2 powder was added to 36 mL of ethyl acetate and stirred for 30 min, followed by ultrasonic dispersion for 1 h to obtain a first mixed solution. 20 g of organosilicon-modified aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0078] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0079] Comparative Example 5 (the only difference from Example 2 is that the amount of glyceryl monostearate added in step (2) is too much and exceeds the scope defined in the claims)

[0080] (1) Pre-dissolve polytetrahydrofuran (17.44 g, 0.00872 mol) and polypropylene glycol (8.72 g, 0.00436 mol) in a molar ratio of 2:1. Simultaneously, add 6.67 g of isophorone diisocyanate and 40 mL of acetone to reduce the viscosity. Transfer the pre-dissolved mixed sample to a 250 mL three-necked flask and add 115 μL of dibutyltin dilaurate. Incubate at 60°C under nitrogen at a speed of 200 rpm for 2 h.

[0081] (2) 2.15 g of glyceryl monostearate was added to the reaction solution and the reaction was continued for 1 h. Then, 1.88 g of 2,2-dihydroxymethylpropionic acid was added and the reaction was continued for 2 h. The temperature of the water bath was lowered to 40° C., and 1.42 g of triethylamine was added to the three-necked flask for neutralization and the reaction was continued for 1 h. The temperature of the water bath was lowered to room temperature, and ice water (the amount added was 30% of the total reactant mass after neutralization) was added to the three-necked flask. The mixture was stirred and emulsified at a speed of 2000 r / min for 40 min. Finally, the mixture was subjected to rotary evaporation at 40° C. for 40 min until no bubbles were generated, thereby obtaining a glyceryl monostearate-modified aqueous polyurethane emulsion.

[0082] (3) Weigh 2 g of SiO2 powder and dissolve it in 30 mL of methanol. Ultrasonicate for 30 min, then add octadecyltrichlorosilane and stir magnetically at room temperature for 6 h. Then, centrifuge the solution at a speed of 6000 r / min and finally vacuum dry it to obtain hydrophobic SiO2 powder.

[0083] (4) 4 g of hydrophobic SiO2 powder was added to 36 mL of ethyl acetate and stirred for 30 min, followed by ultrasonic dispersion for 1 h to obtain a first mixed solution. 20 g of monostearate-modified aqueous polyurethane emulsion was added to 30 mL of ethyl acetate, stirred vigorously for 30 min, followed by ultrasonic dispersion for 1 h to obtain a second mixed solution. The first mixed solution was added to the second mixed solution, stirred vigorously for 30 min, and then ultrasonically dispersed for 1 h. The mixture was uniformly mixed to obtain a hydrophobically modified polyurethane nanocomposite.

[0084] (5) The hydrophobically modified polyurethane nanocomposite was loaded into a spray gun and sprayed onto the surface of a substrate glass sheet and dried at room temperature for 7 days, then dried in a vacuum drying oven for 24 h to completely remove the solvent, and then stored in a desiccator to avoid moisture, thereby obtaining a coating with a thickness of 50 μm.

[0085] Table 1

[0086]

[0087]

[0088] like Figure 1 The infrared spectra of the modified waterborne polyurethane in Example 1 are shown, from top to bottom, the infrared spectra of pure WPU, WPU-PDMS, and IPDI, 3324 cm -1 and 1712cm -1 The peak at 1540 cm corresponds to the stretching vibration of the NH bond and the C=O bond. -1 The peak at 2854-2941 cm originates from the bending vibration of the NH bond, which means the formation of carbamate groups; -1 There are characteristic peaks attributable to -CH3, -CH2- and -CH-; 2200-2300cm -1 The -NCO stretching vibration peak at 1103 disappears, which means that the active NCO group of IPDI is completely consumed by the -OH group; 804cm is the COC stretching vibration absorption peak in the soft segment polyether polyol structure, indicating that the polyol is successfully introduced into the chain. -1 The -Si-C- absorption shown at the bottom is a characteristic of the silicone segment. The above results indicate that waterborne polyurethane was successfully synthesized and PDMS was successfully introduced into the WPU polymer chain.

[0089] like Figure 2 The infrared spectrum of modified nano-silica in Example 1 is shown, where the peak at 467 cm -1 , 800cm -1 , 1000cm -1The reason for the appearance of these three absorption peaks is the stretching vibration of Si-O bond and Si-O-Si bond, which proves the existence of SiO2. The infrared characteristic peak of hydrophobic SiO2 is at 2700-3000cm -1 A new absorption peak appears at , which is the stretching vibration peak of saturated CH, proving that the silane coupling agent is successfully grafted onto SiO2 and that hydrophobic silica is successfully synthesized.

[0090] Table 1 shows the contact angle before polishing, the sliding angle before polishing, the contact angle after polishing, and the sliding angle after polishing of the modified waterborne polyurethane / modified nano-SiO2 composite film formed in Examples 1-2 and Comparative Examples 1-2. Figure 3 The contact angle diagrams without sandpaper polishing are shown in Examples 1 and 2. It can be seen that the modified waterborne polyurethane / modified nano-SiO2 composite film coatings in Examples 1-2 of the present application have excellent hydrophobic properties and good anti-friction properties.

[0091] In Comparative Example 1, when the polyurethane lacked the organosilicon component, the coating had very poor hydrophobicity, with a water contact angle of only 101°. In Comparative Example 2, when the polyurethane lacked the glycerol monostearate component, the coating also had very poor hydrophobicity, with a water contact angle of only 101.2°. In contrast, in Examples 1-2, the silica particles and modified polyurethane formed a complete coating with a distinct micro-nano roughness on the surface and an optimal water contact angle.

[0092] In Comparative Example 3, when the amount of hydrophobic silica powder is small, the overall hydrophobicity cannot reach the maximum value. As the amount of polyurethane used increases further, the coating surface becomes smoother, and many micropores and micro-nano structures formed on the surface are covered by polyurethane. Therefore, the roughness is reduced, and the water contact angle cannot reach the maximum value.

[0093] In Comparative Example 5, when the amount of dihydroxy polydimethylsiloxane or glyceryl monostearate is too much, the overall chain segments will be entangled, resulting in a decrease in hydrophobicity.

[0094] The above embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations and modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrophobically modified polyurethane nanocomposite material, characterized in that: The process includes the following steps: (1) Mix polytetrahydrofuran, polypropylene glycol, and isophorone diisocyanate, add a solvent to reduce the viscosity, control the reaction temperature at 60-80°C under catalyst conditions, and react for 2-4 hours under an inert gas atmosphere; (2) adding a modifier to the reaction solution, wherein the modifier is dihydroxy-terminated polydimethylsiloxane or glyceryl monostearate, and reacting for 1-2 hours, then adding a chain extender and reacting for 1-2 hours, then cooling to 30-40° C., adding triethylamine for neutralization for 1-2 hours, and finally adding ice water for emulsification, and removing the solvent by rotary evaporation to obtain a modified waterborne polyurethane emulsion; (3) dissolving SiO2 powder in methanol, ultrasonically stirring, adding octadecyltrichlorosilane, reacting at room temperature for 6-12 hours, then centrifuging and vacuum drying to obtain hydrophobic SiO2 powder; (4) adding hydrophobic SiO2 powder to ethyl acetate, stirring, and then ultrasonically dispersing to obtain a first mixed solution; adding the modified aqueous polyurethane emulsion to ethyl acetate, stirring, and then ultrasonically dispersing to obtain a second mixed solution; adding the first mixed solution to the second mixed solution, stirring, and then ultrasonically dispersing to obtain a hydrophobically modified polyurethane nanocomposite material.

2. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (1), the molar ratio of polytetrahydrofuran, polypropylene glycol and isophorone diisocyanate is (2-3):1:(4-7).

3. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (1), the ratio of the amount of the catalyst and the solvent used to the total mass of polytetrahydrofuran, polypropylene glycol, and isophorone diisocyanate is 100-150 μL:20-50 mL:30-45 g; the catalyst is dibutyltin dilaurate; and the solvent is acetone.

4. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (2), the molar ratio of isophorone diisocyanate, dihydroxy-terminated polydimethylsiloxane, chain extender and ethylenediamine is 0.03: 0.001-0.003: 0.01-0.02: 0.01-0.02; the molar ratio of isophorone diisocyanate, glyceryl monostearate, chain extender and ethylenediamine is 0.03: 0.003-0.005: 0.01-0.02: 0.01-0.02; and the chain extender is 2,2-dihydroxymethylpropionic acid.

5. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (2), the amount of ice water used is 20-40% of the total mass of the reactants after neutralization; the temperature of the rotary evaporation is 30-60° C., and the time is 30-60 min.

6. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (3), the ratio of the amount of SiO2 powder, methanol and octadecyltrichlorosilane used is 1-5g:20-50mL:1-5mL; the speed of the centrifugation is 4000-8000rpm; and the temperature of the vacuum drying is 60-80℃.

7. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (4), during the preparation of the first mixed solution, the ratio of the amount of hydrophobic SiO2 powder and ethyl acetate used is 1-5g:30-40mL, stirring for 1-2h, and ultrasonic dispersion for 10-40min.

8. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (4), during the preparation of the second mixed solution, the ratio of the modified aqueous polyurethane emulsion to ethyl acetate is 30-50 mL: 20-30 mL, stirring is performed for 1-2 hours, and ultrasonic dispersion is performed for 1-2 hours.

9. The method for preparing the hydrophobically modified polyurethane nanocomposite material according to claim 1, wherein: In step (4), the first mixed solution is added to the second mixed solution and stirred for 1-2 hours, and ultrasonically dispersed for 1-2 hours.

10. Use of the hydrophobically modified polyurethane nanocomposite material prepared by the preparation method according to any one of claims 1 to 9 in coating.

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