Self-cleaning polyurethane protective coating as well as preparation method and application thereof

Abstract

The invention discloses a self-cleaning polyurethane protective coating as well as a preparation method and application thereof. Hydrophobic nano silicon dioxide is modified by using an organic modifier, polyisocyanate is used as a curing agent, and both the hydroxyl-containing organic modifier and hydroxyl of a polyurethane prepolymer can chemically react with isocyanate groups in the curing agent; the hydroxyl-containing organic modifier can also chemically react with isocyanate groups of the polyurethane prepolymer to generate connection containing carbamate bonds and form a double-crosslinking network, so that silicon dioxide is introduced through chemical bonds, the cohesion of the coating is enhanced, and the self-cleaning performance and the corrosion resistance of the coating are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion coatings, and in particular to a self-cleaning polyurethane protective coating, a preparation method thereof, and applications thereof. Background Art

[0002] For anti-corrosion coating systems used in the fields of construction, energy, transportation, marine engineering, etc., the topcoat serves as the last coating layer to play the role of anti-corrosion, aesthetics, and environmental protection. Polyurethane coatings are widely used in surface protection due to their excellent wear resistance, weather resistance and adhesion. However, traditional polyurethane coatings are easily affected by surface pollution such as dust, oil stains, acid rain deposition, etc. during long-term use, which reduces their aesthetics and functionality and even affects the corrosion resistance of the substrate. In addition, the corrosive factors contained in the attached rainwater will also corrode the steel due to staying on the coating surface for a long time, causing electrochemical corrosion, chloride ion, acidic or alkaline particle corrosion. Therefore, it is of great significance to develop polyurethane coatings with both self-cleaning and long-term protective functions.

[0003] At present, the realization of self-cleaning coatings mainly relies on two technical routes: one is photocatalytic self-cleaning (such as TiO2 coating): using ultraviolet rays to stimulate photocatalytic reactions to decompose pollutants, but there are problems such as the need for light conditions, easy deactivation after long-term use, and possible accelerated resin aging; the second is super-hydrophobic self-cleaning (such as fluorine / silicon hydrophobic coating): through low surface energy substances (such as fluorocarbons) and micro-nano rough structures to achieve a hydrophobic effect, making it difficult for pollutants to adhere. However, existing super-hydrophobic coatings mostly rely on physical blending of hydrophobic fillers (such as unmodified SiO2), resulting in uneven dispersion of fillers, easy agglomeration, insufficient mechanical properties and durability of the coating, and easy degradation of the self-cleaning function after long-term use. In addition, the inorganic fillers (such as SiO2, TiO2) in traditional polyurethane coatings are usually only introduced through physical blending, and the interfacial bonding force with the resin matrix is ​​weak, which can easily lead to the following problems: poor filler dispersion affects the uniformity of the coating; insufficient coating cohesion, reduced wear resistance and adhesion; after long-term exposure, the filler-resin interface is easily corroded and the anti-corrosion performance decays. Existing modification technologies still have problems such as complex modification methods, high industrial production costs, insufficient dispersion stability of modified fillers, short storage period, and difficulty in balancing the self-cleaning and anti-corrosion properties of the coating. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, embodiments of the present invention provide a self-cleaning polyurethane protective coating, a preparation method thereof, and an application thereof.

[0006] In the first aspect, the present invention proposes a self-cleaning polyurethane protective coating, comprising component A and component B in a mass ratio of 100:(15-25), wherein, by mass content, the component A comprises 40%-60% polyurethane prepolymer, 3%-8% modified hydrophobic nano-silica, 12%-20% solvent, and 25%-35% additive; the component B comprises a polyisocyanate curing agent.

[0007] Furthermore, the method for preparing the modified hydrophobic nano-silica comprises:

[0008] Dispersing hydrophobic nano-silica in a solvent, adding a silane coupling agent to react, and after the reaction is completed, centrifuging to remove the solvent to obtain intermediate particles;

[0009] The intermediate particles are dispersed in a solvent, and an organic modifier is added to react to obtain modified hydrophobic nano-silica.

[0010] Furthermore, the silane coupling agent includes one or more of γ-glycidyloxypropyltrimethoxysilane (KH-560), γ-aminopropyltriethoxysilane (KH-550), and methyltrimethoxysilane (MTMS).

[0011] Furthermore, the organic modifier is a hydroxyl-containing acrylate monomer, polyetheramine, glycidyl ether or long-chain alkyl alcohol.

[0012] Furthermore, the particle size of the modified hydrophobic nano-silica is 5 to 80 nm.

[0013] Furthermore, the content of hydroxyl groups in the polyurethane prepolymer is 100 to 200 mgKOH / g.

[0014] Furthermore, the component A further comprises a hydrophobic additive in an amount of 0.1% to 2% by mass, and the hydrophobic additive is fluorosilane or perfluoropolyether.

[0015] Furthermore, the solvent includes one or more of toluene, xylene, ethanol, n-butanol, and isobutanol.

[0016] Furthermore, the auxiliary agent includes one or more of a dispersant, a defoaming agent, a thixotropic agent, a light stabilizer, a pigment, and a leveling agent.

[0017] In a second aspect, the present invention provides a method for preparing the self-cleaning polyurethane protective coating proposed in the first aspect, comprising the following steps:

[0018] The modified hydrophobic nano-silica and the polyurethane prepolymer are uniformly mixed, and a solvent and an additive are added to form component A;

[0019] Component A and component B are evenly mixed to obtain the self-cleaning polyurethane protective coating.

[0020] In the third aspect, the present invention proposes the application of the self-cleaning polyurethane protective coating proposed in the first aspect or the self-cleaning polyurethane protective coating prepared by the method proposed in the second aspect in the fields of building exterior walls, automobile coatings, ship corrosion protection, and wind turbine tower protection.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention utilizes an organic modifier to modify hydrophobic nano-silica, and uses polyisocyanate as a curing agent. The hydroxyl-containing organic modifier and the hydroxyl group of the polyurethane prepolymer can both chemically react with the isocyanate group (-NCO) in the curing agent. The hydroxyl-containing organic modifier can also chemically react with the isocyanate group (-NCO) of the polyurethane prepolymer to generate a connection containing a carbamate bond, forming a double-crosslinked network. Thus, silica is introduced through chemical bonds, the cohesion of the coating is enhanced, and the self-cleaning performance and corrosion resistance of the coating are improved.

[0023] The present invention modifies the hydrophobic silica of the inorganic nanofiller, and designs the nanofiller to be chemically bonded in the coating matrix to form a three-dimensional network structure through a surface activation-grafting approach, thereby changing the simple physical blending of the inorganic filler to chemical bonding at the resin-filler interface, thereby improving the dispersibility of the nanofiller, enhancing the cohesion of the coating, and improving the self-cleaning performance and anti-corrosion performance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 This is a flow chart of the preparation method of the modified hydrophobic nano-silica of the present invention;

[0026] Figure 2 The present invention is a flow chart of the preparation method of the self-cleaning polyurethane protective coating. DETAILED DESCRIPTION

[0027] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0028] The following describes the self-cleaning polyurethane protective coating proposed by the present invention, its preparation method and application with reference to the accompanying drawings.

[0029] The self-cleaning polyurethane protective coating of the present application comprises A component and B component, the mass ratio of A component and B component is 100:(15-25), wherein, the A component comprises 40%-60% polyurethane prepolymer, 3%-8% modified hydrophobic nanosilica, 12%-20% solvent, 25%-35% auxiliary agent in mass content. The B component comprises a polyisocyanate curing agent, the polyisocyanate is an organic compound containing two or more isocyanate groups (-NCO) in the molecule.

[0030] In some embodiments, as shown in FIG. 1, the method for preparing the modified hydrophobic nanosilica comprises: Figure 1

[0031] (a) dispersing the hydrophobic nanosilica in a solvent, adding a silane coupling agent to react, and then removing the solvent by centrifugation to obtain intermediate particles;

[0032] (b) dispersing the intermediate particles in a solvent, adding an organic modifier to react to obtain the modified hydrophobic nanosilica.

[0033] In some embodiments, the hydrophobic nanosilica is first dispersed in a solvent, then a silane coupling agent is added, and the reaction is carried out at a temperature of 60-80°C for 2-4h, and then the solvent is removed by centrifugation to obtain intermediate particles. In some embodiments, the solvent used to disperse the hydrophobic silica includes one or more of ethanol, methanol, and propanol.

[0034] In step (b), the intermediate particles are dispersed in a solvent, then an organic modifier is added, and the reaction is carried out at a temperature of 60-80°C for 2-4h to obtain an epoxy group grafted silica sol, i.e. the modified hydrophobic silica.

[0035] In some embodiments, the silane coupling agent includes one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and methyltrimethoxysilane, and the silane coupling agent is used to connect the hydrophobic silica and the organic modifier.

[0036] In some embodiments, the organic modifier is a hydroxyl-containing acrylate monomer, a polyether amine, a glycidyl ether, or a long-chain alkyl alcohol. In some embodiments, the mass ratio of the organic modifier to the hydrophobic nanosilica is 1:1.5-5.

[0037] In some embodiments, the particle size of the modified hydrophobic nanosilica prepared is 5-80nm.

[0038] In some embodiments, the content of hydroxyl groups in the polyurethane prepolymer in the A component is 100-200mgKOH / g.

[0039] ​In some embodiments, the solvent for component A includes one or more of toluene, xylene, ethanol, n-butanol, and isobutanol.

[0040] In some embodiments, the auxiliary agent includes one or more of a dispersant, a defoaming agent, a thixotropic agent, a light stabilizer, a pigment, and a leveling agent.

[0041] Among them, the dispersant includes one or more of dodecylbenzene sulfonate wetting agents, phenolic resin wetting agents, and alkyl methyl acrylate copolymers; the defoaming agent includes one or more of polysiloxane defoaming agents and modified silicone oil defoaming agents; the thixotropic agent includes one or more of organic bentonite, polyethylene wax, and fumed silica; the light stabilizer includes UV-531, Chiguard 81, Cyasorb UV-1164 (Solvay), and Tinuvin 1600 / 1577 (BASF); the pigment includes one or more of titanium dioxide, zinc oxide, carbon black, iron red, iron yellow, iron brown, and iron black; the leveling agent includes one or more of PDMS (polydimethylsiloxane), ODPO (diphenyl-octyl phosphite), DDA (dodecylamine), and DMPA (dihydroxymethylpropionic acid).

[0042] In some embodiments, the component A further comprises a hydrophobic agent in an amount of 0.1% to 2% by weight, wherein the hydrophobic agent comprises fluorosilane or perfluoropolyether.

[0043] Preparation method of self-cleaning polyurethane protective coating, such as Figure 2 As shown, the following steps are included:

[0044] (1) uniformly mixing the modified hydrophobic nano-silica with the polyurethane prepolymer, and adding a solvent and an additive to form component A;

[0045] (2) Component A and component B are mixed evenly to obtain the self-cleaning polyurethane protective coating.

[0046] The self-cleaning polyurethane protective coating of the present invention is applied in the fields of building exterior walls, automobile coatings, ship corrosion protection, and wind power tower protection.

[0047] The present invention utilizes an organic modifier to modify hydrophobic nano-silica, and uses polyisocyanate as a curing agent. The hydroxyl-containing organic modifier and the hydroxyl group of the polyurethane prepolymer can both chemically react with the isocyanate group (-NCO) in the curing agent. The hydroxyl-containing organic modifier can also chemically react with the isocyanate group (-NCO) of the polyurethane prepolymer to generate a connection containing a carbamate bond, forming a double-crosslinked network. Thus, silica is introduced through chemical bonds, the cohesion of the coating is enhanced, and the self-cleaning performance and corrosion resistance of the coating are improved.

[0048] The present invention is described in detail below with reference to the embodiments.

[0049] Example 1

[0050] Preparation of modified hydrophobic nanosilica:

[0051] 10 g of hydrophobic fumed silica (Aerosil R812, particle size 7 nm) was dispersed in 200 mL of anhydrous ethanol and sonicated for 30 min;

[0052] Add 2 g of γ-aminopropyltriethoxysilane (KH-550), react at 80°C for 3 h, and centrifuge to remove the solvent to obtain intermediate particles;

[0053] The intermediate particles were dispersed in 100 mL of toluene, 5 g of glycidyl ether was added, and the mixture was reacted at 70°C for 4 h to obtain epoxy-grafted SiO2 sol.

[0054] Prepare component A with the following formula:

[0055] Polycaprolactone polyol (OH value 112mgKOH / g): 50g,

[0056] Modified hydrophobic SiO2: 6g,

[0057] Dibutyltin dilaurate (catalyst): 0.5g,

[0058] Perfluorooctyltriethoxysilane (hydrophobic additive): 1g,

[0059] Xylene / n-butanol (solvent, mass ratio is 7:3): 18g (adjust viscosity to coat 4 cups in 25s),

[0060] The amount of titanium dioxide is 18.5 g, and the silane-modified rutile titanium dioxide with the brand (or model) LR-972 produced by China Longbai Group is used.

[0061] The thixotropic agent is 2g, and the BYK-425 thixotropic agent produced by German BYK Chemical Company is used.

[0062] The defoamer is 1g, and the defoamer is BYK066N produced by BYK in Germany.

[0063] The leveling agent is 1.5g, and the leveling agent with the brand BYK300 produced by German BYK company is used.

[0064] The amount of the wetting and dispersing agent is 1.5 g, and the functional additive used is phobe 1500N produced by Degussa Digo Company.

[0065] The curing agent of component B is produced by BASF of Germany, with the brand (or model) HP 1600 aliphatic isocyanate curing agent.

[0066] Preparation of the coating:

[0067] Mix the modified hydrophobic silica with polycaprolactone polyol, disperse at 60℃ for 1h under high speed shearing, then ultrasonic treatment for 30min, then add solvent and additives to obtain component A;

[0068] Mix component A and component B with mass ratio of 100:20 to obtain the coating.

[0069] Preparation of the coating:

[0070] Spray the coating on the surface of steel, and cure at room temperature for 7 days to obtain the coating.

[0071] Example 2:

[0072] Preparation of modified hydrophobic nano-silica:

[0073] Disperse 10g hydrophobic fumed silica (Aerosil R812, particle size 7nm) in 200mL anhydrous ethanol, ultrasonic treatment for 30min;

[0074] Add 2g γ-glycidyloxypropyltrimethoxysilane (KH-560), react at 80℃ for 3h, centrifugal removal of solvent to obtain intermediate particles;

[0075] Disperse the intermediate particles in 100mL toluene, add 5g glycidyl ether, react at 70℃ for 4h to obtain epoxy group grafted SiO2 sol.

[0076] Other processes are the same as example 1.

[0077] Comparative example 1

[0078] Preparation of modified hydrophobic nano-silica:

[0079] Disperse 10g hydrophobic fumed silica (Aerosil R812, particle size 7nm) in 200mL anhydrous ethanol, ultrasonic treatment for 30min;

[0080] Add 2g dodecyltrimethoxysilane, react at 80℃ for 3h, centrifugal removal of solvent to obtain intermediate particles;

[0081] Disperse the intermediate particles in 100mL toluene, add 5g glycidyl ether, react at 70℃ for 4h to obtain epoxy group grafted SiO2 sol.

[0082] Other processes are the same as example 1.

[0083] Comparative example 2

[0084] The difference from Example 1 is that hydrophobic fumed silica is used instead of modified hydrophobic silica, and the other processes are the same as Example 1.

[0085] Comparative Example 3

[0086] The difference from Example 1 is that silicon dioxide is not added to component A, and the other processes are the same as Example 1.

[0087] Test example

[0088] The coatings prepared in Example 1, Example 2 and Comparative Examples 1 to 3 were subjected to salt spray test, adhesion, wear resistance, water contact angle, rolling angle, and stain removal rate tests. The test results are shown in Table 1 below.

[0089] The salt spray test is in accordance with GB / T 1771-2007; the adhesion test method is in accordance with GB / T 5210; the abrasion resistance test method is in accordance with GB / T 1768-2006; the water contact angle is tested using a contact angle meter (JC2000D1); the rolling angle test is the angle at which a 5μL water droplet can completely roll off a coating surface tilted at a certain angle; the stain removal rate test method is in accordance with GB / T 9780-2013, after coating carbon black pollution, it is washed with artificial rainwater and the removal rate is calculated; the adhesion test adopts the cross-hatch method; the abrasion resistance test method is in accordance with GB / T 1768-2006, 1000 frictions under a load of 500g.

[0090] Table 1:

[0091]

[0092] According to Example 1 and Example 2, the coating of the present application passed the salt spray test for 1000 hours, with a stain removal rate of more than 94%, has a self-cleaning effect, and has excellent anti-corrosion performance.

[0093] According to Example 1, Example 2 and Comparative Example 1, Comparative Example 1 has a cleaning effect, but a poor anti-corrosion effect. When preparing modified hydrophobic silica, an epoxy coupling agent is used for modification to achieve a balance between self-cleaning and anti-corrosion performance.

[0094] According to Example 1, Example 2, Comparative Example 2 and Comparative Example 3, when no silicon dioxide is added or unmodified silicon dioxide is added, the self-cleaning effect and anti-corrosion performance of the coating are poor.

[0095] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms may be directed to different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are mutually inconsistent.

[0096] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0097] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A self-cleaning polyurethane protective coating, characterized in that: It includes component A and component B with a mass ratio of 100:(15-25), in, Calculated by mass content, the component A includes 40% to 60% of polyurethane prepolymer, 3% to 8% of modified hydrophobic nano-silica, 12% to 20% of solvent, and 25% to 35% of additives; The B component includes a polyisocyanate curing agent.

2. The self-cleaning polyurethane protective coating according to claim 1, characterized in that: The method for preparing the modified hydrophobic nano-silica comprises: Dispersing hydrophobic nano-silica in a solvent, adding a silane coupling agent to react, and after the reaction is completed, centrifuging to remove the solvent to obtain intermediate particles; The intermediate particles are dispersed in a solvent, and an organic modifier is added to react to obtain modified hydrophobic nano-silica.

3. The self-cleaning polyurethane protective coating according to claim 2, characterized in that: The silane coupling agent includes one or more of γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and methyltrimethoxysilane; And / or, the organic modifier is a hydroxyl-containing acrylate monomer, polyetheramine, glycidyl ether or long-chain alkyl alcohol.

4. The self-cleaning polyurethane protective coating according to claim 2, characterized in that: The particle size of the modified hydrophobic nano-silica is 5 to 80 nm.

5. The self-cleaning polyurethane protective coating according to claim 1, characterized in that: The hydroxyl content in the polyurethane prepolymer is 100-200 mgKOH / g.

6. The self-cleaning polyurethane protective coating according to claim 1, characterized in that: The component A further comprises a hydrophobic auxiliary agent with a mass content of 0.1% to 2%, and the hydrophobic auxiliary agent is fluorosilane or perfluoropolyether.

7. The self-cleaning polyurethane protective coating according to claim 1, characterized in that: The solvent includes one or more of toluene, xylene, ethanol, n-butanol, and isobutanol.

8. The self-cleaning polyurethane protective coating according to claim 1, characterized in that: The auxiliary agent includes one or more of a dispersant, a defoaming agent, a thixotropic agent, a light stabilizer, a pigment, and a leveling agent.

9. A method for preparing a self-cleaning polyurethane protective coating, characterized in that: The self-cleaning polyurethane protective coating according to any one of claims 1 to 8 comprises the following steps: The modified hydrophobic nano-silica and the polyurethane prepolymer are uniformly mixed, and a solvent and an additive are added to form component A; The component A and the component B are evenly mixed to obtain the self-cleaning polyurethane protective coating.

10. Use of the self-cleaning polyurethane protective coating according to any one of claims 1 to 8 or the self-cleaning polyurethane protective coating prepared by the method according to claim 9 in the fields of building exterior walls, automobile coatings, ship corrosion protection, and wind power tower protection.

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