A super-hydrophobic coating based on water-based resin composite modification and a preparation method and application thereof

Abstract

The present application relates to a kind of based on water-based resin composite modification super-hydrophobic coating and its preparation method and application, belong to coating technical field.Super-hydrophobic coating, including the following weight parts of raw materials: methyl acrylate 10~15 parts;Acrylic acid 0.1~0.2 parts;Hexamethyl silazane 2~4 parts;Tetraethoxysilane 1~3 parts;Emulsifier 0.3~0.6 parts;Polymerization initiator 0.1~0.2 parts;Water 80~100 parts;Hexadecyl trimethoxysilane accounting for 2~5% of the total mass percentage of super-hydrophobic coating and amino-modified nanometer silicon dioxide accounting for 0.3~0.6% of the total mass percentage of super-hydrophobic coating.Used raw material is all environmental friendly substance;And can reduce surface energy, increase contact angle, the liquid with smaller surface tension can also show "lotus effect";Droplet can freely roll, no soaking occurs, can be applied to the liquid with smaller surface tension than water.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and particularly relates to a super-hydrophobic coating based on water-based resin composite modification and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant(s) that this information constitutes prior art.

[0003] Coating is a liquid or solid material coated on the surface of an object, which is used to provide protection, decoration, corrosion resistance, etc. Its main components include solvents, resins, fillers, etc. In the fields of metal protection, fluid drag reduction, marine corrosion and fouling prevention, and oil-water separation, the coating is often required to have excellent hydrophobic properties to achieve self-cleaning and protection of the internal coating. Existing hydrophobic coatings mainly use two principles to achieve hydrophobic effect: microstructure hydrophobicity and surface modification hydrophobicity. Among them, microstructure hydrophobicity refers to the formation of micro-protrusions or fine pores on the surface of the coating, so that water droplets and dirt cannot adhere; surface modification hydrophobicity refers to the introduction of hydrophobic group molecules to form a hydrophobic structure on the surface of the coating, so that water droplets and dirt cannot adhere. Coating with excellent performance and high hydrophobicity is called super-hydrophobic coating.

[0004] Current super-hydrophobic coatings include two types, namely super-hydrophobic coatings based on fluorocarbon compounds and super-hydrophobic coatings based on low surface energy modification.

[0005] A typical super-hydrophobic coating based on fluorocarbon compounds is the invention patent with publication number CN115181466B. It discloses a high-temperature-resistant fluorocarbon super-hydrophobic coating. In the coating, the intermediate product with branched structure reacts with the isocyanate groups on the surface of modified titanium dioxide to obtain perfluorobenzenesulfonate modified nano-titanium dioxide. Through in-situ polymerization, butyl acrylate, hexafluorobutyl acrylate and other pre-polymer monomers are in-situ cross-linked and polymerized on the surface of the modified nano-titanium dioxide to obtain a high-temperature-resistant fluorocarbon super-hydrophobic coating. After the nano-titanium dioxide is hydrophobically modified by the branched perfluoroalkyl chain, it has better dispersion stability in the fluorocarbon coating, forms a micro-nano rough structure on the surface of the fluorocarbon coating, and exhibits excellent super-hydrophobic properties. At the same time, the cross-linked fluorocarbon resin has better thermal stability and high-temperature resistance.

[0006] A typical low-surface-energy modification-based super-hydrophobic coating is the invention patent with publication number CN114657789B. It discloses an organic silicon super-hydrophobic coating, which includes tetraethyl orthosilicate 2.0-5.0 parts, end hydroxyl blocking agent 2.0-6.0 parts, silicon dioxide particles 0.05-0.5 parts, and catalyst. The tetraethyl orthosilicate and end hydroxyl blocking agent in the coating and the hydroxyl group on the surface of the silicon dioxide undergo hydrolysis and condensation reaction, constructing a nano-composite rough structure with low surface energy and rigid structure in situ on the surface of the substrate, effectively reducing the surface energy of the substrate interface and increasing the interface roughness.

[0007] However, the above-mentioned existing super-hydrophobic coating has the following problems:

[0008] In CN115181466B, fluorocarbons are expensive and have greater biological toxicity, accumulate in the body, are not easy to degrade, and are not environmentally friendly.

[0009] In CN114657789B, the hydrolysis and condensation reaction of organic silicon using silicon-oxygen bonds is limited by the bond energy, has certain limitations, and the formed coating only has liquid-repellent effect on liquids with surface tension of 20-74 mN / m. However, in nature, there are liquids with surface tension lower than 20 mN / m or close to it, such as cyclohexane, methanol, diethyl ether, acetone, etc. The coating in the above-mentioned patent has limitations in use and is difficult to deal with liquids with surface tension smaller than water or aqueous solutions. SUMMARY

[0010] To solve the above-mentioned technical problems, the purpose of the present application is to provide a super-hydrophobic coating based on water-based resin composite modification and its preparation method and application, which is environmentally friendly and can be applied to liquids with lower surface tension.

[0011] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0012] In the first aspect, a super-hydrophobic coating based on water-based resin composite modification includes the following raw materials by weight:

[0013] Methyl acrylate 10-15 parts;

[0014] Acrylic acid 0.1-0.2 parts;

[0015] Hexamethylsilazane 2-4 parts;

[0016] Tetraethoxysilane 1-3 parts;

[0017] Emulsifier 0.3-0.6 parts;

[0018] Polymerization initiator 0.1-0.2 parts;

[0019] Water 80-100 parts;

[0020] Hexadecyl trimethoxysilane;

[0021] And amino-modified nanosilica;

[0022] Wherein, the total mass percentage of hexadecyl trimethoxysilane in the super-hydrophobic coating is 2-5%;

[0023] The total mass percentage of amino-modified nanosilica in the super-hydrophobic coating is 0.3-0.6%.

[0024] Optionally, the preparation method of the amino-modified nanosilica comprises:

[0025] It is made by coating and grafting a silane coupling agent containing amino groups with nanosilica;

[0026] Or, after complexing nanosilica with silver nitrate, it is made by reduction and acid washing;

[0027] Or, it is made by ion exchange of nanosilica with soluble ammonium salt under acidic conditions.

[0028] Optionally, the specification of nanosilica is specifically: particle size 100-500 nm.

[0029] Optionally, the emulsifier is selected from octanol polyoxyethylene ether.

[0030] Optionally, the emulsifier is selected from octanol polyoxyethylene ether.

[0031] In the second aspect, the preparation method of the above-mentioned super-hydrophobic coating based on water-based resin composite modification comprises the following steps:

[0032] S1, weigh the methyl acrylate, acrylic acid, hexamethylsilane, tetraethoxysilane and water, stir and mix to obtain a first mixture;

[0033] S2, weigh the emulsifier, add it dropwise into the first mixture, heat under inert gas protection atmosphere to obtain a pre-polymer emulsion;

[0034] S3, weigh the polymerization initiator, slowly drop it into the pre-polymer emulsion under continuous stirring, and continuously stir to obtain a water-based resin;

[0035] S4, weigh the hexadecyl trimethoxysilane and the amino-modified nanosilica, add them into the water-based resin, and stir to obtain a super-hydrophobic coating based on water-based resin composite modification.

[0036] Optionally, in S1, the stirring and mixing method is: stirring in a reaction kettle at a speed not less than 100 r / min for at least 20 min.

[0037] Optionally, in S2, the first mixing temperature is maintained at 50-65 DEG C during the process of adding the emulsifier drop by drop.

[0038] Optionally, in S2, the inert gas comprises one or more of nitrogen, helium and argon.

[0039] Optionally, in S3, the pre-polymer emulsion is maintained in a continuous stirring state at a stirring speed of 60-80 r / min and a temperature of 25-40 DEG C.

[0040] Optionally, in S3, the polymerization initiator is added to the pre-polymer emulsion at a dropwise adding speed of 1-2 ml / min, and after the dropwise adding is completed, the stirring is continuously maintained for 2-4 h.

[0041] Optionally, in S4, the stirring method is stirring in the reaction kettle at 160-180 r / min for 15-20 min.

[0042] In the third aspect, the application of the super-hydrophobic coating based on the water-based resin composite modification is used for preparing a super-hydrophobic coating, which is formed after being sprayed, roller coated or brush coated on the surface of an object and then solidified.

[0043] Optionally, the solidification method is normal temperature solidification for 48 h.

[0044] Optionally, the super-hydrophobic coating can be applied to the liquid-repellent use of a liquid with a surface tension smaller than water.

[0045] The application has the following beneficial effects:

[0046] 1. The raw materials used in the application are all environmentally friendly substances, which are better than fluorocarbon. The application utilizes the polymerization of acrylic acid and methyl acrylate, the hydrolysis and condensation of hexamethylsilazane and tetraethoxysilane, and then fills hexadecyl trimethoxysilane and amino-modified nano-silicon dioxide into the water-based resin, so that the surface energy is reduced and the contact angle is increased from different angles, and the super-hydrophobic performance of the coating is increased by synergistic cooperation; the "lotus effect" can also be exhibited for cyclohexane with a smaller surface tension, the liquid drops can freely roll, no soaking occurs, and the obtained super-hydrophobic coating can be applied to the liquid-repellent use of a liquid with a surface tension smaller than water.

[0047] 2. The present application uses methyl acrylate, acrylic acid, hexamethyl silazane, and tetraethoxysilane as polymerization monomers to form a polymer network structure; both hexamethyl silazane and tetraethoxysilane are organosilicon compounds, so that the network structure after polymerization has good hydrophobicity, and also provides a carrier and position for subsequent filling of the filler. After polymerization, there is still the problem of the limitation of organosilicon compounds relying on the hydrolysis and condensation reaction of siloxane, so hexadecyl trimethoxysilane and amino-modified nano-silicon dioxide are mixed with the water-based resin as fillers, the alkyl chain of hexadecyl trimethoxysilane can form a hydrophobic layer on the surface of the coating, reduce the surface free energy, make it difficult for liquid to penetrate into the interior of the coating, and improve the hydrophobicity of the coating; the amino-modified nano-silicon dioxide is more easily dispersed in the water-based resin due to the presence of amino groups, and increases the micro-roughness of the surface, forming more air / liquid interfaces, such a rough surface structure makes the liquid droplets unable to fully spread out, significantly improving the super-hydrophobic effect. Therefore, the amino-modified nano-silicon dioxide and hexadecyl trimethoxysilane synergistically cooperate from two different levels, making up for the defect that the hydrophobic effect of organosilicon compounds after their own hydrolysis and condensation is relatively limited.

[0048] 3. The amino-modified nano-silicon dioxide in the present application can be prepared by various methods such as: coating and grafting of silane coupling agent containing amino groups with nano-silicon dioxide; complexing nano-silicon dioxide with silver nitrate, and then preparing by reduction and acid washing; ion exchange of nano-silicon dioxide with soluble ammonium salt under acidic conditions, etc. The purpose is to graft amino groups on the surface of nano-silicon dioxide, so that the silica has better dispersibility and interfacial compatibility, to increase the hydrophobicity of the coating after the coating is formed.

[0049] 4. The polymerization initiator selected in the present application is benzoyl peroxide or ammonium persulfate, which has the following advantages: ① Both benzoyl peroxide and ammonium persulfate can generate free radicals to initiate the polymerization reaction of methyl acrylate, acrylic acid, hexamethyl silazane, and tetraethoxysilane, and at the same time, they have good activity and relatively short initiation time, which is helpful to realize a rapid and efficient polymerization process; ② Benzoyl peroxide and ammonium persulfate have a wide applicable temperature range, and the temperature change before and after the polymerization reaction has no significant effect on the initiation efficiency of the two, and they have good stability.

[0050] 5. The polymerization initiator of the present application may not be compatible with ionic emulsifiers, so a non-ionic emulsifier, octanol polyoxyethylene ether, is selected; in the chemical structure of octanol polyoxyethylene ether, the ethoxy group provides hydrophilicity, and the octanol chain provides hydrophobicity, so the two groups make octanol polyoxyethylene ether have good surface activity and emulsifying performance, and can form a stable emulsion system between water and oil.

[0051] 6. The preparation method of the application in S1, methyl acrylate, acrylic acid, hexamethyl silazane, tetraethoxysilane and water are mixed and dissolved, ensuring uniform dispersion of the monomers, providing a good starting system for the subsequent steps; in S2, the emulsifier is added dropwise into the mixture, and heated under controlled temperature to form a pre-polymer emulsion, which helps to improve the stability of the mixture, forms a stable emulsion of the emulsifier and the monomer, and promotes the pre-polymerization process; in S3, the polymerization initiator is added dropwise into the pre-polymer emulsion, and stirring is continued to realize the polymerization reaction, which can control the rate and degree of polymerization reaction, ensure the synthesis of water-based resin, and form a polymer; in S4, hexadecyl trimethoxysilane and amino-modified nano-silica are added to the water-based resin, and stirring is performed to disperse them uniformly, which helps to uniformly disperse the fillers in the water-based resin and improve the super-hydrophobic properties of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The flowchart of the preparation method of the super-hydrophobic coating based on the composite modification of water-based resin in the detailed description of the application. DETAILED DESCRIPTION

[0053] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0054] It should be noted that the terms used herein are only for the purpose of describing the specific embodiments and are not intended to limit the exemplary embodiments according to the application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0055] A super-hydrophobic coating based on the composite modification of water-based resin comprises the following raw materials by weight:

[0056] Methyl acrylate 10-15 parts;

[0057] Acrylic acid 0.1-0.2 parts;

[0058] Hexamethyl silazane 2-4 parts;

[0059] Tetraethoxysilane 1-3 parts;

[0060] Emulsifier 0.3-0.6 parts;

[0061] Polymerization initiator 0.1-0.2 parts;

[0062] Water 80-100 parts;

[0063] Hexadecyl trimethoxysilane and amino-modified nanosilica;

[0064] The hexadecyl trimethoxysilane accounts for 2-5% of the total mass percentage of the super-hydrophobic coating; and the amino-modified nanosilica accounts for 0.3-0.6% of the total mass percentage of the super-hydrophobic coating.

[0065] The methyl acrylate and the acrylic acid are polymerized, the hexamethyl silazane and the tetraethoxysilane are hydrolyzed and condensed, and are synergistically polymerized into a network-structured polymeric water-based resin; the hexamethyl silazane and the tetraethoxysilane are organosilicon compounds, and there are space defects in the network structure generated by the hydrolysis and condensation reaction of the ethoxyl groups themselves, and then the amino-modified nanosilica and the hexadecyl trimethoxysilane are filled into the network structure as fillers, which overcomes the above defects, so that the coating not only has a super-hydrophobic effect, but also has good liquid-repellent ability to cyclohexane with a surface tension of less than 20 mN / m; and the problem that the existing super-hydrophobic coating relying on organosilicon to reduce the surface energy cannot repel liquids with low surface tension is solved.

[0066] Optionally, the preparation method of the amino-modified nanosilica comprises:

[0067] The amino-modified nanosilica is prepared by coating and grafting a silane coupling agent containing an amino group on nanosilica;

[0068] Or, after the nanosilica is complexed with silver nitrate, the amino-modified nanosilica is prepared by reduction and acid washing;

[0069] Or, the amino-modified nanosilica is prepared by ion exchange of nanosilica and soluble ammonium salt under acidic conditions.

[0070] Different preparation methods may have slight differences in efficiency and amino grafting rate. The amino-modified nanosilica has better hydrophilicity and is easier to disperse in the water-based resin because the particle surface is grafted with an amino group. The amino part is "sunk" below the liquid surface of the water-based resin because of the formation of hydrogen bonds or van der Waals forces with the electrophilic units in the water-based resin, so that the silica is exposed to the outside, forming a specific microstructure.

[0071] Optionally, the specification of the nanosilica is: particle size 100-500 nm.

[0072] Optionally, the polymerization initiator is selected from benzoyl peroxide or ammonium persulfate;

[0073] Both benzoyl peroxide and ammonium persulfate can generate free radicals to initiate the polymerization of methyl acrylate, acrylic acid, hexamethyl silazane and tetraethoxysilane, and both have good activity and relatively short initiation time, which is helpful to realize fast and efficient polymerization process;

[0074] Benzoyl peroxide and ammonium persulfate have a wide applicable temperature range, and the temperature change before and after the polymerization reaction has no significant effect on the initiation efficiency of the two.

[0075] Optionally, the emulsifier is selected from octanol polyoxyethylene ether;

[0076] The polymerization initiator may not be compatible with the ionic emulsifier, so the non-ionic emulsifier octanol polyoxyethylene ether is selected; in the chemical structure of octanol polyoxyethylene ether, the ethoxy group provides hydrophilicity, and the octanol chain provides hydrophobicity, so that the octanol polyoxyethylene ether has good surface activity and emulsifying performance, and can form a stable emulsion system between water and oil.

[0077] The above preparation method of the super-hydrophobic coating based on water-based resin composite modification, as shown in Figure 1 includes the following steps:

[0078] S1, weigh methyl acrylate, acrylic acid, hexamethyl silazane, tetraethoxysilane and water, mix and stir to obtain a first mixture;

[0079] S2, weigh the emulsifier, add it dropwise into the first mixture, heat and reflux under an inert gas protective atmosphere to obtain a pre-polymer emulsion;

[0080] In this step, heating and refluxing is a process of continuously evaporating the solvent, condensing in the condenser and continuously dropping back into the reaction system, which can increase the contact rate of reactants and increase the reaction rate. By heating and refluxing, a uniformly dispersed pre-polymer emulsion can be obtained;

[0081] S3, weigh the polymerization initiator, slowly drop it into the pre-polymer emulsion under continuous stirring, and continuously stir to obtain a water-based resin;

[0082] In this step, methyl acrylate, acrylic acid, hexamethyl silazane and tetraethoxysilane are used as polymerization monomers to form a polymer network structure;

[0083] S4, weigh the hexadecyl trimethoxysilane and the amino-modified nano-silicon dioxide, add them into the water-based resin, and stir to obtain a super-hydrophobic coating based on water-based resin composite modification;

[0084] In the step, the alkyl chain of the hexadecyl trimethoxysilane can form a hydrophobic layer on the surface of the coating, reduce the surface free energy, make it difficult for liquid to penetrate into the interior of the coating, and improve the hydrophobicity of the coating; the amino-modified nanosilica is more easily dispersed in the water-based resin due to the presence of the amino groups, and the micro-roughness of the surface is increased, more air / liquid interfaces are formed, and the hydrophobicity of the coating is improved.

[0085] Optionally, in S1, the stirring and mixing method is that the stirring speed in the reaction kettle is not less than 100 r / min and the stirring time is at least 20 min.

[0086] Optionally, in S2, the first mixing temperature is maintained at 50-65 DEG C during the dropwise addition of the emulsifier.

[0087] Optionally, in S2, the inert gas includes one or more of nitrogen, helium and argon, as long as the inert gas does not react with the components.

[0088] Optionally, in S2, the heating and reflux method uses a reaction kettle container.

[0089] Optionally, in S3, the pre-polymer emulsion is maintained in a continuous stirring state at a stirring speed of 60-80 r / min and a temperature of 25-40 DEG C.

[0090] Optionally, in S3, the polymerization initiator is added to the pre-polymer emulsion at a dropwise addition speed of 1-2 ml / min, and the stirring is continued for 2-4 h after the dropwise addition is completed.

[0091] Optionally, in S4, the stirring method is that the stirring speed in the reaction kettle is 160-180 r / min and the stirring time is 15-20 min.

[0092] The super-hydrophobic coating prepared based on the water-based resin composite modification is formed after being sprayed, roller coated or brushed on the surface of a substrate and being cured.

[0093] Optionally, the curing method is normal temperature curing for 48 h.

[0094] Optionally, the substrate surface includes a metal surface such as an iron, aluminum, stainless steel or copper surface, a high polymer plastic surface such as a PVC, PE, PP or PS surface, and a cellulose-based material surface such as a paper or cellulose film surface.

[0095] Optionally, the substrate can be polished and primed before use.

[0096] In order to further illustrate the application, the following examples are used for detailed description, in which the materials used are commercially available products.

[0097] I. Preparation Example of Amino-modified Nanosilica

[0098] Preparation Example 1.

[0099] The preparation example uses a method of coating and grafting of a silane coupling agent containing amino groups with nanosilica to prepare amino-modified nanosilica, including the following steps:

[0100] S1, weigh 0.1 kg of nanosilica, add 100 ml of n-hexane, and ultrasonic treat for 20 min;

[0101] S2, mix 0.01 kg of amino silane coupling agent with n-hexane, stir at 100 r / min for 15 min, then mix with nanosilica, control the temperature to be 60°C, and react and graft for 2 h;

[0102] S3, centrifugal separate the product of S2, and wash with ethanol for three times, then dry treat with anhydrous calcium chloride to obtain amino-modified nanosilica.

[0103] Preparation Example 2.

[0104] The preparation example uses a method of nanosilica and silver nitrate complex to prepare amino-modified nanosilica, including the following steps:

[0105] S1, weigh 0.1 kg of nanosilica, add 100 ml of n-hexane, and ultrasonic treat for 20 min;

[0106] S2, mix the treated nanosilica in S1 with 100 ml of silver nitrate solution with a concentration of 0.1 mol / L to react;

[0107] S3, mix the complexed sample in S2 with glucose, heat in water bath to 75°C, reduce the silver ions in the complex to elemental silver, and recover;

[0108] S4, acid wash the reduced sample with dilute hydrochloric acid, then wash with ethanol for three times, and finally dry treat with anhydrous calcium chloride to obtain amino-modified nanosilica.

[0109] Preparation Example 3.

[0110] The preparation example uses an ion exchange method to prepare amino-modified nanosilica, including the following steps:

[0111] S1, weigh 0.1 kg of nanosilica, add 100 ml of n-hexane, and ultrasonic treat for 20 min;

[0112] S2, control the temperature to be 45°C, mix the ultrasonic treated nanosilica with 100 ml of 0.1 mol / L ammonium nitrate (acidified with nitric acid);

[0113] S3, filter, wash the filtered solid with ethanol three times, and then dry treat with anhydrous calcium chloride to obtain the amino-modified nanosilica.

[0114] II. Example of preparing super-hydrophobic coating layer based on water-based resin composite modified super-hydrophobic coating

[0115] Example 1

[0116] S1, weigh 1 kg of methyl acrylate, 0.01 kg of acrylic acid, 0.2 kg of hexamethylsilazane, 0.1 kg of tetraethoxysilane, and 8 kg of water, and place them in a reaction device for stirring at a speed of 100 r / min for 20 min to obtain a first mixture;

[0117] S2, weigh 0.03 kg of emulsifier (octanol polyoxyethylene ether), and add it dropwise to the first mixture, control the temperature to be 50°C, and heat it under reflux for 20 min under nitrogen protection to obtain a prepolymer emulsion;

[0118] S3, maintain the stirring speed of the prepolymer emulsion to be 60 r / min and the temperature to be 25°C, weigh 0.01 kg of polymerization initiator (benzoyl peroxide), and add it dropwise to the prepolymer emulsion at a speed of 1 ml / min, and continue to stir for 2 h to obtain a water-based resin;

[0119] S4, weigh hexadecyltrimethoxysilane and amino-modified nanosilica, and add them to the water-based resin obtained in S3, so that the mass percentage of hexadecyltrimethoxysilane in the total mass of the super-hydrophobic coating is 2%, and the mass percentage of amino-modified nanosilica in the total mass of the super-hydrophobic coating is 0.3%, control the stirring speed to be 160 r / min and stir for 15 min to obtain a super-hydrophobic coating based on water-based resin composite modification;

[0120] The amino-modified nanosilica is prepared by the preparation example 1;

[0121] S5, apply the coating of S4 to the surface of a substrate, and cure it for 48 h to obtain a super-hydrophobic coating layer.

[0122] Example 2

[0123] S1, weigh 1.3 kg of methyl acrylate, 0.02 kg of acrylic acid, 0.3 kg of hexamethylsilazane, 0.2 kg of tetraethoxysilane, and 8 kg of water, and place them in a reaction device for stirring at a speed of 120 r / min for 25 min to obtain a first mixture;

[0124] S2, weigh 0.04 kg of emulsifier (octanol polyoxyethylene ether), and add it dropwise to the first mixture, control the temperature to be 60°C, and heat it under reflux for 25 min under nitrogen protection to obtain a prepolymer emulsion;

[0125] S3, maintain the stirring speed of the prepolymer emulsion at 70 r / min and the temperature at 35°C, weigh 0.02 kg of a polymerization initiator (ammonium persulfate), and drop it into the prepolymer emulsion at a speed of 1 ml / min, and continue stirring for 3 h to obtain a water-based resin;

[0126] S4, weigh hexadecyl trimethoxysilane and amino-modified nano-silica, and add them to the water-based resin obtained in S3, so that the hexadecyl trimethoxysilane accounts for 4% of the total mass percentage of the super-hydrophobic coating, and the amino-modified nano-silica accounts for 0.4% of the total mass percentage of the super-hydrophobic coating, control the stirring speed at 160 r / min and stir for 20 min to obtain a super-hydrophobic coating based on water-based resin composite modification;

[0127] The amino-modified nano-silica is prepared according to Preparation Example 1.

[0128] S5, apply the coating of S4 to the surface of the substrate, and cure for 48 h to obtain a super-hydrophobic coating.

[0129] Example 3

[0130] S1, weigh 1.5 kg of methyl acrylate, 0.02 kg of acrylic acid, 0.4 kg of hexamethylsilazane, 0.3 kg of tetraethoxysilane, and 10 kg of water, and place them in a reaction device, stir at a speed of 140 r / min for 30 min to obtain a first mixture;

[0131] S2, weigh 0.06 kg of an emulsifier (octanol polyoxyethylene ether), and add it dropwise to the first mixture, control the temperature at 65°C, and heat under reflux for 30 min under nitrogen protection to obtain a prepolymer emulsion;

[0132] S3, maintain the stirring speed of the prepolymer emulsion at 80 r / min and the temperature at 40°C, weigh 0.02 kg of a polymerization initiator (ammonium persulfate), and drop it into the prepolymer emulsion at a speed of 2 ml / min, and continue stirring for 4 h to obtain a water-based resin;

[0133] S4, weigh hexadecyl trimethoxysilane and amino-modified nano-silica, and add them to the water-based resin obtained in S3, so that the hexadecyl trimethoxysilane accounts for 5% of the total mass percentage of the super-hydrophobic coating, and the amino-modified nano-silica accounts for 0.6% of the total mass percentage of the super-hydrophobic coating, control the stirring speed at 180 r / min and stir for 20 min to obtain a super-hydrophobic coating based on water-based resin composite modification;

[0134] The amino-modified nano-silica is prepared according to Preparation Example 1.

[0135] S5, apply the coating of S4 to the surface of the substrate, and cure for 48 h to obtain a super-hydrophobic coating.

[0136] Example 4

[0137] The difference between this example and Example 1 is that the amino-modified nanosilica is prepared according to Preparation Example 2.

[0138] Example 5

[0139] The difference between this example and Example 1 is that the amino-modified nanosilica is prepared according to Preparation Example 3.

[0140] III. Preparation of super-hydrophobic coating based on water-based resin composite modified super-hydrophobic coating

[0141] Comparative Example 1

[0142] The difference between this comparative example and Example 1 is that no hexadecyltrimethoxysilane is added.

[0143] Comparative Example 2

[0144] The difference between this comparative example and Example 1 is that no amino-modified nanosilica is added, but an equivalent amount of nanosilica that is not amino-modified is added instead.

[0145] In the above examples and comparative examples, the inert gas used is nitrogen, but it can also be helium, argon, etc., as long as it does not react with the components and can be used as an atmosphere gas;

[0146] The application method is spraying, but it can also be roll coating, brush coating, etc.

[0147] The substrate is a PVC plate, but it can also be a metal surface, a high-molecular plastic surface, or a cellulose-based material surface.

[0148] Performance testing

[0149] The super-hydrophobic coatings obtained in Examples 1-5 and Comparative Examples 1-2 are tested for performance, including:

[0150] Contact angle testing: DSA25 contact angle tester is used;

[0151] Rolling angle testing: LAUDA water droplet angle measuring instrument is used;

[0152] Liquid surface tension testing: FD-NST type surface tension coefficient tester is used.

[0153] The liquid used for testing is water, with a surface tension of 73.1 mN / m, and the test results are shown in Table 1.

[0154] Table 1

[0155] Sample Contact angle / ° Rolling angle / ° Example 1 151 4.7 Example 2 159 3.8 Example 3 153 4.5 Example 4 150 4.7 Example 5 151 4.6 Comparative Example 1 132 5.9 Comparative Example 2 139 5.4

[0156] The liquid with lower surface tension, specifically cyclohexane with surface tension of 18.1 mN / m, was added dropwise to the coating layer of Examples 1-5, all showing "lotus effect", and the liquid drops can roll freely without penetration.

[0157] Result analysis

[0158] Performance test can draw the following conclusions:

[0159] 1. The hydrophobicity of Examples 1-5 is excellent; the liquid-repellent effect on cyclohexane is also excellent;

[0160] This is because the present application utilizes methyl acrylate and acrylic acid to polymerize, and utilizes hexamethyl silazane and tetraethoxysilane to hydrolyze and condense, and synergistically polymerize into a network structure polymeric aqueous resin; hexamethyl silazane and tetraethoxysilane are organosilicon compounds, and have the defect of hydrolysis and condensation reaction of the ethoxyl group itself, and the present application utilizes amino-modified nano-silicon dioxide and hexadecyl trimethoxysilane as fillers to overcome the above defects, so that the coating of the present application not only has super-hydrophobic effect;

[0161] and also has good liquid-repellent ability to cyclohexane with surface tension lower than 20 mN / m, solving the problem that the existing super-hydrophobic coating relying on organosilicon to reduce surface energy cannot repel liquids with low surface tension, therefore, the coating of Examples 1-5 shows good hydrophobic performance in the detection of water drop contact angle and rolling angle, and can be applied to liquid-repellent purposes of liquids or aqueous solutions with surface tension smaller than water.

[0162] 2. The hydrophobic effect of Example 2 is the best;

[0163] It can be seen that the material ratio and process parameters of Example 2 are more excellent, the emulsion polymerization process is more stable, and the dispersion between the filler and the aqueous resin is more uniform and stable, therefore, Example 2 is the optimal embodiment among the numerous embodiments.

[0164] 3. The data difference between Examples 4-5 and Example 1 is not significant;

[0165] It can be seen that the amino-modified nanosilica prepared by different methods may have slight differences in efficiency and amino grafting rate, but the effect on the test results is not significant. During the coating formation process, the amino-modified nanosilica has better hydrophilicity due to the amino groups grafted on the surface of the particles, and is easier to disperse in the aqueous resin. The amino groups are "sunk" below the liquid surface of the aqueous resin due to the formation of hydrogen bonds or van der Waals forces with the electrophilic units in the aqueous resin, thereby exposing the silica to the outside. Therefore, the amino-modified nanosilica not only has good compatibility with the hydrophilic resin, but also increases the micro-roughness of the surface, forming more air / liquid interfaces. Such rough surface structure makes the liquid droplets unable to fully spread, thereby reducing the contact area between the liquid and the coating surface, increasing the contact angle, and achieving the super-hydrophobic effect of the coating.

[0166] 4. The hydrophobic effect of Comparative Example 1 is not good compared with Example 1;

[0167] It can be seen that this is mainly due to the lack of hexadecyltrimethoxysilane in Comparative Example 1. The role of hexadecyltrimethoxysilane in the coating includes the following aspects: ① The alkyl chain of hexadecyltrimethoxysilane can form a hydrophobic layer on the surface of the coating, reduce the surface free energy, make it difficult for the liquid to penetrate into the interior of the coating, and improve the hydrophobicity of the coating; ② Hexadecyltrimethoxysilane forms a self-assembled monolayer through the hydrophobic properties of its hexadecyl chain and the hydrophilic properties of the siloxane chain, thereby improving the anti-permeation performance of the coating and blocking the liquid droplets; ③ The siloxy group in hexadecyltrimethoxysilane can interact with the amino group of the amino-modified nanosilica, thereby promoting the formation of an ordered arrangement structure of the two on the surface of the coating, increasing the nanoscale roughness of the coating surface, and further improving the hydrophobic performance of the coating.

[0168] 5. The hydrophobic effect of Comparative Example 2 is not good compared with Example 1;

[0169] It can be seen from Conclusion 3 that the grafting rate of amino groups cannot directly affect the dispersion and bonding effect of silica, and the presence or absence of amino grafting is the key.

[0170] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A superhydrophobic coating based on waterborne resin composite modification, characterized in that, The ingredients include the following parts by weight: 10-15 parts of methyl acrylate; Acrylic acid 0.1~0.2 parts; 2-4 parts of hexamethylsilane; 1-3 parts of tetraethoxysilane; Emulsifier 0.3~0.6 parts; Polymerization initiator 0.1~0.2 parts; 80-100 parts water; Hexadecyltrimethoxysilane and amino-modified nano-silica; Of which, hexadecyltrimethoxysilane accounts for 2-5% of the total mass of the superhydrophobic coating; The amino-modified nano-silica accounts for 0.3% to 0.6% of the total mass of the superhydrophobic coating; The preparation method of the amino-modified nano-silica includes: It is made by grafting amino-containing silane coupling agents with nano-silica; Alternatively, it can be produced by complexing nano-silica with silver nitrate, followed by reduction and acid washing. Alternatively, it can be made by ion exchange between nano-silica and soluble ammonium salt under acidic conditions; The preparation method of the superhydrophobic coating includes the following steps: S1. Weigh methyl acrylate, acrylic acid, hexamethylsilane, tetraethoxysilane and water, stir and mix to obtain the first mixture; S2. Weigh the emulsifier and add it dropwise to the first mixture. Heat and reflux under an inert gas protective atmosphere to obtain a prepolymer emulsion. S3. Weigh the polymerization initiator and slowly add it dropwise to the prepolymer emulsion while maintaining continuous stirring. Continue stirring to obtain the aqueous resin. S4. Weigh hexadecyltrimethoxysilane and amino-modified nano-silica, add them to the aqueous resin, and stir to obtain a superhydrophobic coating based on aqueous resin composite modification.

2. The superhydrophobic coating based on waterborne resin composite modification as described in claim 1, characterized in that, The polymerization initiator is selected from benzoyl peroxide or ammonium persulfate.

3. The superhydrophobic coating based on waterborne resin composite modification as described in claim 1, characterized in that, The emulsifier is selected as octanol polyoxyethylene ether.

4. A method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Weigh methyl acrylate, acrylic acid, hexamethylsilane, tetraethoxysilane and water, stir and mix to obtain the first mixture; S2. Weigh the emulsifier and add it dropwise to the first mixture. Heat and reflux under an inert gas protective atmosphere to obtain a prepolymer emulsion. S3. Weigh the polymerization initiator and slowly add it dropwise to the prepolymer emulsion while maintaining continuous stirring. Continue stirring to obtain the aqueous resin. S4. Weigh hexadecyltrimethoxysilane and amino-modified nano-silica, add them to the aqueous resin, and stir to obtain a superhydrophobic coating based on aqueous resin composite modification.

5. The method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in claim 4, characterized in that, In S1, the mixing method is as follows: stir at a speed of not less than 100 r / min for at least 20 min.

6. The method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in claim 4, characterized in that, In S2, during the process of adding the emulsifier dropwise, the temperature of the first mixing step is maintained at 50~65℃.

7. The method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in claim 4, characterized in that, In S2, the inert gas includes one or more of nitrogen, helium, and argon.

8. The method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in claim 4, characterized in that, In S3, the prepolymer emulsion is continuously stirred at a stirring speed of 60~80 r / min and the temperature is maintained at 25~40℃.

9. The method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in claim 4, characterized in that, In S3, the polymerization initiator is added to the prepolymer emulsion at a dropping rate of 1~2 ml / min, and stirring is continued for 2~4 hours after the addition is complete.

10. The method for preparing a superhydrophobic coating based on waterborne resin composite modification as described in claim 4, characterized in that, In S4, the stirring method is: stir at 160~180r / min for 15~20min.

11. A coating obtained by the preparation method of a superhydrophobic coating based on waterborne resin composite modification as described in any one of claims 1-3 and / or the superhydrophobic coating based on waterborne resin composite modification as described in any one of claims 4-10, characterized in that, The contact angle with water is greater than 151°, and the roll-off angle is less than 5°.

12. The coating as claimed in claim 11, characterized in that, It is formed by spraying, roller coating, or brushing superhydrophobic coating onto the surface of a substrate and then curing it.

13. The coating as claimed in claim 11, characterized in that, The curing method is: room temperature curing for 48 hours.

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