Super-hydrophobic composite coating and preparation process thereof

Abstract

The invention relates to the technical field of hydrophobic coatings, in particular to a super-hydrophobic composite coating and a preparation process thereof. The composite coating is prepared by coating a substrate with a first coating solution and a second coating solution, and the first coating solution comprises the following components in parts by weight: 10-20 parts of modified calcium carbonate, 3-5 parts of gamma-chloropropyltriethoxysilane, 10-15 parts of modified sodium alginate and 70-90 parts of deionized water; the second coating liquid is prepared from the following components in parts by weight: 5 to 15 parts of citric acid, 4 to 8 parts of glucolactone, 8 to 12 parts of sodium polyacrylate and 50 to 60 parts of deionized water. The modified calcium carbonate of the composite coating can release calcium ions under the action of the second coating liquid, so that the modified sodium alginate is crosslinked under the action of the calcium ions to form the composite coating, the preparation process is simple, the cost is relatively low, and the modified sodium alginate can be matched with the modified calcium carbonate to improve the hydrophobicity of the composite coating and avoid corrosion of a substrate.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrophobic coatings, and in particular to a super-hydrophobic composite coating and a preparation process thereof. Background Art

[0002] Orthopedic biomedical materials are widely used in the treatment of orthopedic-related diseases (such as trauma, bone diseases or tumors, etc.), and can repair or replace damaged bones and bone tissues. Degradable medical magnesium alloys are widely used in the treatment of orthopedic-related diseases due to their good biosafety and compatibility.

[0003] However, after being implanted in the human body, magnesium alloy will gradually corrode until it degrades in the physiological environment. Therefore, in order to improve the life of magnesium alloy, it is necessary to cover the surface of the magnesium alloy with a super-hydrophobic coating to effectively prevent the magnesium alloy from being wetting and extend the service life of the magnesium alloy. However, the existing super-hydrophobic coatings are mostly prepared by electrodeposition, resulting in a high coating manufacturing cost. In addition, the super-hydrophobic coatings prepared by electrodeposition are easily affected by parameters such as electrolyte composition, current density, temperature, and pulse frequency, resulting in the inability to form a uniform micro-nano structure on the surface of the super-hydrophobic coating, which affects the hydrophobic properties of the super-hydrophobic coating. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a super-hydrophobic composite coating and a preparation process thereof.

[0005] The technical solution of the present invention is: a super-hydrophobic composite coating, wherein the composite coating is prepared by coating a first coating liquid and a second coating liquid on a substrate, wherein the first coating liquid comprises the following components in parts by weight: 10 to 20 parts of modified calcium carbonate, 3 to 5 parts of γ-chloropropyltriethoxysilane, 10 to 15 parts of modified sodium alginate, and 70 to 90 parts of deionized water; the second coating liquid comprises the following components in parts by weight: 5 to 15 parts of citric acid, 4 to 8 parts of gluconolactone, 8 to 12 parts of sodium polyacrylate, and 50 to 60 parts of deionized water.

[0006] Description: The above-mentioned composite coating is made by combining a first coating liquid and a second coating liquid. The modified calcium carbonate in the first coating liquid can release calcium ions under the action of the second coating liquid, so that the modified sodium alginate is cross-linked under the action of calcium ions to form a composite coating. The preparation process is simple and the cost is low. In addition, the modified sodium alginate can be combined with the modified calcium carbonate to improve the hydrophobicity of the composite coating and prevent corrosion of the substrate.

[0007] Furthermore, the preparation method of the modified calcium carbonate comprises:

[0008] 1) adding nano-calcium carbonate to an ethanol solution 3 to 5 times its own mass, and ultrasonically dispersing for 20 to 30 minutes to obtain a dispersion; wherein the mass concentration of the ethanol solution is 60 to 70%;

[0009] 2) adding octadecyltrichlorosilane to the dispersion, stirring at 60-70° C. for 4-6 hours, then filtering and drying to obtain modified calcium carbonate; wherein the amount of octadecyltrichlorosilane added accounts for 1-5% of the mass of the dispersion.

[0010] Description: The above method modifies nano-calcium carbonate by using octadecyltrichlorosilane to improve the hydrophobicity of nano-calcium carbonate, so that the modified calcium carbonate can be effectively combined with the modified sodium alginate to ensure the uniformity of the composite coating.

[0011] Furthermore, the drying temperature is 120-140°C.

[0012] Note: Limiting the drying temperature can ensure that the anhydrous ethanol on the surface of modified calcium carbonate can be fully removed.

[0013] Furthermore, the preparation method of the modified sodium alginate comprises the following steps:

[0014] 1) Sodium alginate is added to deionized water, stirred until completely dissolved, and then diisopropylcarbodiimide is added and stirred for 20-30 minutes to obtain a colloidal solution; wherein the mass ratio of sodium alginate, diisopropylcarbodiimide, and deionized water is 1:0.1-0.3:8-10;

[0015] 2) adding glyceryl monostearate to anhydrous ethanol and stirring for 10 to 15 minutes to obtain a mixed solution; wherein the mass ratio of glyceryl monostearate to anhydrous ethanol is 1:4 to 6;

[0016] 3) adding the mixed solution to the colloidal solution to obtain a mixture, adjusting the pH of the mixture to 5-6 using 2-5% dilute hydrochloric acid, then heating the mixture to 40-50° C. and adding 4-dimethylaminopyridine, stirring and reacting for 8-12 hours to obtain a reactant; wherein the mass ratio of the mixed solution to the colloidal solution is 1:3-5, and the amount of 4-dimethylaminopyridine added accounts for 2-4% of the total mass of the mixture;

[0017] 4) The reactants are centrifuged and filtered to obtain solid particles, which are then freeze-dried to obtain modified sodium alginate.

[0018] Description: The above method improves the hydrophobicity of sodium alginate by grafting glycerol monostearate onto sodium alginate, and the modified sodium alginate can be well combined with modified calcium carbonate to form a composite coating with a rough surface, thereby ensuring the hydrophobicity of the composite coating.

[0019] Furthermore, the rotation speed during the centrifugal separation is 3000-4000 rpm, and the centrifugal separation time is 10-15 minutes.

[0020] Note: The above centrifugal separation parameters can fully separate the sodium alginate colloid from water and ensure the yield of modified sodium alginate.

[0021] Furthermore, the freeze-drying temperature is -60 to -50°C.

[0022] Note: The above freeze-drying temperature can effectively dry the modified sodium alginate and prevent ice crystals from damaging the structure of the modified sodium alginate, thereby ensuring the structural strength of the modified sodium alginate.

[0023] On the other hand, the present invention also provides a preparation process of a super-hydrophobic composite coating, comprising the following steps:

[0024] S1. According to the composition and weight of the first coating liquid, modified calcium carbonate and γ-chloropropyltriethoxysilane are added to deionized water, and ultrasonically dispersed for 20 to 30 minutes. Then, modified sodium alginate is added and stirred for 10 to 20 minutes to obtain a first coating liquid;

[0025] S2. Add citric acid, gluconolactone, and sodium polyacrylate to deionized water according to the composition and weight of the second coating solution, and stir for 10 to 15 minutes to obtain a second coating solution;

[0026] S3, alternately apply the first coating liquid and the second coating liquid to the substrate surface, with the coating amount of the first coating liquid each time being 3-5 ml / cm 2 The initial coating amount of the second coating liquid is 0.5~1ml / cm 2 After each application of the second coating liquid, the substrate is dried in a carbon dioxide gas environment at 90-100°C for 20-30 minutes. The amount of the second coating liquid applied each time is increased by 0.2-0.5 ml / cm2 compared to the previous application. 2 , until the first coating liquid and the second coating liquid are alternately applied 3 to 5 times, and then allowed to stand for 10 to 16 hours to obtain a super hydrophobic coating.

[0027] Description: The above preparation process involves alternating application of the first coating liquid and the second coating liquid, so that the modified calcium carbonate can release calcium ions to promote the cross-linking of the modified sodium alginate to form a composite coating. The application amount of the second coating liquid gradually increases, which can gradually increase the calcium ion release rate and form a composite coating with micro-protrusions under the action of carbon dioxide, further improving the hydrophobicity of the composite coating.

[0028] Furthermore, the carbon dioxide volume concentration of the carbon dioxide gas environment is 40-60%.

[0029] Note: Limiting the carbon dioxide concentration can promote the release of calcium ions on the surface of the composite coating, forming a micro-protrusion structure on the surface of the composite coating, and improving the hydrophobicity of the composite coating.

[0030] The beneficial effects of the present invention are:

[0031] (1) The composite coating of the present invention is prepared by combining a first coating liquid and a second coating liquid. The modified calcium carbonate in the first coating liquid can release calcium ions under the action of the second coating liquid, so that the modified sodium alginate is cross-linked under the action of calcium ions to form a composite coating. The preparation process is simple and the cost is low. In addition, the modified sodium alginate can be combined with the modified calcium carbonate to improve the hydrophobicity of the composite coating and avoid corrosion of the substrate.

[0032] (2) The preparation process of the present invention alternately applies the first coating liquid and the second coating liquid, so that the modified calcium carbonate can release calcium ions to promote the cross-linking of the modified sodium alginate to form a composite coating, and the coating amount of the second coating liquid gradually increases, which can gradually increase the calcium ion release rate and form a composite coating with a micro-protrusion surface under the action of carbon dioxide, further improving the hydrophobicity of the composite coating. DETAILED DESCRIPTION

[0033] In order to further illustrate the approach and effects achieved by the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with experiments.

[0034] Example 1: A super-hydrophobic composite coating, the composite coating being prepared by coating a first coating liquid and a second coating liquid on a substrate, wherein the first coating liquid comprises the following components, by weight: 15 parts of modified calcium carbonate, 4 parts of γ-chloropropyltriethoxysilane, 12 parts of modified sodium alginate, and 80 parts of deionized water; the second coating liquid comprises the following components, by weight: 10 parts of citric acid, 6 parts of glucone lactone, 10 parts of sodium polyacrylate, and 55 parts of deionized water;

[0035] The preparation method of modified calcium carbonate comprises:

[0036] 1) adding nano-calcium carbonate to an ethanol solution of 4 times its own mass and ultrasonically dispersing for 25 minutes to obtain a dispersion; wherein the mass concentration of the ethanol solution is 65%;

[0037] 2) adding octadecyltrichlorosilane to the dispersion, stirring at 65° C. for 5 h, then filtering and drying to obtain modified calcium carbonate; wherein the amount of octadecyltrichlorosilane added is 3% by weight of the dispersion, and the drying temperature is 130° C.;

[0038] The preparation method of modified sodium alginate comprises the following steps:

[0039] 1) Sodium alginate was added to deionized water and stirred until completely dissolved, followed by addition of diisopropylcarbodiimide and continued stirring for 25 minutes to obtain a colloidal solution; wherein the mass ratio of sodium alginate, diisopropylcarbodiimide, and deionized water was 1:0.2:9;

[0040] 2) adding glyceryl monostearate to anhydrous ethanol and stirring for 12 minutes to obtain a mixed solution; wherein the mass ratio of glyceryl monostearate to anhydrous ethanol is 1:5;

[0041] 3) adding the mixed solution to the colloidal solution to obtain a mixture, adjusting the pH of the mixture to 5.5 using 3% dilute hydrochloric acid, then heating the mixture to 45° C. and adding 4-dimethylaminopyridine, stirring and reacting for 10 hours to obtain a reactant; wherein the mass ratio of the mixed solution to the colloidal solution is 1:4, and the amount of 4-dimethylaminopyridine added accounts for 3% of the total mass of the mixture;

[0042] 4) centrifuging and filtering the reactants to obtain solid particles, which are then freeze-dried to obtain modified sodium alginate; wherein the centrifugal speed is 3500 rpm, the centrifugal time is 12 minutes, and the freeze-drying temperature is -55°C;

[0043] The preparation process of the composite coating comprises the following steps:

[0044] S1. According to the composition and weight of the first coating liquid, modified calcium carbonate and γ-chloropropyltriethoxysilane were added to deionized water, and ultrasonically dispersed for 25 minutes. Then, modified sodium alginate was added and stirred for 15 minutes to obtain a first coating liquid;

[0045] S2. According to the composition and weight of the second coating liquid, citric acid, gluconolactone, and sodium polyacrylate were added to deionized water and stirred for 12 minutes to obtain a second coating liquid;

[0046] S3, alternately apply the first coating liquid and the second coating liquid to the substrate surface, and the coating amount of the first coating liquid each time is 4ml / cm 2 The initial coating amount of the second coating liquid is 0.75ml / cm 2 After each application of the second coating liquid, the substrate was dried in a carbon dioxide gas environment at 95°C for 25 minutes. The amount of the second coating liquid applied each time was increased by 0.4 ml / cm2 compared to the previous application. 2 , until the first coating liquid and the second coating liquid are alternately applied 4 times, and then allowed to stand for 14 hours to obtain a super-hydrophobic coating; wherein the carbon dioxide volume concentration of the carbon dioxide gas environment is 50%, and the substrate in this embodiment is a magnesium alloy substrate.

[0047] Example 2: This example is basically the same as Example 1, except that the first coating liquid comprises the following components in parts by weight: 10 parts of modified calcium carbonate, 3 parts of γ-chloropropyltriethoxysilane, 10 parts of modified sodium alginate, and 70 parts of deionized water; the second coating liquid comprises the following components in parts by weight: 5 parts of citric acid, 4 parts of glucone lactone, 8 parts of sodium polyacrylate, and 50 parts of deionized water.

[0048] Example 3: This example is basically the same as Example 1, except that the first coating liquid comprises the following components in parts by weight: 20 parts of modified calcium carbonate, 5 parts of γ-chloropropyltriethoxysilane, 15 parts of modified sodium alginate, and 90 parts of deionized water; the second coating liquid comprises the following components in parts by weight: 15 parts of citric acid, 8 parts of glucone lactone, 12 parts of sodium polyacrylate, and 60 parts of deionized water.

[0049] Example 4: This example is basically the same as Example 1, except that nano calcium carbonate is added into an ethanol solution that is 3 times the mass of the nano calcium carbonate.

[0050] Example 5: This example is basically the same as Example 1, except that nano calcium carbonate is added into an ethanol solution that is 5 times the mass of the nano calcium carbonate.

[0051] Example 6: This example is basically the same as Example 1, except that the added amount of octadecyltrichlorosilane accounts for 1% of the mass of the dispersion.

[0052] Example 7: This example is basically the same as Example 1, except that the added amount of octadecyltrichlorosilane accounts for 5% of the mass of the dispersion.

[0053] Example 8: This example is basically the same as Example 1, except that the mass ratio of sodium alginate, diisopropylcarbodiimide, and deionized water is 1:0.1:8.

[0054] Example 9: This example is basically the same as Example 1, except that the mass ratio of sodium alginate, diisopropylcarbodiimide and deionized water is 1:0.3:10.

[0055] Example 10: This example is basically the same as Example 1, except that the mass ratio of glyceryl monostearate to anhydrous ethanol is 1:4.

[0056] Example 11: This example is basically the same as Example 1, except that the mass ratio of glyceryl monostearate to anhydrous ethanol is 1:6.

[0057] Example 12: This example is basically the same as Example 1, except that the mass ratio of the mixed liquid to the colloidal liquid is 1:3.

[0058] Example 13: This example is basically the same as Example 1, except that the mass ratio of the mixed liquid to the colloidal liquid is 1:5.

[0059] Example 14: This example is basically the same as Example 1, except that the added amount of 4-dimethylaminopyridine accounts for 2% of the total mass of the mixture.

[0060] Example 15: This example is basically the same as Example 1, except that the added amount of 4-dimethylaminopyridine accounts for 4% of the total mass of the mixture.

[0061] Example 16: This example is basically the same as Example 1, except that the coating amount of the first coating liquid is 3 ml / cm 2 .

[0062] Example 17: This example is basically the same as Example 1, except that the coating amount of the first coating liquid is 5 ml / cm 2 .

[0063] Example 18: This example is basically the same as Example 1, except that the initial coating amount of the second coating liquid is 0.5 ml / cm 2 The coating amount of the second coating liquid is increased by 0.2ml / cm2 each time compared with the previous coating liquid. 2 .

[0064] Example 19: This example is basically the same as Example 1, except that the initial coating amount of the second coating liquid is 1 ml / cm 2 The coating amount of the second coating liquid is increased by 0.5ml / cm2 each time compared with the previous coating amount. 2 .

[0065] Example 20: This example is basically the same as Example 1, except that the first coating liquid and the second coating liquid are applied alternately three times.

[0066] Example 21: This example is basically the same as Example 1, except that the first coating liquid and the second coating liquid are applied alternately 5 times.

[0067] Example 22: This example is basically the same as Example 1, except that the volume concentration of carbon dioxide in the carbon dioxide gas environment is 40%.

[0068] Example 23: This example is basically the same as Example 1, except that the volume concentration of carbon dioxide in the carbon dioxide gas environment is 60%.

[0069] Comparative Example 1: Using Example 1 as a reference, the modified calcium carbonate was replaced with unmodified calcium carbonate.

[0070] Comparative Example 2: Taking Example 1 as a reference, the modified sodium alginate was replaced with unmodified sodium alginate.

[0071] Comparative Example 3: Using Example 1 as a reference, the coating amount of the second coating liquid is constant at 0.75 ml / cm 2 .

[0072] Comparative Example 4: Using Example 1 as a reference, the carbon dioxide gas environment was replaced with an air environment.

[0073] Experimental Example: In order to explore the performance of the composite coatings prepared in each embodiment, the surface water contact angle of the composite coatings prepared in each embodiment was tested, and the specific exploration is as follows:

[0074] 1. Explore the influence of composite coating composition on composite coating performance

[0075] Using Examples 1 to 3 as experimental comparison, the performance of the composite coatings under different compositions is shown in Table 1 below:

[0076] Table 1 Properties of composite coatings under different compositions

[0077] Group contact angle Example 1 164° Example 2 160° Example 3 158°

[0078] It can be seen from the data in Table 1 that, compared with Examples 1, 2, and 3, the water contact angle of the composite coating surface of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobic performance. This may be because the roughness of the composite coating surface under the composite coating composition of Example 1 is most suitable, so Example 1 selects the best composite coating composition.

[0079] 2. Investigate the influence of modified calcium carbonate preparation parameters on the performance of composite coatings

[0080] Using Examples 1, 4 to 7 and Comparative Example 1 as experimental comparisons, the composite coating properties obtained under different preparation parameters of modified calcium carbonate are shown in Table 2 below:

[0081] Table 2 Properties of composite coatings under different preparation parameters of modified calcium carbonate

[0082] Group contact angle Example 1 164° Example 4 161° Example 5 160° Example 6 157° Example 7 159° Comparative Example 1 143°

[0083] It can be seen from the data in Table 2 that, compared with Examples 1, 4, and 5, the water contact angle of the composite coating surface of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because under the dispersion ratio of Example 1, the surface of the nano-calcium carbonate can fully load the siloxy groups, so the dispersion ratio selected in Example 1 is optimal.

[0084] Comparing Examples 1, 6, and 7: The water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the excessive addition of octadecyltrichlorosilane may lead to the agglomeration of the modified calcium carbonate. Therefore, the addition amount of octadecyltrichlorosilane selected in Example 1 is the optimal;

[0085] Example 1 is compared with Comparative Example 1: After the modified calcium carbonate is replaced by unmodified calcium carbonate, the hydrophobic performance of the composite coating is significantly reduced. This may be because the unmodified calcium carbonate destroys the hydrophobic stability of the composite coating. Therefore, the composite coating composition selected in Example 1 is better.

[0086] 3. Investigate the influence of modified sodium alginate preparation parameters on the performance of composite coatings

[0087] Using Examples 1, 8 to 15 and Comparative Example 2 as experimental comparisons, the performance of the composite coating obtained under different preparation parameters of modified sodium alginate is shown in Table 3 below:

[0088] Table 3 Properties of composite coatings with modified sodium alginate under different preparation parameters

[0089]

[0090]

[0091] As can be seen from the data in Table 3, compared with Examples 1, 8, and 9, the water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the sodium alginate colloid is uniform and stable under the colloidal liquid composition of Example 1, so the colloidal liquid composition selected in Example 1 is optimal.

[0092] Comparing Examples 1, 10, and 11: the water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the glyceryl monostearate can fully react with sodium alginate under the mixed solution composition of Example 1, so the mixed solution composition selected in Example 1 is optimal;

[0093] Comparing Examples 1, 12, and 13: the water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the modified sodium alginate has the best hydrophobicity at the ratio of the mixed liquid to the colloid liquid in Example 1, so the ratio of the mixed liquid to the colloid liquid selected in Example 1 is the best;

[0094] Comparing Examples 1, 14, and 15: As the amount of 4-dimethylaminopyridine added increases, the surface water contact angle of the composite coating also increases until the surface water contact angle of Example 1 reaches the maximum. As the amount of 4-dimethylaminopyridine added continues to increase, the surface water contact angle of the composite coating begins to have no obvious change. Therefore, from a cost perspective, the amount of 4-dimethylaminopyridine added selected in Example 1 is optimal;

[0095] Example 1 is compared with Comparative Example 2: After the modified sodium alginate is replaced by unmodified sodium alginate, the hydrophobicity of the composite coating is significantly reduced. This may be because the hydrophobicity of the unmodified sodium alginate is deteriorated. Therefore, the composite coating component selected in Example 1 is better.

[0096] 4. Investigate the influence of composite coating preparation process parameters on composite coating performance

[0097] Using Examples 1, 16 to 23 and Comparative Examples 3 to 4 as experimental comparisons, the properties of the composite coatings obtained under different preparation process parameters are shown in Table 4 below:

[0098] Table 4 Properties of composite coatings under different preparation process parameters

[0099] Group contact angle Example 1 164° Example 16 161° Example 17 158° Example 18 157° Example 19 160° Example 20 156° Example 21 162° Example 22 160° Example 23 163° Comparative Example 3 148° Comparative Example 4 153°

[0100] As can be seen from the data in Table 4, compared with Examples 1, 16, and 17, the water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the composite coating of Example 1 has a dense structure, so the coating amount of the first coating liquid selected in Example 1 is optimal.

[0101] Comparing Examples 1, 18, and 19: the water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the micro-protrusion structure on the surface of the composite coating of Example 1 is evenly distributed, so the coating amount of the second coating liquid selected in Example 1 is optimal;

[0102] Comparing Examples 1, 20, and 21: The water contact angle of the composite coating surface of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the number of times the first coating liquid and the second coating liquid are applied is too many or more or less uniform, which affects the surface structure of the composite coating. Therefore, the number of times the first coating liquid and the second coating liquid are applied in Example 1 is optimal.

[0103] Comparing Examples 1, 22, and 23: The water contact angle on the surface of the composite coating of Example 1 is the largest, indicating that the composite coating of Example 1 has the best hydrophobicity. This may be because the modified sodium alginate can be fully cross-linked under the carbon dioxide volume concentration of Example 1, so the carbon dioxide volume concentration selected in Example 1 is the optimal;

[0104] Compared with Comparative Example 3, Example 1 shows that the hydrophobicity of the composite coating decreases significantly after the coating amount of the second coating liquid is kept constant. This may be because the coating amount of the second coating liquid remains constant, resulting in the inability to form micro-protrusion structures on the surface of the composite coating. Therefore, the coating amount of the second coating liquid selected in Example 1 is optimal.

[0105] Example 1 is compared with Comparative Example 4: After the carbon dioxide gas environment is replaced with an air environment, the hydrophobicity of the composite coating decreases. This may be because the release rate of calcium ions on the surface of the composite coating slows down, which affects the cross-linking of the modified sodium alginate. Therefore, the carbon dioxide volume concentration selected in Example 1 is optimal.

Claims

1. A super-hydrophobic composite coating, characterized in that: The composite coating is prepared by coating a first coating liquid and a second coating liquid on a substrate, wherein the first coating liquid comprises the following components in parts by weight: 10 to 20 parts of modified calcium carbonate, 3 to 5 parts of γ-chloropropyltriethoxysilane, 10 to 15 parts of modified sodium alginate, and 70 to 90 parts of deionized water; the second coating liquid comprises the following components in parts by weight: 5 to 15 parts of citric acid, 4 to 8 parts of gluconolactone, 8 to 12 parts of sodium polyacrylate, and 50 to 60 parts of deionized water.

2. A super-hydrophobic composite coating according to claim 1, characterized in that, The preparation method of the modified calcium carbonate comprises: 1) adding nano-calcium carbonate to an ethanol solution 3 to 5 times its own mass, and ultrasonically dispersing for 20 to 30 minutes to obtain a dispersion; wherein the mass concentration of the ethanol solution is 60 to 70%; 2) adding octadecyltrichlorosilane to the dispersion, stirring at 60-70° C. for 4-6 hours, then filtering and drying to obtain modified calcium carbonate; wherein the amount of octadecyltrichlorosilane added accounts for 1-5% of the mass of the dispersion.

3. A super-hydrophobic composite coating according to claim 2, characterized in that, The drying temperature is 120-140°C.

4. A super-hydrophobic composite coating according to claim 1, characterized in that, The preparation method of the modified sodium alginate comprises the following steps: 1) Sodium alginate is added to deionized water, stirred until completely dissolved, and then diisopropylcarbodiimide is added and stirred for 20-30 minutes to obtain a colloidal solution; wherein the mass ratio of sodium alginate, diisopropylcarbodiimide, and deionized water is 1:0.1-0.3:8-10; 2) adding glyceryl monostearate to anhydrous ethanol and stirring for 10 to 15 minutes to obtain a mixed solution; wherein the mass ratio of glyceryl monostearate to anhydrous ethanol is 1:4 to 6; 3) adding the mixed solution to the colloidal solution to obtain a mixture, adjusting the pH of the mixture to 5-6 using 2-5% dilute hydrochloric acid, then heating the mixture to 40-50° C. and adding 4-dimethylaminopyridine, stirring and reacting for 8-12 hours to obtain a reactant; wherein the mass ratio of the mixed solution to the colloidal solution is 1:3-5, and the amount of 4-dimethylaminopyridine added accounts for 2-4% of the total mass of the mixture; 4) The reactants are centrifuged and filtered to obtain solid particles, which are then freeze-dried to obtain modified sodium alginate.

5. A super-hydrophobic composite coating according to claim 4, characterized in that, The rotation speed during the centrifugal separation is 3000-4000 rpm, and the centrifugal separation time is 10-15 minutes.

6. A super-hydrophobic composite coating according to claim 4, characterized in that, The freeze-drying temperature is -60 to -50°C.

7. The process for preparing a super-hydrophobic composite coating according to any one of claims 1 to 6, wherein: The following steps are involved: S1. According to the composition and weight of the first coating liquid, modified calcium carbonate and γ-chloropropyltriethoxysilane are added to deionized water, and ultrasonically dispersed for 20 to 30 minutes. Then, modified sodium alginate is added and stirred for 10 to 20 minutes to obtain a first coating liquid; S2. Add citric acid, gluconolactone, and sodium polyacrylate to deionized water according to the composition and weight of the second coating solution, and stir for 10 to 15 minutes to obtain a second coating solution; S3, alternately apply the first coating liquid and the second coating liquid to the substrate surface, with the coating amount of the first coating liquid each time being 3-5 ml / cm 2 The initial coating amount of the second coating liquid is 0.5~1ml / cm 2 After each application of the second coating liquid, the substrate is dried in a carbon dioxide gas environment at 90-100°C for 20-30 minutes. The amount of the second coating liquid applied each time is increased by 0.2-0.5 ml / cm2 compared to the previous application. 2 , until the first coating liquid and the second coating liquid are alternately applied 3 to 5 times, and then allowed to stand for 10 to 16 hours to obtain a super hydrophobic coating.

8. A process for preparing a super-hydrophobic composite coating according to claim 7, characterized in that, The carbon dioxide volume concentration of the carbon dioxide gas environment is 40-60%.

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