A polysiloxane elastic waterproof coating and its preparation process

Abstract

The present invention discloses a polysiloxane elastic waterproof coating and a preparation method thereof. The polysiloxane elastic waterproof coating comprises the following raw materials: 35-60 parts of methyl polysiloxane resin, 8-12 parts of acrylic resin, 15-20 parts of filler, 2-5 parts of thickener, 1-3 parts of dispersant, 1-3 parts of film-forming aid, 1-2 parts of defoamer, 1-3 parts of leveling agent, and 10-20 parts of water. The polysiloxane elastic waterproof coating is obtained by mixing and stirring the raw materials in a reasonable proportion. The polysiloxane elastic waterproof coating is obtained after the coating is dried. The polysiloxane elastic waterproof coating provided by the present invention has excellent adhesion performance, waterproof performance, tensile strength and aging resistance, and can be widely used in waterproofing of metal materials and the construction industry.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a polysiloxane elastic waterproof coating and a preparation process thereof. Background Art

[0002] Polysiloxane is a polymer with Si-O-Si bonds as its backbone. Polysiloxane coatings exhibit excellent weather resistance, chemical resistance, and a low coefficient of thermal expansion. These properties have led to their widespread use in corrosion protection and protection applications in bridges, oil rigs, ships, and aerospace. In recent years, with the application of nanotechnology and functional additives, the performance of polysiloxane coatings has been significantly improved, including enhanced resistance to UV radiation, longer service life, and superior adhesion. In addition, the development of environmentally friendly water-based polysiloxane coatings has reduced emissions of volatile organic compounds (VOCs), meeting the needs of green building and industrial coatings. However, pure polysiloxane coatings have drawbacks such as low film hardness, poor flexibility, and low adhesion. Currently, polysiloxane composite coatings, which use polysiloxane as the primary film-forming substance in combination with other polymer resins, can improve the hardness, flexibility, and impact resistance of polysiloxane coatings to a certain extent.

[0003] CN114836127A discloses a high-toughness polysiloxane composite coating and its preparation method. The preparation method comprises: (1) mixing bisphenol A epoxy resin, fused silica powder, a dispersant, and a solvent, and dispersing the mixture under high pressure and high speed; (2) adding methyl polysiloxane resin, adjusting the pressure, heating under high pressure and stirring, slowly adding nano-titanium dioxide, and maintaining the pressure to increase the stirring speed; (3) adding titanium dioxide and barium sulfate, mixing, grinding, and adding an auxiliary agent to obtain an organic dispersion mixture C; (4) adding a mixture of aminosilane and cobalt naphthenate to the organic dispersion mixture C, and mixing uniformly to obtain the polysiloxane composite coating. The polysiloxane composite coating prepared by this invention has a low VOC content, significantly improved curing rate, and enhanced mechanical properties. However, the waterproof effect is poor, and moisture may penetrate into the matrix structure, thereby damaging the structural strength and stability of the matrix.

[0004] CN118562384A discloses a room-temperature-curing organosilicon resin coating and its preparation method. The invention produces the room-temperature-curing organosilicon resin coating by mixing a hydroxyl organopolysiloxane resin A, an alkoxy organopolysiloxane resin B, a modified filler, and dibutyltin diacetate. The modified filler is prepared by reacting cuprous oxide with carbon nanotubes as a carrier, followed by reaction with alkyltrimethoxysilane and 3-aminopropyltrimethoxysilane. The coating produced by this invention exhibits corrosion resistance, high temperature resistance, and quick drying at room temperature. However, the coating formed by this coating may crack when exposed to long-term ultraviolet radiation, resulting in a short service life. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a polysiloxane elastic waterproof coating and a preparation process thereof.

[0006] To solve the above technical problems, the present invention provides a preparation process of a polysiloxane elastic waterproof coating, comprising the following steps:

[0007] (1) Mixing methyl polysiloxane resin, dispersant and water, stirring at 60-100 MPa and 1000-1500 rpm for 20-30 minutes to obtain mixture A;

[0008] (2) adding acrylic resin, filler, film-forming aid and thickener to mixture A and mixing them uniformly; stirring at 30-50 MPa, 400-600 r / min, and 40-50° C. for 20-50 min to obtain mixture B;

[0009] (3) Add defoaming agent and leveling agent to mixture B, mix and stir at 500-600 rpm for 20-40 minutes to obtain polysiloxane elastic waterproof coating; apply polysiloxane elastic waterproof coating, dry and obtain polysiloxane elastic waterproof coating.

[0010] Preferably, the weight ratio of each raw material component is:

[0011] 35-60 parts of methyl polysiloxane resin, 8-12 parts of acrylic resin, 15-20 parts of filler, 2-5 parts of thickener, 1-3 parts of dispersant, 1-3 parts of film-forming aid, 1-2 parts of defoaming agent, 1-3 parts of leveling agent, and 10-20 parts of water.

[0012] Preferably, the filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1-3:1.

[0013] Preferably, the preparation method of the composite modified carbon nanotubes comprises the following steps, in parts by weight:

[0014] S1. Adding 3-6 parts of carbon nanotubes to a mixed acid solution of 350-450 parts of nitric acid and sulfuric acid in a volume ratio of 1:2-3, stirring the solution at 24-26° C. for 12-16 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:4-8 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect the product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 95-105° C. for 1-3 hours to obtain acid-modified carbon nanotubes;

[0015] S2, petroleum ether and sunflower pollen are mixed and stirred in a weight ratio of 1:4-8 for 20-40min, filtered, and then vacuum dried at 55-65°C for 6-10h to obtain dried defatted sunflower pollen; thereafter, the dried defatted sunflower pollen is mixed with 0.1-0.3g / mL phosphoric acid aqueous solution in a weight ratio of 1:10-20, refluxed and stirred at 60-80°C for 4-6h, filtered, and then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to a constant weight to obtain sunflower sporopollenin microcapsules;

[0016] S3. 5-8 parts of acid-modified carbon nanotubes, 1-3 parts of sunflower sporopollenin microcapsules and 30-40 parts of isopropanol are mixed, and then ultrasonically treated at 300-500 W for 20-30 min. Then, 0.05-0.2 parts of toluenesulfonic acid are added under a nitrogen atmosphere. Then, the mixture is mixed and stirred at 90-100° C. and 300-600 r / min for 1-3 h. The mixture is filtered, washed, and vacuum-dried at 75-85° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes, that is, composite modified carbon nanotubes.

[0017] Preferably, the step S3 may also be, by weight:

[0018] 5-8 parts of acid-modified carbon nanotubes, 1-3 parts of sunflower sporopollenin microcapsules and 30-40 parts of isopropanol are mixed, and then ultrasonically treated at 300-500W for 20-30 minutes. Then, 0.0.5-0.2 parts of toluenesulfonic acid are added under a nitrogen atmosphere. Then, the mixture is stirred at 90-100°C and 300-600r / min for 1-3 hours. The mixture is filtered, washed, and vacuum-dried at 75-85°C to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes. Then, 3-5 parts of sunflower sporopollenin microcapsule-modified carbon nanotubes and 8-15 parts of isopropanol are stirred and mixed. Then, 1-2 parts of an amino modifier and 0.05-0.2 parts of a photoinitiator 651 are added. The mixture is stirred and mixed under ultraviolet irradiation with a wavelength of 365-400nm for 3-5 hours. The mixture is filtered, washed, and vacuum-dried to obtain a composite modified carbon nanotube.

[0019] Preferably, the amino modifier is selected from one of oleylamine, octadecylamine, N-isopropyloctadecylamine and hexadecylamine.

[0020] Preferably, the thickener is Hemmings 299.

[0021] Preferably, the film-forming aid is propylene glycol methyl ether acetate.

[0022] Preferably, the dispersant is selected from Digo Dispers650, One of Dispers655.

[0023] Preferably, the defoaming agent is selected from one of German BYK BYK-092, BYK-141, BYK-01610, and BYK-01615.

[0024] Preferably, the leveling agent is selected from one of German BYK-345, BYK-333 and BYK-330.

[0025] Carbon nanotubes, as a nanoscale seamless tubular carbon material, have a large specific surface area and excellent mechanical properties. They also possess multiple effects, such as microscopic nanometer effects and macroscopic quantum tunneling effects, which give them extremely strong adsorption capacity. However, due to the lack of active groups on their surfaces, their large specific surface area, and their high aspect ratio, they easily aggregate, making dispersion difficult in a resin matrix. To address this problem, the present invention first modifies their surfaces with a mixed acid solution to introduce carboxyl and hydroxyl groups, and then introduces sunflower sporopollenin microcapsules to react with them. The sunflower sporopollenin microcapsules have a porous structure and abundant functional groups on their surfaces. The abundant functional groups on the surface of the sunflower sporopollenin microcapsules react with the hydroxyl and carboxyl groups on the surface of the acid-modified carbon nanotubes to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes. Subsequently, an organic amine with a long-chain alkyl group is introduced to react with the functional groups on the surface of the sunflower sporopollenin microcapsules, thereby grafting alkylamine groups on the surface of the modified carbon nanotubes to obtain composite modified carbon nanotubes. The hydroxyl and amino groups grafted onto the surface of the composite modified carbon nanotubes can form hydrogen bonds or covalent bonds with the resin matrix, enhancing the interaction between the composite modified carbon nanotubes and the resin matrix. This interaction improves the dispersion and compatibility of the carbon nanotubes in the resin matrix, reduces agglomeration, and thus enhances the uniformity and performance of the composite material. The introduction of composite modified carbon nanotubes can increase the crosslinking points of the resin system and improve the crosslinking density of the composite material.

[0026] The present invention also discovered that the composite modified carbon nanotubes and talc are used in synergistic fashion as coating fillers. During the coating preparation process, the functional groups on the surface of the composite modified carbon nanotubes may react with the hydroxyl groups on the surface of the talc by forming chemical bonds, forming a stable chemical adsorption layer. This alters the chemical properties of the talc surface, increases its compatibility with the resin phase, and thereby improves the dispersibility of the talc in the resin, reduces agglomeration, and thus enhances the uniformity and mechanical properties of the coating. Furthermore, the different morphologies of the talc, which is a flaky structure, and the carbon nanotubes, which are tubular, allow them to be uniformly dispersed and intertwined in the mixed resin during the coating preparation process, forming a physical network that further enhances the uniformity, water resistance, aging resistance, and mechanical properties of the coating.

[0027] The present invention also provides a polysiloxane elastic waterproof coating, which is prepared by the above process.

[0028] In the present invention, talc powder acts as a filler to increase the thickness and density of the coating, thereby increasing the contact area between the coating and the substrate and enhancing adhesion. Its flaky structure forms a physical barrier, hindering water penetration and improving the coating's waterproof properties. Furthermore, talc powder reflects and scatters ultraviolet light, reducing photodegradation of the resin and thus improving the coating's anti-aging properties.

[0029] Beneficial effects of the present invention:

[0030] 1. Compared with the prior art, the present invention prepares a polysiloxane elastic waterproof coating through reasonable proportions, utilizes the interaction between various substances, and optimizes the preparation process parameters. After the coating dries, the polysiloxane elastic waterproof coating is obtained, which not only has strong adhesion but also good tensile and waterproof properties. Under the irradiation of ultraviolet light, it has a long service life, ensures overall anti-aging performance, and avoids the problem of cracking and falling off after long-term use.

[0031] 2. Compared with the existing technology, the present invention uses composite modified carbon nanotubes and talcum powder in combination as coating fillers to prepare a polysiloxane elastic waterproof coating. The composite modified carbon nanotubes are not only well dispersed in the polysiloxane elastic waterproof coating and have good compatibility with the system, but also improve the dispersibility of talcum powder in the matrix resin, effectively improving the adhesion performance, waterproof performance, tensile performance and aging resistance of the polysiloxane elastic waterproof coating.

[0032] 3. Compared with the existing technology, the preparation process of the present invention is simple, has low production cost, is environmentally friendly, and has good economic, ecological and social benefits. DETAILED DESCRIPTION

[0033] Parameters for specific chemical substances used, sources.

[0034] Talc, particle size: 10 μm;

[0035] Sunflower powder, mesh number: 100 mesh;

[0036] Methyl polysiloxane resin, product number: SH-5201S, brand: Longsheng Sihai.

[0037] Carbon nanotubes, length: 15 μm, diameter: 15 nm;

[0038] Acrylic resin, solid content: 30%, brand: SEARESIN 142, brand: Sidon.

[0039] Example 1

[0040] A preparation process of a polysiloxane elastic waterproof coating comprises the following steps:

[0041] (1) 45 parts by weight of methyl polysiloxane resin, 2 parts by weight of Dispers 650 and 12 parts by weight of water were mixed and stirred at 80 MPa and 1200 rpm for 25 min to obtain a mixture A;

[0042] (2) 10 parts by weight of acrylic resin, 18 parts by weight of filler, 2 parts by weight of propylene glycol methyl ether acetate and 3 parts by weight of Hemmings 299 were added to mixture A and mixed uniformly, and the mixture was stirred at 40 MPa, 500 rpm and 45° C. for 40 minutes to obtain mixture B;

[0043] (3) Add 1.5 parts by weight of BYK-141 and 2.5 parts by weight of BYK-333 to mixture B, mix and stir at 550 rpm for 30 minutes to obtain a polysiloxane elastic waterproof coating; apply the polysiloxane elastic waterproof coating, and dry to obtain a polysiloxane elastic waterproof coating.

[0044] The filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1:1;

[0045] The preparation method of the composite modified carbon nanotubes comprises the following steps:

[0046] S1. Adding 4.5 parts by weight of carbon nanotubes to a mixed acid solution of 400 parts by weight of nitric acid (60 wt%) and sulfuric acid (97 wt%) in a volume ratio of 1:3, stirring the solution at 25° C. for 15 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:6 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect a product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 100° C. for 2 hours to obtain acid-modified carbon nanotubes;

[0047] S2. Petroleum ether and sunflower pollen were mixed and stirred in a weight ratio of 1:6 for 30 min, filtered, and then vacuum-dried at 62 ° C for 8 h to obtain dried defatted sunflower pollen; thereafter, the dried defatted sunflower pollen was mixed with 0.2 g / mL phosphoric acid aqueous solution in a weight ratio of 1:16, refluxed at 70 ° C for 5.5 h, filtered, and then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to a constant weight to obtain sunflower sporopollenin microcapsules;

[0048] S3. 6 parts by weight of acid-modified carbon nanotubes, 2.5 parts by weight of sunflower sporopollenin microcapsules and 35 parts by weight of isopropanol are mixed, and then ultrasonically treated at 450 W for 25 min. Then, 0.12 parts by weight of toluenesulfonic acid are added under a nitrogen atmosphere, and then mixed and stirred at 98° C. and 450 r / min for 2 h. The mixture is filtered, washed, and vacuum-dried at 72° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes; then 4.5 parts by weight of sunflower sporopollenin microcapsule-modified carbon nanotubes and 13 parts by weight of isopropanol are stirred and mixed, and 1.5 parts by weight of oleylamine and 0.12 parts by weight of photoinitiator 651 are added. The mixture is stirred and mixed under ultraviolet light with a wavelength of 365 nm for 4.5 h. The mixture is filtered, washed, and vacuum-dried to obtain composite modified carbon nanotubes.

[0049] Example 2

[0050] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1:1;

[0051] The preparation method of the composite modified carbon nanotubes comprises the following steps:

[0052] S1. Adding 4.5 parts by weight of carbon nanotubes to a mixed acid solution of 400 parts by weight of nitric acid (60 wt%) and sulfuric acid (97 wt%) in a volume ratio of 1:3, stirring the solution at 25° C. for 15 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:6 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect a product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 100° C. for 2 hours to obtain acid-modified carbon nanotubes;

[0053] S2. Petroleum ether and sunflower pollen were mixed and stirred in a weight ratio of 1:6 for 30 min, filtered, and then vacuum-dried at 62 ° C for 8 h to obtain dried defatted sunflower pollen; thereafter, the dried defatted sunflower pollen was mixed with 0.2 g / mL phosphoric acid aqueous solution in a weight ratio of 1:16, refluxed at 70 ° C for 5.5 h, filtered, and then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to a constant weight to obtain sunflower sporopollenin microcapsules;

[0054] S3. 6 parts by weight of acid-modified carbon nanotubes, 2.5 parts by weight of sunflower sporopollenin microcapsules and 35 parts by weight of isopropanol are mixed, and then ultrasonically treated at 450 W for 25 min. Then, 0.12 parts by weight of toluenesulfonic acid are added under a nitrogen atmosphere, and then mixed and stirred at 98° C. and 450 r / min for 2 h. The mixture is filtered, washed, and vacuum-dried at 72° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes; then 4.5 parts by weight of sunflower sporopollenin microcapsule-modified carbon nanotubes and 13 parts by weight of isopropanol are stirred and mixed, and 1.5 parts by weight of octadecylamine and 0.12 parts by weight of photoinitiator 651 are added. The mixture is stirred and mixed under ultraviolet irradiation with a wavelength of 365 nm for 4.5 h. The mixture is filtered, washed, and vacuum-dried to obtain composite modified carbon nanotubes.

[0055] Example 3

[0056] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1:1;

[0057] The preparation method of the composite modified carbon nanotubes comprises the following steps:

[0058] S1. Adding 4.5 parts by weight of carbon nanotubes to a mixed acid solution of 400 parts by weight of nitric acid (60 wt%) and sulfuric acid (97 wt%) in a volume ratio of 1:3, stirring the solution at 25° C. for 15 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:6 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect a product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 100° C. for 2 hours to obtain acid-modified carbon nanotubes;

[0059] S2. Petroleum ether and sunflower pollen were mixed and stirred in a weight ratio of 1:6 for 30 min, filtered, and then vacuum-dried at 62 ° C for 8 h to obtain dried defatted sunflower pollen; thereafter, the dried defatted sunflower pollen was mixed with 0.2 g / mL phosphoric acid aqueous solution in a weight ratio of 1:16, refluxed at 70 ° C for 5.5 h, filtered, and then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to a constant weight to obtain sunflower sporopollenin microcapsules;

[0060] S3. 6 parts by weight of acid-modified carbon nanotubes, 2.5 parts by weight of sunflower sporopollenin microcapsules and 35 parts by weight of isopropanol are mixed, and then ultrasonically treated at 450 W for 25 min. Then, 0.12 parts by weight of toluenesulfonic acid are added under a nitrogen atmosphere, and then mixed and stirred at 98° C. and 450 r / min for 2 h. The mixture is filtered, washed, and vacuum-dried at 72° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes; then 4.5 parts by weight of sunflower sporopollenin microcapsule-modified carbon nanotubes and 13 parts by weight of isopropanol are stirred and mixed, and then 1.5 parts by weight of N-isopropyl octadecylamine and 0.12 parts by weight of photoinitiator 651 are added. The mixture is stirred and mixed under ultraviolet irradiation with a wavelength of 365 nm for 4.5 h. The mixture is filtered, washed, and vacuum-dried to obtain composite modified carbon nanotubes.

[0061] Example 4

[0062] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1:1;

[0063] The preparation method of the composite modified carbon nanotubes comprises the following steps:

[0064] S1. Adding 4.5 parts by weight of carbon nanotubes to a mixed acid solution of 400 parts by weight of nitric acid (60 wt%) and sulfuric acid (97 wt%) in a volume ratio of 1:3, stirring the solution at 25° C. for 15 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:6 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect a product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 100° C. for 2 hours to obtain acid-modified carbon nanotubes;

[0065] S2. Petroleum ether and sunflower pollen were mixed and stirred in a weight ratio of 1:6 for 30 min, filtered, and then vacuum-dried at 62 ° C for 8 h to obtain dried defatted sunflower pollen; thereafter, the dried defatted sunflower pollen was mixed with 0.2 g / mL phosphoric acid aqueous solution in a weight ratio of 1:16, refluxed at 70 ° C for 5.5 h, filtered, and then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to a constant weight to obtain sunflower sporopollenin microcapsules;

[0066] S3. 6 parts by weight of acid-modified carbon nanotubes, 2.5 parts by weight of sunflower sporopollenin microcapsules and 35 parts by weight of isopropanol are mixed, and then ultrasonically treated at 450 W for 25 min. Then, 0.12 parts by weight of toluenesulfonic acid are added under a nitrogen atmosphere, and then mixed and stirred at 98° C. and 450 r / min for 2 h. The mixture is filtered, washed, and vacuum-dried at 72° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes; then 4.5 parts by weight of sunflower sporopollenin microcapsule-modified carbon nanotubes and 13 parts by weight of isopropanol are stirred and mixed, and 1.5 parts by weight of hexadecylamine and 0.12 parts by weight of photoinitiator 651 are added. The mixture is stirred and mixed under ultraviolet irradiation with a wavelength of 365 nm for 4.5 h. The mixture is filtered, washed, and vacuum-dried to obtain composite modified carbon nanotubes.

[0067] Example 5

[0068] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1:1;

[0069] The preparation method of the composite modified carbon nanotubes comprises the following steps:

[0070] S1. Adding 4.5 parts by weight of carbon nanotubes to a mixed acid solution of 400 parts by weight of nitric acid (60 wt%) and sulfuric acid (97 wt%) in a volume ratio of 1:3, stirring the solution at 25° C. for 15 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:6 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect a product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 100° C. for 2 hours to obtain acid-modified carbon nanotubes;

[0071] S2. Petroleum ether and sunflower pollen were mixed and stirred in a weight ratio of 1:6 for 30 min, filtered, and then vacuum-dried at 62 ° C for 8 h to obtain dried defatted sunflower pollen; thereafter, the dried defatted sunflower pollen was mixed with 0.2 g / mL phosphoric acid aqueous solution in a weight ratio of 1:16, refluxed at 70 ° C for 5.5 h, filtered, and then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to a constant weight to obtain sunflower sporopollenin microcapsules;

[0072] S3. 6 parts by weight of acid-modified carbon nanotubes, 2.5 parts by weight of sunflower sporopollenin microcapsules and 35 parts by weight of isopropanol are mixed, and then ultrasonically treated at 450 W for 25 min. Then, 0.12 parts by weight of toluenesulfonic acid are added under a nitrogen atmosphere. Then, the mixture is mixed and stirred at 98° C. and 450 r / min for 2 h. The mixture is filtered, washed, and vacuum-dried at 72° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes, i.e., composite modified carbon nanotubes are obtained.

[0073] Comparative Example 1

[0074] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a composite modified carbon nanotube;

[0075] The preparation method of the composite modified carbon nanotubes is consistent with that of Example 1.

[0076] Comparative Example 2

[0077] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a mixture of talc powder and acid-modified carbon nanotubes in a weight ratio of 1:1;

[0078] The method for preparing the acid-modified carbon nanotubes comprises the following steps:

[0079] 4.5 parts of carbon nanotubes were added to a mixed acid solution of 400 parts of nitric acid (60wt%) and sulfuric acid (97wt%) in a volume ratio of 1:3, and the solution was stirred at 25°C for 15 hours to obtain a mixture; then, the mixture was mixed with water in a weight ratio of 1:6 to obtain a mixed solution, the mixed solution was filtered with a vacuum filter, the product was collected, and the obtained product was washed with water until the pH reached neutral; finally, the product was dried at 100°C for 2 hours to obtain acid-modified carbon nanotubes.

[0080] Comparative Example 3

[0081] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is a mixture of talcum powder and carbon nanotubes in a weight ratio of 1:1.

[0082] Comparative Example 4

[0083] A preparation process of a polysiloxane elastic waterproof coating, which differs from Example 1 in that the filler is talcum powder.

[0084] Test Example 1

[0085] Performance Testing

[0086] The polysiloxane elastic waterproof coating obtained in Examples 1-5 and Comparative Examples 1-4 of the present invention was applied to the surface of the fiber-reinforced cement board specified in the national standard GB / T 9271-2008 "Standard Test Plate for Paints and Varnishes". After conditioning for 24 hours at 25°C and a relative humidity of 50%, a coating with a thickness of 1.5 mm was obtained. This was used as a test plate and the following tests were performed: the adhesion of the sample was tested according to the "GB / T9286-2021 Paint and Varnish Cross-cut Test"; the tensile properties of the sample were tested according to the "GB / T 1040.1-2018 Determination of Tensile Properties of Plastics" standard, and the sample was placed in an ultraviolet wavelength of 313 nm and an irradiance of 0.54 W / m 2The samples were aged in a UV aging box for 120 hours, and then the tensile properties were tested. Deionized water was added to the coating surface of the sample through a pinhole syringe, and the water contact angle of the coating was measured using an SDC-100S contact angle tester. The test was performed at three different locations on each sample, with each location measured twice, and the average of the six values ​​was taken. The test results are shown in Table 1 below:

[0087] Table 1 Performance test results of various embodiments and comparative examples

[0088]

[0089] As can be seen from Table 1, the adhesion of Examples 1-4 is level 1, all showing good adhesion, while the adhesion test results of Example 5 and Comparative Examples 1-4 are slightly worse than those of the Examples, especially the adhesion level of Comparative Example 4 is 4, indicating that the addition of talcum powder and composite modified carbon nanotubes can improve the adhesion between the coating and the substrate, while the adhesion of the coating without composite modified carbon nanotubes is relatively weak. Analysis shows that the reason may be that the composite modified carbon nanotubes have nanometer size and a high surface area. When used in conjunction with talcum powder, which also has a high specific surface area, they can provide more "mechanical locking" points, which may help form a good mechanical anchoring effect between the coating and the substrate, thereby increasing the adhesion of the coating; at the same time, the composite modified carbon nanotubes introduce hydrophobic long-chain alkylamines and the rich functional groups on the surface of the sunflower spore pollenin microcapsules through chemical modification, which may form hydrogen bonds or chemical bonds with the polar groups on the surface of the substrate, thereby enhancing the adhesion between the coating and the substrate; in addition, the composite modified carbon nanotubes have both hydroxyl groups and amino groups, which may promote the cross-linking reaction of the resin, increase the cross-linking density of the coating, and further improve the cohesion and adhesion of the coating.

[0090] As shown in Table 1, by comparing Examples 1-5 with Comparative Examples 1-4, it was found that the water contact angles of Examples 1-5 were all higher than 150°, with Example 1 having the highest water contact angle of 163°, indicating that the coating had good hydrophobicity. The water contact angles of Comparative Examples 1-4 were lower, especially the lowest water contact angle of Comparative Example 4, which was 105°. This indicates that the addition of talcum powder and composite modified carbon nanotubes can significantly improve the hydrophobicity of the coating, while the coating without composite modified carbon nanotubes has poor hydrophobicity. Analysis suggests that the reason may be that the synergistic use of composite modified carbon nanotubes and talcum powder helps to improve the dispersibility of talcum powder in the matrix resin, increase the density of the coating, and reduce the pores and microcracks in the coating, which can hinder the penetration of water molecules into the interior of the coating. In addition, the long-chain alkylamine structure on the surface of the composite modified carbon nanotubes provides hydrophobicity, increases the contact angle of the coating, and may play a role similar to the lotus leaf effect, causing water to form water droplets on the surface of the coating, thereby improving the waterproofness of the coating. At the same time, the addition of composite modified carbon nanotubes and talc increased the roughness of the coating surface, thereby further increasing the contact angle and showing better hydrophobicity.

[0091] As can be seen from Table 1, by comparing Examples 1-5 with Comparative Examples 1-4, it is found that the tensile strength and elongation at break of Examples 1-5 are higher, indicating that the addition of talc powder and composite modified carbon nanotubes can improve the mechanical properties of the coating; after aging, the tensile strength and elongation at break of Examples 1-5 both decrease, but the decrease is small, indicating that the coating has good resistance to ultraviolet aging; the tensile strength and elongation at break of Comparative Examples 1-4 are low, and the decrease after aging is large, indicating that the mechanical properties and ultraviolet aging resistance of the coating without composite modified carbon nanotubes are poor. Analysis shows that the reason may be that the carbon atoms in the composite modified carbon nanotubes can absorb the electronic energy levels of light of a specific wavelength. When ultraviolet light irradiates the coating, its energy can be absorbed by the electrons in the composite modified carbon nanotubes, causing the electrons to jump from low energy levels to high energy levels, thereby reducing the direct irradiation of ultraviolet light on the matrix resin; at the same time, the composite modified carbon nanotubes are tubular nanoscale structures composed of carbon atoms with a high aspect ratio and a large surface area. Due to their size and shape, the composite modified carbon nanotubes can serve as the center of light scattering. When ultraviolet light irradiates the coating, part of the light will be scattered to other directions by the composite modified carbon nanotubes, reducing the direct irradiation on the coating matrix resin; sunflower sporopollenin microcapsules have a large specific surface area and a complex molecular structure. When they are coated or grafted to the surface of carbon nanotubes, they can increase the total absorption cross-section of the carbon nanotubes, thereby improving the absorption of ultraviolet rays, and the introduction of sunflower sporopollenin microcapsules may form an uneven surface structure on the surface of carbon nanotubes, thereby improving the scattering effect of ultraviolet rays. Because the composite modified carbon nanotubes have a strong absorption and scattering effect on ultraviolet rays, and the composite modified carbon nanotubes have good dispersibility and compatibility with the matrix resin, the composite modified carbon nanotubes are more evenly distributed in the coating, thereby more effectively absorbing and scattering ultraviolet rays, and the ultraviolet radiation intensity received by the matrix resin is significantly reduced, thereby slowing down the photodegradation process and extending the service life of the coating. In addition, the composite modified carbon nanotubes may promote the cross-linking reaction of the resin, increase the cross-linking density of the coating, thereby improving the cohesion and tensile strength of the coating. In addition, the composite modified carbon nanotubes are used in conjunction with talcum powder, and both have excellent mechanical properties, such as high strength and high modulus, and the composite modified carbon nanotubes can improve these properties and can be directly transferred to the coating, improving its overall tensile strength, and in the coating preparation process, the two can be uniformly dispersed and interlaced in the mixed resin to form a physical network, and the functional groups on the surface of the composite modified carbon nanotubes may promote the interaction between the carbon nanotubes and the talcum powder, enhancing the stability of the network structure. The existence of the two network structures can disperse and transfer stress when the coating is subjected to external force, reduce stress concentration, and thus further improve the tensile strength and toughness of the coating.

[0092] Comparing Examples 1-4, it was found that Example 1, which used oleylamine as the amino modifier, exhibited significantly better water contact angle, tensile strength, elongation at break, and UV aging resistance than Examples 2-4, which used octadecylamine, N-isopropyloctadecylamine, and hexadecylamine, respectively. This indicates that the water contact angle, tensile strength, elongation at break, and UV aging resistance of the coating decreased with the type of amino modifier in the composite modified carbon nanotubes. The coating prepared using oleylamine in the composite modified carbon nanotubes exhibited the best performance. This is likely due to oleylamine's unique long chain and double bond structure, which allows it to more easily approach and penetrate the surface of the modified carbon nanotubes during reaction, forming a more uniform modified layer, thereby imparting excellent dispersibility and hydrophobicity. The long chain alkyl group and double bonds of oleylamine not only enhance its flexibility within the matrix but also effectively form a dense hydrophobic film on the carbon nanotube surface. This film, through the hydrophobic effect, blocks the penetration of water molecules, significantly increasing the water contact angle of the coating and demonstrating excellent water repellency. Furthermore, oleylamine's long-chain structure creates a strong "mechanical interlocking" effect between the carbon nanotubes and the substrate. This cross-linked network evenly distributes stress when applied, reducing stress concentration and significantly improving the coating's tensile strength and toughness. More importantly, oleylamine provides excellent protection against UV aging. Its long-chain double bonds scatter UV light on the carbon nanotube surface, slowing down direct UV degradation of the substrate. This protective effect not only extends the coating's service life but also maintains its long-term structural stability.

Claims

1. A process for preparing a polysiloxane elastic waterproof coating, characterized in that: The following steps are involved: (1) Mix methyl polysiloxane resin, dispersant and water, and stir at 60-100 MPa and 1000-1500 rpm for 20-30 minutes to obtain mixture A; (2) Add acrylic resin, filler, film-forming aid and thickener to mixture A and mix evenly, and stir at 30-50 MPa, 400-600 r / min, 40-50°C for 20-50 minutes to obtain mixture B; (3) Adding a defoaming agent and a leveling agent to the mixture B, mixing and stirring at 500-600 rpm for 20-40 minutes to obtain a polysiloxane elastic waterproof coating; applying the polysiloxane elastic waterproof coating, and drying to obtain a polysiloxane elastic waterproof coating; The filler is a mixture of talc powder and composite modified carbon nanotubes in a weight ratio of 1-3:1; The preparation method of the composite modified carbon nanotubes comprises the following steps, calculated by weight: S1. Adding 3-6 parts of carbon nanotubes to a mixed acid solution of 350-450 parts of nitric acid and sulfuric acid in a volume ratio of 1:2-3, stirring the solution at 24-26° C. for 12-16 hours to obtain a mixture; then, mixing the mixture with water in a weight ratio of 1:4-8 to obtain a mixed solution, filtering the mixed solution with a vacuum filter to collect the product, and washing the obtained product with water until the pH reaches neutral; finally, drying the product at 95-105° C. for 1-3 hours to obtain acid-modified carbon nanotubes; S2, petroleum ether and sunflower pollen are mixed and stirred in a weight ratio of 1: 4-8 for 20-40min, filtered, and then vacuum dried at 55-65°C for 6-10h to obtain dried defatted sunflower pollen; afterwards the dried defatted sunflower pollen is mixed with a 0.1-0.3g / mL aqueous phosphoric acid solution in a weight ratio of 1: 10-20, filtered after reflux stirring at 60-80°C for 4-6h, then washed with water, acetone, hydrochloric acid and ethanol in sequence, and dried to constant weight to obtain sunflower sporopollenin microcapsules; S3. 5-8 parts of acid-modified carbon nanotubes, 1-3 parts of sunflower sporopollenin microcapsules and 30-40 parts of isopropanol are mixed, and then ultrasonically treated at 300-500 W for 20-30 min. Then, 0.05-0.2 parts of toluenesulfonic acid are added under a nitrogen atmosphere. Then, the mixture is mixed and stirred at 90-100° C. and 300-600 r / min for 1-3 h. The mixture is filtered, washed, and vacuum-dried at 75-85° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes, that is, composite modified carbon nanotubes.

2. The process for preparing the polysiloxane elastic waterproof coating according to claim 1, wherein: The weight ratio of each raw material component is: 35-60 parts of methyl polysiloxane resin, 8-12 parts of acrylic resin, 15-20 parts of filler, 2-5 parts of thickener, 1-3 parts of dispersant, 1-3 parts of film-forming aid, 1-2 parts of defoaming agent, 1-3 parts of leveling agent, and 10-20 parts of water.

3. The process for preparing the polysiloxane elastic waterproof coating according to claim 1, wherein: The step S3 is, by weight: 5-8 parts of acid-modified carbon nanotubes, 1-3 parts of sunflower sporopollenin microcapsules, and 30-40 parts of isopropanol are mixed, and then ultrasonically treated at 300-500 W for 20-30 minutes. Then, 0.05-0.2 parts of toluenesulfonic acid are added under a nitrogen atmosphere. The mixture is then stirred at 90-100° C. and 300-600 rpm for 1-3 hours. The mixture is filtered, washed, and dried in vacuo at 75-85° C. to obtain sunflower sporopollenin microcapsule-modified carbon nanotubes. Then, 3-5 parts of sunflower sporopollenin microcapsule-modified carbon nanotubes and 8-15 parts of isopropyl alcohol are stirred and mixed, and then 1-2 parts of an amino modifier and 0.05-0.2 parts of a photoinitiator 651 are added. The mixture is stirred and mixed for 3-5 hours under ultraviolet irradiation with a wavelength of 365-400 nm, filtered, washed, and vacuum-dried to obtain composite modified carbon nanotubes.

4. The process for preparing the polysiloxane elastic waterproof coating according to claim 3, wherein: The amino modifier is selected from one of oleylamine, octadecylamine, N-isopropyloctadecylamine and hexadecylamine.

5. The process for preparing the polysiloxane elastic waterproof coating according to claim 1 or 2, wherein: The thickener is Hemmings 299; the film-forming aid is propylene glycol methyl ether acetate.

6. The process for preparing the polysiloxane elastic waterproof coating according to claim 1 or 2, wherein: The dispersant is selected from one of TEGO® Dispers650 and TEGO® Dispers655; the defoamer is selected from one of BYK-092 and BYK-141 of Germany; and the leveling agent is selected from one of BYK-345, BYK-333 and BYK-330 of Germany.

7. A polysiloxane elastic waterproof coating, characterized by: Prepared by the process according to any one of claims 1 to 6.

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