A waterborne weatherable polysiloxane self-primer and a method of making the same

Abstract

This invention relates to the field of polysiloxane coating technology, and more particularly to a water-based weather-resistant polysiloxane spray paint and its preparation method. The invention employs a technical route of compounding grafted polysiloxane emulsion with highly branched silicone-acrylic emulsion: the grafted polysiloxane emulsion introduces ketone crosslinking sites and organosilicon segments by synergistic modification of the acrylate copolymer with diacetone acrylamide and γ-methacryloyloxypropyltrimethoxysilane; the highly branched silicone-acrylic emulsion introduces isoborneol-based branched polysiloxane macromonomers into the acrylic backbone through hydrosilylation, ring-opening polymerization, and emulsion polymerization; the two emulsions are blended to formulate the spray paint, which, in conjunction with adipic acid dihydrazide, constructs a latent ketone-hydrazide crosslinking system. The reaction is inhibited under alkaline conditions in the can, and after spraying, water evaporation triggers ketone-hydrazide crosslinking and silanol condensation, resulting in rapid curing of the paint film, exhibiting high adhesion, high hardness, flexibility, and excellent weather resistance.

Description

Technical Field

[0001] This invention relates to the field of polysiloxane coating technology, and in particular to a water-based weather-resistant polysiloxane spray paint and its preparation method. Background Technology

[0002] Spray paint is widely used in home repairs, car repair, hardware coating, and handicrafts due to its convenient application, lack of specialized equipment, and instant drying. Traditional spray paints are mainly solvent-based thermoplastic acrylic systems, using organic solvents such as toluene, xylene, and butyl acetate as thinners, and liquefied petroleum gas as a propellant. They offer short application times, fast drying, and high surface gloss, meeting general indoor and outdoor decoration and protection needs.

[0003] To address the aforementioned issues, the industry has developed various water-based spray paint systems. Current water-based spray paints primarily use water-based acrylic emulsions as the film-forming substance, water as the main dispersion medium, supplemented with alcohol ether film-forming aids and co-solvents, and dimethyl ether as a propellant. For example, some products use pure acrylic ester emulsions combined with fast-drying solvents, forming a film at room temperature through water evaporation and latex particle fusion, resulting in low odor and significantly lower VOC content than solvent-based products. Other technical solutions attempt to introduce organosilicon components into the water-based acrylic system, such as adding silica sol or silane coupling agents through physical blending, to improve the water resistance, weather resistance, and hardness of the paint film.

[0004] However, the existing water-based spray paint technologies still have the following shortcomings: First, the drying speed of water-based systems is greatly affected by ambient temperature and humidity. Especially under low temperature and high humidity conditions, moisture evaporates slowly, and the touch-dry time and dry time are significantly prolonged, which easily leads to problems such as sagging, dust accumulation, and poor early water resistance, failing to achieve the ease of application of solvent-based spray paints. Second, the adhesion of ordinary water-based acrylic emulsions is limited, and defects such as insufficient adhesion, poor wet adhesion, blistering and peeling upon contact with water are easily found on smooth substrates such as metal, glass, and stainless steel. Third, the weather resistance of existing water-based spray paints is generally weaker than that of solvent-based products. Long-term outdoor exposure can easily lead to problems such as chalking, loss of gloss, and yellowing, making it difficult to meet the requirements for long-term protection.

[0005] Therefore, there is an urgent need to develop a water-based polysiloxane self-spraying paint that combines rapid curing, high adhesion, excellent weather resistance, and storage stability to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a water-based, weather-resistant polysiloxane spray paint and its preparation method. This invention employs a technical route combining grafted polysiloxane emulsion and highly branched silicone-acrylic emulsion: the grafted polysiloxane emulsion introduces ketone crosslinking sites and organosilicon segments by synergistic modification of the acrylate copolymer with diacetone acrylamide and γ-methacryloyloxypropyltrimethoxysilane; the highly branched silicone-acrylic emulsion introduces isoborneol-based branched polysiloxane macromonomers into the acrylic backbone through hydrosilylation, ring-opening polymerization, and emulsion polymerization; the two emulsions are blended to formulate the spray paint, which, combined with adipic acid dihydrazide, constructs a latent ketone-hydrazide crosslinking system. The reaction is inhibited under alkaline conditions in the can; after spraying, water evaporation triggers ketone-hydrazide crosslinking and silanol condensation, resulting in rapid curing of the paint film, exhibiting high adhesion, high hardness, flexibility, and excellent weather resistance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a water-based weather-resistant polysiloxane spray paint, comprising the following steps: Step S1: Weigh the following raw materials in parts by weight: 35-40 parts grafted polysiloxane emulsion, 35-40 parts highly branched silicone acrylic emulsion, 8 parts deionized water, 12 parts isopropanol, 3 parts propylene glycol methyl ether, 0.6 parts adipate dihydrazide, 0.1 parts defoamer, 0.2 parts wetting agent, and 0.1 parts corrosion inhibitor, and adjust the pH by adding a pH adjuster; Step S2: Mix the grafted polysiloxane emulsion, highly branched silicone-acrylic emulsion, deionized water, isopropanol, propylene glycol methyl ether, adipate dihydrazide, defoamer, wetting agent, and corrosion inhibitor. Add a pH adjuster to adjust the pH to 8.5, stir for 30 minutes, and sieve through a 300-mesh screen to obtain a water-based coating. Pour the water-based coating into an aerosol can, insert the valve, and fill it with dimethyl ether propellant. The mass ratio of water-based coating to dimethyl ether propellant is 60:40. After water bath leak testing, install the nozzle to obtain water-based weather-resistant polysiloxane spray paint.

[0008] The grafted polysiloxane emulsion is prepared by the following steps: Step A1: Methyl methacrylate, butyl acrylate, acrylic acid, diacetone acrylamide and γ-methacryloyloxypropyltrimethoxysilane are mixed and stirred at 800 rpm at room temperature. The mixture is then added to a mixture of deionized water, compound emulsifier and sodium bicarbonate. The mixture is stirred for 20 min to obtain a pre-emulsion. Furthermore, in step A1, the ratio of methyl methacrylate, butyl acrylate, acrylic acid, diacetone acrylamide, γ-methacryloyloxypropyltrimethoxysilane, deionized water, compound emulsifier, and sodium bicarbonate is 5.5g:4g:2g:3-3.5g:4-5g:80mL:0.25g:0.02g, wherein the weight ratio of sodium dodecyl sulfate and OP-10 in the compound emulsifier is 1:1.

[0009] Step A2: Add ammonium persulfate solution to the pre-emulsion, react for 3 hours at a stirring speed of 200 rpm and a temperature of 80℃, cool, adjust the pH value to 8.5 with ammonia solution, filter, add deionized water, adjust the solid content to 40%, and obtain grafted polysiloxane emulsion. Furthermore, in step A2: the ratio of pre-emulsion to ammonium persulfate solution is 90 mL: 1 mL, and the mass fraction of ammonia solution is 25%.

[0010] The highly branched silicone-acrylic emulsion is prepared by the following steps: Step B1: Isobornyl acrylate, hydrogen-containing silicone oil, and Karstedt catalyst were mixed and stirred at 300 rpm for 15 min under nitrogen protection. The mixture was then heated to 80 °C and reacted for another 30 min. After cooling, isobornyl acrylate-based polysiloxane was obtained. The isobornyl acrylate-based polysiloxane was added to potassium hydroxide solution and reacted at 80 °C for 30 min. The pH was adjusted to neutral, and the mixture was rotary evaporated and dried to obtain hydroxyl-containing isobornyl acrylate-based polysiloxane. Furthermore, in step B1: the ratio of isobornyl acrylate, hydrogen-containing silicone oil, and Karstedt catalyst is 4.1-4.2 g: 2.5 g: 0.02 mL, the hydrogen content in the hydrogen-containing silicone oil is 0.8%, and the mass fraction of potassium hydroxide solution is 5%.

[0011] Step B2: Mix octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hydroxyl-containing isoborneol ester-based polysiloxane and hexamethyldisiloxane, stir and add potassium hydroxide solution, react for 4 hours at a stirring rate of 300 rpm and a temperature of 100℃, cool and dry to obtain branched isoborneol ester-based polysiloxane. Furthermore, in step B2, the ratio of the amounts of octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hydroxyisoborneol-based polysiloxane, hexamethyldisiloxane, and potassium hydroxide solution is 10.1g:3.2g:2.8-3g:1.2g:10mL, and the mass fraction of the potassium hydroxide solution is 0.1%.

[0012] Step B3: Mix butyl acrylate, acrylic acid, methyl methacrylate, branched isoborneol-based polysiloxane and deionized water. Stir at 800 rpm and room temperature, add compound emulsifier, stir for 15 min, then heat to 85℃ and add ammonium persulfate solution. React for 6 h, cool to room temperature, adjust the pH to 8.5 with ammonia solution, and add deionized water to adjust the solid content to 45% to obtain highly branched silicone-acrylic emulsion. Furthermore, in step B3, the ratio of butyl acrylate, acrylic acid, methyl methacrylate, branched isoborneol-based polysiloxane, deionized water, compound emulsifier, and ammonium persulfate solution is 12-14g:1.5g:10g:8-10g:80mL:1.6g:6mL, wherein the weight ratio of sodium dodecyl sulfate and OP-10 in the compound emulsifier is 1:1, the mass fraction of ammonium persulfate solution is 5%, and the mass fraction of ammonia solution is 25%.

[0013] Compared with the prior art, the beneficial effects of this invention are as follows: This invention discloses a water-based weather-resistant polysiloxane spray paint and its preparation method; it adopts a technical route of compounding grafted polysiloxane emulsion and highly branched silicone-acrylic emulsion: the grafted polysiloxane emulsion introduces ketone crosslinking sites and organosilicon segments by synergistic modification of acrylate copolymers with diacetone acrylamide and γ-methacryloyloxypropyltrimethoxysilane; the highly branched silicone-acrylic emulsion introduces isoborneol-based branched polysiloxane macromonomers into the acrylic backbone through hydrosilylation, ring-opening polymerization and emulsion polymerization reactions; the two emulsions are blended to formulate the spray paint, and a latent ketone-hydrazine crosslinking system is constructed with adipate dihydrazide. The reaction is inhibited under alkaline conditions in the can, and after spraying, water evaporation triggers ketone-hydrazine crosslinking and silanol condensation, resulting in rapid curing of the paint film, which combines high adhesion, high hardness, flexibility and excellent weather resistance.

[0014] This invention employs two structurally complementary polysiloxane-modified acrylic emulsions as the main film-forming substances: the first is a grafted polysiloxane emulsion, in which diacetone acrylamide (DAAM) and γ-methacryloyloxypropyltrimethoxysilane (KH-570) are copolymerized with methyl methacrylate, butyl acrylate, and acrylic acid during the preparation process; the ketone groups of DAAM form a latent crosslinking system with the added adipate dihydrazide (ADH) when formulating the spray paint, giving the paint film the ability to cure quickly; the trimethoxysilyl groups of KH-570 generate silanol groups during emulsion polymerization, which can not only enhance the crosslinking within the paint film, but also form chemical bonds with the hydroxyl groups on the surface of the metal substrate, greatly improving wet adhesion; at the same time, the Si-O-Si segments act as ultraviolet-inert groups, effectively delaying the photo-oxidative degradation of the acrylate backbone.

[0015] The second type is a highly branched silicone-acrylic emulsion. First, isoborneol acrylate and hydrogen-containing silicone oil are hydrosilylated to prepare a polysiloxane oligomer containing isoborneol ester groups. Then, it undergoes anionic ring-opening copolymerization with octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane to obtain a branched polysiloxane macromonomer with vinyl and isoborneol ester groups on the side groups. This macromonomer is then emulsion polymerized with butyl acrylate, methyl methacrylate, and acrylic acid to form a highly branched silicone-acrylic emulsion. The rigid bicyclic structure of isoborneol ester imparts high hardness and fast drying properties to the paint film, while the volume effect reduces the system viscosity, facilitating application. Multiple vinyl branching points participate in copolymerization to form a micro-crosslinked network, enhancing cohesion and heat resistance. The polysiloxane backbone provides flexibility and weather resistance.

[0016] When the two emulsions are blended in a certain proportion, the ketone-hydrazine crosslinking system of the grafted polysiloxane emulsion provides rapid curing and initial strength. Its silanol groups co-condense with the silanol groups or residual alkoxy groups of the highly branched emulsion during film formation, forming an organosilicon bridging network between emulsion particles, which further enhances the crosslinking density. The rigid isoborneol ester groups of the highly branched emulsion are interspersed in the crosslinking network, which improves the overall hardness without significantly reducing the flexibility. The organosilicon segments of both are enriched on the paint film surface, forming a low surface energy hydrophobic layer, which improves self-cleaning and anti-graffiti properties. This blending design comprehensively improves the overall performance of water-based spray paint. Detailed Implementation

[0017] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0018] Furthermore, in the following preparation examples, embodiments, and comparative examples: the defoamer used was BYK-024 from BYK Chemicals Ltd.; the wetting agent was BYK-346 from BYK Chemicals Ltd.; and the corrosion inhibitor was Irgamet 42 from BASF GmbH, Germany.

[0019] Preparation Example 1: The grafted polysiloxane emulsion was prepared by the following steps: Step A1: Mix 5.5g methyl methacrylate, 4g butyl acrylate, 2g acrylic acid, 3.5g diacetone acrylamide and 5g γ-methacryloyloxypropyltrimethoxysilane. Stir at 800 rpm at room temperature and add the mixture to 80mL deionized water, 0.25g compound emulsifier and 0.02g sodium bicarbonate mixture. Stir for 20min to obtain a pre-emulsion. The weight ratio of sodium dodecyl sulfate and OP-10 in the compound emulsifier is 1:1.

[0020] Step A2: Add 1 mL of 5% ammonium persulfate solution to 90 mL of pre-emulsion, react for 3 h at a stirring speed of 200 rpm and a temperature of 80 °C, cool, adjust the pH to 8.5 with 25% ammonia solution, filter, add deionized water, adjust the solid content to 40%, and obtain grafted polysiloxane emulsion.

[0021] Preparation Example 2: Compared with Preparation Example 1, Preparation Example 2 changed step A1 to 3g of diacetone acrylamide and 4g of γ-methacryloxypropyltrimethoxysilane, while the other steps were the same.

[0022] Preparation Example 3: Compared with Preparation Example 1, Preparation Example 3 changed step A1 to 1g of diacetone acrylamide and 5g of γ-methacryloxypropyltrimethoxysilane, while the other steps were the same.

[0023] Preparation Example 4: The highly branched silicone-acrylic emulsion was prepared by the following steps: Step B1: Mix 4.2g of isobornyl acrylate, 2.5g of hydrogen-containing silicone oil with a hydrogen content of 0.8% and 0.02mL of Karstedt catalyst. Under nitrogen protection and stirring at a stirring rate of 300rpm, stir for 15min, then heat to 80℃ and continue the reaction for 30min. Cool to obtain isobornyl acrylate-based polysiloxane. Add the isobornyl acrylate-based polysiloxane to a 5% potassium hydroxide solution and react at 80℃ for 30min. Adjust the pH to neutral, rotary evaporate, and dry to obtain hydroxyl-containing isobornyl acrylate-based polysiloxane. Step B2: Mix 10.1g of octamethylcyclotetrasiloxane, 3.2g of tetramethyltetravinylcyclotetrasiloxane, 3g of hydroxyl-containing isoborneol-based polysiloxane and 1.2g of hexamethyldisiloxane, stir and add 10mL of 0.1% potassium hydroxide solution. React for 4h at a stirring speed of 300rpm and a temperature of 100℃. Cool and dry to obtain branched isoborneol-based polysiloxane. Step B3: Mix 14g butyl acrylate, 1.5g acrylic acid, 10g methyl methacrylate, 10g branched isoborneol-based polysiloxane, and 80mL deionized water. Stir at 800rpm and room temperature, add 1.6g of compound emulsifier, stir for 15min, then heat to 85℃ and add 6mL of 5% ammonium persulfate solution. React for 6h, cool to room temperature, adjust the pH to 8.5 with 25% ammonia solution, and add deionized water to adjust the solid content to 45%, thus obtaining a highly branched silicone-acrylic emulsion. The weight ratio of sodium dodecyl sulfate and OP-10 in the compound emulsifier is 1:1.

[0024] Preparation Example 5: Compared with Preparation Example 4, Preparation Example 5 changed step B1 to 4.1g of isobornyl acrylate, while the other steps were the same.

[0025] Preparation Example 6: Compared with Preparation Example 4, Preparation Example 6 changed step B2 to 2.8g of hydroxyisoborneol-based polysiloxane, while the other steps were the same.

[0026] Preparation Example 7: Compared with Preparation Example 4, Preparation Example 7 changed step B3 to 12g of butyl acrylate and 8g of branched isoborneol ester-based polysiloxane, while the other steps were the same.

[0027] Comparative Preparation Example 1: Compared to Preparation Example 1, the diacetone acrylamide in step A1 was removed from Comparative Preparation Example 1, while the other steps were the same.

[0028] Comparative Preparation Example 2: Compared with Preparation Example 1, in Comparative Preparation Example 2, isobornyl acrylate in step B1 is replaced with methyl acrylate, and the other steps are the same.

[0029] Comparative Preparation Example 3: Compared with Preparation Example 1, the step B3 of Comparative Preparation Example 3 was changed to 2g of branched isoborneol ester-based polysiloxane, while the other steps were the same.

[0030] Example 1: A method for preparing a water-based weather-resistant polysiloxane spray paint, comprising the following steps: Step S1: Weigh the following raw materials in parts by weight: 40 parts of grafted polysiloxane emulsion in Preparation Example 1, 40 parts of highly branched silicone-acrylic emulsion in Preparation Example 4, 8 parts of deionized water, 12 parts of isopropanol, 3 parts of propylene glycol methyl ether, 0.6 parts of adipate dihydrazide, 0.1 parts of defoamer, 0.2 parts of wetting agent, and 0.1 parts of corrosion inhibitor, and adjust the pH by adding a pH adjuster; Step S2: Mix the grafted polysiloxane emulsion, highly branched silicone-acrylic emulsion, deionized water, isopropanol, propylene glycol methyl ether, adipate dihydrazide, defoamer, wetting agent, and corrosion inhibitor. Add a pH adjuster to adjust the pH to 8.5, stir for 30 minutes, and sieve through a 300-mesh screen to obtain a water-based coating. Pour the water-based coating into an aerosol can, insert the valve, and fill it with dimethyl ether propellant. The mass ratio of water-based coating to dimethyl ether propellant is 60:40. After water bath leak testing, install the nozzle to obtain water-based weather-resistant polysiloxane spray paint.

[0031] Example 2: Compared with Example 1, Example 2 adjusts step S1 to 35 parts of grafted polysiloxane emulsion and 35 parts of highly branched silicone acrylic emulsion, while the other steps are the same.

[0032] Example 3: Compared with Example 1, the grafted polysiloxane emulsion in Example 3 was adjusted to be the one obtained in Preparation Example 2, while the other steps were the same.

[0033] Example 4: Compared with Example 1, the grafted polysiloxane emulsion in Example 4 was adjusted to be the one obtained in Preparation Example 3, while the other steps were the same.

[0034] Example 5: Compared with Example 1, the highly branched silicone-acrylic emulsion in Example 5 was adjusted to be the one obtained in Preparation Example 5, while the other steps were the same.

[0035] Example 6: Compared with Example 1, the highly branched silicone-acrylic emulsion in Example 6 was adjusted to be the one obtained in Preparation Example 6, while the other steps were the same.

[0036] Example 7: Compared with Example 1, the highly branched silicone-acrylic emulsion in Example 7 was adjusted to be the one obtained in Preparation Example 7, while the other steps were the same.

[0037] Comparative Example 1: Compared with Example 1, the grafted polysiloxane emulsion in Comparative Example 1 was adjusted to be the one prepared in Comparative Preparation Example 1, while the other steps were the same.

[0038] Comparative Example 2: Compared with Example 1, the highly branched silicone-acrylic emulsion in Comparative Example 2 was adjusted to be the one prepared in Comparative Preparation Example 2, while the other steps were the same.

[0039] Comparative Example 3: Compared with Example 1, the highly branched silicone-acrylic emulsion in Comparative Example 3 was adjusted to be the one prepared in Comparative Preparation Example 3, while the other steps were the same.

[0040] The water-based weather-resistant polysiloxane spray paint prepared in the examples and comparative examples was sprayed onto tinplate (film thickness 20-25μm) to obtain samples, and its performance was tested: 1) Surface drying time: Refer to GB / T 1728-2020, finger touch method; under an environment of temperature 23±2℃ and relative humidity 50±5%, lightly touch the edge of the paint film with your finger every 10 seconds. If it is not sticky to the touch, it is considered surface dry.

[0041] 2) Drying time: Refer to GB / T 1728-2020, filter paper method; place filter paper on the paint film, apply a 200g weight (contact area 1cm²) for 30 seconds, remove the filter paper, and observe that there is no fiber adhesion, which means it is dry.

[0042] 3) Adhesion: Refer to GB / T 9286-2021 cross-cut test (1mm spacing). Draw a cross on the test board after 24 hours of spray curing, stick 3M tape on it and then peel it off. Grade according to the area of ​​peeling off, with grade 0 being the best.

[0043] 4) Pencil hardness: The pencil hardness was measured in accordance with GB / T 6739-2022.

[0044] 5) Water resistance: Referring to GB / T 1733-1993, the sample cured for 24 hours was immersed in deionized water at 23±2℃. After 24 hours, it was taken out and observed for blistering, peeling, whitening, etc., and the adhesion was tested at the same time.

[0045] 6) Resistance to artificial weathering: In accordance with GB / T 1865-2009, a QUV accelerated aging instrument (UVB-313 lamp) was used with an irradiation intensity of 0.71W / m². The cycle consisted of 4 hours of light exposure at 60℃ and 4 hours of condensation at 50℃. After 1500 hours, the 60° gloss was tested, and the gloss retention rate was calculated.

[0046] The test results are shown in the table below: Table 1 Performance Test Results The test results shown in the table indicate that the examples and comparative examples are compared as follows: Comparison of Comparative Example 1 and Example 1: Since Comparative Example 1 does not contain DAAM, the grafted emulsion lacks ketone groups and cannot construct a ketone-hydrazine crosslinking system with ADH. Curing relies solely on water evaporation and weak silanol condensation. Therefore, it lacks the mechanism for rapidly establishing film strength through a covalent crosslinking network, resulting in a significantly longer drying time compared to Example 1. The dry adhesion dropped from grade 0 to grade 1, and the lack of crosslinking protection after immersion in water caused the adhesion to drop to grade 4. Water resistance exhibited numerous small bubbles and peeling. The gloss retention rate decreased because the absence of a crosslinking network inhibited the diffusion of degradation products, weakening the protective effect of the organosilicon. This further illustrates the critical role of ketone-hydrazine crosslinking in the rapid curing and long-term protection of water-based spray paints.

[0047] Comparison Example 2 with Example 1: In Comparative Example 2, isoborneol was replaced with methyl acrylate. The highly branched emulsion lacks a rigid bicyclic structure, resulting in a reduction in the free volume between molecular chains and a lower plastic deformation threshold of the paint film. It also lacks the hardness and scratch resistance mechanism provided by rigid groups, leading to a significant decrease in pencil hardness. At the same time, the ester groups of methyl acrylate are easily hydrolyzed and unstable under ultraviolet light, resulting in a significant deterioration in water resistance and weather resistance, and a decrease in gloss retention. This proves that the introduction of isoborneol groups is an important structural factor in achieving high hardness and weather resistance of the paint film.

[0048] Comparison of Comparative Example 3 and Example 1: The amount of branched isoborneol ester-based polysiloxane in Comparative Example 3 was drastically reduced from 10g to 2g, resulting in a significant decrease in the silicone content and degree of branching of the highly branched emulsion. It lacked sufficient silicone segments to form a hydrophobic surface layer and UV shielding network, as well as the micro-crosslinking enhancement effect generated by polyvinyl branching points. Therefore, wet adhesion was reduced, water resistance bubbling occurred, and gloss retention was reduced, indicating that a sufficient amount of branched silicone components is a necessary condition to ensure adhesion strength and weather resistance.

[0049] Example 3 reduced the DAAM content; due to the decrease in ketone concentration, the number of ketone-hydrazine crosslinking points decreased, the drying time was prolonged, the wet adhesion decreased, and the weather resistance and gloss retention also slightly declined, demonstrating the direct impact of DAAM dosage on curing speed and crosslinking density. Example 4 further reduced the amount of ketone, resulting in a further decrease in crosslinking density, a prolonged drying time, a decrease in dry / wet adhesion, and the appearance of small bubbles in water resistance, verifying that sufficient ketone groups are a prerequisite for ensuring the effectiveness of the latent crosslinking system. Example 5 reduced the amount of isobornyl acrylate in the highly branched emulsion, resulting in a slight decrease in rigid groups and a decrease in pencil hardness, but other properties did not change significantly, indicating that moderate fluctuations in the amount of isobornyl acrylate within a certain range have a direct impact on hardness, but the overall compound can still maintain comprehensive performance. Example 6 reduced the amount of hydroxyisobornyl acrylate-containing polysiloxane, resulting in a decrease in the branching degree of branched macromonomers, a slight decrease in crosslinking points, a slight extension of drying time, and a slight decrease in gloss retention, indicating that the amount of intermediates affects the branching and crosslinking efficiency of the final emulsion. Example 7 shows that the flexible component of the paint film is reduced, the rigidity ratio is relatively increased, the flexibility is slightly reduced, and slight whitening occurs after immersion in water, and the wet adhesion is reduced. This reflects that the ratio of soft and hard monomers and the content of organosilicon jointly affect the wet adhesion and durability of the paint film.

[0050] In summary, Example 1, through the synergy of two emulsions, utilizes a comprehensive mechanism involving ketone-hydrazine crosslinking, silanol chemical bonding, rigid isoborneol ester support, multi-branched organosilicon networks, and surface hydrophobic enrichment to achieve rapid curing, high adhesion, high hardness, and excellent weather resistance.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for the preparation of an aqueous weatherable polysiloxane self- spray paint, characterized in that: Includes the following steps: Step S1: Weigh the following raw materials in parts by weight: 35-40 parts grafted polysiloxane emulsion, 35-40 parts highly branched silicone acrylic emulsion, 8 parts deionized water, 12 parts isopropanol, 3 parts propylene glycol methyl ether, 0.6 parts adipate dihydrazide, 0.1 parts defoamer, 0.2 parts wetting agent, and 0.1 parts corrosion inhibitor, and adjust the pH by adding a pH adjuster; Step S2: Mix the grafted polysiloxane emulsion, highly branched silicone-acrylic emulsion, deionized water, isopropanol, propylene glycol methyl ether, adipate dihydrazide, defoamer, wetting agent, and corrosion inhibitor. Add a pH adjuster to adjust the pH to 8.5, stir for 30 minutes, and sieve through a 300-mesh screen to obtain a water-based coating. Pour the water-based coating into an aerosol can, insert the valve, and fill it with dimethyl ether propellant. The mass ratio of water-based coating to dimethyl ether propellant is 60:

40. After water bath leak testing, install the nozzle to obtain water-based weather-resistant polysiloxane spray paint.

2. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 1, characterized in that: The grafted polysiloxane emulsion is prepared by the following steps: Step A1: Methyl methacrylate, butyl acrylate, acrylic acid, diacetone acrylamide and γ-methacryloyloxypropyltrimethoxysilane are mixed and stirred at 800 rpm at room temperature. The mixture is then added to a mixture of deionized water, compound emulsifier and sodium bicarbonate. The mixture is stirred for 20 min to obtain a pre-emulsion. Step A2: Add ammonium persulfate solution to the pre-emulsion, react for 3 hours at a stirring speed of 200 rpm and a temperature of 80℃, cool, adjust the pH to 8.5 with ammonia solution, filter, add deionized water, and adjust the solid content to 40% to obtain the grafted polysiloxane emulsion.

3. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 2, characterized in that: In step A1, the ratio of methyl methacrylate, butyl acrylate, acrylic acid, diacetone acrylamide, γ-methacryloyloxypropyltrimethoxysilane, deionized water, compound emulsifier, and sodium bicarbonate is 5.5g:4g:2g:3-3.5g:4-5g:80mL:0.25g:0.02g, wherein the weight ratio of sodium dodecyl sulfate and OP-10 in the compound emulsifier is 1:

1.

4. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 2, characterized in that: In step A2: the ratio of pre-emulsion to ammonium persulfate solution is 90 mL: 1 mL, and the mass fraction of ammonia solution is 25%.

5. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 1, characterized in that: The highly branched silicone-acrylic emulsion is prepared by the following steps: Step B1: Isobornyl acrylate, hydrogen-containing silicone oil, and Karstedt catalyst were mixed and stirred at 300 rpm for 15 min under nitrogen protection. The mixture was then heated to 80 °C and reacted for another 30 min. After cooling, isobornyl acrylate-based polysiloxane was obtained. The isobornyl acrylate-based polysiloxane was added to potassium hydroxide solution and reacted at 80 °C for 30 min. The pH was adjusted to neutral, and the mixture was rotary evaporated and dried to obtain hydroxyl-containing isobornyl acrylate-based polysiloxane. Step B2: Mix octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hydroxyl-containing isoborneol ester-based polysiloxane and hexamethyldisiloxane, stir and add potassium hydroxide solution, react for 4 hours at a stirring rate of 300 rpm and a temperature of 100℃, cool and dry to obtain branched isoborneol ester-based polysiloxane. Step B3: Mix butyl acrylate, acrylic acid, methyl methacrylate, branched isoborneol-based polysiloxane, and deionized water. Stir at 800 rpm and room temperature, add a compound emulsifier, stir for 15 min, then heat to 85℃ and add ammonium persulfate solution. React for 6 h, cool to room temperature, adjust the pH to 8.5 with ammonia solution, and add deionized water to adjust the solid content to 45%, thus obtaining a highly branched silicone-acrylic emulsion.

6. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 5, characterized in that: In step B1: the ratio of isobornyl acrylate, hydrogen-containing silicone oil and Karstedt catalyst is 4.1-4.2 g: 2.5 g: 0.02 mL, the hydrogen content in the hydrogen-containing silicone oil is 0.8%, and the mass fraction of potassium hydroxide solution is 5%.

7. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 5, characterized in that: In step B2, the ratio of octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hydroxyisoborneol-based polysiloxane, hexamethyldisiloxane, and potassium hydroxide solution is 10.1g:3.2g:2.8-3g:1.2g:10mL, and the mass fraction of potassium hydroxide solution is 0.1%.

8. The method for preparing a water-based weather-resistant polysiloxane spray paint according to claim 5, characterized in that: In step B3, the ratio of butyl acrylate, acrylic acid, methyl methacrylate, branched isoborneol-based polysiloxane, deionized water, compound emulsifier, and ammonium persulfate solution is 12-14g:1.5g:10g:8-10g:80mL:1.6g:6mL. The weight ratio of sodium dodecyl sulfate and OP-10 in the compound emulsifier is 1:

1. The mass fraction of ammonium persulfate solution is 5%, and the mass fraction of ammonia solution is 25%.

9. A water-based weather-resistant polysiloxane self-spraying paint, characterized in that: Prepared according to any one of the preparation methods described in claims 1-8.

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