Fluorosilane-modified pvb resin, method for preparing the same, and coating material

Abstract

The application relates to the technical field of high-molecular resins and coating, and discloses a fluorosilane modified PVB resin, a preparation method thereof and a coating, which comprises the following steps: the resin is prepared by grafting a pre-reaction solution containing fluorosilane oligomers with active silicon hydroxyl groups and epoxy groups and PVB resin; the silicon hydroxyl groups are condensed to form Si-O-C bonds, and the epoxy groups are ring-opened to form ether bonds, so that double chemical grafting of the fluorine-containing chain segment is realized; the preparation method is that the pre-reaction solution is added into a PVB solution, heated to react, and then precipitated by a non-solvent to obtain the resin; and the coating is prepared by using the modified resin as a core film-forming material. The fluorine-containing unit is covalently fixed in the resin network through double chemical bonding, the defects of fluorine component separation and loss caused by conventional physical blending are overcome, the material can maintain stable low surface energy and physical corrosion resistance for a long time while the flexibility of the matrix is retained.

Description

Technical Field

[0001] This invention relates to the field of polymer resins and coatings, specifically to a fluorosilane-modified PVB resin, its preparation method, and a coating. Background Technology

[0002] Polyvinyl butyral (PVB) resin possesses excellent film-forming properties and substrate adhesion, making it widely used in coatings and adhesives. However, due to its synthesis mechanism, the PVB molecular chain retains a significant number of unreacted hydroxyl groups, giving it a degree of hydrophilicity. This structure allows moisture and electrolytes to easily permeate the PVB coating, limiting the material's resistance to water immersion and its corrosion barrier properties, making it difficult to meet the long-term protection requirements of heavy-duty corrosion environments.

[0003] To reduce the surface energy of PVB systems, the industry typically introduces fluorinated or siloxane-based substances for modification. Currently, physical blending is the most common method, where fluorinated additives are directly dispersed in the resin solution. Since no covalent bonds are formed between the fluorinated additives and the resin matrix, they accumulate at the coating interface solely due to surface tension. During actual service, due to solvent contact, rain erosion, and physical wear, free fluorinated molecules easily migrate and are lost, leading to irreversible degradation of the coating's hydrophobic properties.

[0004] To address the small molecule migration problem, some technologies have shifted towards chemical modification, attempting to graft silane coupling agents onto the hydroxyl groups of PVB chains via condensation. However, the grafting process of free monomers is difficult to control during operation. The self-condensation tendency between silane molecules is often greater than their grafting tendency with the polymer matrix, leading to the formation of gel particles or even overall cross-linking in the reaction system. The solubility of the cross-linked modified resin in organic solvents decreases significantly, severely affecting the formulation of subsequent liquid coatings. Furthermore, relying solely on a single Si-OC bond to connect fluorinated silanes to the main chain carries the risk of bond breakage due to long-term corrosion under humid, hot, or acidic / alkaline media, making it difficult to ensure the long-term stability of the material's microstructure. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fluorosilane-modified PVB resin, its preparation method, and a coating. This solves the problem that in existing technologies, when fluorosilanes are introduced into polyvinyl butyral resin systems through physical blending, the fluorine-containing components are often free outside the resin matrix. Under conditions such as environmental exposure or solvent contact, these components are prone to migration and loss, leading to a decrease in the hydrophobic and anti-corrosion properties of the coating, making it difficult to adapt to long-term weather-resistant applications.

[0006] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a fluorosilane-modified PVB resin, which adopts the following technical solution: A fluorosilane-modified PVB resin is prepared by a chemical grafting reaction of raw materials comprising a pre-reaction solution and polyvinyl butyral resin. The pre-reaction liquid contains fluorinated siloxane oligomers, which have active silanol groups and epoxy groups. The chemical grafting reaction involves the condensation reaction between the active silanol groups in the pre-reaction solution and some of the hydroxyl groups on the polyvinyl butyral resin main chain to form Si-OC bonds. At the same time, the epoxy groups open and react with the hydroxyl groups on the polyvinyl butyral resin main chain to form ether bonds, thereby achieving dual chemical grafting of fluorinated siloxane oligomer segments into the main chain. In the raw materials, the total molar ratio of fluorosilane and silane coupling agent used to prepare the pre-reaction solution to the molar equivalent ratio of hydroxyl groups in polyvinyl butyral resin is (0.1~0.4):1; the fluorine content of the obtained fluorosilane-modified PVB resin is 5%~15%.

[0007] By employing the above technical solution, compared to physical blending, this solution primarily uses chemical bonding to connect the fluorinated components to the resin backbone. Specifically, fluorinated oligomers with silanol and epoxy groups are first formed in the pre-reaction system; Subsequently, the silanol groups on the periphery of the oligomer undergo dehydration condensation with the alcohol hydroxyl groups on the side chain of polyvinyl butyral, i.e. (resin—OH + oligomer—Si—OH → resin—O—Si—oligomer + H2O), generating Si-OC bonds; At the same time, under heated conditions, the epoxy groups remaining in the system undergo ring-opening; and addition with the free hydroxyl groups on the resin (resin) OH+ oligomers Epoxy groups → resin O C C(OH) (Oligomers) form ether bonds. Through the above process, fluorinated segments can be more firmly attached to the main chain. By controlling the equivalent ratio of (0.1~0.4):1, the free migration of fluorinated components can be restricted while maintaining the original flexibility and adhesion of the resin, thereby helping to maintain the long-term stability of surface energy.

[0008] Preferably, the pre-reaction liquid is prepared by reacting raw materials containing the following components: 1H,1H,2H,2H-perfluorooctyltriethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane in a molar ratio of 1:(1-2); and an acidic catalyst and deionized water.

[0009] By employing the above technical solution, fluorine atoms are introduced through perfluorooctyltriethoxysilane to reduce the surface energy of the material, while glycidyl etheroxypropyltrimethoxysilane provides the active sites for crosslinking. Controlling the molar ratio of the two silanes within the range of 1:(1-2) helps to adjust the steric hindrance of the generated oligomers, enabling the system to possess both good matrix compatibility and subsequent grafting activity.

[0010] Preferably, the Fourier transform infrared spectrum of the fluorosilane-modified PVB resin is in the range of 1050–1100 cm⁻¹. -1 The vicinity exhibits characteristic absorption peaks of Si-OC, in the range of 1150–1250 cm⁻¹. -1 The area near it exhibits characteristic Si-O-Si absorption peaks, and the range is 910–920 cm⁻¹. -1 The characteristic peaks of nearby epoxy groups disappeared; and X-ray photoelectron spectroscopy showed that the fluorosilane-modified PVB resin had chemical bonding signals between Si and C elements.

[0011] By employing the above technical solutions and using infrared spectroscopy and X-ray photoelectron spectroscopy to characterize specific groups and chemical bonds, it can be confirmed that fluorosilanes have largely been transformed into components of polymer chains, which provides an explanation for the physicochemical stability of the resin at the structural level.

[0012] Secondly, the present invention provides a method for preparing fluorosilane-modified PVB resin, which adopts the following technical solution: A method for preparing a fluorosilane-modified PVB resin includes the following steps: Polyvinyl butyral resin is completely dissolved in an organic solvent to obtain a resin solution; A pre-reaction solution was added to the resin solution, and a chemical grafting reaction was carried out under heating and stirring. After the reaction was completed, a modified resin solution was obtained. The modified resin solution was poured into a mixture of methanol and water for precipitation. After filtration, the precipitate was washed and vacuum dried to obtain solid fluorosilane-modified PVB resin.

[0013] By employing the above technical solution, dissolving the resin in an organic solvent helps to moderately extend its molecular chains and expose reactive groups. After adding the pre-reaction solution, the system completes condensation and ring-opening addition under heating. After the reaction, a mixture of methanol and water is used as a precipitation medium. The change in solubility promotes the precipitation of the grafted product. At the same time, this mixed non-solvent can remove some unreacted monomers and free oligomers, thereby improving the purity of the product.

[0014] Preferably, before carrying out the chemical grafting reaction, a pre-reaction solution is prepared by the following steps: 1H,1H,2H,2H-perfluorooctyltriethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane are added to a solvent, and an acidic catalyst is added and stirred until homogeneous. Then, deionized water is slowly added dropwise to the system, and partial hydrolysis and partial condensation reactions are carried out under constant temperature stirring under heating conditions to obtain a clear, transparent, gel-free pre-reaction solution. By adopting the above technical solution, under acidic conditions, the alkoxy moiety of silane undergoes hydrolysis to generate silanol groups, which are then dehydrated and condensed to form oligomers with siloxane bonds.

[0015] During this process, the hydrolysis and condensation processes are appropriately controlled to keep the system in a flowing sol state to avoid excessive cross-linking and gelation, thus preserving the active fluorinated intermediates for subsequent grafting reactions.

[0016] Preferably, in the preparation of the pre-reaction solution, the total solid content of silane is controlled to be 15%–30%, the molar ratio of water to the total alkoxy groups in the two silanes is controlled to be (0.8–0.9):1, the pH of the system is stabilized at 4.5–5.5, the reaction temperature is 40–60°C, the reaction time is 2–4 h, and the epoxy group retention rate is controlled to be not less than 85%; the solvent is propylene glycol methyl ether acetate, and the acidic catalyst is p-toluenesulfonic acid or acetic acid.

[0017] By employing the above-mentioned technical solution and controlling the molar ratio of water to alkoxy groups, along with appropriate temperature and pH, the elongation of siloxane chains can be effectively constrained, reducing the risk of macroscopic gelation of the system. Especially in a slightly acidic pH environment (4.5–5.5), premature hydrolysis and ring-opening of epoxy groups can be relatively suppressed, allowing most epoxy groups to be retained (retention rate not less than 85%) for subsequent ether grafting reactions.

[0018] Preferably, the organic solvent is one or more of butanone, ethyl acetate, or isopropanol; in the chemical grafting reaction, the reaction temperature under heating conditions is 70-85°C, and the reaction time is 5-8 hours; during precipitation, the volume of the methanol-water mixture is 5-10 times the volume of the modified resin solution, and the volume ratio of methanol to water in the methanol-water mixture is 4:1.

[0019] By adopting the above technical solution, the selected solvents such as methyl ethyl ketone have good solubility and compatibility with the matrix resin. The grafting stage, using a temperature of 70-85℃, can promote condensation and activate the ring-opening of epoxy groups; while in the post-treatment step, a large volume of methanol / water mixture (with a methanol to water ratio of 4:1) helps the modified resin to aggregate and precipitate more quickly, and usually does not affect the removal of small molecule byproducts.

[0020] Thirdly, the present invention provides a coating, which adopts the following technical solution: A coating is made by mixing raw materials comprising the following parts by weight: 30-50 parts of fluorosilane-modified PVB resin; 40-60 parts of mixed solvent; 0.5-3 parts of curing accelerator; Pigment or filler 0-20 parts; coating additives 0.2-1.5 parts; wherein, fluorosilane modified PVB resin is made by chemical grafting reaction of raw materials including pre-reaction liquid and polyvinyl butyral resin, the pre-reaction liquid contains fluorosiloxane oligomers with active silanol and epoxy groups, and the fluorine content of fluorosilane modified PVB resin is 5%-15% by mass.

[0021] By employing the above technical solution, this coating system uses modified PVB resin as the base film-forming material, combined with relevant solvents and additives. During film formation, the fluorinated segments within the resin structure readily orient towards the surface, thereby forming regions with low surface energy on the coating surface. This structure, to some extent, helps to block moisture and corrosive media. The overall formulation exhibits suitable film-forming properties and adhesion.

[0022] Preferably, the coating is used in the preparation of anti-corrosion topcoats for outdoor steel structures, self-cleaning and anti-reflective coatings for photovoltaic glass, or conformal coatings for electronic products.

[0023] This invention provides a fluorosilane-modified PVB resin, its preparation method, and a coating. It offers the following advantages: 1. This invention utilizes a dual chemical grafting process between a pre-reaction liquid and polyvinyl butyral resin. By employing Si-OC bonds formed by silanol condensation and ether bonds formed by epoxy ring opening, fluorinated siloxane oligomers are covalently linked to the resin backbone. The total molar ratio of fluorosilanes and silane coupling agents used to prepare the pre-reaction liquid to the molar equivalent ratio of hydroxyl groups in the resin is set to (0.1-0.4):1. This approach restricts the free migration of fluorinated components while preserving the original flexibility of the matrix, overcoming the shortcomings of conventional physical blending systems that are susceptible to fluorine loss due to solvents or environmental factors. This allows the material to maintain a stable low surface energy over a long period.

[0024] 2. This invention controls the molar ratio of water to the total amount of silane alkoxy groups at (0.8-0.9):1 and stabilizes the pH of the system at 4.5-5.5 during the pre-reaction solution preparation stage, so that the silane monomer is in a sol state of partial hydrolysis and partial condensation. This avoids the excessive condensation of siloxane to produce macroscopic gelation and inhibits the premature ring-opening consumption of epoxy groups, thus preserving sufficient dual active groups for subsequent grafting steps and ensuring the controllability of the resin synthesis process in a homogeneous solution.

[0025] 3. This invention uses the fluorosilane-modified PVB resin as the core film-forming material, and utilizes the outward orientation of fluorinated segments during the curing process to construct the surface hydrophobic region. At the same time, a mixed solvent of propylene glycol methyl ether acetate and butanone with a volatility gradient is introduced to reduce the film porosity. In addition, aluminum triacetylacetonate promotes the continued cross-linking of residual hydroxyl groups in the system in the later stage of film formation, thereby improving the overall density of the coating and enabling the final coating to have corresponding physical barrier capabilities against water vapor and corrosive media. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The chemical agents and materials used in the embodiments and comparative examples of this invention specifically include 1H,1H,2H,2H-perfluorooctyltriethoxysilane (CAS No.: 51851-37-7) for providing low surface energy, γ-glycidyl etheroxypropyltrimethoxysilane (CAS No.: 2530-83-8) as a silane coupling agent for providing reactivity and compatibility, p-toluenesulfonic acid and acetic acid as pre-hydrolyzed acid catalysts, propylene glycol methyl ether acetate, butanone, ethyl acetate, isopropanol and methanol as reaction solvents and coating diluents, aluminum triacetylacetonate or aminosilane as curing accelerators, rutile titanium dioxide as pigments, and fillers, coating additives, leveling agent BYK-306 and defoamer BYK-055 commonly used in the art.

[0028] The aforementioned chemical reagents, solvents, and auxiliaries are all commercially available conventional products commonly used in this field. The main resin used in the chemical grafting reaction is polyvinyl butyral resin (CAS No.: 63148-65-2), whose molecular backbone has a random copolymer structure, mainly composed of butyral structural units, polyvinyl alcohol structural units, and a small amount of polyvinyl acetate structural units. The specific commercially available brand used in this embodiment is SD-18, with a nominal hydroxyl content of 18wt%. In this invention, the hydroxyl equivalent of PVB resin is calculated based on the content of its polyvinyl alcohol structural units, i.e., based on 18g of polyvinyl alcohol structural units per 100g of PVB resin, and using the molar mass of polyvinyl alcohol structural units of 44g / mol as the conversion basis, the hydroxyl equivalent in PVB resin that can participate in the reaction is calculated.

[0029] In a specific embodiment of the present invention, the pre-hydrolysis reaction control conditions during the preparation of the pre-reaction solution are as follows: partial hydrolysis and partial condensation reactions are carried out in the presence of a quantitative amount of water; the pH of the system is controlled at 4.5–5.5; the reaction temperature is 40–60°C; the reaction time is 2–4 h; the total solid content of silane is controlled at 15%–30%; the reaction system remains clear and transparent, without gelation; and the epoxy group retention rate is controlled to be not less than 85%. In the chemical grafting reaction, the initial total molar ratio of the silicon-containing monomers (i.e., fluorosilanes and silane coupling agents) used to prepare the pre-reaction solution to the molar equivalent ratio of the hydroxyl groups in the PVB resin is controlled within the range of (0.1–0.4):1. The final PVB resin based on fluorosilane modification has a fluorine content controlled within the range of 5%–15%.

[0030] In the modified PVB resin obtained in this invention, fluorinated siloxane oligomer segments are grafted onto the PVB backbone via Si-OC bonds and ether bonds formed by ring-opening of epoxy groups. This dual chemical grafting structure can be confirmed by FTIR spectroscopy, XPS testing, and the retention rate of fluorine content after Soxhlet extraction, wherein the 1050–1100 cm⁻¹ fluorine content is optimal in the FTIR spectrum. -1 Si-OC related characteristic absorptions are observed in the vicinity, 1150–1250 cm⁻¹. -1 Si-O-Si related characteristic absorptions are observed in the vicinity, 910–920 cm⁻¹ -1 The characteristic peaks of nearby epoxy groups disappeared or almost disappeared; XPS detection showed that there were chemical bonding signals between Si and C elements; after Soxhlet extraction with methyl ethyl ketone for 24 hours, the fluorine content retention rate of the coating surface was not less than 80%.

[0031] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a pre-reaction solution, including the following steps: In a reaction vessel equipped with a stirrer, thermometer, and condenser, 10.0 g (approximately 20 mmol) of 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 6.0 g (approximately 25 mmol) of γ-glycidyl etheroxypropyltrimethoxysilane, and 40 g of propylene glycol methyl ether acetate were added as solvents, along with 0.16 g of p-toluenesulfonic acid as an acidic catalyst. The mixture was stirred until homogeneous. Calculations showed that the total mass fraction of silane in the system was approximately 27.4%, which falls within the range of 15%–30%. 2.16 g of deionized water was slowly added dropwise to the above system. Calculations showed that the amount of deionized water added resulted in a molar ratio of water to the total amount of alkoxy groups provided by the two silanes of approximately 0.89:1, which is within the range of (0.8–0.9):1. The system was also controlled to be weakly acidic, and the pH was stabilized at 5.0 ± 0.2 by controlling the dropping rate and adjusting the pH. After the addition of materials is completed, the mixture is stirred at a constant temperature of 50°C for 3 hours to carry out partial hydrolysis and partial condensation reaction. During the reaction, the degree of hydrolysis and condensation is strictly controlled to avoid excessive condensation and gelation, and to avoid premature ring opening of epoxy groups. After the reaction, a pale yellow, transparent, gel-free oligomer solution containing active silanol and epoxy groups was obtained, which is the pre-reaction solution. Fluorine-containing active siloxane oligomers were generated in this pre-reaction solution. These oligomers were determined by epoxy titration or FTIR spectroscopy in the 910–920 cm⁻¹ range. -1 The intensity of the characteristic peak of the epoxy group confirmed that the epoxy group retention rate was 88%.

[0032] Preparation Example 2: This preparation example provides a method for preparing a pre-reaction solution, including the following steps: 1H,1H,2H,2H-perfluorooctyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane were mixed at a molar ratio of 1:1, wherein 10.0 g (approximately 20 mmol) of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and approximately 4.8 g (approximately 20 mmol) of γ-glycidoxypropyltrimethoxysilane were added. 40 g of propylene glycol methyl ether acetate was added as a solvent, and 0.16 g of p-toluenesulfonic acid was added as an acidic catalyst. The mixture was stirred until homogeneous. The total solid content of silane in the system was calculated to be approximately 26.1%, which is within the range of 15% to 30%. Approximately 1.73 g of deionized water was slowly added dropwise to the above system. Calculations showed that the amount of deionized water added resulted in a molar ratio of water to the total alkoxy groups provided by the two silanes of approximately 0.8:1 (approximately 120 mmol of alkoxy groups and 96 mmol of water), meeting the control requirements and maintaining the system as weakly acidic, with the pH stabilized within the range of 4.5–5.5. After the addition of materials is completed, the mixture is stirred at a constant temperature of 50°C for 3 hours to carry out partial hydrolysis and partial condensation reaction. During the reaction, the degree of hydrolysis and condensation is strictly controlled to avoid excessive condensation and gelation, and to avoid premature ring opening of epoxy groups. After the reaction, a clear, transparent, gel-free oligomer solution containing active silanol and epoxy groups was obtained, which is the pre-reaction solution. Fluorine-containing active siloxane oligomers were generated in this pre-reaction solution. These oligomers were determined by epoxy titration or FTIR spectroscopy in the 910–920 cm⁻¹ range. -1 The intensity of the characteristic peak of the epoxy group confirmed that the epoxy group retention rate is not less than 85%.

[0033] Preparation Example 3: This preparation example provides a method for preparing a pre-reaction solution, including the following steps: 1H,1H,2H,2H-perfluorooctyltriethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane were mixed at a molar ratio of 1:2. Propylene glycol methyl ether acetate was added as a solvent, and 0.5% to 2% of acetic acid by mass of the two silanes was added as an acidic catalyst. The mixture was stirred until homogeneous. The amount of solvent added was such that the total solid content of silanes in the system was controlled within the range of 15% to 30%. Slowly add a fixed amount of deionized water to the above system, wherein the amount of deionized water added is such that the molar ratio of water to silane alkoxy group is controlled within the range of approximately (0.8 to 0.9):1, and the system is controlled to be weakly acidic, so that the pH of the system is stabilized within the range of 4.5 to 5.5. After the addition of materials is completed, the mixture is stirred at a constant temperature of 40-60℃ for 2-4 hours to carry out partial hydrolysis and partial condensation reaction. During the reaction, the degree of hydrolysis and condensation is strictly controlled to avoid excessive condensation and gelation, and to avoid premature ring opening of epoxy groups. After the reaction, a clear, transparent, gel-free oligomer solution containing active silanol and epoxy groups was obtained, which is the pre-reaction solution. Fluorine-containing active siloxane oligomers were generated in this pre-reaction solution. These oligomers were determined by epoxy titration or FTIR spectroscopy in the 910–920 cm⁻¹ range. -1 The intensity of the characteristic peak of the epoxy group confirmed that the epoxy group retention rate is not less than 85%.

[0034] Examples 1-3: Example 1: This embodiment provides a method for preparing a fluorosilane-modified PVB resin, including the following steps: (1) Chemical grafting reaction and post-treatment: 50.0 g of polyvinyl butyral (PVB) resin and 300 g of butanone were added to a reaction vessel and stirred at 75 °C to completely dissolve the PVB resin. Then, all the pre-reaction solution obtained in Preparation Example 1 was slowly added dropwise to the PVB resin solution. After the addition was complete, the reaction was continued to be stirred for 6 h under reflux at about 80 °C, so that the silanol groups in the pre-reaction solution could undergo a condensation reaction with some of the hydroxyl groups on the PVB resin chain to form Si-OC bonds. At the same time, the epoxy groups could open the ring and react with the hydroxyl groups on the PVB resin chain to form ether bonds. After the reaction was completed, a modified resin solution was obtained. The modified resin solution obtained above was cooled to room temperature and then slowly poured into a 1.5 L methanol / water mixture under high-speed stirring to induce precipitation. The volume ratio of methanol to water in the methanol / water mixture was 4:1. After filtration, the precipitate was washed three times with methanol and finally placed in a vacuum drying oven at 60 °C for 24 h to obtain a slightly yellow granular solid, which is the fluorosilane-modified PVB resin. Elemental analysis showed that the fluorine content of this modified resin was approximately 8.5% by mass, and the yield was approximately 92%.

[0035] (2) Formulation of high-performance coatings: By weight, 40 parts of the modified PVB resin prepared above were added to 45 parts of a mixed solvent, which was a mixture of propylene glycol methyl ether acetate and butanone in a mass ratio of 1:2. The mixture was stirred thoroughly until the resin was completely dissolved. Then, 1.5 parts of aluminum triacetylacetonate as a curing accelerator, 15 parts of rutile titanium dioxide, 0.4 parts of leveling agent BYK-306, and 0.2 parts of defoamer BYK-055 were added to the system. The above materials were stirred at high speed and mixed evenly, then ground and dispersed to the specified fineness. After passing through an 80-mesh sieve and degassing, a colored high-performance anti-corrosion coating was obtained.

[0036] Example 2: This embodiment provides a method for preparing a fluorosilane-modified PVB resin, including the following steps: (1) Chemical grafting reaction and post-treatment: 50.0 g of polyvinyl butyral (PVB) resin and 300 g of butanone were added to a reaction vessel and stirred at 75 °C to completely dissolve the PVB resin. Then, the pre-reaction solution obtained in Preparation Example 2 was slowly added dropwise to the PVB resin solution. After the addition was complete, the reaction was continued to be stirred for 7 h under reflux heating at about 83 °C, so that the active silanol groups in the pre-reaction solution could undergo a condensation reaction with some of the hydroxyl groups on the PVB resin chain to form Si-OC bonds. At the same time, the epoxy groups could open the ring and react with the hydroxyl groups on the PVB resin chain to form ether bonds. The total molar ratio of the fluorosilane and silane coupling agent used to prepare the pre-reaction solution to the molar equivalent ratio of the hydroxyl groups in the PVB resin was controlled within the range of (0.1 to 0.4):1. After the reaction was completed, a modified resin solution was obtained. The modified resin solution obtained above was cooled to room temperature and then slowly poured into a methanol / water mixture under high-speed stirring to induce precipitation. The volume ratio of methanol to water in the methanol / water mixture was 4:1. After filtration, the precipitate was washed three times with methanol and finally placed in a vacuum drying oven at 60°C for 24 hours to obtain a solid PVB resin modified with fluorosilane. Elemental analysis showed that the fluorine content of this modified resin was approximately 10.2% by mass.

[0037] (2) Formulation of high-performance coatings: By weight, 40 parts of the modified PVB resin prepared above were added to 45 parts of a mixed solvent, which was a mixture of propylene glycol methyl ether acetate and butanone in a mass ratio of 1:2. The mixture was stirred thoroughly until the resin was completely dissolved. Then, 1.5 parts of aluminum triacetylacetonate as a curing accelerator, 15 parts of rutile titanium dioxide, 0.4 parts of leveling agent BYK-306, and 0.2 parts of defoamer BYK-055 were added to the system. The above materials were stirred at high speed and mixed evenly, then ground and dispersed to the specified fineness. After passing through an 80-mesh sieve and degassing, a colored high-performance anti-corrosion coating was obtained.

[0038] Example 3: This embodiment provides a method for preparing a fluorosilane-modified PVB resin, including the following steps: (1) Chemical grafting reaction and post-treatment: Polyvinyl butyral (PVB) resin was completely dissolved in one or more organic solvents, such as butanone, ethyl acetate, or isopropanol. Then, the pre-reaction solution obtained in Preparation Example 3 was added. The total molar ratio of fluorosilane and silane coupling agent used to prepare the pre-reaction solution to the molar equivalent ratio of hydroxyl groups in the PVB resin was controlled to be (0.1-0.4):1. The mixture was stirred and reacted at 70-85°C for 5-8 hours, so that the silanol groups in the pre-reaction solution reacted with some of the hydroxyl groups on the PVB resin chain to form Si-OC bonds. At the same time, the epoxy groups opened and reacted with the hydroxyl groups on the PVB resin chain to form ether bonds. After the reaction was completed, a modified resin solution was obtained. The modified resin solution obtained above was slowly poured into a methanol / water mixture with a volume 5 to 10 times that of the modified resin solution for precipitation. The volume ratio of methanol to water in the methanol / water mixture was 4:1. After filtration, the precipitate was washed three times and finally placed in a vacuum drying oven at 60°C to dry under vacuum, obtaining a solid PVB resin based on fluorosilane modification. The fluorine content of the obtained modified PVB resin can be controlled within the range of 5% to 15%.

[0039] (2) Formulation of high-performance coatings: By weight, 30-50 parts of the modified PVB resin prepared above are added to 40-60 parts of a mixed solvent, which is a mixture of propylene glycol methyl ether acetate and butanone at a mass ratio of 1:(1-3). The mixture is stirred thoroughly until the resin is completely dissolved. Then, 0.5-3 parts of a curing accelerator, 0-20 parts of pigment or filler, and 0.2-1.5 parts of coating additives are added to the system. The curing accelerator is aluminum triacetylacetonate or aminosilane, and the coating additives include leveling agent BYK-306 and defoamer BYK-055. The above materials are stirred at high speed and mixed evenly, and then ground and dispersed to the specified fineness. After degassing and filtration, a high-performance anti-corrosion coating is obtained.

[0040] Comparative example: Compared to Example 1, the difference lies in that: instead of preparing a pre-reaction solution for chemical grafting, 10.0 g of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 6.0 g of γ-glycidyl etheroxypropyltrimethoxysilane were directly added to 300 g of butanone solvent containing 50.0 g of PVB resin for physical mixing. No deionized water or acidic catalyst was added, and no pre-hydrolysis or partial condensation reaction was performed. The mixture was stirred and mixed at 50°C for 4 hours. Then, post-treatment was carried out according to the same precipitation, washing, and drying steps as in Example 1 to obtain a physically blended sample. A comparative coating was prepared using the same coating base formulation as in Example 1.

[0041] Test Example 1-3: Test Example 1: 1. Unmodified PVB coatings, coatings prepared in Examples 1 and 2, and coatings prepared in comparative examples were selected as test objects. The unmodified PVB coatings were prepared according to the same basic formulation as in Example 1, except that the modified PVB resin in Example 1 was replaced with unmodified SD-18 type PVB resin. Each test coating was sprayed onto a pre-sandblasted Q235 steel plate and a clean glass plate using an air spraying method.

[0042] 2. Place the coated substrate sample at room temperature for 20 minutes to allow it to level naturally, then transfer it to an electric heating drying oven and bake at 150℃ for 20 minutes. After baking, allow it to cool naturally to room temperature and remove it. Use a coating thickness gauge to measure the thickness of the cured coating dry film, and control the dry film thickness of each sample within the range of 30±5μm.

[0043] 3. Scrape samples of the cured resin or cured coating from Examples 1, 2, and the comparative examples, and perform Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) tests, observing the samples at 1050–1100 cm⁻¹. -1 1150~1250cm -1 and 910-920cm -1 The changes in nearby characteristic absorption signals, combined with the changes in the chemical environment of elements in XPS, were analyzed to determine the grafting reaction. The focus was on observing whether chemical bonding signals between Si and C elements appeared in the XPS spectrum.

[0044] 4. Using the coatings of Examples 1, 2 and the comparative example as test objects, and methyl ethyl ketone as the extraction solvent, the coatings were continuously Soxhlet extracted for 24 hours under reflux. The relative content of fluorine on the surface of the coating before and after extraction was tested by XPS, and the fluorine content retention rate was calculated.

[0045] Table 1. Fluorine content retention rate of coatings after Soxhlet extraction in each example and comparative example According to the data in Table 1, Examples 1 and 2 maintained a high relative surface fluorine content after 24 hours of continuous Soxhlet extraction with methyl ethyl ketone (MEK), with a fluorine content retention rate of no less than 80%. The comparative example used physical blending, and the ungrafted fluorinated silane components were prone to migration or extraction under organic solvent extraction conditions, resulting in a significant decrease in the fluorine content retention rate after extraction.

[0046] FTIR measurements show that the comparative physical blend system still retains a distinct 910–920 cm⁻¹ spectrum. -1 The characteristic absorption peaks of the epoxy groups in the vicinity are absent; however, in the spectra of Examples 1 and 2, these characteristic peaks of the epoxy groups disappear or almost disappear, while the peaks in the 1050–1100 cm⁻¹ range are absent. -1 The region exhibits characteristic absorption peaks related to Si-OC, in the range of 1150–1250 cm⁻¹. -1 The region exhibits Si-O-Si related characteristic absorption peaks.

[0047] Furthermore, XPS testing revealed chemical bonding signals between Si and C elements in the modified resin system. The aforementioned infrared, XPS, and Soxhlet extraction results collectively confirm that the fluorinated siloxane oligomers do not primarily exist in a free state within the coating film. Instead, they undergo pre-hydrolysis condensation via an epoxy-containing silane coupling agent, followed by a chemical grafting reaction with the hydroxyl groups on the PVB matrix. Specifically, the silanol groups condense with PVB hydroxyl groups to form Si-OC bonds, while the epoxy groups open and react with PVB hydroxyl groups to form ether bonds, thus stably introducing the fluorinated segments into the PVB system.

[0048] Test Example 2: 1. Unmodified PVB coating, samples of Q235 steel plate coating and glass coating prepared in Examples 1 and 2, and comparative examples were selected as test subjects. Before testing, the samples were placed in an environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours for conditioning.

[0049] 2. Use a contact angle meter to test the static contact angle of deionized water on the surface of each sample. Measure at least 5 different locations for each sample, remove obvious outliers, and take the average value as the water contact angle of that sample.

[0050] 3. Use 3 μL of deionized water droplets to test the roll angle of each sample. During the test, slowly adjust the tilt angle of the sample and record the tilt angle when the water droplet begins to roll continuously. Each sample should be tested at least 5 times, and the average value should be taken as the roll angle result.

[0051] 4. The coating adhesion was tested using the cross-cut adhesion test (GB / T 9286); the coating pencil hardness was tested using GB / T 6739; and the coating flexibility was evaluated using conventional coating flexibility testing methods in this field. All test samples were cured Q235 steel plate coatings.

[0052] 5. Immerse each sample in room temperature deionized water for 168 hours. After removing them, wipe off the surface moisture and observe whether the coating shows whitening, blistering, cracking, or peeling. Test the adhesion after immersion. Take another sample from the same batch and boil it in boiling water for 2 hours. After cooling to room temperature, observe the appearance of the coating and test the adhesion after boiling.

[0053] Table 2. Surface properties, mechanical properties, and water resistance test results of unmodified PVB coatings, Example 1, Example 2, and comparative examples. Note: — indicates that the effective roll angle was not measured; The adhesion rating is evaluated according to the cross-cut test method of GB / T 9286, with grade 0 indicating the best adhesion and the higher the grade number, the worse the adhesion. The pencil hardness is tested according to GB / T 6739; 0 to 1 indicates that the adhesion rating is between grade 0 and grade 1.

[0054] According to the data in Table 2, the initial water contact angles of Examples 1 and 2 were both greater than 130°, and the roll-off angles were both no higher than 15°. This indicates that the PVB coatings modified by the synergistic effect of fluorosilane and KH560 have low surface energy and exhibit high hydrophobicity and low roll-off angle characteristics. The comparative example, although possessing some initial hydrophobicity, had a roll-off angle greater than 90°, making it difficult for water droplets to roll off. Furthermore, its adhesion decreased significantly after immersion in warm water and boiling water treatment, indicating insufficient stability of the hydrophobic surface formed by physical blending. The unmodified PVB coating, while having good initial adhesion, had a low water contact angle, and its adhesion decreased significantly after water-resistant treatment, making it difficult to meet the requirements for high hydrophobicity and long-term water resistance protection. Examples 1 and 2, while improving the high hydrophobicity, hardness, and water resistance stability of the coating, still maintained the good flexibility of the PVB matrix, making them suitable for use as protective coatings with both adhesion and flexibility.

[0055] Test Example 3: 1. Unmodified PVB coatings, Example 1, Example 2, and Q235 steel plate coating samples prepared by comparative example were selected as the test objects for corrosion resistance and artificial weathering resistance.

[0056] 2. The scribing samples were tested using the neutral salt spray test according to GB / T 1771. During the test, the samples were taken out for observation at 200 hours, 500 hours and 800 hours, and the corrosion expansion on one side of the scratch and the blistering, rusting or peeling of the coating surface were recorded. When obvious blistering or rusting appeared on the sample, the corresponding time was recorded as the salt spray resistance result.

[0057] 3. Xenon lamp artificial weathering test was conducted using GB / T 1865 Cycle B method. Samples were removed after 600 hours and 1000 hours respectively to test the coating gloss loss and assess the discoloration and chalking grades. Samples were equilibrated before and after testing in an environment of 23±2℃ and 50±5% relative humidity.

[0058] Table 3. Salt spray and artificial weathering resistance test results of unmodified PVB coatings, Example 1, Example 2 and comparative coatings Note: — indicates that the sample has obviously failed or no valid test results were obtained; The corrosion width is the width of corrosion spread on one side of the scratch; the lower the gloss loss rate value, the better the resistance to artificial weathering.

[0059] According to the data in Table 3, Examples 1 and 2 maintained good coating integrity after 800 hours of neutral salt spray testing, with small unilateral corrosion spread width of scratches; after 1000 hours of xenon lamp artificial weathering, the gloss loss rate remained at a low level. Although the salt spray and aging resistance of the comparative examples were improved compared to the unmodified PVB coating, they were still significantly inferior to Examples 1 and 2 under long-term salt spray and artificial weathering conditions, indicating that long-term stable bonding between fluorinated silane segments and the PVB matrix cannot be achieved solely through physical blending.

[0060] Based on the comprehensive test results above, it can be seen that the coating prepared in the embodiments of the present invention has excellent adhesion, good flexibility, long-lasting high hydrophobicity and low roll-off angle characteristics, as well as outstanding resistance to salt spray and artificial weathering. It is particularly suitable for preparing outdoor steel structure anti-corrosion topcoat, photovoltaic glass high hydrophobic self-cleaning anti-reflective coating or electronic product three-proof coating, and has broad industrial application prospects.

Claims

1. A fluorosilane-modified PVB resin, characterized in that, It is made by chemical grafting of raw materials containing pre-reaction liquid and polyvinyl butyral resin; The pre-reaction liquid contains fluorinated siloxane oligomers, which have active silanol groups and epoxy groups. The chemical grafting reaction involves the condensation reaction between the active silanol groups in the pre-reaction solution and some of the hydroxyl groups on the polyvinyl butyral resin main chain to form Si-OC bonds. At the same time, the epoxy groups open and react with the hydroxyl groups on the polyvinyl butyral resin main chain to form ether bonds, thereby achieving dual chemical grafting of fluorinated siloxane oligomer segments into the main chain. In the raw materials, the total molar ratio of fluorosilane and silane coupling agent used to prepare the pre-reaction solution to the molar equivalent ratio of hydroxyl groups in the polyvinyl butyral resin is (0.1-0.4):

1. The fluorine content of the prepared fluorosilane-modified PVB resin is 5% to 15% by mass.

2. The fluorosilane-modified PVB resin according to claim 1, characterized in that, The pre-reaction liquid is prepared by reacting raw materials containing the following components: 1H,1H,2H,2H-perfluorooctyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane, in a molar ratio of 1:(0.5~2). In addition to acidic catalysts and deionized water.

3. The fluorosilane-modified PVB resin according to claim 1, characterized in that, The Fourier transform infrared spectrum of the fluorosilane-modified PVB resin shows a value in the range of 1050–1100 cm⁻¹. -1 The vicinity exhibits characteristic absorption peaks of Si-OC, in the range of 1150–1250 cm⁻¹. -1 The area near it exhibits characteristic Si-O-Si absorption peaks, and the range is 910–920 cm⁻¹. -1 The characteristic peak of the nearby cyclooxygen group disappears; Furthermore, X-ray photoelectron spectroscopy revealed that the fluorosilane-modified PVB resin exhibited chemical bonding signals between Si and C elements.

4. A method for preparing a fluorosilane-modified PVB resin as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Polyvinyl butyral resin is completely dissolved in an organic solvent to obtain a resin solution; A pre-reaction solution is added to the resin solution, and a chemical grafting reaction is carried out under heating and stirring. After the reaction is completed, a modified resin solution is obtained. The modified resin solution was poured into a methanol / water mixture for precipitation. After filtration, the precipitate was washed and vacuum dried to obtain solid fluorosilane-modified PVB resin.

5. The method for preparing fluorosilane-modified PVB resin according to claim 4, characterized in that, Prior to the chemical grafting reaction, the pre-reaction solution is prepared by the following treatment steps: 1H,1H,2H,2H-perfluorooctyltriethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane were added to a solvent, and an acidic catalyst was added and stirred until homogeneous. Then, deionized water was slowly added dropwise to the system, and the mixture was stirred at a constant temperature under heating conditions to carry out partial hydrolysis and partial condensation reactions, resulting in a clear, transparent, gel-free pre-reaction solution.

6. The method for preparing fluorosilane-modified PVB resin according to claim 5, characterized in that, In the preparation of the pre-reaction solution, the total solid content of silane is controlled to be 15% to 30%, the molar ratio of water to the total alkoxy group in the two silanes is controlled to be (0.8 to 0.9):1, and the pH of the system is stabilized at 4.5 to 5.

5. The reaction is carried out at a temperature of 40–60°C for 2–4 hours, and the epoxy group retention rate is controlled to be no less than 85%. The solvent is propylene glycol methyl ether acetate, and the acidic catalyst is p-toluenesulfonic acid or acetic acid.

7. The method for preparing fluorosilane-modified PVB resin according to claim 4, characterized in that, The organic solvent is one or more of butanone, ethyl acetate, or isopropanol; In the chemical grafting reaction, the reaction temperature under heating conditions is 70–85°C, and the reaction time is 5–8 hours. During precipitation, the volume of the methanol / water mixture is 5 to 10 times the volume of the modified resin solution, and the volume ratio of methanol to water in the methanol / water mixture is 4:

1.

8. A coating, characterized in that, It is made from a mixture of the following ingredients in parts by weight: 30-50 parts of fluorosilane-modified PVB resin; 40-60 parts of mixed solvent; Curing accelerator 0.5-3 parts; 0-20 parts of pigment or filler; 0.2 to 1.5 parts of coating additives; The fluorosilane-modified PVB resin is prepared by chemical grafting of raw materials including a pre-reaction liquid and polyvinyl butyral resin. The pre-reaction liquid contains fluorosiloxane oligomers with active silanol and epoxy groups. The fluorine content of the fluorosilane-modified PVB resin is 5% to 15% by mass.

9. The coating according to claim 8, characterized in that, The mixed solvent is composed of propylene glycol methyl ether acetate and butanone in a mass ratio of 1:(1-3); The curing accelerator is aluminum triacetylacetonate or aminosilane; The coating additives include leveling agents and defoamers.

10. A coating as described in any one of claims 8-9, characterized in that, Applications in the preparation of anti-corrosion topcoats for outdoor steel structures, self-cleaning and anti-reflective coatings for photovoltaic glass, or conformal coatings for electronic products.

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