Nano silicon dioxide filler, nano composite anticorrosive paint containing nano silicon dioxide filler and preparation method of anticorrosive paint

Abstract

The invention discloses a nano silicon dioxide filler, a nano composite anti-corrosion coating containing the nano silicon dioxide filler and a preparation method of the anti-corrosion coating. The nano silicon dioxide filler is prepared by a low-temperature molten salt method and is treated by a surface modifier; the low-temperature molten salt method comprises the following steps: preparing a molten salt medium, wherein the molten salt medium consists of one or more soluble inorganic salts; mixing a silicon source, the molten salt medium and a precipitator to obtain a reaction precursor; the reaction precursor is subjected to a reaction for 2-24 h at the temperature of 150-350 DEG C, and nano silicon dioxide is generated; and cooling the reaction product, dissolving, removing soluble salt, separating, and drying to obtain the nano silicon dioxide filler. The invention aims to construct a physical shielding, cathode protection and interface enhancement multi-synergistic anti-corrosion system, so that the corrosion resistance, the mechanical property and the storage stability of the coating are remarkably improved, and a technical scheme suitable for industrial production is obtained.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion coating technology. More specifically, this invention relates to a nano-silica filler, a nano-composite anti-corrosion coating containing the same, and a method for preparing the anti-corrosion coating. Background Technology

[0002] Metal corrosion is a global economic problem. In marine environments, the corrosion rate of steel structures can reach 0.1-0.3 mm / year, seriously threatening engineering safety. Coating protection, as the most economical and effective means of corrosion prevention, directly determines the service life of metal structures.

[0003] Currently, the mainstream anti-corrosion coating systems mainly include: 1. Epoxy zinc-rich primer system: relies on the cathodic protection effect of zinc powder, but has problems such as large zinc powder consumption, usually accounting for more than 50%, easy coating cracking, and rapid zinc powder consumption; 2. Polyurethane coating system: excellent weather resistance but insufficient chemical resistance; 3. Fluorocarbon coating system: excellent comprehensive performance but high cost and strict construction requirements.

[0004] Specific defects of existing technology: 1. Insufficient coating density: The porosity of traditional coatings is usually 5-10%, and the water vapor permeability reaches 10%. -9 ~10 -11 g / (m²•s•Pa), making it difficult to effectively block corrosive media. 2. Bottlenecks in the application of nanomaterials: Although nanomaterials have been developed... While there are reports on its application in anti-corrosion coatings, all of them use commercial nanoparticles, which suffer from problems such as severe agglomeration, uneven dispersion, and poor compatibility with resins, resulting in limited improvement in actual performance. 3. Single function: Existing coatings mostly rely on a single anti-corrosion mechanism and lack synergistic effects.

[0005] Therefore, developing a new coating system that combines high density, strong adhesion, and long-lasting anti-corrosion performance is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention aims to provide a nano-silica filler synthesized and modified via a low-temperature molten salt method, addressing the technical bottlenecks of commercial nanomaterials in anti-corrosion coatings, such as easy agglomeration, poor dispersion, and limited performance improvement. Furthermore, this invention provides a nanocomposite anti-corrosion coating containing this filler and its preparation method, aiming to construct a multi-layered synergistic anti-corrosion system integrating physical shielding, cathodic protection, and interface enhancement, thereby significantly improving the coating's corrosion resistance, mechanical properties, and storage stability, and obtaining a technical solution suitable for industrial production.

[0007] The technical solution adopted by this invention to solve this technical problem is: a nano-silica filler for anti-corrosion coatings, which is prepared by a low-temperature molten salt method and treated with a surface modifier; the low-temperature molten salt method includes the following steps: S1. Preparing a molten salt medium, wherein the molten salt medium is composed of one or more soluble inorganic salts; Preferably, in step S1, the soluble inorganic salt includes at least one of nitrate, chloride, and acetate; more preferably, the molten salt medium is a mixture of lithium nitrate and potassium nitrate in a mass ratio of (40~60):(60~40).

[0008] S2. Mix the silicon source, the molten salt medium, and the precipitant to obtain the reaction precursor; Preferably, in step S2, the silicon source is at least one of methyl orthosilicate, ethyl orthosilicate, and sodium silicate.

[0009] Preferably, in step S2, the precipitant is a compound that can decompose to produce alkaline substances under heating conditions, preferably urea or hexamethylenetetramine.

[0010] Preferably, in step S2, the mass ratio of the silicon source, molten salt medium and precipitant is 1:(2~10):(0.5~3).

[0011] S3. The reaction precursor is reacted at 150℃~350℃ for 2~24 hours to generate nano-silica; Preferably, in step S3, the reaction temperature is 180℃~250℃ and the reaction time is 4~12 hours.

[0012] Preferably, in step S3, the reaction precursor mixture is placed in a closed reactor for reaction, wherein the closed reactor is a covered ceramic crucible or a stainless steel reactor lined with polytetrafluoroethylene.

[0013] S4. Cool the reaction product, dissolve and remove soluble salts, separate and dry to obtain the nano-silica filler.

[0014] As a further aspect of the present invention, the surface modifier is a silane coupling agent; preferably, the silane coupling agent is selected from at least one of KH-550, KH-560, and KH-570.

[0015] As a further aspect of the present invention, the specific surface area of ​​the nano-silica is 200~800 m² / g, the average particle size is 10~100 nm, and the particle size distribution variation coefficient is <20%.

[0016] The present invention also provides a nanocomposite anticorrosive coating comprising nano-silica filler, film-forming resin and anticorrosive pigment as described in any one of claims 1-3.

[0017] As a further aspect of the present invention, the following components are included by mass fraction: 20-40 parts of film-forming resin (preferably epoxy resin); 20-60 parts of anti-corrosion pigment (preferably zinc powder); and 1-10 parts of nano-silica filler.

[0018] As a further aspect of the present invention, the film-forming resin is epoxy resin; and the anti-corrosion pigment is zinc powder.

[0019] As a further aspect of the present invention, the coating is a two-component system, comprising component A and component B; Component A comprises the film-forming resin, the anti-corrosion pigment, the nano-silica filler, a solvent, and additives, wherein the additives include dispersants, defoamers, and leveling agents; Component B is a curing agent that is compatible with the film-forming resin, and it is packaged separately.

[0020] This invention also provides a method for preparing the aforementioned nanocomposite anticorrosive coating, wherein the preparation of component A includes the following steps: 1) Mix the nano-silica filler, solvent, dispersant and part of the film-forming resin, and pre-disperse them; 2) Grind the pre-dispersed slurry until the fineness is ≤30μm; 3) Add the remaining film-forming resin, anti-corrosion pigments and other additives to the ground slurry, stir evenly, and obtain coating component A; Before application, mix component A and component B, allow them to mature, and then use. Preferably, the amount of component B is 5%-15% of the total mass of component A. Component B can be a polyamide curing agent.

[0021] As a further aspect of the present invention, the pre-dispersion in step 1) is high-speed stirring dispersion with a rotation speed of 1000~1500 r / min and a time of 15~30 minutes; the grinding in step 2) is sand milling or ball milling.

[0022] The present invention has at least the following beneficial effects: 1. Significantly improved corrosion resistance: Salt spray resistance has increased from 500 hours for traditional coatings to over 1200 hours (ASTM B117 standard); water vapor permeability has decreased by 60-80%, reaching 2×10⁻⁶ hours. -12 g / (m²•s•Pa) or less; coating porosity reduced from 5-10% to below 1%.

[0023] 2. Adhesion reaches level 0, pencil hardness is increased to 2H, abrasion resistance is significantly improved, and the cathode peel radius is significantly reduced, proving that it possesses ultra-long-lasting protective capabilities and excellent mechanical properties. 3. While improving performance, this coating slows down zinc powder consumption through the dense physical barrier effect of nanofillers. Under the premise of ensuring the same anti-corrosion effect, the amount of zinc powder used can be reduced by 10-20%; the zinc powder consumption rate is reduced by 30-50%, and the protection cycle is extended.

[0024] 4. Successfully overcame the technical challenge of easy agglomeration and difficulty in dispersion of high specific surface area nanomaterials in coating systems. The prepared nano-silica has a specific surface area of ​​over 550 m² / g. Through targeted surface modification and adaptation processes, uniform dispersion and long-term storage stability in coatings were achieved, solving the problems of easy sedimentation and difficulty in redispersibility of commercial nanopowders.

[0025] 5. Significant economic benefits: The overall cost of coatings is reduced by 5-15%; the service life of the coating is extended by 2-3 times, and maintenance costs are greatly reduced.

[0026] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0027] Figure 1 This is a TEM image (a) of the modified nano-silica filler synthesized by the low-temperature molten salt method of this invention. Figure 2 This is a TEM image (b) of the modified nano-silica filler synthesized by the low-temperature molten salt method of this invention. Detailed Implementation

[0028] The present invention will now be described in detail and completely with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0029] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows: Example 1: Synthesis of Nano-Silica and Surface Modification by Low-Temperature Molten Salt Method This embodiment details the synthesis and modification process of the core functional filler, nano-silica, using the low-temperature molten salt method. Specifically, it includes the following steps: S1. Preparation of molten salt medium: Weigh lithium nitrate ( 45g and potassium nitrate ( 55g of the mixture was placed in a mortar and thoroughly mixed and ground to form a uniform eutectic mixture, which was used as the reaction medium.

[0031] S2. Mixing of reactants: Add 10g of tetraethyl orthosilicate (TEOS, as a silicon source), 100g of the above molten salt medium and 5g of urea (as a precipitant) to a stainless steel reactor lined with polytetrafluoroethylene and stir for 5 minutes to form a uniform milky white mixture of reaction precursors.

[0032] S3. Low-temperature molten salt reaction: The mixture of reaction precursors is added to a stainless steel reactor lined with polytetrafluoroethylene and sealed. The reactor is then kept at 200°C for 8 hours. During this process, TEOS hydrolyzes and condenses in the homogeneous liquid phase environment provided by the molten salt medium. Urea decomposes upon heating to produce ammonia, creating a weakly alkaline environment that promotes the nucleation and growth of nano-silica particles.

[0033] S4. Product Post-processing: After the reaction is complete, allow it to cool naturally to room temperature. Open the reactor, remove the blocky reaction product, and dissolve it in deionized water with stirring to completely dissolve the nitrates. Then, centrifuge, washing and centrifuging three times with deionized water until the conductivity of the supernatant is close to that of deionized water. Dry the obtained material in a vacuum drying oven to obtain nano-silica. BET analysis shows its specific surface area is 550 m² / g.

[0034] S5. Surface Modification: 10g of nano-silica was dispersed in 200mL of anhydrous ethanol and sonicated for 30 minutes. Then, 0.3g of KH-550 silane coupling agent was added, and the mixture was refluxed with magnetic stirring at 80℃ for 3 hours. After the reaction, the mixture was centrifuged, washed three times with ethanol, and dried in a vacuum drying oven at 80℃ to obtain hydrophobic modified nano-silica filler. TEM observation was performed (see attached image). Figures 1-2 The particles were well-dispersed spherical nanoparticles with a diameter mainly between 10 and 100 nm, and no obvious hard agglomeration. This proves that the low-temperature molten salt method used in this invention can effectively suppress excessive aggregation of nanoparticles during the generation and growth process through the spatial barrier effect of the molten salt medium, thereby successfully obtaining high-quality nano-silica products with good dispersion and uniform particle size.

[0035] Example 2: Preparation of Nanocomposite Anticorrosive Coating In this embodiment, the modified nano-silica filler obtained in Example 1 is used to prepare component A of the nanocomposite anticorrosive coating of the present invention.

[0036] The preparation formula of component A is as follows: 30 parts epoxy resin (E-20); 50 parts zinc powder; 3 parts modified nano silica filler; 16 parts mixed solvent (xylene: n-butanol = 7:3); 0.5 parts dispersant (BYK-163); 0.5 parts defoamer (BYK-066).

[0037] Preparation method of component A: 15 parts of epoxy resin, all mixed solvent, all modified nano silica filler and dispersant are put into a mixing tank and dispersed at a high speed of 1200 r / min for 20 minutes to obtain a uniform premixed slurry.

[0038] The premixed slurry was transferred to a sand mill and ground to a fineness of ≤25μm.

[0039] Transfer the ground slurry back to the dispersion vessel, add the remaining 15 parts of epoxy resin, all the zinc powder and defoamer, and stir at a low speed of 500 r / min for 30 minutes until the system is uniform, thus obtaining coating component A.

[0040] Matching curing agent (component B): Polyamide curing agent, packaged separately.

[0041] Construction and film formation: Before application, mix component A and component B at a mass ratio of 100:12, allow to mature for 15 minutes, and then apply by brushing or spraying onto a Q235 steel plate (150mm × 70mm × 1mm) that has been sandblasted to Sa2.5 grade. Control the dry film thickness to (80±5) μm. After curing under standard conditions (temperature 23±2℃, relative humidity 50±5%) for 7 days, conduct various performance tests.

[0042] Example 3a The formulation and process of this embodiment are the same as those of Embodiment 2, except that the amount of modified nano-silica filler added is changed to 1 part.

[0043] Example 3b The formulation and process of this embodiment are the same as those of Embodiment 2, except that the amount of modified nano-silica filler added is changed to 5 parts.

[0044] Example 3c The formulation and process of this embodiment are the same as those of Example 2, except that the amount of modified nano-silica filler added is changed to 8 parts. In Example 3c, the modified nano-silica filler is synthesized using the method of Example 1, but the reaction temperature is 180℃, and the specific surface area of ​​the obtained modified nano-silica filler is 620 m² / g.

[0045] Example 4 The modified nano-silica filler used in this embodiment is the same as in Example 1, except for the surface modification step. KH-560 is used as the modifier for the modified nano-silica filler. Using this modified nano-silica filler, a coating is prepared according to the formulation and process of Example 2.

[0046] Example 5 The A-component coating prepared in Example 2 was sealed and stored in a cool place. Samples were taken at 0, 3 and 6 months to check its sedimentation state. After re-stirring, the coating was made into a board and its salt spray resistance was tested to evaluate the industrial applicability of the product.

[0047] Comparative Example 1 (Blank Control Group) The formulation and preparation process are the same as in Example 2, the only difference being that no modified nano-silica filler is added.

[0048] Comparative Example 2: Coating using commercial nano silica The formulation and preparation process are the same as in Example 2, except that the modified nano-silica filler is replaced with an equal amount (3 parts) of commercially available fumed nano-silica (A200, specific surface area 200±25 m² / g). This commercial powder is used directly without special surface modification to produce the coating.

[0049] Comparative Example 3: Coating using conventional precipitation method for nano-silica The formulation and preparation process are the same as in Example 2, except that the modified nano-silica filler is replaced with an equal amount (3 parts) of commercially available nano-silica produced by precipitation. Before use, the powder is treated with the same KH-550 surface modification process as in Example 1 to obtain the coating.

[0050] Performance testing The coatings prepared in the above examples and comparative examples were used to make test samples under the same construction and curing conditions. The specific preparation method was to conduct the following performance tests, and the results are summarized in Table 1 and Table 2.

[0051] Table 1 Comparison of performance test results for coating components Table 2 Comparison of Residual Performance Test Results of Coatings Results analysis: 1. Compared with Comparative Example 1 (blank control): Example 2 shows a significant improvement in all key performance aspects. Salt spray resistance time is extended by more than double, adhesion, hardness, and abrasion resistance are significantly enhanced, and the cathode peel radius is greatly reduced, proving that the synergistic mechanism of physical shielding, cathodic protection, and interface enhancement constructed in this invention is highly effective.

[0052] 2. The coating of Example 2 using the nanomaterial of the present invention far surpasses the coating of Comparative Example 2 of commercial products in all key indicators such as adhesion, abrasion resistance, and long-term corrosion resistance.

[0053] 3. Compared with Comparative Example 3 (Commercial Precipitation Method) In contrast, even with the same surface modification, conventional precipitation-based SiO2 exhibits limited modification effects and final coating performance improvements due to uneven particle morphology, low specific surface area, and severe primary agglomeration, and also suffers from poor storage stability. This further highlights the unique advantages of the low-temperature molten salt synthesis process of this invention in obtaining nanomaterials with uniform particle size, high specific surface area, and good primary dispersion.

[0054] 4. After 6 months of storage, the product of Example 2 showed only slight sedimentation, was easy to stir and redisperse, and its performance did not decrease significantly after recoating, meeting the requirements for industrial production, storage and transportation.

[0055] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A nano-silica filler for use in anti-corrosion coatings, characterized in that, It is prepared by a low-temperature molten salt method and treated with a surface modifier; the low-temperature molten salt method includes the following steps: S1. Preparing a molten salt medium, wherein the molten salt medium is composed of one or more soluble inorganic salts; S2. Mix the silicon source, the molten salt medium, and the precipitant to obtain the reaction precursor; S3. The reaction precursor is reacted at 150℃~350℃ for 2~24 hours to generate nano-silica; S4. Cool the reaction product, dissolve and remove soluble salts, separate and dry to obtain the nano-silica filler.

2. The nano-silica filler as described in claim 1, characterized in that, The surface modifier is a silane coupling agent.

3. The nano-silica filler as described in claim 1 or 2, characterized in that, The nano-silica has a specific surface area of ​​200~800 m² / g, an average particle size of 10~100 nm, and a particle size distribution variation coefficient of <20%.

4. A nano-composite anti-corrosion coating, characterized in that, It comprises nano-silica filler, film-forming resin and anti-corrosion pigment as described in any one of claims 1-3.

5. The nanocomposite anticorrosive coating as described in claim 4, characterized in that, By mass fraction, the film-forming resin is 20-40 parts; the anti-corrosion pigment is 20-60 parts; and the nano-silica filler is 1-10 parts.

6. The nanocomposite anticorrosive coating as described in claim 4 or 5, characterized in that, The film-forming resin is epoxy resin; the anti-corrosion pigment is zinc powder.

7. The nanocomposite anticorrosive coating according to any one of claims 4 to 6, characterized in that, The coating is a two-component system, comprising component A and component B; Component A comprises the film-forming resin, the anti-corrosion pigment, the nano-silica filler, the solvent, and the additives, including dispersants, defoamers, and leveling agents. Component B is a curing agent that is compatible with the film-forming resin.

8. A method for preparing the nanocomposite anticorrosive coating as described in claim 7, characterized in that, The preparation of component A includes the following steps: 1) Mix the nano-silica filler, solvent, dispersant and part of the film-forming resin, and pre-disperse them; 2) Grind the pre-dispersed slurry until the fineness is ≤30μm; 3) Add the remaining film-forming resin, anti-corrosion pigments and other additives to the ground slurry, stir evenly, and obtain coating component A; Before construction, mix component A and component B, and allow them to mature before use.

9. The method as described in claim 8, characterized in that, The pre-dispersion mentioned in step 1) is high-speed stirring dispersion, with a rotation speed of 1000~1500 r / min and a time of 15~30 minutes; the grinding mentioned in step 2) is sand milling or ball milling.

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