A modified phenoxy resin cold spray zinc coating, its preparation method and application

Abstract

This invention belongs to the field of coating technology and discloses a modified phenoxy resin cold-spray zinc coating, its preparation method, and its application. The modified phenoxy resin cold-spray zinc coating comprises the following components: phenoxy resin, styrene-acrylonitrile copolymer, polymethyl silicate hydrolytic condensate, zinc powder, and solvent; the mass ratio of zinc powder to phenoxy resin is (80-88):(1.6-2.5). In this modified phenoxy resin cold-spray zinc coating, the styrene-acrylonitrile copolymer modifies the phenoxy resin, effectively improving the dispersion of zinc powder in the coating. This ensures that the high-density zinc powder remains stably suspended in the coating without sedimentation, and during film formation, the zinc powder is evenly distributed, thus forming an excellent, stable, and blind-spot-free cathodic protection network on the coating surface, resulting in excellent salt spray resistance. The polymethyl silicate hydrolytic condensate undergoes a complexation reaction with the zinc powder, resulting in excellent resistance to rain streaks and blooming of the coating.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a modified phenoxy resin cold spray zinc coating, its preparation method, and its application. Background Technology

[0002] Existing protective coatings and primers for heavy-duty corrosion protection in the steel structure industry widely adopt epoxy zinc-rich coatings and inorganic zinc-rich coatings. Theoretically, the higher the zinc content in the coating, the better the cathodic protection effect and the better the corrosion resistance.

[0003] Epoxy zinc-rich coatings are two-component coatings that use bisphenol A epoxy resin as a binder for zinc powder and typically employ amine curing agents. The active hydrogen atoms on the nitrogen atoms of primary and secondary amines open the epoxy groups, causing cross-linking and curing. Because its film-forming mechanism is reactive cross-linking, there is a shelf life issue. Generally, the shelf life of epoxy zinc-rich coatings is 4 hours. Beyond this period, the viscosity of the epoxy zinc-rich coating system increases sharply, and its performance deteriorates drastically, rendering it unusable. The national standard for epoxy zinc-rich coatings specifies a zinc content of 70%, with the remaining 30% consisting of film-forming resin, curing agent, additives, and other relatively insulating materials. Zinc powder in contact with the steel substrate forms a conductive path, providing cathodic protection. However, zinc powder particles dispersed within the coating and encapsulated by insulating materials, not in direct contact with the substrate, do not undergo galvanic cell reactions, leading to a reduction in the coating's anti-corrosion performance.

[0004] Inorganic zinc-rich coatings are two-component coatings that use ethyl silicate hydrolysate prepolymer as the film-forming material. Through the bonding of zinc powder and the substrate, they form zinc-silica-zinc and zinc-silica-iron composites, tightly covering the steel surface. Together with the electrochemical action of the zinc powder, they provide excellent protection for the steel. The standard zinc content of the dry film in inorganic zinc-rich coatings is generally 80%. The ethyl silicate hydrolysate prepolymer film-forming material is purely inorganic, resulting in poor flexibility, adhesion, and density. Polyvinyl butyral (PVB) is often added to improve flexibility and adhesion. However, because PVB has a high viscosity, it emits significant amounts of VOCs during production and application, causing air pollution. The application of inorganic zinc-rich coatings also has strict requirements regarding humidity, film thickness, and substrate cleanliness; improper process control can easily lead to paint film defects. Practice has shown that once inorganic zinc-rich coatings develop defects such as cracking, peeling, blistering, pinholes, or softening, the impact is often very wide, with a rework rate of over 90%, which has a significant impact on coating costs and product delivery cycles.

[0005] In recent years, with the development of science and technology, new materials and technologies have emerged in the field of industrial heavy-duty corrosion protection. The high performance and ease of application of zinc-rich coatings have become an important direction and research hotspot for the development of industrial anti-corrosion coatings. Cold-sprayed zinc coatings have been widely used in industrial corrosion protection in recent years due to their technological advantages, but they have also exposed many problems. For example, conventional cold-sprayed zinc coatings cannot be stored for too long; after 90 days, high-density zinc powder will deposit at the bottom of the container, forming hard sediment, indicating poor storage stability. After conventional cold-sprayed zinc coatings are exposed to rain, the zinc powder reacts with the rainwater to produce a large amount of zinc hydroxide. This zinc hydroxide absorbs the surrounding rainwater, forming a viscous white paste. During the drying process, the zinc hydroxide reacts with carbon dioxide to form zinc carbonate, which then discolors into a solid white zinc salt, causing the coating to turn white and mottled. Conventional cold-sprayed zinc coatings often use thermoplastic acrylic resin as the main film-forming material, and when the pigment-to-binder ratio exceeds a critical value, the coating is prone to detaching from the substrate.

[0006] Therefore, there is an urgent need to provide a new zinc coating that has good storage stability, as well as good anti-corrosion and film-forming properties. Summary of the Invention

[0007] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a modified phenoxy resin cold-spray zinc coating, its preparation method, and its application. In the modified phenoxy resin cold-spray zinc coating of this invention, the styrene-acrylonitrile copolymer modifies the phenoxy resin, effectively improving the dispersion of zinc powder in the coating. This ensures that the high-density zinc powder is stably suspended in the coating without sedimentation, and during film formation, the zinc powder can be evenly arranged, thereby forming an excellent, stable, and blind-spot-free cathodic protection network on the coating surface, resulting in excellent salt spray resistance. The polymethyl methacrylate hydrolytic condensate undergoes a complexation reaction with the zinc powder, inhibiting rapid oxidation of the zinc powder. The zinc powder coating does not form white spots after rain, resulting in excellent resistance to rain streaks and blooming.

[0008] The modified phenoxy resin cold-spray zinc coating of this invention addresses some shortcomings of existing technologies, such as the relatively low zinc content of epoxy zinc-rich coatings, which cannot form a complete conductive path to ensure that all zinc powders play the role of sacrificial anode to protect the cathode; the high VOC (volatile organic compound) content and low volume solids content of alcohol-soluble inorganic zinc-rich primers, which require high requirements for the on-site coating environment and coating process during construction, and are prone to paint film defects if the process is not properly controlled; and the defects of conventional cold-spray zinc coatings, such as easy precipitation during storage, whitening and mottling of the coating when exposed to rain, and poor coating adhesion.

[0009] A first aspect of the present invention provides a modified phenoxy resin cold spray zinc coating.

[0010] Specifically, a modified phenoxy resin cold spray zinc coating comprises the following components: phenoxy resin, styrene-acrylonitrile copolymer, polymethyl methacrylate hydrolysate condensate, zinc powder, and solvent;

[0011] The mass ratio of zinc powder to phenoxy resin is (80-88):(1.6-2.5).

[0012] Preferably, a modified phenoxy resin cold-spray zinc coating comprises, by weight parts: 1.6-2.0 parts phenoxy resin, 0.6-1.8 parts styrene-acrylonitrile copolymer, 0.1-0.8 parts hydrolyzed polymethyl methacrylate condensate, 80-88 parts zinc powder, and 10-20 parts solvent. Appropriate selection of each component can yield a coating with better performance.

[0013] A further preferred embodiment of the modified phenoxy resin cold spray zinc coating comprises, by weight parts, the following components: 1.6-2.0 parts of phenoxy resin, 0.8-1.2 parts of styrene-acrylonitrile copolymer, 0.2-0.3 parts of polymethyl silicate hydrolysate condensate, 80-83 parts of zinc powder, and 12-15 parts of solvent.

[0014] Preferably, the phenoxy resin is a thermoplastic epoxy resin obtained by reacting bisphenol A and epichlorohydrin. Phenoxy resin contains a large amount of hydroxyl groups, resulting in a paint film (or coating) with high adhesion to the metal substrate, capable of supporting zinc powder, and providing excellent paint film flexibility.

[0015] Preferably, the weight-average molecular weight of the phenoxy resin is 25,000-70,000, and more preferably 25,000-60,000.

[0016] Preferably, the phenoxy resin contains a polyhydroxy ether structure of α-ethylene glycol.

[0017] Preferably, the zinc powder contains more than 99.5% zinc by mass and more than 97% metallic zinc.

[0018] Preferably, the zinc powder has a mesh size of at least one of 500-600 mesh, 700-800 mesh, and 900-1000 mesh.

[0019] Preferably, the solvent is an organic solvent, and more preferably cyclohexanone. Cyclohexanone is a strong solvent with excellent solubility for phenoxy resins, which improves the adhesion of the paint film and reduces the viscosity of the coating. Its slow evaporation rate results in a smooth and aesthetically pleasing paint film.

[0020] Preferably, the styrene-acrylonitrile copolymer is a solid resin with amino functional groups in its structure, which can generate a large number of hydrogen bonds. The association of hydrogen bonds can form a thixotropic effect.

[0021] The styrene-acrylonitrile copolymer used has a very large molecular weight and extremely high thixotropy, which effectively improves the dispersion of zinc powder in the coating. During storage, it can effectively fix the zinc powder, so that the high-density zinc powder is stably suspended in the coating without settling. During construction and spraying, it prevents the zinc powder coating from sagging and ensures that the zinc powder is evenly arranged during film formation.

[0022] Preferably, the molecular formula of the polymethyl silicate hydrolysate condensate is C 10 H 30 O 13 Si4 has a molecular weight of 470.68.

[0023] The polymethyl silicate hydrolytic condensate used imparts low surface tension and excellent hydrophobic properties to the coating. During the drying and film formation process, the alkoxy groups in the polymethyl silicate hydrolytic condensate absorb moisture from the air and undergo hydrolysis. This generates methyl silicate oligomers containing certain hydroxyl groups, which undergo a complexation reaction with zinc powder, inhibiting the rapid oxidation of zinc powder. This prevents the zinc-rich coating from developing common defects such as black spots and uneven color when exposed to outdoor rain.

[0024] More preferably, the SiO2 mass fraction content in the polymethyl silicate hydrolysate condensate is 51%.

[0025] Preferably, the preparation process of the polymethyl silicate hydrolysate condensate is as follows:

[0026] (1) Take 180-185 parts by weight of methyl silicate and put it into a container (e.g., a three-necked flask);

[0027] (2) Add 90-100 parts by weight of isopropanol while stirring, stir and heat to 32-35℃, and keep warm;

[0028] (3) Prepare a mixture consisting of 0.8-1.1 parts by mass of hydrochloric acid, 1.5-1.6 parts by mass of zinc chloride, and 25-27 parts by mass of deionized water. Add the mixture dropwise to the container in step (1) and control the temperature of the material in the container to ≤55℃.

[0029] (4) After the dropwise addition is complete, keep the temperature at 45-55℃ and stir for 1-2 hours;

[0030] (5) After the heat preservation is completed, the product is tested after standing for 3-4 hours. The product gels within 10-15 minutes to obtain polymethyl silicate condensate.

[0031] Preferably, a modified phenoxy resin cold spray zinc coating comprises, by weight parts, the following components: 1.6-2.0 parts of phenoxy resin, 0.8-1.2 parts of styrene-acrylonitrile copolymer, 0.2-0.3 parts of polymethyl silicate hydrolysate condensate, 80-83 parts of zinc powder, and 12-15 parts of cyclohexanone.

[0032] The zinc powder used is more reactive than iron and readily loses electrons. In the early stages of corrosion, the zinc powder and the steel substrate form a galvanic cell. Zinc has a more negative electrode potential than iron, acting as the anode (often called a sacrificial anode) and iron as the cathode. Current flows from zinc to iron, thus providing cathodic protection to the steel substrate. In the later stages of corrosion, the zinc powder is continuously corroded during the coating's service life. Corrosion products, namely basic zinc carbonate, commonly known as "white rust," are deposited in the gaps between the zinc powder and on the steel surface. This dense, non-conductive, and sparingly soluble compound acts as a barrier against corrosive media, providing corrosion protection.

[0033] A second aspect of the present invention provides a method for preparing a modified phenoxy resin cold spray zinc coating.

[0034] Specifically, a method for preparing a modified phenoxy resin cold-spray zinc coating includes the following steps:

[0035] The components are mixed to obtain the modified phenoxy resin cold spray zinc coating.

[0036] Preferably, the preparation method includes the following steps:

[0037] Add solvent to a container, add phenoxy resin while stirring at a constant speed, and disperse at high speed until the solid phenoxy resin dissolves and the solution is transparent and free of particles. While stirring at a constant speed, add styrene-acrylonitrile copolymer and disperse at high speed for 20-30 minutes until the solid styrene-acrylonitrile copolymer is completely dissolved and the resin liquid is in the form of a paste. While stirring at a constant speed, add zinc powder and disperse at high speed for 20-30 minutes until the fineness is ≤30μm. Purge nitrogen into the container, add polymethyl silicate hydrolysis condensate while stirring at a constant speed, stir for 5-10 minutes, filter, and discharge to obtain the modified phenoxy resin cold spray zinc coating.

[0038] A method for applying a modified phenoxy resin cold spray zinc coating includes the following steps:

[0039] During construction, modified phenoxy resin cold spray zinc coating is applied to the metal substrate, and after drying, a modified phenoxy resin cold spray zinc coating is obtained.

[0040] Preferably, the coating method includes any one of roller coating, spray coating, and brush coating.

[0041] A third aspect of the present invention provides an application of a modified phenoxy resin cold spray zinc coating.

[0042] Specifically, the above-mentioned modified phenoxy resin cold spray zinc coating is used in the field of corrosion protection.

[0043] Preferably, the application is in the field of corrosion protection for metal equipment.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) The styrene-acrylonitrile copolymer in the modified phenoxy resin cold spray zinc coating of the present invention can modify the phenoxy resin, effectively improve the dispersion of zinc powder in the coating, so that the high specific gravity zinc powder is stably suspended in the coating without precipitation, and can make the zinc powder evenly arranged during the film formation process, thereby forming an excellent, stable, and blind spot-free cathodic protection network on the coating surface, and the coating has excellent salt spray resistance; the polymethyl silicate hydrolysis condensate reacts with the zinc powder to inhibit the rapid oxidation of zinc powder, and the zinc powder coating will not generate white spots after rain, so the coating has excellent anti-rain streaking and anti-blooming performance.

[0046] (2) The modified phenoxy resin cold spray zinc coating of this invention is not limited by environment, equipment, or site, making construction more convenient. It is mainly composed of zinc powder with a purity higher than 99.9%, volatile solvent, and organic film-forming resin. Compared with other two-component zinc-rich coatings, this invention is a single-component coating with no shelf life limitation. The modified phenoxy resin cold spray zinc coating has a higher zinc content, with the dry film containing more than 95% metallic zinc, and the coating resistance is extremely low, down to 10 ohms. 3 With a viscosity of Ω·cm, it exhibits excellent cathodic protection. Its main film-forming material is ultra-high molecular weight phenoxy resin and styrene-acrylonitrile copolymer. The phenoxy resin imparts excellent adhesion, durability, and solvent resistance to the coating. The styrene-acrylonitrile copolymer's molecular chemical structure contains amino groups that form a three-dimensional network structure through hydrogen bonding. This structure is disrupted under shear stress, resulting in a mobile phase. When the shear force is removed, the three-dimensional structure of the hydrogen bonds recovers, increasing the system viscosity and effectively improving the dispersion of zinc powder in the coating. This ensures that the high-density zinc powder remains stably suspended in the coating without sedimentation, and the zinc powder is evenly distributed during film formation. This results in a superior, stable, and spotless cathodic protection network on the coating surface, providing excellent salt spray resistance. The introduction of polymethyl methacrylate condensate polymers enhances the coating's resistance to rain streaks and blooming. Its coating properties also meet the performance requirements of the "JT / T 1266-2019 Technical Conditions for Cold Spray Zinc Anti-corrosion of Bridge Steel Structures" for cold spray zinc coatings. Detailed Implementation

[0047] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0048] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0049] The model numbers of some components used in the following examples or comparative examples are shown in Table 1 below.

[0050] Table 1

[0051]

[0052] The preparation process of polymethyl silicate hydrolysate condensate is as follows:

[0053] (1) Take 185 parts by weight of methyl silicate and put it into a container (e.g., a three-necked flask);

[0054] (2) Add 100 parts by weight of isopropanol to the container in step (1) while stirring, stir and heat to 35°C, and keep warm;

[0055] (3) Prepare a mixture consisting of 1.1 parts by mass of hydrochloric acid, 1.6 parts by mass of zinc chloride, and 27 parts by mass of deionized water. Add the mixture dropwise to the container in step (1) and control the temperature of the material in the container to ≤55℃.

[0056] (4) After the addition is complete, keep the temperature at 55℃ and stir for 2 hours;

[0057] (5) After the heat preservation is completed, the product is tested after standing for 4 hours. The product gels within 10-15 minutes to obtain polymethyl silicate condensate.

[0058] Example 1

[0059] A modified phenoxy resin cold spray zinc coating comprises the following components by mass parts: 1.6 parts of phenoxy resin YP-50S, 0.9 parts of styrene-acrylonitrile copolymer, 0.2 parts of polymethyl silicate hydrolysate condensate, 81 parts of 600-mesh zinc powder, and 12 parts of cyclohexanone.

[0060] A method for preparing a modified phenoxy resin cold spray zinc coating includes the following steps:

[0061] Add cyclohexanone to the reactor according to the formula, and add phenoxy resin YP-50S under uniform stirring. Disperse at high speed (500 rpm) until the solid phenoxy resin is dissolved and the solution is clear and free of particles. Add styrene-acrylonitrile copolymer while maintaining uniform stirring, and disperse at high speed for 30 minutes until the solid styrene-acrylonitrile copolymer is completely dissolved and the resin liquid is in the form of a paste. Add 600-mesh zinc powder while maintaining uniform stirring, and disperse at high speed for 30 minutes until the fineness is ≤30μm. Purge the reactor with nitrogen gas, and add polymethyl silicate hydrolysate condensate under nitrogen protection while maintaining uniform stirring. Stir at medium speed (100 rpm) for 10 minutes, filter and discharge to obtain modified phenoxy resin cold spray zinc coating.

[0062] Example 2

[0063] A modified phenoxy resin cold spray zinc coating comprises the following components by mass parts: 1.6 parts of phenoxy resin JER-1256, 1.2 parts of styrene-acrylonitrile copolymer, 0.2 parts of polymethyl silicate hydrolysate condensate, 82 parts of zinc powder (42 parts of 600 mesh zinc powder and 40 parts of 1000 mesh zinc powder), and 15 parts of cyclohexanone.

[0064] A method for preparing a modified phenoxy resin cold spray zinc coating includes the following steps:

[0065] Add cyclohexanone to the reactor according to the formula, and add phenoxy resin JER-1256 under uniform stirring. Disperse at high speed (500 rpm) until the solid phenoxy resin is dissolved and the solution is clear and free of particles. Add styrene-acrylonitrile copolymer while maintaining uniform stirring, and disperse at high speed for 30 min until the solid styrene-acrylonitrile copolymer is completely dissolved and the resin liquid is paste-like. Add zinc powder while maintaining uniform stirring, and disperse at high speed for 30 min until the fineness is ≤30μm. Purge the reactor with nitrogen gas, and add polymethyl silicate hydrolysate condensate under nitrogen protection while maintaining uniform stirring. Stir at medium speed (100 rpm) for 10 minutes, filter and discharge to obtain modified phenoxy resin cold spray zinc coating.

[0066] Example 3

[0067] A modified phenoxy resin cold spray zinc coating comprises the following components by mass parts: 2 parts phenoxy resin PKHA, 1.2 parts styrene-acrylonitrile copolymer, 0.3 parts polymethyl silicate hydrolysate condensate, 82 parts zinc powder (42 parts 800 mesh zinc powder and 40 parts 1000 mesh zinc powder), and 15 parts cyclohexanone.

[0068] A method for preparing a modified phenoxy resin cold spray zinc coating includes the following steps:

[0069] Add cyclohexanone to the reactor according to the formula, and add phenyl oxy ketone (PKHA) resin while stirring at a constant speed. Disperse at high speed (500 rpm) until the solid phenyl oxy ketone resin is dissolved and the solution is clear and free of particles. Add styrene-acrylonitrile copolymer while stirring at a constant speed, and disperse at high speed for 30 minutes until the solid styrene-acrylonitrile copolymer is completely dissolved and the resin solution is paste-like. Add 600-mesh zinc powder while stirring at a constant speed, and disperse at high speed for 30 minutes until the fineness is ≤30μm. Purge the reactor with nitrogen gas, and add polymethyl methacrylate hydrolysate condensate under nitrogen protection while stirring at a constant speed. Stir at medium speed (100 rpm) for 10 minutes, filter and discharge to obtain the modified phenyl oxy ketone resin cold spray zinc coating.

[0070] Comparative Example 1

[0071] A conventional method for preparing cold-sprayed zinc coatings includes the following steps:

[0072] Add 20 parts by weight of W770 cold spray zinc resin from Wuhan Modern Company to the reactor according to the formula, add 80 parts by weight of 800 mesh zinc powder while stirring at a uniform speed, disperse at high speed for 30 minutes until the fineness is ≤30μm, filter and discharge to obtain conventional cold spray zinc coating.

[0073] Comparative Example 2

[0074] An epoxy zinc-rich coating comprises a main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is 10:1.

[0075] The preparation method of epoxy zinc-rich coating includes the following steps:

[0076] Preparation of the main agent: Add 17 parts by weight of 601-75 epoxy resin from Jiangsu Sanmu Chemical Co., Ltd. to a kettle according to the formula amount, add 3 parts by weight of polyamide wax slurry under uniform stirring, disperse at high speed for 10 minutes until there are no obvious particles in the resin liquid, add 70 parts by weight of 600 mesh zinc powder while maintaining uniform stirring, disperse at high speed for 30 minutes until the fineness is ≤30μm, filter and discharge to obtain the epoxy zinc-rich coating main agent.

[0077] Preparation of curing agent: Add 80 parts by weight of polyamide curing agent and 20 parts by weight of xylene to the kettle according to the formula, disperse at medium speed for 10 minutes until the solution is mixed evenly and transparent, filter and discharge to obtain curing agent.

[0078] During construction, the main agent and curing agent are mixed and stirred evenly at a mass ratio of 10:1 to obtain epoxy zinc-rich coating.

[0079] Comparative Example 3

[0080] An inorganic zinc-rich coating comprises a main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is 5:1.

[0081] A method for preparing an inorganic zinc-rich coating includes the following steps:

[0082] Preparation of the main agent: Add 25 parts by weight of PVB (polyvinyl butyral) resin liquid with a solid content of 17% to the kettle according to the formula. Add 3 parts by weight of polyamide wax slurry while stirring at a constant speed. Disperse at high speed for 10 minutes until there are no obvious particles in the resin liquid. Add 80 parts by weight of 600 mesh zinc powder while stirring at a constant speed. Disperse at high speed for 30 minutes until the fineness is ≤30μm. Filter the material to obtain the inorganic zinc-rich coating main agent.

[0083] The curing agent is a commercially available ethyl silicate hydrolysate solution with a solid content of 22%. During construction, the main agent and curing agent are mixed and stirred evenly at a mass ratio of 5:1 to obtain an inorganic zinc-rich coating.

[0084] Comparative Example 4

[0085] The phenoxy resin in Example 1 of this invention was replaced with an equal amount of epoxy resin, while the remaining components and preparation process remained the same.

[0086] Because epoxy resin has a low TG point (glass transition temperature), it usually exists in liquid form and needs to react with a curing agent to crosslink and cure into a film, making it impossible to make a single-component coating. Zinc powder coatings prepared without curing agents have poor salt spray resistance and blistering occurs after 200 hours. Bisphenol A epoxy resin has a weight-average molecular weight of 350-1500, which is much lower than that of phenyl oxy resin (25000-60000). The small amount of bisphenol A epoxy resin added is insufficient to bond the zinc powder in the coating, resulting in poor adhesion when the coating is pulled apart.

[0087] Comparative Example 5

[0088] The styrene-acrylonitrile copolymer in Example 1 of this invention was replaced with an acrylonitrile-butadiene-styrene copolymer, while the remaining components and preparation process remained the same.

[0089] Because the amino group in the molecular structure of acrylonitrile-butadiene-styrene copolymer is cross-linked and shielded, it cannot form hydrogen bond complexes in the liquid phase after dissolution, and therefore has no thixotropic effect. As a result, the zinc powder coating made from it is very prone to settling at the bottom and forming a hard precipitate. Furthermore, since acrylonitrile-butadiene-styrene copolymer is an elastic plastic, the zinc powder coating prepared from it has very poor adhesion to metal substrates.

[0090] Comparative Example 6

[0091] The polymethyl silicate hydrolysate condensate in Example 1 of this invention is replaced with polyethyl silicate hydrolysate condensate, while the remaining components and preparation process are the same.

[0092] Because the methoxy groups in methyl silicate are much more reactive than the ethoxy groups in ethyl silicate, the polymethyl silicate condensate solidifies rapidly during the hydrolysis-condensation curing reaction, resulting in a significant difference in the drying time of the coatings. The coating prepared in Example 1 can be dried and hardened in 50 minutes at 25°C and 60% air humidity, while the coating in Comparative Example 6 cannot be dried and hardened in 130 minutes. It cannot quickly undergo a complexation reaction with zinc powder in the air, and it also affects the flexibility and resistance to rain and blooming of the paint film.

[0093] Product effectiveness test

[0094] The coatings prepared in the above examples and comparative examples were tested for neutral salt spray resistance, pull-out adhesion, flexibility, pot life, and resistance to rain-induced blooming. The results are shown in Table 2.

[0095] The examples and comparative examples were prepared to test the coating performance. For the neutral salt spray resistance and pull-off adhesion test, the substrate was a 150*70*5mm sandblasted steel plate with a sandblasting cleanliness of Sa2.5 and a film thickness of 80-100μm. For the flexibility test, the substrate was a 150*70*5*0.2mm tinplate with a film thickness of 21-25μm after thorough sanding with 400-grit sandpaper. For the rain resistance and colorfastness test, the substrate was a 400mm*400mm*1mm carbon steel plate with a film thickness of 90μm after thorough sanding with 400-grit sandpaper.

[0096] The resistance of the coating to neutral salt spray was tested according to GB / T 1771.

[0097] The pull-off adhesion properties of the coating were tested according to the method of GB / T 5210;

[0098] The flexibility properties of the coating were tested according to GB / T 1731.

[0099] The pot life performance of the coating was tested according to the method of GB / T 31416;

[0100] The storage stability of the coating was tested according to GB 6753.3.

[0101] The test for the resistance of coating to rain blooming involves placing the test panel in a rain test chamber and taking it out after 168 hours to observe the changes in the appearance of the coating, whether there are white zinc salt spots seeping out, and whether the paint film has obvious blooming.

[0102] Table 2

[0103]

[0104]

[0105] As can be seen from Table 2, the coating prepared in the embodiments of the present invention has significantly better neutral salt spray resistance and pull-out adhesion than the coatings in the comparative examples.

[0106] Moreover, it can be seen from Table 2 that (1) the coating formed by the modified phenoxy resin cold spray zinc coating of the present invention has excellent salt spray resistance, and the salt spray resistance can reach more than 8000h.

[0107] (2) The modified phenoxy resin cold spray zinc coating of the present invention has excellent adhesion, and the pull-out adhesion can reach more than 8MPa.

[0108] (3) The modified phenoxy resin cold spray zinc coating of the present invention has excellent flexibility, with a flexibility of 1 mm passing.

[0109] (4) Compared with traditional two-component zinc-rich coatings, the modified phenoxy resin cold spray zinc coating of the present invention is a single-component coating with no applicable period.

[0110] (5) The modified phenoxy resin cold spray zinc coating of the present invention has excellent thermal storage stability compared with traditional two-component zinc-rich coatings and conventional cold spray zinc coatings, with a sedimentation level of 10.

[0111] (6) The modified phenoxy resin cold spray zinc coating of the present invention has superior resistance to rain and blooming compared with conventional cold spray zinc coating.

[0112] The above embodiments are merely examples to clearly illustrate the technical solutions of the present invention, and are not intended to limit the specific implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A modified phenoxy resin cold spray zinc coating, characterized in that, By weight, it includes the following components: 1.6-2.0 parts phenoxy resin, 0.8-1.2 parts styrene-acrylonitrile copolymer, 0.2-0.3 parts polymethyl silicate hydrolysate condensate, 80-83 parts zinc powder, and 12-15 parts cyclohexanone; The preparation process of the polymethyl silicate hydrolysate condensate is as follows: (1) Take 180-185 parts by weight of methyl silicate and put it into a container; (2) Add 90-100 parts by weight of isopropanol while stirring, stir and heat to 32-35℃, and keep warm; (3) Prepare a mixture. The mixture consists of 0.8-1.1 parts by mass of hydrochloric acid, 1.5-1.6 parts by mass of zinc chloride, and 25-27 parts by mass of deionized water. Add the mixture dropwise to the container in step (1) and control the temperature of the material in the container to ≤55℃. (4) After the addition is complete, keep the mixture at 45-55℃ and stir for 1-2 hours; (5) After the heat preservation is completed, the product is tested after standing for 3-4 hours. The product gels within 10-15 minutes to obtain polymethyl silicate condensate.

2. The modified phenoxy resin cold spray zinc coating according to claim 1, characterized in that, The weight-average molecular weight of the phenoxy resin is 25,000-70,000.

3. The modified phenoxy resin cold spray zinc coating according to claim 1, characterized in that, The zinc powder contains more than 99.5% zinc by mass and more than 97% metallic zinc.

4. The modified phenoxy resin cold-spray zinc coating according to any one of claims 1-3, characterized in that, The zinc powder has a mesh size of at least one of 500-600 mesh, 700-800 mesh, and 900-1000 mesh.

5. The method for preparing the modified phenoxy resin cold spray zinc coating according to any one of claims 1-4, characterized in that, Includes the following steps: The components are mixed to obtain the modified phenoxy resin cold spray zinc coating.

6. The method of using the modified phenoxy resin cold-spray zinc coating according to any one of claims 1-4, characterized in that, Includes the following steps: During construction, the modified phenoxy resin cold spray zinc coating is applied to the metal substrate, and after drying, the modified phenoxy resin cold spray zinc coating is obtained.

7. The application of the modified phenoxy resin cold spray zinc coating according to any one of claims 1-4 in the field of corrosion protection.

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