Corrosion-resistant and weather-resistant powder coating as well as preparation method and application thereof

Abstract

The invention provides an anti-corrosion and weather-resistant powder coating as well as a preparation method and application thereof. The anti-corrosion and weather-resistant powder coating comprises a base powder coating for providing anti-corrosion performance and a flour coating for providing weather-resistant performance, the base powder coating comprises the following raw materials in parts by weight: 54-60 parts of polyester resin, 4-5.5 parts of a TGIC curing agent, 1.5-3 parts of a conductive intermediate and 10-30 parts of zinc powder; the flour coating comprises the following raw materials in parts by weight: 55-65 parts of polyester resin and 4-5.8 parts of a TGIC curing agent; wherein the conductive intermediate is a mixture of a hydroxyl trimethoxy polymer, a carbon nanotube, graphene and quartzite which are subjected to pre-dispersion treatment, and the mass ratio of the hydroxyl trimethoxy polymer to the carbon nanotube to the graphene to the quartzite is 100: (0.2-0.5): (0.3-0.8): 100. The corrosion-resistant and weather-resistant powder coating is coated on a base material by adopting a two-coating and one-baking process, and a formed corrosion-resistant and weather-resistant composite coating has excellent corrosion resistance, meets the use requirements of an environment with a corrosion grade of C5 or above to the maximum extent, and has excellent performances such as salt mist resistance, damp heat resistance and boiling resistance and good adhesive force and impact toughness.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder coatings, and specifically includes an anti-corrosion and weather-resistant powder coating, a preparation method thereof, and an application thereof. Background Art

[0002] As a new type of 100% solid powder coating, powder coatings have characteristics such as low VOC, recyclability, high powder adhesion rate, environmental protection and energy saving, and high mechanical properties of the coating film, and are gradually recognized by more industries. In many special fields, powder coatings have more functional options compared to liquid coatings, and can effectively solve the VOC problems that occur during the coating process and improve the overall performance of the coating. Powder composite coatings are mainly applied to environments with a C4 corrosion grade such as being outdoors, by the sea, in a mine cave for a long time. By using a structure composed of a bottom layer of pure epoxy powder coating primer and a top layer of pure polyester powder coating to form an anti-corrosion and weather-resistant composite coating, the protection of the substrate is achieved. This anti-corrosion and weather-resistant composite coating not only has excellent adhesion, anti-permeation and cathodic disbondment resistance properties of pure epoxy powder coatings, but also can provide good weather resistance. However, due to the large differences in the reactions of various active groups during the curing of the pure epoxy system and the pure polyester system, simultaneous curing cannot be achieved, and the coating process of the composite coating must be realized through separate spraying and curing, that is, two-coat two-bake. The operation is relatively cumbersome. In addition, due to the generally high insulation of powder coatings, the bottom powder coating is poorly charged during the application of the top coat, which increases the difficulty of powder adhesion to the top coat. In addition, for environments with a corrosion grade above C5, even if the bottom and top coatings of different resin systems are prepared using the two-coat two-bake process, the actual anti-corrosion still cannot meet the application requirements of environments with a corrosion grade above C5.

[0003] In the prior art, for anti-corrosion above the C5 level, the bottom layer is mainly prepared by a galvanizing process or using a zinc-rich primer, and then the top layer is prepared using fluorocarbon paint or weather-resistant powder coatings. A primary battery is formed between the metallic zinc in the galvanized layer or zinc-rich primer and the substrate, and finally the anti-corrosion protection effect of the substrate is obtained. Since the galvanized layer used is a pure zinc structure, and the dry film zinc content of the zinc-rich primer is generally not less than 70%, a large amount of zinc powder is wasted during preparation, and it is also affected by VOC. In addition, due to the relatively low resin content of the zinc-rich primer, the basic physical properties and adhesion of the bottom layer are poor, and it cannot provide good performance support for the coating system.

[0004] Therefore, there are still relatively few coating compositions that can be applied to environments with a corrosion grade above C5, and it is difficult to meet the requirements of actual applications. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the first object of the present invention is to provide an anti-corrosion and weather-resistant powder coating. The anti-corrosion and weather-resistant powder coating includes a base powder coating and a top powder coating having the same resin system. Among them, the base powder coating can form a conductive path and a primary battery structure when the zinc powder content is not higher than 35 wt%, reducing the consumption of zinc-based raw materials and meeting the usage requirements for environments with a corrosion grade above C5. Combined with the excellent weather resistance of the top powder coating, it can ultimately meet the requirements of practical applications.

[0006] The second object of the present invention is to provide a method for preparing the anti-corrosion and weather-resistant powder coating as described above.

[0007] The third object of the present invention is to provide an application of the anti-corrosion and weather-resistant powder coating in the painting of transportation tools as described above.

[0008] The fourth object of the present invention is to provide an anti-corrosion and weather-resistant composite coating.

[0009] To achieve the above first object, the technical solution adopted by the present invention includes:

[0010] The present invention discloses an anti-corrosion and weather-resistant powder coating, comprising a base powder coating providing anti-corrosion performance and a top powder coating providing weather resistance;

[0011] The base powder coating contains the following raw materials in parts by weight: 54 - 60 parts of polyester resin, 4 - 5.5 parts of TGIC curing agent, 1.5 - 3 parts of conductive intermediate, and 10 - 30 parts of zinc powder;

[0012] The top powder coating contains the following raw materials in parts by weight: 55 - 65 parts of polyester resin and 4 - 5.8 parts of TGIC curing agent;

[0013] Among them, the conductive intermediate is a mixture of pre-dispersed hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone, and their mass ratio is 100:0.2 - 0.5:0.3 - 0.8:100.

[0014] Further, in the conductive intermediate, the mass ratio of hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone is 100:0.3:0.5:100.

[0015] Further, the polyester resin in the base powder coating and the top powder coating is an outdoor polyester resin.

[0016] Further, the graphene is single-layer graphene, with a specific surface area ≥ 2500 m 2 / g and a particle structure thickness of 0.3 - 0.5 nm; the carbon nanotubes are single-walled carbon nanotubes, with an aspect ratio > 10000 and a particle structure tube diameter of 1 - 2 nm.

[0017] Further, the steps of the pre-dispersion treatment are as follows:

[0018] Mix the hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone in proportion, and perform stirring pre-dispersion through a high-speed mixer. After stirring for 5 - 8 minutes, it is obtained.

[0019] Further, the particle size of the anti-corrosion and weather-resistant powder coating is 35 - 45 μm, that is, the particle sizes of both the base powder coating and the flour coating are 35 - 45 μm.

[0020] Further, by weight, the base powder coating further comprises 1.5 - 3 parts of a leveling and wetting aid;

[0021] 1 - 10 parts of a pigment; and

[0022] 1.2 - 34 parts of a filler;

[0023] The flour coating further comprises 1.5 - 3 parts of a leveling and wetting aid;

[0024] 1 - 20 parts of a pigment; and

[0025] 5 - 34 parts of a filler.

[0026] To achieve the above second object, the technical solution adopted by the present invention includes:

[0027] The present invention discloses a preparation method of the anti-corrosion and weather-resistant powder coating as described above, including the following steps:

[0028] Mix the raw materials of the base powder coating in the formula amount evenly to obtain the base powder raw material, then put the base powder raw material into a twin-screw extruder and melt-extrude it at 90 - 105 °C. After pressing into sheets and cooling, it is crushed and sieved to obtain the base powder coating;

[0029] Mix the raw materials of the flour coating in the formula amount evenly to obtain the flour raw material, then put the flour raw material into a twin-screw extruder and melt-extrude it at 90 - 105 °C. After pressing into sheets and cooling, it is crushed and sieved to obtain the flour coating.

[0030] To achieve the above third object, the technical solution adopted by the present invention includes:

[0031] The present invention discloses an application of the anti-corrosion and weather-resistant powder coating as described above in the anti-corrosion and weather-resistant substrate coating of ACE construction machinery, containers, chemical industrial park pipeline equipment, and coastal environments, etc.

[0032] To achieve the above fourth object, the technical solution adopted by the present invention includes:

[0033] The present invention discloses an anti-corrosion and weather-resistant composite coating, which is characterized in that the anti-corrosion and weather-resistant composite coating is prepared according to the following steps:

[0034] At room temperature, the primer coating and the topcoat of the above-mentioned anti-corrosion and weather-resistant powder coating are sequentially sprayed on the surface of the substrate, and then cured and formed to obtain the coating.

[0035] Furthermore, the curing conditions are baking at 150 - 200 °C for 5 - 15 min.

[0036] Advantages of the present invention:

[0037] The present invention provides an anti-corrosion and weather-resistant powder coating, its preparation method and application. The anti-corrosion and weather-resistant powder coating includes a primer coating and a topcoat. The primer coating provides anti-corrosion performance. By introducing a pre-dispersed conductive intermediate into the primer coating formulation, using its large specific surface area and small conductivity coefficient, an interpenetrating network is formed with zinc powder, establishing an effective conductive network, enabling zinc powder to form a conductive path and a primary battery structure at a zinc-based raw material content not higher than 35 wt%. This not only reduces the usage amount of zinc-based raw materials, lowers costs and environmental pollution, ensures the sufficiency of the resin amount in the primer coating itself, but also, while providing sacrificial anodes, ensures that the coating has the physical and chemical properties possessed by the powder coating of the corresponding system. The anti-corrosion performance can reach up to C5 or above level, the salt spray resistance can reach 1500 hours of neutral salt spray, and the unilateral rust is ≤1 mm. At the same time, a topcoat with the same resin system is introduced to provide weather resistance, eliminating the process interference caused by the reaction difference between the bottom and top layers. The weather resistance level can reach 1500 hours of xenon lamp, the light retention rate ≥50%, and the quality assurance period can reach more than 10 years.

[0038] The present invention can obtain the target coating by using a two-coat one-bake process. The two-coat one-bake process can significantly reduce the construction difficulty, save the coating cycle time, and save the energy consumption increase caused by baking and curing. At the same time, the double-layer structure will have an interpenetrating effect during the melting process, improving the interlayer adhesion. The interlayer adhesion can reach a pull-off adhesion ≥20 MPa. Additionally, the primer coating also has good conductivity, and the surface resistivity of the primer coating is 10 4 -10 6 Ω, which also solves to a certain extent the problem that it is difficult to powder coat the top layer due to the insulation of the primer coating. Specific embodiments

[0039] To illustrate the present invention more clearly, the following further describes the present invention with reference to preferred embodiments. It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0040] In the prior art, for anti-corrosion at C5 and above levels, the bottom layer is mainly prepared by galvanizing process or using zinc-rich primer, and then the top layer is prepared by fluorocarbon paint or weather-resistant powder coating. There is no report on pure powder coating. When using zinc-rich primer, due to the strong coating effect of resin on zinc powder, it is difficult for zinc powder to connect with the substrate. In order to establish the electron path required for sacrificial anode, a large amount of zinc powder is usually incorporated to form an effective conductive network. The zinc powder content in the coating is generally not less than 70wt%. Based on the waste of a large amount of zinc powder resources, the low resin content also makes the basic physical properties and adhesion of the zinc-rich bottom powder poor, unable to provide good performance support for the coating system. Moreover, powder coatings generally have high insulation. If both the bottom and top layers use powder coatings, the charging of the bottom powder coating will be very poor during the top coating process, and the powder uptake rate of the top powder will be low, affecting the painting efficiency.

[0041] To solve the problems existing in the prior art, the present invention first develops a bottom powder coating with strong anti-corrosion performance. The pre-dispersed conductive intermediate is introduced into the polyester resin system. The single-layer graphene and single-walled carbon nanotubes in the conductive intermediate provide many excellent properties. On the one hand, graphene and carbon nanotubes have a large specific surface area, which can form an interpenetrating network with a small amount of zinc powder, thus reducing the amount of zinc powder used and improving the film adhesion and impact toughness. On the other hand, single-layer graphene and single-walled carbon nanotubes have lower conductivity than multi-layer graphene and multi-walled carbon nanotubes. Therefore, in the case of introducing a very small amount of single-layer graphene and single-walled carbon nanotubes, the volume resistivity of the coating is significantly reduced, completing the connection between the sacrificial anode zinc powder and the substrate, forming a primary battery to protect the substrate metal, and completing the composition of the anti-corrosion coating system. Due to the development of the new formula of this bottom powder coating, considering the consistency problem in the curing process, the present invention also develops a top powder coating with excellent weather resistance, which is also a polyester resin system. It not only ensures the feasibility of the two-coat one-bake process, reduces the construction difficulty and energy consumption, saves the painting cycle time, but also expands the applicability of pure powder coatings in environments with corrosion grades above C5, which is conducive to the better promotion and application of pure powder coatings.

[0042] The first aspect of the present invention discloses an anti-corrosion and weather-resistant powder coating, comprising a bottom powder coating providing anti-corrosion performance and a top powder coating providing weather resistance;

[0043] The bottom powder coating comprises the following raw materials in parts by weight: 54 - 60 parts of polyester resin, 4 - 5.5 parts of TGIC curing agent, 1.5 - 3 parts of conductive intermediate, and 10 - 30 parts of zinc powder;

[0044] The top powder coating comprises the following raw materials in parts by weight: 55 - 65 parts of polyester resin and 4 - 5.8 parts of TGIC curing agent;

[0045] Among them, the conductive intermediate is a mixture of pre-dispersed hydroxytrimethoxy polymer, carbon nanotubes, graphene and quartz stone, and their mass ratio is 100:0.2 - 0.5:0.3 - 0.8:100.

[0046] Furthermore, the polyester resin in the base powder coating and the top powder coating is an outdoor polyester resin. Selecting an outdoor polyester resin in the top powder coating can provide excellent weather resistance when cured with TGIC. The main reason for also selecting an outdoor polyester resin in the base powder coating is to maintain the same polyester resin system for the base and top layers, making it easier to control the consistency during the curing stage and facilitating the smooth implementation of the two-coat one-bake process.

[0047] In the above anti-corrosion and weather-resistant powder coating formulation, according to application requirements, the base powder coating also needs to add 1.5 - 3 parts of leveling and wetting agents, 1 - 10 parts of pigments, and 1.2 - 34 parts of fillers. The top powder coating also needs to add 1.5 - 3 parts of leveling and wetting agents, 1 - 20 parts of pigments, and 5 - 34 parts of fillers. In a preferred embodiment, the raw materials of the base powder coating and the top powder coating also include 0.8 - 3.1 parts of other additives, and the other additives are selected from auxiliary additives such as silane coupling agents, benzoin, antioxidants, ultraviolet absorbers, and salt spray resistance aids.

[0048] In the selection of the conductive intermediate, traditional conductive carbon black, conductive mica, multi-layer graphene, etc. commonly used in the prior art are not selected. Instead, a combination of single-walled carbon nanotubes and single-layer graphene is chosen. This is because single-walled carbon nanotubes and single-layer graphene have a lower conductivity than multi-layer graphene, reducing the addition amount in the formulation, preventing the increase in coating viscosity, and can also provide better adhesion and mechanical properties to the coating to ensure the stability during coating use. Moreover, by using conductive materials with different structures, the probability of contact between conductive materials is increased, and a better volume resistivity reduction effect can be obtained with a lower dosage. However, at the same time, due to the small addition amount of carbon nanotubes and graphene, easy adhesion, and easy agglomeration due to their large specific surface area, and the easy structural change after agglomeration, resulting in a decline in their unique properties. When directly mixed with other components in the coating formulation, it will cause unstable dispersion, local differences in coating properties, and other problems, and ultimately lead to the inability to achieve the designed indicators. Therefore, the inventor first pre-disperses carbon nanotubes, graphene, quartz stone, and hydroxytrimethoxy polymer, and then puts the uniformly dispersed conductive intermediate into the coating formulation, which can ensure the dispersion of carbon nanotubes and graphene and prevent the occurrence of local differences in coating properties. It has been found through research that when the mass ratio of hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone is 100:0.3:0.5:100, it has the best effect on the various properties of the coating film.

[0049] Furthermore, traditional zinc-rich powder forms a coating through the contact between zinc powders and then establishes an electronic channel through the coating. In contrast, in the present invention, through the combination of carbon nanotubes and graphene, the volume resistivity of the bottom powder coating film is reduced from 10 9 -10 11 Ω·m of traditional zinc-rich powder to 10 4 -10 6 Ω·m, and it no longer relies on the lap joint between zinc powders to reduce resistance, which is more conducive to providing anti-corrosion protection for the substrate.

[0050] Furthermore, the conductive intermediate is prepared according to the following steps:

[0051] Mix the hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone in proportion, and perform stirring and pre-dispersion through a high-speed mixer. After stirring for 5 - 8 min, it is obtained.

[0052] Furthermore, the particle size of the anti-corrosion and weather-resistant powder coating is 35 - 45 μm, that is, it is required that the particle sizes of both the bottom powder coating and the top powder coating are within the range of 35 - 45 μm. If the particle size difference between the bottom powder coating and the top powder coating exceeds 10 μm, it will have an adverse effect on the surface of the obtained paint film.

[0053] Table 1 shows the basic information of each raw material.

[0054] Table 1

[0055]

[0056] The second aspect of the present invention discloses a preparation method of the anti-corrosion and weather-resistant powder coating as described above, including the following steps:

[0057] Mix the raw materials of the bottom powder coating in formula quantity (including polyester resin, conductive intermediate, zinc powder, filler, pigment, TGIC curing agent, and various additives) by high-speed rotation to obtain the bottom powder raw material, and then put the bottom powder raw material into a twin-screw extruder and melt-extrude at 90 - 105 °C. After pressing, cooling, pulverizing, and sieving, the bottom powder coating is obtained;

[0058] Mix the raw materials of the top powder coating in formula quantity (including polyester resin, filler, TGIC curing agent, pigment, and various additives) by high-speed rotation to obtain the top powder raw material, and then put the top powder raw material into a twin-screw extruder and melt-extrude at 90 - 105 °C. After pressing, cooling, pulverizing, and sieving, the top powder coating is obtained.

[0059] Furthermore, the rotation speed of the high-speed rotation is 300 - 400 r / min, and the mixing time is 5 - 10 min.

[0060] The third aspect of the present invention discloses an anti-corrosion and weather-resistant composite coating obtained by spraying as described above. At room temperature, the primer powder coating is first sprayed on the surface of the substrate by electrostatic spraying using the classic two-coat and one-bake process, then the topcoat powder coating is sprayed, and then it is cured and formed simultaneously to obtain the coating. The anti-corrosion performance of the anti-corrosion and weather-resistant composite coating reaches the level of C5 or above at most.

[0061] Further, the curing conditions are baking at 150 - 200 °C for 5 - 15 min.

[0062] Further, the material of the substrate includes an iron substrate or an aluminum substrate; especially, it has obvious advantages when the substrate is selected from ACE construction machinery components such as tipping buckets and hooks or containers.

[0063] Further, the substrate does not need to be preheated before spraying, and its surface temperature is the same as the room temperature during spraying.

[0064] Further, the dry film thickness of the coating formed by the primer powder coating is 50 - 200 μm, preferably 70 - 150 μm; the dry film thickness of the coating formed by the topcoat powder coating is 50 - 150 μm, preferably 80 - 150 μm. Since the primer powder coating has good conductivity, it is easier to powder on during the topcoat powder coating, and the dry film thickness of the coating formed by the topcoat powder coating is significantly higher than the film thickness that can be achieved by the conventional coating process.

[0065] Table 2 shows the performance test items and detection methods of the coating formed by the primer powder coating.

[0066] Table 2

[0067]

[0068] Table 3 shows the performance test items and detection methods of the coating formed by the topcoat powder coating.

[0069] Table 3

[0070]

[0071]

[0072] The following will be illustrated by specific examples:

[0073] Example 1

[0074] This example discloses an anti-corrosion and weather-resistant powder coating, which includes a primer powder coating and a topcoat powder coating;

[0075] By weight parts, the formulation of the base powder coating is 56 parts of outdoor polyester resin, 4.2 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 3 parts of titanium dioxide, 30 parts of zinc powder, 1.5 parts of conductive intermediate, 0.8 part of aluminum metaphosphate, 0.8 part of silane coupling agent, and 1.2 parts of precipitated barium sulfate;

[0076] By weight parts, the formulation of the topcoat powder is 60 parts of outdoor polyester resin, 4.5 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 15 parts of titanium dioxide, 1 part of other pigments, 1 part of silane coupling agent, and 16 parts of precipitated barium sulfate;

[0077] Among them, the conductive intermediate is pre-dispersed according to the mass ratio of hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone of 100:0.3:0.5:100 and set aside.

[0078] This embodiment also discloses an anti-corrosion and weather-resistant composite coating, and the preparation process is as follows:

[0079] The polyester resin, TGIC, conductive intermediate, zinc powder, filler, auxiliary agent, and pigment are formulated into a masterbatch. After being mixed by high-speed rotation, it is put into a twin-screw extruder and melt-extruded at 105 °C, then pressed into sheets and cooled, crushed, and sieved to obtain the base powder coating;

[0080] The polyester resin, TGIC, auxiliary agent, pigment, and filler are mixed evenly to obtain the topcoat raw material. Then the topcoat raw material is put into a twin-screw extruder and melt-extruded at 105 °C. After being pressed into sheets and cooled, it is crushed and sieved to obtain the topcoat powder;

[0081] At room temperature, the base powder coating is sprayed on the surface of the substrate without high-temperature preheating treatment, and then the topcoat powder is sprayed. After spraying, it is heated, melted, and cured to form a film to obtain the anti-corrosion and weather-resistant composite coating, and its performance parameters are shown in Table 4.

[0082] Example 2

[0083] This embodiment discloses an anti-corrosion and weather-resistant powder coating, which comprises a base powder coating and a topcoat powder;

[0084] By weight parts, the formulation of the base powder coating is 54 parts of outdoor polyester resin, 4.1 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 3 parts of titanium dioxide, 10 parts of zinc powder, 2.5 parts of conductive intermediate, 0.5 part of aluminum metaphosphate, 0.8 part of silane coupling agent, and 22.6 parts of precipitated barium sulfate;

[0085] By weight parts, the formula of the flour coating is 56 parts of outdoor polyester resin, 4.2 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 15 parts of titanium dioxide, 1 part of other pigments, 0.8 part of silane coupling agent, and 21 parts of precipitated barium sulfate;

[0086] Among them, the conductive intermediate is pre-dispersed according to the mass ratio of hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone of 100:0.3:0.5:100 and reserved for use.

[0087] This embodiment also discloses an anti-corrosion and weather-resistant composite coating, and the preparation process is as follows:

[0088] The polyester resin, TGIC, conductive intermediate, zinc powder, filler, auxiliary agent, and pigment are formulated into a masterbatch. After being mixed by high-speed rotation, it is put into a twin-screw extruder and melt-extruded at 105°C, then pressed into sheets and cooled, crushed, and sieved to obtain the base powder coating;

[0089] The polyester resin, TGIC, auxiliary agent, pigment, and filler are mixed evenly to obtain the raw flour material. Then the raw flour material is put into a twin-screw extruder and melt-extruded at 105°C. After being pressed into sheets and cooled, it is crushed and sieved to obtain the flour coating;

[0090] At room temperature, the base powder coating is sprayed on the surface of the substrate that has not been preheated at high temperature, and then the flour coating is sprayed. After spraying, it is heated, melted, and cured into a film to obtain the anti-corrosion and weather-resistant composite coating, and its performance parameters are shown in Table 4.

[0091] Example 3

[0092] This embodiment discloses an anti-corrosion and weather-resistant powder coating, which includes a base powder coating and a flour coating;

[0093] By weight parts, the formula of the base powder coating is 56 parts of outdoor polyester resin, 4.2 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 3 parts of titanium dioxide, 30 parts of zinc powder, 1.5 parts of conductive intermediate, 0.8 part of meta-phosphoric acid aluminum, 0.8 part of silane coupling agent, and 1.2 parts of precipitated barium sulfate;

[0094] By weight parts, the formula of the flour coating is 60 parts of outdoor polyester resin, 4.5 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 15 parts of titanium dioxide, 1 part of other pigments, 1 part of silane coupling agent, 0.8 part of antioxidant, 0.8 part of ultraviolet absorber, and 15 parts of precipitated barium sulfate;

[0095] Among them, the conductive intermediate is pre-dispersed according to the mass ratio of hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone of 100:0.3:0.5:100 and reserved for use.

[0096] This embodiment also discloses an anti-corrosion and weather-resistant composite coating, and the preparation process is as follows:

[0097] A masterbatch is prepared by mixing polyester resin, TGIC, conductive intermediate, zinc powder, filler, additive, and pigment. After high-speed rotation mixing, it is put into a twin-screw extruder and melt-extruded at 105 °C, then pressed into sheets, cooled, crushed, and sieved to obtain the primer powder coating;

[0098] The polyester resin, TGIC, additive, pigment, and filler are mixed evenly to obtain the semifinished flour material. Then, the semifinished flour material is put into a twin-screw extruder and melt-extruded at 105 °C. After pressing into sheets and cooling, it is crushed and sieved to obtain the flour coating;

[0099] At room temperature, the primer powder coating is sprayed on the surface of the substrate without high-temperature preheating treatment, and then the flour coating is sprayed. After spraying, it is heated, melted, and cured into a film to obtain the anti-corrosion and weather-resistant composite coating. The performance parameters are shown in Table 4.

[0100] Table 4 Performance test data of the composite coatings prepared in Examples 1-3

[0101]

[0102]

[0103] As can be seen from Table 4, the composite coatings prepared in Examples 1-3 all have good film adhesion, impact toughness, and interlayer pull-off adhesion, and also have excellent salt spray resistance, damp heat resistance, boiling water resistance, etc. Further subdividing their application scenarios (distinguished according to different environmental classifications in the ISO12944 standard), the formulation of Example 1 can be applied to the primer or primer-surface combination protection of iron-based workpieces in heavy anti-corrosion environments such as outdoor chemical industrial parks and construction machinery (the application environment is above C4 level), the formulation of Example 2 can be applied to the primer or primer-surface combination protection of iron-based workpieces in mild anti-corrosion environments such as outdoor communication equipment, public facilities, and transportation equipment (the application environment is above C3 level), and the formulation of Example 3 can be applied to the primer or primer-surface combination protection of iron-based workpieces such as containers and coastal environmental facilities (the application environment is above C5 level). The main difference between Example 3 and Example 1 is that the thickness of the underlying zinc-rich layer needs to reach 150-200 μm to ensure the anti-corrosion performance of the system. At the same time, the weather resistance of the system applied to the surface layer is also higher.

[0104] Comparative Example 1

[0105] This comparative example refers to the formulation and preparation process of Example 1, with the only difference being that the conductive intermediate in the base powder coating was not pre-dispersed. Instead, the hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone were directly mixed with other components to prepare the base powder raw material. It was found through testing that the volume resistivity was abnormal, and the volume resistivity in local areas was as high as 10 9 Ω·m. This is because the addition amounts of carbon nanotubes and graphene are small and cannot achieve the effect of uniform dispersion, which will have a certain adverse impact on the local volume resistivity. After using the two-coat one-bake process for painting, due to the relatively high conductivity of the bottom layer, electrostatic saturation occurs during the painting of the top layer, and the thickness of the top layer drops below 50 μm. After the composite coating is cured, phenomena such as orange peel appear, and the weather resistance performance cannot meet the design requirements.

[0106] Comparative Example 2

[0107] This comparative example refers to the formulation and preparation process of Example 1, with the only difference being that the dosage of the conductive intermediate in the base powder coating was changed to 1 part; when the dosage of the conductive intermediate is 1 part, due to the insufficient addition amount of the conductive additive, the reduction of the volume resistivity is insufficient, and the volume resistivity of the coating can only reach 10 7 -10 8 Ω·m, while the upper limit of the volume resistivity of the conductive coating and the antistatic coating is 10 6 Ω·m. Eventually, the effect of the primary battery formed is poor, resulting in a decrease in the actual corrosion resistance effect. After using the two-coat one-bake process for painting, due to the insufficient corrosion resistance of the bottom layer, the salt spray resistance of the coating decreases, and the unilateral rust distance after 1500 h is greater than 5 mm.

[0108] Comparative Example 3

[0109] This comparative example refers to the formulation and preparation process of Example 1, with the only difference being that the dosage of the conductive intermediate in the base powder coating was changed to 4 parts; when the dosage of the conductive intermediate is 4 parts, due to the too large specific surface area of carbon nanotubes and graphene, the melting viscosity of the coating will increase, resulting in a decrease in the mechanical properties of the coating after curing. After using the two-coat one-bake process for painting, the surface effect of the coating is poor, phenomena such as orange peel and loss of gloss appear, the flexibility is 2 mm, and there are cracks when the impact resistance is 50 kg·cm.

[0110] Comparative Example 4

[0111] This comparative example refers to the formulation and preparation process of Example 1, with the only difference being that the combination of resin and curing agent used in the base powder coating is epoxy resin and phenolic curing agent. The amount of epoxy resin used is 52 parts; the amount of phenolic curing agent used is 10 parts. Due to the inconsistency of the resin and curing system used in the bottom layer and the top layer, there is a difference in the reaction system during the two-coat one-bake curing process. After curing, the polyester top layer loses gloss significantly, and the surface gloss decreases to below 60°, resulting in a decline in weather resistance and failing to meet the design requirements. If a two-coat two-bake process is used, the surface layer performance can meet the design requirements. However, when the top layer is coated, the bottom layer has been cured, and the surface layer is smooth, which affects the interlayer adhesion of the final composite coating. The interlayer adhesion (pull-off method) drops to about 10 MPa.

[0112] Comparative Example 5

[0113] This comparative example refers to the formulation and preparation process of Example 1, with the difference being that the base powder coating uses a commonly available polyester-based base powder in the market, which consists of 60 parts of polyester resin, 4.5 parts of TGIC, 1 part of leveling agent, 1 part of wetting agent, 0.5 part of benzoin, 15 parts of titanium dioxide, 1 part of other pigments, 1 part of silane coupling agent, and 16 parts of precipitated barium sulfate. This system is suitable for the two-coat one-bake process, and the appearance effect of the composite coating is good. However, due to the lack of anti-corrosion performance in the bottom layer, the salt spray resistance of the composite coating is poor, and the unilateral rust of the 1500h neutral salt spray is greater than 7 mm.

[0114] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to list all the implementation manners here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. An anti-corrosion and weather-resistant powder coating, characterized in that, It includes a primer powder coating providing anti-corrosion performance and a topcoat powder coating providing weather resistance; The primer powder coating comprises raw materials in the following parts by weight: 54 - 60 parts of polyester resin, 4 - 5.5 parts of TGIC curing agent, 1.5 - 3 parts of conductive intermediate, and 10 - 30 parts of zinc powder; The topcoat powder coating comprises raw materials in the following parts by weight: 55 - 65 parts of polyester resin and 4 - 5.8 parts of TGIC curing agent; Among them, the conductive intermediate is a mixture of pre-dispersed hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone, and their mass ratio is 100:0.2 - 0.5:0.3 - 0.8:

100.

2. The anti-corrosion and weather-resistant powder coating according to claim 1, characterized in that, In the conductive intermediate, the mass ratio of hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone is 100:0.3:0.5:

100.

3. The anti-corrosion and weather-resistant powder coating according to claim 1, characterized in that, The polyester resin in the primer powder coating and the topcoat powder coating is an outdoor polyester resin.

4. The anti-corrosion and weather-resistant powder coating according to claim 1, characterized in that, The graphene is monolayer graphene with a specific surface area ≥ 2500 m 2 / g, and the thickness of the particle structure is 0.3 - 0.5 nm; the carbon nanotube is a single-walled carbon nanotube with an aspect ratio > 10000, and the particle structure tube diameter is 1 - 2 nm; Preferably, the steps of the pre-dispersion treatment are as follows: Mix hydroxytrimethoxy polymer, carbon nanotubes, graphene, and quartz stone in proportion, and perform stirring pre-dispersion through a high-speed mixer. After stirring for 5 - 8 min, it is obtained.

5. The anti-corrosion and weather-resistant powder coating according to claim 1, characterized in that, The particle size of the anti-corrosion and weather-resistant powder coating is 35 - 45 μm.

6. The anti-corrosion and weather-resistant powder coating according to claim 1, characterized in that, By weight, the primer powder coating further comprises 1.5 - 3 parts of leveling and wetting aids; 1 - 10 parts of pigment; and 1.2 - 34 parts of filler; The topcoat powder coating further comprises 1.5 - 3 parts of leveling and wetting aids; 1 - 20 parts of pigment; and 5 - 34 parts of filler.

7. A method for preparing the anti-corrosion and weather-resistant powder coating according to any one of claims 1-6, characterized in that, It includes the following steps: Mix the raw materials of the primer powder coating in the formula amount evenly to obtain the primer raw material, then put the primer raw material into a twin-screw extruder and melt-extrude it at 90 - 105 °C. After pressing into sheets and cooling, crush and screen it to obtain the primer powder coating; Mix the raw materials of the topcoat powder coating in the formula amount evenly to obtain the topcoat raw material, then put the topcoat raw material into a twin-screw extruder and melt-extrude it at 90 - 105 °C. After pressing into sheets and cooling, crush and screen it to obtain the topcoat powder coating.

8. The application of the anti-corrosion and weather-resistant powder coating according to any one of claims 1-6 in the anti-corrosion and weather-resistant substrate coating of ACE construction machinery, containers, chemical industrial park pipeline equipment and coastal environments.

9. An anti-corrosion and weather-resistant composite coating, characterized in that, At room temperature, spray the primer powder coating and the topcoat powder coating of the anti-corrosion and weather-resistant powder coating according to any one of claims 1 - 6 on the surface of the substrate in sequence, and then cure and form it to obtain.

10. The anti-corrosion and weather-resistant composite coating according to claim 9, characterized in that, The curing conditions are baking at 150 - 200 °C for 5 - 15 min.

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