Process for the preparation of zinc-rich epoxy powder coatings with high adhesion

Abstract

The present application relates to the technical field of paint, in particular to a method for preparing zinc-rich epoxy powder coating with high adhesion, and the method comprises the following steps: S1, preparing modified graphene; S2, taking each raw material component of component A according to the proportion, mixing and uniformly dispersing by a dispersing machine to obtain component A; S3, taking each raw material component of component B according to the proportion, mixing and uniformly dispersing, then grinding and sieving the mixture to obtain component B. The modified graphene is used to form a conductive path between zinc powder particles, reduce the amount of zinc powder, improve the overall utilization rate of zinc powder in the coating, form a good shielding effect, block the penetration of corrosive medium and enhance the corrosion resistance of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a method for preparing zinc-rich epoxy powder coatings with high adhesion. Background Technology

[0002] Epoxy zinc-rich coatings possess advantages such as a hard film and excellent adhesion to metals, making them widely used in heavy-duty corrosion protection applications such as bridges, ships, buildings, and pipelines. The zinc powder content in epoxy zinc-rich coatings varies depending on the required corrosion protection level. In harsh corrosive environments such as marine environments, a zinc powder content greater than 50 wt% is necessary. However, excessive zinc powder content leads to severe zinc powder sedimentation in the coating, resulting in numerous porosity defects and reduced mechanical properties. Improving the corrosion protection performance of epoxy zinc-rich coatings while reducing the zinc powder content is of significant practical importance and research value.

[0003] Numerous studies have been conducted on the application of graphene in epoxy zinc-rich coatings. Existing literature shows that the addition of graphene to solvent-based epoxy zinc-rich primers significantly improves their corrosion resistance, with a maximum neutral salt spray resistance time of up to 4000 hours. However, the selection of graphene, the optimal dosage, and the corrosion resistance mechanism of graphene in coatings remain unclear. Selecting suitable graphene types and optimizing the dosage to prepare epoxy zinc-rich primers with stable and excellent anti-corrosion properties has been a key focus of research. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing zinc-rich epoxy powder coatings with high adhesion. The method utilizes modified graphene to form conductive pathways between zinc powder particles, thereby reducing the amount of zinc powder used, improving the overall utilization rate of zinc powder in the coating, and forming a good shielding effect to block the penetration of corrosive media and enhance the anti-corrosion performance of the coating.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for preparing a high-adhesion zinc-rich epoxy powder coating, wherein the zinc-rich epoxy powder coating is composed of component A and component B; wherein component A is prepared from the following components in the indicated mass fractions: 70-80% epoxy resin, 1-15% modified graphene, 2-12% water and 0.4-2% additive A; component B is prepared from the following components in the indicated mass fractions: 3-10% epoxy curing agent, 15-50% zinc powder, 10-30% superphosphorus zinc white, 1-3% sericite, 3-15% propylene glycol methyl ether acetate, 0.1-0.5% bentonite, 1-5% corrosion inhibitor and 0.6-3.0% additive B;

[0007] The preparation method of this zinc-rich epoxy powder coating includes the following steps:

[0008] S1, Preparation of modified graphene;

[0009] S2, Weigh out the raw material components of component A except for the phenolic curing agent according to the formula, mix them, disperse and mix them evenly using a disperser, then add the phenolic curing agent and continue to stir and disperse, grind and sieve again to obtain component A;

[0010] S3. Weigh each raw material component of component B according to the formula, disperse and shear them evenly using a disperser, and then grind and sieve the mixture to obtain component B.

[0011] Preferably, the additive A includes 0.1-0.5% of defoamer, 0.1-0.5% of wetting agent, 0.1-0.5% of thickener, and 0.1-0.5% of flash rust inhibitor.

[0012] Preferably, the additive B comprises 0.5-2.0% dispersant, 0.1-0.5% defoamer, and 0.1-0.3% leveling agent.

[0013] Preferably, the corrosion inhibitor is bio-based nano-cerium phytate.

[0014] Preferably, the specific method for preparing modified graphene in step S1 is as follows:

[0015] S11 uses plasma-assisted high-energy ball milling equipment to process expanded graphite and Ti3C. 2、 After being ultrasonically mixed with ZrP and oleic acid solution, the mixture was placed in a tank and subjected to plasma-assisted high-energy ball milling for 10 hours to obtain primary powder.

[0016] S12, use petroleum ether as an extractant to treat the primary powder prepared in step S11, and centrifuge repeatedly until the upper petroleum ether solution after extraction is clear and transparent, and take the precipitate.

[0017] S13, take the precipitate from step S12 and dry it in a drying oven at 90°C for 30-40 minutes to make it into powder and obtain modified graphene.

[0018] Preferably, the ball milling conditions in step S11 are: discharge voltage of 22kV, ball mill vibration frequency of 16Hz, amplitude of 10mm, and ball mill jar in an atmospheric environment of 0.1MPa.

[0019] Preferably, the specific method for preparing component A in step S2 is as follows:

[0020] S21, after mixing solid epoxy resin, defoamer, wetting agent and anti-flash rust agent, disperse the mixture evenly with a disperser at a speed of 1000 r / min to obtain mixture 1;

[0021] S22, add the thickener to the phenolic curing agent, heat to 140-180℃ and stir evenly to form a molten substance, then add it to the mixture 1 obtained in step S21, and continue to heat and disperse for 30 minutes to obtain mixture 2;

[0022] S23, add graphene to the mixture 2 obtained in step S22, adjust the speed of the disperser to 1800 r / min and continue to disperse and shear for 30 min, transfer to the screw extruder for extrusion, tableting, and crushing to obtain the pre-cured powder, take it out and grind it again with a grinder, and then sieve it to obtain component A.

[0023] Preferably, the specific method for preparing component B in step S3 is as follows:

[0024] S31, after mixing epoxy curing agent, defoamer, dispersant, leveling agent and propylene glycol methyl ether acetate, disperse the mixture evenly using a disperser at 1000 r / min to obtain mixture 3;

[0025] S32, add bentonite to the mixture 3 obtained in step S31 and stir for 60 minutes to obtain mixture 4;

[0026] S33, add sericite, superphosphorus zinc white and zinc powder to the mixture 4 obtained in step S32 in sequence, stir for 30 minutes to obtain mixture 5;

[0027] S34. Add the corrosion inhibitor to the mixture 5 obtained in step S33, stir evenly, pour into a sand mill, grind at 2000 r / min for 30 min, and sieve to obtain component B.

[0028] The beneficial effects of this invention are:

[0029] 1. The present invention uses modified graphene added to epoxy zinc-rich primer to improve the shielding performance of the coating, extend its cathodic protection time, and enhance the anti-corrosion performance and corrosion resistance of the coating; the covalent grafting method is used to modify graphene, which reduces the aggregation of graphene oxide flakes in the epoxy matrix, which can significantly increase the concentration and stability of the graphene dispersion, and improve the density and adhesion of the coating.

[0030] 2. This invention uses Ti3C 2、 Grafting graphene onto ZrP allows the modified graphene to possess strong corrosion resistance while maintaining excellent tensile strength and thermal stability. Furthermore, the modified graphene forms conductive pathways between zinc powder particles, reducing the amount of zinc powder used and improving the overall utilization rate of zinc powder in the coating. At the same time, it forms a good shielding effect, blocking the penetration of corrosive media, enhancing the anti-corrosion performance of the coating, and helping to improve adhesion.

[0031] 3. The present invention also adds bio-based nano-cerium phytate as a corrosion inhibitor, which is uniformly dispersed in the epoxy zinc-rich coating, forming a protective film on the surface of the substrate and helping to enhance the corrosion resistance. Detailed Implementation

[0032] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0033] Solid epoxy resin 604 (industrial grade): Jinan Baorui Resin Chemical Co., Ltd.; Polyamide curing agent, phenolic amine curing agent, fatty amine curing agent (industrial grade): Guangdong Tongde Co., Ltd.; Propylene glycol methyl ether acetate (industrial grade): Xinchuan Chemical Co., Ltd.; Thickener (industrial grade), anti-flash rust agent (industrial grade): Tianjin Shangde Xinjia Co., Ltd.; Dispersant, defoamer, wetting agent, leveling agent are all industrial grade: Evcona Polymer Co., Ltd.; Zinc powder (industrial grade): Jiangsu Shenlong Zinc Industry Co., Ltd.; Phosphorus iron powder (industrial grade), superphosphorus zinc white (industrial grade): Henan Huijin Co., Ltd.; Sericite (industrial grade): Anhui Gerui Co., Ltd.; Bentonite (industrial grade): Zhejiang Hongyu Co., Ltd.; Expanded graphite: Suzhou Greifeng Nanotechnology Co., Ltd.; Oleic acid: Shandong Jubang Chemical Co., Ltd.; Ti3C2, ZrP: Zhongke Leiming (Beijing) Technology Co., Ltd.

[0034] Example 1

[0035] Preparation of modified graphene:

[0036] A plasma-assisted high-energy ball mill was used. 1g of expanded graphite, 3g of Ti3C2, 2g of ZrP, and 500ml of oleic acid solution were ultrasonically mixed and placed in a jar for plasma-assisted high-energy ball milling. The milling conditions were: discharge voltage of 22kV, ball mill vibration frequency of 16Hz, amplitude of 10mm, and atmospheric environment of 0.1MPa in the milling jar. After milling for 10 hours, primary powder was obtained. The primary powder was treated with petroleum ether as an extractant and repeatedly centrifuged until the upper petroleum ether solution after extraction was clear and transparent. The precipitate was collected and placed in a drying oven at 90℃ for 30-40 minutes to obtain modified graphene powder.

[0037] Example 2

[0038] Preparation of component A:

[0039] Mix 100g of solid epoxy resin, 0.3g of defoamer, 0.2g of wetting agent, and 0.2g of anti-flash rust agent, and disperse evenly using a disperser at 1000r / min to obtain mixture 1. Add 0.4g of thickener to 6.8g of phenolic curing agent, heat to 158℃ and stir evenly to form a molten substance, then add it to mixture 1, and continue heating and dispersing for 30min to obtain mixture 2. Add graphene to mixture 2, adjust the disperser speed to 1800r / min and continue dispersing and shearing for 30min, then transfer to a screw extruder for extrusion, tableting, and pulverization to obtain a pre-cured powder. Remove the powder, grind it again using a grinder, and sieve it to obtain component A.

[0040] Modified graphene was added in amounts of 1g, 2g, 4g, 6g, 8g, 10g, 12g, and 14g to prepare components A1-A8.

[0041] Example 3

[0042] Preparation of component B:

[0043] Mix 8g of epoxy curing agent, 1.2g of defoamer, 0.3g of dispersant, 0.2g of leveling agent and 9.8g of propylene glycol methyl ether acetate and disperse evenly using a disperser at 1000r / min to obtain mixture 3;

[0044] Add 0.4g of bentonite to mixture 3 and stir for 60 minutes to obtain mixture 4;

[0045] Add 2.5g of sericite, 18g of superphosphorus zinc white and zinc powder to mixture 4 in sequence, stir for 30 minutes to obtain mixture 5;

[0046] Add 4g of corrosion inhibitor to mixture 5, stir evenly, pour into a sand mill, grind at 2000r / min for 30min, and sieve to obtain component B.

[0047] Zinc powder was added in amounts of 15g, 20g, 25g, 30g, 35g, 40g, 45g, and 50g to prepare components B1-B8.

[0048] Example 4

[0049] Zinc-rich epoxy powder coatings were prepared by combining components A1-A8 with components B1-B8, as shown in Table 1 below.

[0050] Mix components A and B at a mass ratio of 13:1 and stir until homogeneous. After curing, apply two coats with a 24-hour interval between each coat. Cur the coating in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 7 days before testing.

[0051] Table 1 Coating Formulation Table

[0052] Component B1 1 2 3 4 5 6 7 8 Component B2 9 10 11 12 13 14 15 16 Component B3 17 18 19 20 21 22 23 24 Component B4 25 26 27 28 29 30 31 32 Component B5 33 34 35 36 37 38 39 40 Component B6 41 42 43 44 45 46 47 48 Component B7 49 59 51 52 53 54 55 56 Component B8 57 58 59 60 61 62 63 64

[0053] Example 5

[0054] The viscosity of coatings shall be measured in accordance with GB / T 9269–2009 "Determination of viscosity of coatings - Stormer viscometer method".

[0055] The coating's appearance, drying time, bending resistance, and impact resistance were tested by applying the coating to a 120mm×50mm×(0.2-0.3)mm tinplate. For the cross-cut test, the coating was applied to a 150mm×75mm×(0.45-0.55)mm steel plate. Except for the drying time test, all tests required 48 hours of curing, with a dry film thickness of (25±3)μm. The drying time of the coating was determined according to GB / T1728–2020 "Determination of Drying Time of Paint Film and Putty Film", the bending test was conducted according to GB / T 6742–2007 "Bending Test of Paints and Varnishes (Cylindrical Shaft)", and the impact resistance test was conducted according to GB / T 1732–2020 "Determination of Impact Resistance of Paint Film".

[0056] The pull-off adhesion test of the coating was conducted using a PosiTest AT pull-off tester, according to GB / T5210–2006 "Paints and Varnishes - Pull-off Adhesion Test". The dry film thickness of the coating was (45±5) μm. The test substrate was a sandblasted steel plate of 150 mm × 75 mm × (3-5) mm, and the substrate was pretreated according to the requirements of Clause 4.3.1 of the chemical industry standard HG / T 4564–2013 "Epoxy Coatings with Low Surface Treatment Tolerance".

[0057] The coating for corrosion resistance testing was applied to a steel plate that had been sandblasted to Sa 2.5 grade as specified in GB / T 8923.1–2011 "Visual assessment of surface cleanliness of steel surfaces before coating - Part 1: Rust grade and treatment grade of uncoated steel surfaces and steel surfaces after complete removal of original coating". The steel plate had dimensions of 150mm × 75mm × (3-5)mm.

[0058] The alkali resistance of the coating (i.e., the time required for the coating to be damaged in 50 g / L NaOH solution) was tested by immersion method in GB / T9274–1988 "Determination of resistance to liquid media for paints and varnishes". The dry film thickness of the coating was (45±5) μm. The samples were cured in a constant temperature room at (23±2)℃ for 7 days before being tested according to relevant standards.

[0059] The salt spray resistance of the coating (i.e., the time required for the coating to be damaged in a 50 g / L neutral salt spray test) was tested in a Q-FOG salt spray test chamber according to GB / T1771–2007 "Determination of the resistance of paints and varnishes to neutral salt spray" and the dry film thickness of the coating was (90±10) μm.

[0060] The test results are shown in Table 2 below.

[0061] Table 2. Effects of different amounts of modified graphene and zinc powder on coating performance.

[0062]

[0063]

[0064]

[0065] The test results above show that when the amount of modified graphene is between 6% and 10% and the amount of zinc powder is between 35% and 40%, the zinc-rich epoxy powder coating exhibits excellent performance in various tests. It ensures high adhesion while also providing excellent corrosion resistance and flexibility, resulting in the best overall performance.

[0066] Example 6

[0067] Based on the test results of Example 5, formulation A5xB4 was selected, with 8g of modified graphene and 30g of zinc powder used as test example 1 of this invention. A comparative example was prepared, and modified graphene was prepared according to the method of Example 1:

[0068] A plasma-assisted high-energy ball mill was used. 1g of expanded graphite, 5g of Ti3C2, and 500ml of oleic acid solution were ultrasonically mixed and placed in a jar for plasma-assisted high-energy ball milling. The milling conditions were: discharge voltage of 22kV, ball mill vibration frequency of 16Hz, amplitude of 10mm, and atmospheric environment of 0.1MPa in the milling jar. After milling for 10h, primary powder was obtained. The prepared primary powder was treated with petroleum ether as an extractant and repeatedly centrifuged until the upper petroleum ether solution after extraction was clear and transparent. The precipitate was collected and placed in a drying oven at 90℃ for 30-40min to obtain modified graphene 1.

[0069] A plasma-assisted high-energy ball mill was used. 1g of expanded graphite, 5g of ZrP, and 500ml of oleic acid solution were ultrasonically mixed and placed in a jar for plasma-assisted high-energy ball milling. The milling conditions were: discharge voltage of 22kV, ball mill vibration frequency of 16Hz, amplitude of 10mm, and atmospheric environment of 0.1MPa in the milling jar. After milling for 10h, primary powder was obtained. The prepared primary powder was treated with petroleum ether as an extractant and repeatedly centrifuged until the upper petroleum ether solution after extraction was clear and transparent. The precipitate was collected and placed in a drying oven at 90℃ for 30-40min to obtain modified graphene 2 as powder.

[0070] Comparative test examples 1 and 2 were prepared by replacing the modified graphene in component A5 with the modified graphene and then combining it with component B4 to form coatings. Comparative test example 3 was prepared by removing the modified graphene in component A5 and then combining it with component B4 to form a coating. Then, performance comparison tests were conducted.

[0071] The test results are shown in Table 3 below.

[0072] Table 3 Performance tests of different coatings

[0073]

[0074] The test results above show that this invention uses Ti3C. 2、 Grafting graphene onto ZrP allows the modified graphene to possess strong corrosion resistance while maintaining excellent tensile strength and thermal stability. Furthermore, the modified graphene forms conductive pathways between zinc powder particles, reducing the amount of zinc powder needed and improving the overall utilization rate of zinc powder in the coating. Simultaneously, it forms a good shielding effect, preventing the penetration of corrosive media, enhancing the coating's corrosion resistance, and aiding in improving adhesion. Compared to using Ti3C alone... 2、 Alternatively, a coating made of ZrP-modified graphene can be used; the combination of both produces a coating with even better performance. Compared to existing, widely recognized high-performance thermal spray zinc coatings, the coating performance test results of this invention are also superior.

[0075] All technical features in this embodiment can be modified in appearance according to actual needs.

[0076] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

Claims

1. A method for preparing high-adhesion zinc-rich epoxy powder coatings, characterized in that: This zinc-rich epoxy powder coating is composed of component A and component B; Component A is prepared from the following components in the indicated mass fractions: 70-80% epoxy resin, 1-15% modified graphene, 6-12% phenolic curing agent, and 0.4-2% additive A; said additive A includes 0.1-0.5% defoamer, 0.1-0.5% wetting agent, 0.1-0.5% thickener, and 0.1-0.5% flash rust inhibitor. Component B is prepared from the following components in the indicated mass fractions: 3-10% epoxy curing agent, 15-50% zinc powder, 10-30% superphosphorus zinc white, 1-3% sericite, 3-15% propylene glycol methyl ether acetate, 0.1-0.5% bentonite, 1-5% corrosion inhibitor, and 0.6-3.0% additive B; said additive B includes 0.5-2.0% dispersant, 0.1-0.5% defoamer, and 0.1-0.3% leveling agent; The preparation method of this zinc-rich epoxy powder coating includes the following steps: S1, Preparation of modified graphene; S2, Preparation of component A: S21, after mixing solid epoxy resin, defoamer, wetting agent and anti-flash rust agent, disperse the mixture evenly with a disperser at a speed of 1000 r / min to obtain mixture 1; S22, add the thickener to the phenolic curing agent, heat to 140-180℃ and stir evenly to form a molten substance, then add it to the mixture 1 obtained in step S21, and continue to heat and disperse for 30 minutes to obtain mixture 2; S23, add the modified graphene to the mixture 2 obtained in step S22, adjust the speed of the disperser to 1800 r / min and continue to disperse and shear for 30 min, transfer it to the screw extruder for extrusion, tableting, and crushing to obtain the pre-cured powder, take it out and grind it again with a grinder, and then sieve it to obtain component A. S3, Weigh each raw material component of component B according to the ratio, disperse and shear the mixture evenly using a disperser, and then grind and sieve the mixture to obtain component B; The specific method for preparing modified graphene in step S1 is as follows: S11, using plasma-assisted high-energy ball milling equipment, expandable graphite, Ti3C2, ZrP and oleic acid solution are ultrasonically mixed evenly and then placed in a tank for plasma-assisted high-energy ball milling. After ball milling for 10 hours, primary powder is obtained. S12, use petroleum ether as an extractant to treat the primary powder prepared in step S11, and centrifuge repeatedly until the upper petroleum ether solution after extraction is clear and transparent, and take the precipitate. S13, take the precipitate from step S12 and dry it in a drying oven at 90°C for 30-40 minutes to make it into powder and obtain modified graphene.

2. The method for preparing high-adhesion zinc-rich epoxy powder coating according to claim 1, characterized in that: The ball milling conditions in step S11 are: discharge voltage of 22kV, ball mill vibration frequency of 16Hz, amplitude of 10mm, and ball mill jar in an atmospheric environment of 0.1MPa.

3. The method for preparing high-adhesion zinc-rich epoxy powder coating according to claim 1, characterized in that: The corrosion inhibitor is bio-based nano-cerium phytate.

4. The method for preparing high-adhesion zinc-rich epoxy powder coating according to claim 1, characterized in that: The specific method for preparing component B in step S3 is as follows: S31, after mixing epoxy curing agent, defoamer, dispersant, leveling agent and propylene glycol methyl ether acetate, disperse the mixture evenly using a disperser at 1000 r / min to obtain mixture 3; S32, add bentonite to the mixture 3 obtained in step S31 and stir for 60 minutes to obtain mixture 4; S33, add sericite, superphosphorus zinc white and zinc powder to the mixture 4 obtained in step S32 in sequence, stir for 30 minutes to obtain mixture 5; S34. Add the corrosion inhibitor to the mixture 5 obtained in step S33, stir evenly, pour into a sand mill, grind at 2000 r / min for 30 min, and sieve to obtain component B.

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