Epoxy modified coal tar heavy-duty anticorrosive coating and preparation method thereof

Abstract

This invention provides an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating and its preparation method, belonging to the field of coating technology. The method includes the following steps: dispersing Fe-Al LDH precursor powder in a mixed liquid, ultrasonically dispersing under heating, adding PTMS dropwise, reacting for a period of time after the addition is complete, then adding KH-560 dropwise, heating, reacting, centrifuging, washing, and vacuum drying to obtain modified LDH; adding coal tar pitch and CGE to a reaction vessel, homogenizing, shearing and mixing, adding modified LDH powder and mixing to obtain activated asphalt slurry; heating epoxy resin to melt it, pouring it into the activated asphalt slurry, stirring and mixing, cooling, adding mica iron oxide and precipitated barium sulfate, pre-dispersing, grinding, and discharging to obtain the main paint component; when ready for use, stirring and mixing the cashew phenol amine epoxy curing agent with the main paint component to obtain the finished product. The epoxy-modified coal tar pitch heavy-duty anti-corrosion coating obtained by this invention can effectively improve the anti-corrosion performance of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating and its preparation method. Background Technology

[0002] Epoxy coal tar anticorrosive coatings are widely used in various pipeline and environmental remediation coating materials due to their good mechanical strength, water resistance, and resistance to microbial erosion. However, in environments with long-term alternating wet and dry conditions or strong osmotic pressure, traditional epoxy coal tar coatings are prone to impedance attenuation and moisture leakage after a period of service, which may also lead to problems such as deep pitting corrosion or even perforation of pipelines.

[0003] Current epoxy-modified coal tar coatings primarily employ a "physical blending" technique, which involves mechanically mixing E-20 or E-44 type epoxy resin, coal tar pitch, pigments, and a large amount of volatile solvents such as xylene. To improve corrosion resistance, various surfactants are typically added, or silane coupling agents are used to pretreat inorganic fillers to enhance dispersibility. Additionally, grafted modified pitch is introduced to improve compatibility. However, these patchwork improvements, achieved simply by adding functional components or individual components, cannot fundamentally alter the corrosion resistance of the material system.

[0004] The core challenge of this type of coating is that, in simulated groundwater immersion environments, its low-frequency impedance experiences a precipitous drop within the first 1000 hours, from 10... 9 Ω·cm 2 The magnitude was sharply reduced to 10 6 Ω·cm 2 On a large scale, coating blistering and peeling may also occur. From a thermodynamic perspective, the root cause lies in microphase separation. Coal tar pitch contains a large amount of non-polar polycyclic aromatic hydrocarbons (PAHs), while the epoxy-polyamine crosslinking network in the coating is highly polar. As the solvent rapidly evaporates and the epoxy curing crosslinking degree increases, the free energy within the system changes drastically. The interfacial tension between the two phases causes the asphaltene, which was originally uniformly distributed in the solvent, to be "squeezed out" by the polar network, resulting in microscopic and even macroscopic phase separation. This phase separation causes conventional inorganic fillers, such as mica powder and barium sulfate, to decouple from the resin matrix, forming numerous micropores and interconnected capillary channels at the interface between the asphalt and epoxy phases. Water molecules, dissolved oxygen, and chloride ions can then penetrate directly into the metal substrate through these channels created by phase separation, accelerating the corrosion process.

[0005] For example, patent publication number CN105086768A discloses a thick-film epoxy-modified coal tar pitch heavy-duty anti-corrosion coating and its preparation method. This method mainly uses epoxy resin, coal tar pitch, anti-rust pigments, fillers, nanomaterials, additives, solvents, fatty amine epoxy curing agents, polyamide epoxy curing agents, and mixed solvents for preparation. In this method, the polarity difference between epoxy resin and asphalt is significant, and the simple physical mixing method results in poor overall compatibility. Furthermore, the fillers are not modified, making them prone to agglomeration in the epoxy-asphalt two-phase system. This method also heavily relies on volatile organic solvents, and the final coating product cannot effectively improve the overall anti-corrosion performance. Summary of the Invention

[0006] In view of this, the present invention provides an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating and its preparation method. By obtaining "amphiphilic" functionalized fillers, the epoxy resin phase and the pitch phase are forcibly anchored to avoid microphase separation. At the same time, CGE epoxy groups, modified LDH and epoxy resin are copolymerized and cured to avoid macrophase separation, thus effectively improving the anti-corrosion performance of the coating.

[0007] To achieve the above objectives, the specific solution of the present invention is as follows: a method for preparing an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating, comprising the following preparation steps: S1. Disperse Fe-Al LDH precursor powder in a mixture of anhydrous ethanol and deionized water, and ultrasonically disperse it under heating. Add PTMS dropwise, and after the addition is complete, react for a period of time. Then add KH-560 dropwise, heat, stir and reflux to react, centrifuge, wash, vacuum dry, grind and sieve to obtain modified LDH. S2. Add coal tar pitch and CGE to a reactor, heat under N2 atmosphere, homogenize, shear mix, add modified LDH powder, and mix under high shear to obtain activated asphalt slurry, and keep it warm for later use. S3. Add epoxy resin to a mixing tank, heat it to melt, pour in activated asphalt slurry, stir and mix, cool down, add mica iron oxide and precipitated barium sulfate, pre-disperse, grind, discharge, cool to room temperature, and obtain the main paint component; S4. When ready for use, mix the cashew phenol amine epoxy curing agent with the main paint components to obtain the finished product.

[0008] This invention first adds PTMS (phenyltrimethoxysilane), which, due to its small molecular size, easily enters the LDH interlayer in Fe-AlLDH (iron-aluminum layered double hydroxide) precursor powder for hydrophobic intercalation. Then, by adding KH-560 and heating, it causes condensation grafting at the outer edge of the LDH layer. By utilizing the time difference of addition and the steric hindrance effect, a modified LDH with "interlayer affinity for bitumen and edge affinity for epoxy" is obtained, thus realizing the "amphiphilic" functionalization of the filler.

[0009] By utilizing plant-based CGE (cashew phenol glycidyl ether), which contains aliphatic chains and benzene rings up to 15 carbons, it is easy to penetrate into asphaltene clusters, causing swelling and steric hindrance depolymerization. High-temperature thermal shearing of coal tar pitch using CGE and modified LDH allows the free phenolic hydroxyl groups in the asphalt and the ether oxygen bonds of the CGE molecules to interact with the exposed Fe in the embedded Fe-Al LDH layers. 3+ Multi-site dynamic coordination bonding occurs, allowing LDH to be more uniformly exfoliated and dispersed in the asphalt phase, preventing nanomaterial agglomeration, and providing dynamic crosslinking points for the final coating to slide and dissipate energy under stress, thus improving the fracture toughness of the coating under stress changes. At the same time, CGE and asphalt are highly integrated to form "activated asphalt prepolymer," i.e., activated asphalt slurry, which effectively reduces the viscosity of the system, eliminating the need to add volatile organic solvents to further reduce the viscosity.

[0010] During application, in the main paint mixing and curing stages, the phenyl groups between the modified LDH layers "grab" the polycyclic aromatic hydrocarbons in the coal tar pitch through a strong π-π stacking effect, which is equivalent to a "physical hand" reaching into the pitch phase. Meanwhile, the epoxy groups at the edges participate in the curing reaction of the epoxy resin, which is equivalent to a "chemical hand" reaching into the polar epoxy resin phase. This forces the two originally incompatible phases to anchor, avoids micro-phase separation, and fundamentally closes the microscopic leakage channels of the corrosive medium. At the same time, it activates the CGE epoxy groups in the pitch slurry, and the modified LDH edge epoxy groups copolymerize with the epoxy resin, cure and form without macroscopic phase separation, and finally forms a dense coating containing a triple interpenetrating network of "covalent crosslinking + π-π stacking + metal dynamic coordination", which effectively improves the overall anti-corrosion performance of the coating.

[0011] Preferably, the Fe-Al LDH precursor powder is prepared by the following method: FeCl3·6H2O and AlCl3·6H2O are dissolved in deionized water to obtain a mixed salt solution; Na2CO3 and NaOH are dissolved in deionized water to obtain a mixed alkaline solution; Add deionized water to the reactor, turn on the N2 atmosphere for protection, and simultaneously add the mixed salt solution and mixed alkali solution to the reactor at the same rate while stirring. Control the dropping rate to maintain the pH at 9-11, stir and age, heat to crystallize, centrifuge, wash, vacuum dry, and grind to obtain the final product.

[0012] Preferably, in the preparation process of the Fe-Al LDH precursor powder, FeCl3·6H2O and AlCl3·6H2O are dissolved in deionized water and stirred until completely dissolved. The solution is then purged with N2 bubbles for 15 minutes to obtain a mixed salt solution. Na2CO3 and NaOH are dissolved in deionized water under an ice-water bath and purged with N2 bubbles for 15 minutes. The solution is then cooled to room temperature to obtain a mixed alkaline solution. While stirring at 600-800 rpm, the mixed salt solution and mixed alkali solution are simultaneously added dropwise to the reactor at the same rate, maintaining the pH at 9-11 by controlling the dropping rate at 300-400 mL / min. After the addition is complete, stirring and aging continue for 1 hour. The mixture is then transferred to a high-pressure reactor and crystallized at 110-120℃ for 12-24 hours. After centrifugation at 4000-6000 rpm for 10-15 min, the supernatant is discarded. The mixture is washed 3-4 times with deionized water, and finally washed once with anhydrous ethanol. It is then dried in a drying oven with a vacuum degree <0.1 MPa at 60-80℃ for 12-24 hours, and ground through a 200-mesh sieve to obtain the final product.

[0013] By simultaneously adding a mixed salt solution and a mixed alkali solution to a reaction vessel at the same rate, and controlling the dropping rate at 300-400 mL / min to maintain the pH at 9-11, both metal ions are in a supersaturated state, achieving simultaneous co-precipitation to generate layered LDH. Hydrothermal crystallization further enhances the crystallinity and layered structure regularity of the LDH. This method is simple, efficient, and suitable for industrial production. During the reaction, controlling the dropping rate at 300-400 mL / min generally maintains the pH at 9-11. In special circumstances or if rapid pH adjustment is desired, a small amount of dilute hydrochloric acid or sodium hydroxide can be added, such as by slowly adding 0.5-1 M NaOH solution or 0.5-1 M HCl solution for fine-tuning.

[0014] Preferably, in step S1, the Fe-Al LDH precursor powder is dispersed in a mixture of anhydrous ethanol and deionized water, placed in a reactor, kept at a constant temperature of 50±2℃, and ultrasonically dispersed at a power of 800W and a frequency of 40kHz for 30 minutes. Then, PTMS is added dropwise at a rate of 10mL / min using a peristaltic pump. After the addition is complete, the reaction is carried out for 60 minutes. Then, KH-560 is added dropwise at the same rate. After the addition is complete, the temperature is raised to 65-72℃, and the reaction is carried out under mechanical stirring at 300rpm for 240 minutes. After the reaction is completed, the product is centrifuged at 6000rpm for 10 minutes, washed three times with deionized water, dried for 12 hours under a vacuum of <0.1MPa and a temperature of 56-60℃, and ground through a 200-mesh sieve to obtain powdered modified LDH.

[0015] Preferably, in step S2, before adding the modified LDH powder, a petroleum sulfonate dispersant is added for shear mixing.

[0016] Preferably, in step S2, coal tar pitch and CGE are added to a reactor, heated to 105-115°C under N2 atmosphere protection, homogenized, and sheared at 3500 rpm for 30 minutes. Petroleum sulfonate dispersant is added, and sheared and mixed for 10-15 minutes. Then, modified LDH powder is added in five batches, and high sheared at 4500 rpm for 90 minutes to obtain activated asphalt slurry, which is kept warm for later use. The petroleum sulfonate dispersant is sodium petroleum sulfonate or barium petroleum sulfonate.

[0017] To reduce the impact of complex coal tar pitch composition on Fe 3+ Coordination interference is mitigated by adding petroleum sulfonate dispersants. These dispersants, containing polar sulfonate groups and hydrophobic long-chain alkyl groups, stabilize asphaltenes aggregates, reducing their surface energy. Furthermore, the dispersant forms a protective layer on the asphaltenes surface after adsorption, preventing nitrogen-containing heterocyclic compounds from reacting with Fe. 3+ Excessive contact can promote Fe 3+ Coordination reaction with CGE.

[0018] Preferably, in step S3, the epoxy resin is added to a mixing tank and heated to 78-82°C to melt it. Activated asphalt slurry is then poured in and mixed for 60 minutes using a double planetary mixer at 40 rpm and 120 rpm. Subsequently, the system is cooled to 45-55°C, and mica iron oxide and precipitated barium sulfate are added sequentially. After pre-dispersion at 1200 rpm for 45 minutes, the mixture is pumped into a three-roll mill and ground 2-3 times until the fineness is ≤45μm. The material is then discharged and cooled to room temperature to obtain the main paint component. The epoxy resin is epoxy resin E-20.

[0019] Preferably, in step S4, the cashew phenol amine epoxy curing agent and the main paint component are mechanically stirred and mixed at 300 rpm for 10 minutes at room temperature to obtain a uniformly mixed finished product.

[0020] By employing cashew phenol amine epoxy curing agent, utilizing its C 15 The internal plasticizing effect of long aliphatic chains, along with the presence of a large number of phenolic hydroxyl groups that promote epoxy resin curing and highly reactive aliphatic amines, can improve the toughness of the coating curing system and enable rapid curing even at low temperatures. Furthermore, the polar hydroxyl groups can enhance adhesion to the substrate.

[0021] Another object of the present invention is to provide an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating, which is prepared by the above preparation method and comprises the following raw materials in parts by weight: 12-18 parts of cashew phenol amine epoxy curing agent and 90-100 parts of main paint component; The main paint component comprises the following raw materials in parts by weight: 30-40 parts coal tar pitch and 10-15 parts CGE, 25-35 parts epoxy resin, 10-15 parts mica iron oxide, 7.5-8.5 parts precipitated barium sulfate, 2.5-3.5 parts Fe-Al LDH, 15-18 parts anhydrous ethanol, 1.5-1.8 parts deionized water, 0.1-0.2 parts PTMS, and 0.2-0.3 parts KH-560.

[0022] Preferably, it also includes the following raw materials in parts by weight: 0.4-0.9 parts of petroleum sulfonate dispersant; The Fe-Al LDH comprises the following raw materials in parts by mass: 2.0-2.25 parts FeCl3·6H2O, 2.5-4.02 parts AlCl3·6H2O, 0.8-0.9 parts Na2CO3, and 2.8-3.3 parts NaOH.

[0023] By optimizing the component ratio as described above, the effects of each component are fully realized, resulting in superior corrosion resistance.

[0024] The above-described technical solution of the present invention has at least the following beneficial effects: This invention first adds PTMS, which, due to its small molecular size, easily enters the LDH interlayer in Fe-Al LDH precursor powder for hydrophobic intercalation. Then, by adding KH-560 and heating, it causes condensation grafting at the outer edge of the LDH layer. By utilizing the time difference of addition and the steric hindrance effect, a modified LDH with "interlayer affinity for bitumen and edge affinity for epoxy" is obtained, thus realizing the "amphiphilic" functionalization of the filler.

[0025] 2. This invention utilizes CGE, which readily penetrates asphaltene clusters, causing swelling and steric hindrance depolymerization. Furthermore, by employing CGE and modified LDH to subject coal tar pitch to high-temperature thermal shearing, LDH is more uniformly exfoliated and dispersed within the asphalt phase, preventing nanomaterial agglomeration. This also provides the final coating with dynamic crosslinking points that can slide and dissipate energy under stress, improving the coating's fracture toughness under stress variations. Simultaneously, the high degree of integration between CGE and asphalt effectively reduces the system viscosity, eliminating the need for subsequent addition of volatile organic solvents.

[0026] 3. In the main paint mixing and curing stages, the phenyl groups between the modified LDH layers "capture" the polycyclic aromatic hydrocarbons in the coal tar pitch through a strong π-π stacking effect, while the epoxy groups at the edges participate in the curing reaction of the epoxy resin. This forces the two phases to anchor, preventing micro-phase separation and fundamentally closing the microscopic leakage channels of the corrosive medium. At the same time, it activates the CGE epoxy groups in the asphalt slurry, and the modified LDH edge epoxy groups copolymerize with the epoxy resin, cure and form a solid shape without macroscopic phase separation, effectively improving the overall anti-corrosion performance of the coating. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0028] Cashew phenol amine epoxy curing agent can be prepared using existing conventional methods or purchased directly. The cashew phenol amine epoxy curing agent used in this example and comparative example was purchased directly from Changzhou Shanfeng Chemical Co., Ltd., model SF-PAA-2021-D, with an amine value of 310±20mgKOH / g and a viscosity of 1500-2500mPa.s (25℃).

[0029] Preparation Example 1 Dissolve 2.25 kg FeCl3·6H2O and 4.02 kg AlCl3·6H2O in 12 L of deionized water, stirring until completely dissolved. Then purge with N2 bubbles for 15 minutes to remove dissolved oxygen and prevent Fe from being absorbed. 3+ The mixture was reduced to obtain a mixed salt solution. 0.9 kg Na2CO3 and 3.3 kg NaOH were weighed and dissolved in 33 L of deionized water under an ice-water bath. The solution was purged with N2 bubbles for 15 minutes and then allowed to cool to room temperature to prepare a mixed alkaline solution.

[0030] Add 5L of deionized water as the base solution to the reactor. Under a nitrogen atmosphere, stir at 600-800 rpm. Simultaneously add the mixed salt solution and mixed alkali solution dropwise into the reactor at the same rate using a peristaltic pump, maintaining a dropping rate of 300 mL / min to keep the pH at 9-11. Adjust the dropping rate to control the pH value according to the reaction progress. If necessary, add 0.5-1M NaOH solution or 0.5-1M HCl solution for fine-tuning. React at room temperature. After the addition is complete, continue stirring and aging for 1 hour to ensure complete reaction. Transfer to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE). Crystallize at 115℃ for 24 hours. Centrifuge at 5000 rpm for 15 minutes, discard the supernatant, and wash the precipitate four times with deionized water (centrifuging after each wash) until the pH of the washing solution is neutral (close to 7) and no Cl- is detected by AgNO3 solution. - The residue (no longer producing white precipitate in the washing water) was washed once with anhydrous ethanol to facilitate subsequent drying. It was then dried at 70°C for 20 hours in a drying oven with a vacuum degree <0.1MPa, ground, and passed through a 200-mesh sieve to obtain Fe-Al LDH precursor powder.

[0031] Preparation Example 2 Dissolve 2.0 kg FeCl3·6H2O and 2.5 kg AlCl3·6H2O in 12 kg deionized water and stir until completely dissolved. Remove dissolved oxygen by bubbling with N2 for 15 minutes to obtain a mixed salt solution. Weigh 0.8 kg Na2CO3 and 2.8 kg NaOH and dissolve them in 33 L deionized water in an ice-water bath. Blow with N2 for 15 minutes and let stand at room temperature to prepare a mixed alkali solution.

[0032] Add 5L of deionized water as the base solution to the reactor. Under N2 atmosphere protection, and with stirring at 600rpm, simultaneously add the mixed salt solution and mixed alkali solution dropwise into the reactor at the same rate using a peristaltic pump. Control the dropping rate at 400mL / min to maintain the pH at 9-11. The dropping rate can be adjusted according to the reaction progress. If necessary, 0.5-1M NaOH solution or 0.5-1M HCl solution can be added for fine-tuning. The rate can be slightly increased or decreased depending on the reaction progress. The reaction is carried out at room temperature. After the addition is complete, continue stirring and aging for 1 hour to ensure complete reaction. Transfer the solution to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE). Crystallize at 120℃ for 12 hours. Centrifuge at 4000rpm for 10min, discard the supernatant, and wash the precipitate three times with deionized water (centrifuging after each wash) until the pH of the washing solution is neutral (close to 7) and no Cl is detected by AgNO3 solution. - The residue (no longer producing white precipitate in the washing water) was washed once with anhydrous ethanol to facilitate subsequent drying. It was then dried at 80°C for 12 hours in a drying oven with a vacuum degree <0.1MPa, ground, and passed through a 200-mesh sieve to obtain Fe-Al LDH precursor powder.

[0033] Preparation Example 3 Dissolve 2.2 kg FeCl3·6H2O and 3.8 kg AlCl3·6H2O in 12 kg deionized water and stir until completely dissolved. Remove dissolved oxygen by bubbling with N2 for 15 minutes to obtain a mixed salt solution. Weigh 0.85 kg Na2CO3 and 3.1 kg NaOH and dissolve them in 33 L of deionized water in an ice-water bath. Blow with N2 for 15 minutes and let stand at room temperature to prepare a mixed alkali solution.

[0034] Add 5L of deionized water as the base solution to the reactor. Under a nitrogen atmosphere, stir at 700rpm. Simultaneously add the mixed salt solution and mixed alkali solution dropwise at the same rate using a peristaltic pump, maintaining a dropping rate of 350mL / min to keep the pH between 9 and 11. Adjust the dropping rate as needed to maintain the pH. React at room temperature. After the addition is complete, continue stirring and aging for 1 hour to ensure complete reaction. Transfer the solution to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE). Crystallize at 110℃ for 24 hours. Centrifuge at 6000rpm for 15 minutes, discard the supernatant, and wash the precipitate four times with deionized water (centrifuging after each wash) until the pH of the washing solution is close to 7 and no Cl- is detected by AgNO3 solution. - The residue (no longer producing white precipitate in the washing water) was washed once with anhydrous ethanol to facilitate subsequent drying. It was then dried at 60°C for 24 hours in a drying oven with a vacuum degree <0.1MPa, ground, and passed through a 200-mesh sieve to obtain Fe-Al LDH precursor powder.

[0035] Example 1

[0036] 3.0 kg of Fe-Al LDH (iron-aluminum layered double hydroxide) precursor powder obtained in Preparation Example 1 was dispersed in a mixture of 15 kg of anhydrous ethanol and 1.5 kg of deionized water and placed in an ultrasonic reactor with a power of 800 W and a frequency of 40 kHz. The mixture was ultrasonically dispersed at a constant temperature of 50 ± 2 °C for 30 minutes, followed by the addition of 0.15 kg of PTMS (phenyltrimethoxysilane) dropwise at a rate of 10 mL / min using a peristaltic pump, while continuing ultrasonication and stirring. After the addition was complete, the reaction was allowed to proceed for 60 minutes. Then, 0.25 kg of KH-560 was added dropwise at the same rate. After the addition was complete, the temperature was raised to 70 °C, and the mixture was refluxed with mechanical stirring at 300 rpm for 240 minutes. After the reaction was complete, the mixture was centrifuged at 6000 rpm for 10 minutes, washed three times with deionized water, dried under a vacuum of <0.1 MPa and a temperature of 60 °C for 12 hours, and then ground through a 200-mesh sieve to obtain powdered modified LDH.

[0037] 35 kg of coal tar pitch and 12 kg of CGE (cashew phenol glycidyl ether) were added to a reactor equipped with a high-shear homogenizer. The mixture was heated to 110°C under N2 atmosphere protection, and the homogenizer was started. The mixture was sheared and mixed at 3500 rpm for 30 minutes. 0.8 kg of sodium petroleum sulfonate was added, and the mixture was sheared and mixed for another 15 minutes. Then, modified LDH powder was added in five batches and mixed at 4500 rpm for 90 minutes to obtain activated asphalt slurry. The mixture was kept warm for later use.

[0038] Add 30 kg of epoxy resin E-20 to a double planetary mixer and heat it to 80°C to melt it. Pour in the heat-insulated activated asphalt slurry and mix it for 60 minutes using a double planetary mixer with a revolution of 40 rpm and a rotation of 120 rpm. Then, cool the system to 50°C and add 12 kg of mica iron oxide and 8 kg of precipitated barium sulfate in sequence. Pre-disperse the mixture at 1200 rpm for 45 minutes. Pump the material into a three-roll mill and grind it three times until the fineness is ≤45 μm. Discharge the material and cool it to room temperature to obtain the main paint component.

[0039] When needed, mix 18 kg of cashew phenol amine epoxy curing agent (component B) with 100 kg of main paint component by mechanical stirring at 300 rpm for 10 minutes at room temperature to obtain a uniformly mixed finished coating.

[0040] Example 2

[0041] 2.5 kg of Fe-Al LDH (iron-aluminum layered double hydroxide) precursor powder obtained in Preparation Example 2 was dispersed in a mixture of 15 kg of anhydrous ethanol and 1.5 kg of deionized water and placed in an ultrasonic reactor with a power of 800 W and a frequency of 40 kHz. The mixture was kept under ultrasonication and stirring at 300 rpm for 30 minutes at a constant temperature of 50 ± 2 °C. Then, 0.1 kg of PTMS (phenyltrimethoxysilane) was added dropwise at a rate of 10 mL / min using a peristaltic pump, while continuing ultrasonication and stirring. After the addition was complete, the reaction was allowed to proceed for 60 minutes. Next, 0.2 kg of KH-560 was added dropwise at the same rate. After the addition was complete, the temperature was raised to 65 °C, and the mixture was refluxed under mechanical stirring at 300 rpm for 240 minutes. After the reaction was complete, the mixture was centrifuged at 6000 rpm for 10 minutes, washed three times with deionized water, dried for 12 hours under a vacuum of <0.1 MPa and a temperature of 56 °C, and then ground through a 200-mesh sieve to obtain powdered modified LDH.

[0042] 30 kg of coal tar pitch and 10 kg of CGE (cashew phenol glycidyl ether) were added to a reactor equipped with a high-shear homogenizer. The mixture was heated to 105°C under N2 atmosphere protection, and the homogenizer was started. The mixture was sheared and mixed at 3500 rpm for 30 minutes. 0.4 kg of barium petroleum sulfonate was added, and the mixture was sheared and mixed for another 10 minutes. Then, modified LDH powder was added in five batches and mixed at 4500 rpm for 90 minutes to obtain activated asphalt slurry. The mixture was kept warm for later use.

[0043] 25 kg of epoxy resin E-20 was added to a double planetary mixer and heated to 78°C to melt it. Then, activated asphalt slurry with insulation was poured in and mixed for 60 minutes using a double planetary mixer with a revolution of 40 rpm and a rotation of 120 rpm. The system was then cooled to 45°C, and 10 kg of mica iron oxide and 7.5 kg of precipitated barium sulfate were added in sequence. The mixture was pre-dispersed at 1200 rpm for 45 minutes. The material was then pumped into a three-roll mill and ground twice until the fineness was ≤45 μm. The material was then discharged and cooled to room temperature to obtain the main paint component.

[0044] When needed, mix 12 kg of cashew phenol amine epoxy curing agent (component B) with 90 kg of main paint component by mechanical stirring at 300 rpm for 10 minutes at room temperature to obtain a uniformly mixed finished coating.

[0045] Example 3

[0046] Using the precursor powder of Fe-Al LDH (iron-aluminum layered double hydroxide) obtained in Preparation Example 3, 3.5 kg of Fe-Al LDH (iron-aluminum layered double hydroxide) was dispersed in a mixture of 18 kg of anhydrous ethanol and 1.8 kg of deionized water. The mixture was placed in an ultrasonic reactor with a power of 800 W and a frequency of 40 kHz. The mixture was kept under ultrasonication and stirring at 300 rpm for 30 minutes at a constant temperature of 50 ± 2 °C. Then, 0.2 kg of PTMS (phenyltrimethoxysilane) was added dropwise at a rate of 10 mL / min using a peristaltic pump. During this process, ultrasonication and stirring were continued. After the addition was completed, the reaction was carried out for 60 minutes. Then, 0.3 kg of KH-560 was added dropwise at the same rate. After the addition was completed, the temperature was raised to 72 °C and the mixture was refluxed under mechanical stirring at 300 rpm for 240 minutes. After the reaction was completed, the mixture was centrifuged at 6000 rpm for 10 minutes, washed three times with deionized water, dried for 12 hours under a vacuum of <0.1 MPa and a temperature of 60 °C, and ground through a 200-mesh sieve to obtain powdered modified LDH.

[0047] 40 kg of coal tar pitch and 15 kg of CGE (cashew phenol glycidyl ether) were added to a reactor equipped with a high-shear homogenizer. The mixture was heated to 115°C under N2 atmosphere protection, and the homogenizer was started. The mixture was sheared and mixed at 3500 rpm for 30 minutes. 0.9 kg of sodium petroleum sulfonate was added, and the mixture was sheared and mixed for another 15 minutes. Then, modified LDH powder was added in five batches and mixed at 4500 rpm for 90 minutes to obtain activated asphalt slurry, which was then kept warm for later use.

[0048] Add 35 kg of epoxy resin E-20 to a double planetary mixer and heat it to 82°C to melt it. Pour in the heat-insulated activated asphalt slurry and mix it for 60 minutes using a double planetary mixer with a revolution of 40 rpm and a rotation of 120 rpm. Then, cool the system to 55°C and add 15 kg of mica iron oxide and 8.5 kg of precipitated barium sulfate in sequence. Pre-disperse the mixture at 1200 rpm for 45 minutes. Pump the material into a three-roll mill and grind it three times until the fineness is ≤45 μm. Discharge the material and cool it to room temperature to obtain the main paint component.

[0049] When needed, mix 17 kg of cashew phenol amine epoxy curing agent (component B) with 100 kg of main paint component by mechanical stirring at 300 rpm for 10 minutes at room temperature to obtain a uniformly mixed finished coating.

[0050] Example 4

[0051] 3.1 kg of Fe-Al LDH (iron-aluminum layered double hydroxide) precursor powder obtained in Preparation Example 1 was dispersed in a mixture of 15 kg of anhydrous ethanol and 1.5 kg of deionized water and placed in an ultrasonic reactor with a power of 800 W and a frequency of 40 kHz. The mixture was kept under ultrasonication and stirring at 300 rpm for 30 minutes at a constant temperature of 50 ± 2 °C. Then, 0.16 kg of PTMS (phenyltrimethoxysilane) was added dropwise at a rate of 10 mL / min using a peristaltic pump, while continuing ultrasonication and stirring. After the addition was complete, the reaction was allowed to proceed for 60 minutes. Next, 0.26 kg of KH-560 was added dropwise at the same rate. After the addition was complete, the temperature was raised to 70 °C, and the mixture was refluxed under mechanical stirring at 300 rpm for 240 minutes. After the reaction was complete, the mixture was centrifuged at 6000 rpm for 10 minutes, washed three times with deionized water, dried for 12 hours under a vacuum of <0.1 MPa and a temperature of 59 °C, and then ground through a 200-mesh sieve to obtain powdered modified LDH.

[0052] 35 kg of coal tar pitch and 12 kg of CGE (cashew phenol glycidyl ether) were added to a reactor equipped with a high-shear homogenizer. The mixture was heated to 110°C under N2 atmosphere protection, and the homogenizer was started. The mixture was sheared and mixed at 3500 rpm for 30 minutes. 0.8 kg of sodium petroleum sulfonate was added, and the mixture was sheared and mixed for another 15 minutes. Then, modified LDH powder was added in five batches and mixed at 4500 rpm for 90 minutes to obtain activated asphalt slurry. The mixture was kept warm for later use.

[0053] Add 30 kg of epoxy resin E-20 to a double planetary mixer and heat it to 80°C to melt it. Pour in the heat-insulated activated asphalt slurry and mix it for 60 minutes using a double planetary mixer with a revolution of 40 rpm and a rotation of 120 rpm. Then, cool the system to 50°C and add 12 kg of mica iron oxide and 8 kg of precipitated barium sulfate in sequence. Pre-disperse the mixture at 1200 rpm for 45 minutes. Pump the material into a three-roll mill and grind it three times until the fineness is ≤45 μm. Discharge the material and cool it to room temperature to obtain the main paint component.

[0054] When needed, mix 17 kg of cashew phenol amine epoxy curing agent (component B) with 96 kg of main paint component by mechanical stirring at 300 rpm for 10 minutes at room temperature to obtain a uniformly mixed finished coating.

[0055] Example 5

[0056] 3.0 kg of Fe-Al LDH (iron-aluminum layered double hydroxide) precursor powder obtained in Preparation Example 1 was dispersed in a mixture of 15 kg of anhydrous ethanol and 1.5 kg of deionized water and placed in an ultrasonic reactor with a power of 800 W and a frequency of 40 kHz. The mixture was kept under ultrasonication and stirring at 300 rpm for 30 minutes at a constant temperature of 50 ± 2 °C. Then, 0.15 kg of PTMS (phenyltrimethoxysilane) was added dropwise at a rate of 10 mL / min using a peristaltic pump, while continuing ultrasonication and stirring. After the addition was complete, the reaction was allowed to proceed for 60 minutes. Next, 0.25 kg of KH-560 was added dropwise at the same rate. After the addition was complete, the temperature was raised to 68 °C, and the mixture was refluxed under mechanical stirring at 300 rpm for 240 minutes. After the reaction was complete, the mixture was centrifuged at 6000 rpm for 10 minutes, washed three times with deionized water, dried for 12 hours under a vacuum of <0.1 MPa and a temperature of 60 °C, and then ground through a 200-mesh sieve to obtain powdered modified LDH.

[0057] 33 kg of coal tar pitch and 11.5 kg of CGE (cashew phenol glycidyl ether) were added to a reactor equipped with a high-shear homogenizer. The mixture was heated to 110°C under N2 atmosphere protection, and the homogenizer was started. The mixture was sheared and mixed at 3500 rpm for 30 minutes. 0.7 kg of sodium petroleum sulfonate was added, and the mixture was sheared and mixed for another 15 minutes. Then, modified LDH powder was added in five batches and mixed at 4500 rpm for 90 minutes to obtain activated asphalt slurry, which was then kept warm for later use.

[0058] Add 30 kg of epoxy resin E-20 to a double planetary mixer and heat it to 80°C to melt it. Pour in the heat-insulated activated asphalt slurry and mix it for 60 minutes using a double planetary mixer with a revolution of 40 rpm and a rotation of 120 rpm. Then, cool the system to 50°C and add 11.5 kg of mica iron oxide and 8 kg of precipitated barium sulfate in sequence. Pre-disperse the mixture at 1200 rpm for 45 minutes. Pump the material into a three-roll mill and grind it three times until the fineness is ≤45 μm. Discharge the material and cool it to room temperature to obtain the main paint component.

[0059] When needed, mix 15 kg of cashew phenol amine epoxy curing agent (component B) with 100 kg of main paint component by mechanical stirring at 300 rpm for 10 minutes at room temperature to obtain a uniformly mixed finished coating.

[0060] The present invention also includes the following comparative examples 1-5 and related tests were conducted.

[0061] Comparative Example 1 Compared with Example 1, no modified LDH was prepared; instead, Fe-Al LDH precursor powder was used directly. All other preparation steps and condition control were the same, resulting in the finished coating product.

[0062] Comparative Example 2 Compared with Example 1, PTMS and KH-560 were added dropwise simultaneously during the preparation of modified LDH and reacted together. Other preparation steps and condition control were the same, and the finished coating product was obtained.

[0063] Comparative Example 3 Compared with Example 1, PTMS was not added dropwise; instead, KH-560 was used to modify the Fe-Al LDH precursor powder. All other preparation steps and condition controls were the same, resulting in the finished coating product.

[0064] Comparative Example 4 Compared with Example 1, CGE was not added and high-temperature shearing was not performed. Instead, xylene was used and a conventional room-temperature dissolution method was adopted. All other preparation steps and condition control were the same, and the finished coating product was obtained.

[0065] Comparative Example 5 Compared with Example 1, the cashew phenolic amine epoxy curing agent was replaced with T-31 phenolic amine, a commonly used curing agent in the coatings industry. All other preparation steps and condition control were the same, and the finished coating product was obtained.

[0066] The coating products obtained in Examples 1-5 and Comparative Examples 1-5 were uniformly sprayed onto Q235 steel plates treated with Sa2.5 grade sandblasting using a high-pressure airless spraying equipment. The dry film thickness was controlled to be 300±20μm, and the coatings were placed in a standard curing room at a temperature of 25±2℃ and a relative humidity of 50±5% for 7 days to obtain corresponding coating samples for subsequent performance testing.

[0067] (I) Electrochemical Impedance Spectroscopy (EIS) Test: Electrochemical impedance spectroscopy tests were performed on the coating samples formed by the coatings of Examples 1-5 and Comparative Examples 1-5, according to standard GB / T 39482.1-2023. The samples were immersed in 3.5% NaCl solution, and the test frequency range was 10 Hz. 5 -10 -2 Hz, disturbance signal 20mV, detect the low-frequency impedance modulus |Z| after immersion for 1000h. 0.01Hz The unit is Ω·cm², and the summarized data results are shown in Table 1.

[0068] (II) Neutral salt spray resistance test: The coating samples formed by the coatings of Examples 1-5 and Comparative Examples 1-5 were tested in accordance with the standard GB / T 1771-2007. A 5% wt NaCl solution was used at a temperature of 35℃ for continuous spraying. Whether the coating samples showed any abnormalities such as blistering or rust spots and the time of occurrence were recorded. The test results are summarized in Table 1 below.

[0069] Table 1: Results of Electrochemical Impedance Spectroscopy and Neutral Salt Spray Resistance Tests (III) Flexibility test: Referring to GB / T 1731-2020, the coatings of Examples 1-5 and Comparative Examples 1-5 were applied to tinplate test plates with a size of 120mm×25mm. After drying, the test plates were pressed tightly against a standard shaft with the coating facing upward and bent. The minimum shaft diameter at which the coating did not break was tested, and the results were recorded as shown in Table 2 below.

[0070] (iv) Adhesion (pull-off method) test: Refer to GB / T 5210-2006, test the coating samples formed by the coatings of Examples 1-5 and Comparative Examples 1-5. Use test columns with a diameter of 20 mm to test the pull-out strength (MPa) of the coating, and observe whether the failure mode is cohesive failure or interfacial peeling. Record the results and summarize them as shown in Table 2 below.

[0071] Table 2: Results of Flexibility and Adhesion Tests

[0072] As can be seen from the test results in Table 1-2 above, the coatings formed by the coatings obtained in Examples 1-5 of the present invention still have a high low-frequency impedance modulus after immersion for 1000h, indicating that the coatings of this embodiment can effectively inhibit microphase separation, have high anti-permeability, and can withstand 4000h of salt spray resistance test without any abnormalities. They also have strong anti-foaming and anti-corrosion capabilities, and the coatings as a whole have excellent anti-corrosion performance. Furthermore, the adhesion reaches more than 15.3MPa, and the flexibility is within 1mm, showing excellent adhesion and flexibility.

[0073] Comparative Example 1, lacking modification of Fe-Al LDH, exhibited poor compatibility, resulting in a significant decrease in low-frequency impedance modulus, poor salt spray resistance, and an inability to effectively improve corrosion resistance. Adhesion and flexibility were also affected. Comparative Examples 2 and 3, while modifying Fe-Al LDH, showed poor modification effects due to the simultaneous addition of PTMS and KH-560, or the use of only KH-560. This led to a significant decrease in low-frequency impedance modulus, impacted salt spray resistance, and resulted in minor bubbling, ultimately deteriorating overall corrosion resistance. Comparative Example 4 used xylene instead of CGE. Xylene, a volatile organic solvent, rapidly evaporates during use, easily causing numerous pinholes, resulting in ineffective corrosion protection, poor adhesion and flexibility, and even interfacial peeling. Comparative Example 5 used T-31 curing agent instead of cashew phenol amine epoxy curing agent, leading to a significant decrease in adhesion and flexibility.

[0074] The above are preferred embodiments of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating, characterized in that: The preparation steps include the following: S1. Disperse Fe-Al LDH precursor powder in a mixture of anhydrous ethanol and deionized water, and ultrasonically disperse it under heating. Add PTMS dropwise, and after the addition is complete, react for a period of time. Then add KH-560 dropwise, heat, stir and reflux to react, centrifuge, wash, vacuum dry, grind and sieve to obtain modified LDH. S2. Add coal tar pitch and CGE to a reactor, heat under N2 atmosphere, homogenize, shear mix, add modified LDH powder, and mix under high shear to obtain activated asphalt slurry, and keep it warm for later use. S3. Add epoxy resin to a mixing tank, heat it to melt, pour in activated asphalt slurry, stir and mix, cool down, add mica iron oxide and precipitated barium sulfate, pre-disperse, grind, discharge, cool to room temperature, and obtain the main paint component; S4. When ready for use, mix the cashew phenol amine epoxy curing agent with the main paint components to obtain the finished product.

2. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 1, characterized in that: The Fe-Al LDH precursor powder was prepared by the following method: FeCl3·6H2O and AlCl3·6H2O were dissolved in deionized water to obtain a mixed salt solution; Na2CO3 and NaOH were dissolved in deionized water to obtain a mixed alkaline solution. Add deionized water to the reactor, turn on the N2 atmosphere for protection, and simultaneously add the mixed salt solution and mixed alkali solution to the reactor at the same rate while stirring. Control the dropping rate to maintain the pH at 9-11, stir and age, heat to crystallize, centrifuge, wash, vacuum dry, and grind to obtain the final product.

3. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 2, characterized in that: In the preparation of the Fe-Al LDH precursor powder, FeCl3·6H2O and AlCl3·6H2O are dissolved in deionized water and stirred until completely dissolved. The solution is then purged with N2 bubbles for 15 minutes to obtain a mixed salt solution. Na2CO3 and NaOH are dissolved in deionized water under an ice-water bath and purged with N2 bubbles for 15 minutes. The solution is then cooled to room temperature to obtain a mixed alkaline solution. While stirring at 600-800 rpm, the mixed salt solution and mixed alkali solution are simultaneously added dropwise to the reactor at the same rate, maintaining the pH at 9-11 by controlling the dropping rate at 300-400 mL / min. After the addition is complete, stirring and aging continue for 1 hour. The mixture is then transferred to a high-pressure reactor and crystallized at 110-120℃ for 12-24 hours. After centrifugation at 4000-6000 rpm for 10-15 min, the supernatant is discarded. The mixture is washed 3-4 times with deionized water, and finally washed once with anhydrous ethanol. It is then dried in a drying oven with a vacuum degree <0.1 MPa at 60-80℃ for 12-24 hours, and ground through a 200-mesh sieve to obtain the final product.

4. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 1, characterized in that: In step S1, Fe-Al LDH precursor powder is dispersed in a mixture of anhydrous ethanol and deionized water, placed in a reactor, kept at a constant temperature of 50±2℃, and subjected to ultrasonication at 800W power and 40kHz frequency with stirring at 300rpm. After ultrasonic dispersion for 30 minutes, PTMS is added dropwise at a rate of 10mL / min using a peristaltic pump. After the addition is complete, the reaction is allowed to proceed for 60 minutes. Then, KH-560 is added dropwise at the same rate. After the addition is complete, the temperature is raised to 65-72℃, and the reaction is carried out under reflux with mechanical stirring at 300rpm for 240 minutes. After the reaction is completed, the product is centrifuged at 6000rpm for 10 minutes, washed three times with deionized water, dried for 12 hours under a vacuum of <0.1MPa and a temperature of 56-60℃, and ground through a 200-mesh sieve to obtain powdered modified LDH.

5. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 1, characterized in that: In step S2, before adding the modified LDH powder, a petroleum sulfonate dispersant is added for shear mixing.

6. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 5, characterized in that: In step S2, coal tar pitch and CGE are added to a reactor and heated to 105-115°C under N2 atmosphere protection for homogenization. The mixture is sheared and mixed at 3500 rpm for 30 minutes. Petroleum sulfonate dispersant is added and sheared and mixed for 10-15 minutes. Then, modified LDH powder is added in five batches and mixed at 4500 rpm under high shear for 90 minutes to obtain activated asphalt slurry, which is then kept warm for later use. The petroleum sulfonate dispersant is sodium petroleum sulfonate or barium petroleum sulfonate.

7. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 1, characterized in that: In step S3, epoxy resin is added to a mixing tank and heated to 78-82℃ to melt it. Activated asphalt slurry is then poured in and mixed for 60 minutes using a double planetary mixer at 40 rpm and 120 rpm. The system is then cooled to 45-55℃, and mica iron oxide and precipitated barium sulfate are added sequentially. After pre-dispersion at 1200 rpm for 45 minutes, the mixture is pumped into a three-roll mill and ground 2-3 times until the fineness is ≤45μm. The material is then discharged and cooled to room temperature to obtain the main paint component. The epoxy resin is epoxy resin E-20.

8. The preparation method of an epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 1, characterized in that: In step S4, the cashew phenol amine epoxy curing agent and the main paint component are mechanically stirred and mixed at 300 rpm for 10 min at room temperature to obtain a uniformly mixed finished product; the amine value of the cashew phenol amine epoxy curing agent is 310±20 mgKOH / g, and the viscosity at 25℃ is 1500-2500 mPa.s.

9. An epoxy-modified coal tar pitch heavy-duty anti-corrosion coating, characterized in that: The epoxy-modified coal tar pitch heavy-duty anti-corrosion coating is prepared by the preparation method of any one of claims 1-8, comprising the following raw materials in parts by weight: 12-18 parts of cashew phenol amine epoxy curing agent and 90-100 parts of main paint component; The main paint component comprises the following raw materials in parts by weight: 30-40 parts coal tar pitch and 10-15 parts CGE, 25-35 parts epoxy resin, 10-15 parts mica iron oxide, 7.5-8.5 parts precipitated barium sulfate, 2.5-3.5 parts Fe-Al LDH, 15-18 parts anhydrous ethanol, 1.5-1.8 parts deionized water, 0.1-0.2 parts PTMS, and 0.2-0.3 parts KH-560.

10. The epoxy-modified coal tar pitch heavy-duty anti-corrosion coating according to claim 9, characterized in that: It also includes the following raw materials in parts by weight: 0.4-0.9 parts petroleum sulfonate dispersant; The Fe-Al LDH comprises the following raw materials in parts by mass: 2.0-2.25 parts FeCl3·6H2O, 2.5-4.02 parts AlCl3·6H2O, 0.8-0.9 parts Na2CO3, and 2.8-3.3 parts NaOH.

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