N-hap hot-dip plastic steel pipe surface anticorrosion modified polyethylene coating and preparation method thereof

Abstract

This invention discloses an anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipes and its preparation method, belonging to the field of coating technology. The invention comprises the following raw materials in parts by weight: 45-50 parts of synergistic microspheres, 30-32 parts of modified filler, 10-15 parts of nano-fumed silica, 1.5-2 parts of anhydrous ethanol, 50-60 parts of maleic anhydride-grafted polyethylene, 700-800 parts of medium-density polyethylene, 200-240 parts of high-density polyethylene, 100-120 parts of linear low-density polyethylene, 7-8 parts of antioxidant, 20-25 parts of polyethylene wax, and 15-20 parts of black masterbatch. The introduction of synergistic microspheres and modified filler effectively improves the wear resistance, corrosion resistance, scale resistance, and heat resistance of the anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipes. Therefore, this invention has a wider range of application prospects.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipes and its preparation method. Background Technology

[0002] N-HAP hot-dip plastic-coated steel pipes combine the high pressure resistance and impact resistance of steel pipes with the corrosion resistance and insulation advantages of polymer coatings, making them a core pipe material in engineering fields such as municipal water supply and drainage, power and communication wiring, chemical media transportation, and urban and rural pipeline network renovation. The anti-corrosion modified polyethylene coating used on the surface of N-HAP hot-dip plastic-coated steel pipes is the core functional material that determines the pipe's protective effect, service life, and operational stability.

[0003] However, in practical engineering applications, the existing anti-corrosion modified polyethylene coatings used on the surface of N-HAP hot-dip plastic-coated steel pipes still have the following performance shortcomings: First, insufficient wear and scratch resistance; during underground laying and cable routing, the coating is easily damaged by sand and gravel friction and hard object scratches. Second, insufficient long-term anti-corrosion performance; under harsh conditions such as chloride ion corrosion, the adhesion between the coating and the metal substrate rapidly declines, easily leading to blistering, cracking, and peeling. Third, poor anti-scaling performance; in water supply, drainage, and circulating water transportation scenarios, calcium and magnesium scale easily adheres to the coating surface, causing narrowing of the pipe diameter and a continuous decrease in transportation efficiency. Fourth, insufficient heat aging resistance; under long-term hot and humid environments such as high underground temperatures in summer and fluctuating medium temperatures, the coating is prone to creep, aging, and embrittlement, resulting in a significant decrease in structural integrity and adhesion. Therefore, the wear resistance, corrosion resistance, anti-scaling, and heat resistance of the existing anti-corrosion modified polyethylene coatings used on the surface of N-HAP hot-dip plastic-coated steel pipes still need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide an anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipes and its preparation method, thereby solving the following technical problems: The existing N-HAP hot-dip plastic-coated steel pipe surface coating with anti-corrosion modified polyethylene coating still has problems with poor wear resistance, corrosion resistance, scale resistance and heat resistance.

[0005] The objective of this invention can be achieved through the following technical solutions: The composition by weight includes: 45-50 parts of a polyisocyanate-terminated polyurethane prepolymer prepared by reacting polycaprolactone diol and isophorone diisocyanate under stannous octoate catalysis, which is first chain-extended with aminopropyl double-terminated polydimethylsiloxane, then reacted with cross-linked microgel powder to form core-shell microspheres, and then modified with N-(-aminoethyl)-3-aminopropyltrimethoxysilane to form synergistic microspheres; and intercalated nanosheets which are first stepwise intercalated with sodium phytate and ε-polylysine hydrochloride, then ultrasonically exfoliated, and then reacted with cerium nitrate to introduce a cerium source, and then subjected to the original... The modified filler, prepared by precipitation, microwave hydrothermal crystallization, calcination at 300℃ in a nitrogen atmosphere, and finally modified with γ-glycidyl etheroxypropyltrimethoxysilane, consists of 30-32 parts; nano-fumed silica, 10-15 parts; anhydrous ethanol, 1.5-2 parts; maleic anhydride-grafted polyethylene, 50-60 parts; high-density polyethylene, 200-240 parts; linear low-density polyethylene, 100-120 parts; antioxidant, 7-8 parts; polyethylene wax, 20-25 parts; black masterbatch, 15-20 parts; and medium-density polyethylene, 700-800 parts.

[0006] Preferably, the method for preparing the synergistic microspheres is as follows: A1: Add polysuccinimide to N,N-dimethylformamide and stir for 20-30 min. Then add asymmetric monoaminopropyl-terminated polydimethylsiloxane and ethylenediamine and stir for 5 h at 65 °C under a nitrogen atmosphere. Then add deionized water and let stand for 30-60 min. After centrifugation, washing and freeze drying, cross-linked microgel powder is obtained. A2: Polycaprolactone diol, isophorone diisocyanate, and stannous octoate were added to anhydrous tetrahydrofuran and stirred at 60°C under a nitrogen atmosphere for 3 hours. After cooling to 30°C, aminopropyl double-terminated polydimethylsiloxane was added and stirred for 1 hour. Then, cross-linked microgel powder was added and ultrasonically dispersed for 30 minutes. The mixture was then stirred at 60°C under a nitrogen atmosphere for 2 hours. Subsequently, the mixture was distilled under reduced pressure, centrifuged, washed, and dried to obtain core-shell microspheres. A3: Core-shell microspheres were added to toluene and ultrasonically dispersed for 30 min. Then, N-(-aminoethyl)-3-aminopropyltrimethoxysilane and deionized water were added and stirred at 80 °C under a nitrogen atmosphere for 3 h. After centrifugation, washing and drying, the enhanced microspheres were obtained.

[0007] Preferably, the mass ratio of N,N-dimethylformamide, polysuccinimide, asymmetric monoaminopropyl-terminated polydimethylsiloxane, ethylenediamine, and deionized water in A1 is 200-220:50:25:5:1500. The ratio of anhydrous tetrahydrofuran, polycaprolactone diol, isophorone diisocyanate, stannous octoate, aminopropyl double-terminated polydimethylsiloxane, and crosslinked microgel powder in A2 is 900-950mL:8g:2.4g:0.05g:5g:50-52g.

[0008] Preferably, the mass ratio of toluene, core-shell microspheres, N-(-aminoethyl)-3-aminopropyltrimethoxysilane, and deionized water in A3 is 250-260:50-52:2:0.5.

[0009] Preferably, the modified filler is prepared by the following method: B1: Under a nitrogen atmosphere, magnesium nitrate hexahydrate and aluminum nitrate nonahydrate were added to deionized water, and then simultaneously and dropwise with sodium hydroxide aqueous solution into a reaction vessel at 60°C (the pH of the system was controlled at 9.9-10.1, the dropwise addition time was 1 h, and the mixture was stirred while adding). The mixture was then stirred for 1 h, and then transferred to a polytetrafluoroethylene hydrothermal reactor for crystallization at 110°C for 12 h. After that, the mixture was centrifuged, washed, and dried to obtain intercalated nanosheets. B2: Under a nitrogen atmosphere, intercalated nanosheets were added to deionized water and ultrasonically dispersed for 30 min. Then, sodium phytate was added and the pH was adjusted to 9.0. The mixture was stirred at 70 °C for 6 h. ε-polylysine hydrochloride was then added and stirred for 2 h. The mixture was then centrifuged, washed, and dried to obtain co-intercalated modified nanosheets. B3: Under a nitrogen atmosphere, deionized water was added to anhydrous ethanol and stirred for 10-20 min. Then, co-intercalated nanosheets were added and ultrasonically exfoliated for 30 min. The temperature was then raised to 60℃ and cerium nitrate solution was added dropwise at 5 g / min while stirring. The pH was then adjusted to 9.5 with ammonia and stirred for 30 min. The mixture was then transferred to a microwave hydrothermal reactor and microwaved at 140℃ for 30 min at a power of 500 W. After cooling to room temperature, the mixture was centrifuged, washed, and finally calcined at 300℃ under a nitrogen atmosphere for 2 h. After cooling, the heterostructured filler was obtained. B4: Add the heterostructured filler to xylene and ultrasonically disperse for 30 min. Then add deionized water and adjust the pH to 4.0-4.5. Stir for 10 min and then add γ-glycidoxypropyltrimethoxysilane. Stir at 60℃ under nitrogen atmosphere for 1.5 h. Then heat to 140℃ and reflux with water under nitrogen atmosphere for 4 h (a water separator is installed to separate the methanol and excess water generated in the reaction). After cooling to 60℃, centrifuge, wash and dry to obtain the modified filler.

[0010] Preferably, the mass ratio of the deionized water, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and sodium hydroxide aqueous solution in B1 is 200-240:51.2:37.5:400; The concentration of the sodium hydroxide aqueous solution is 1.5 mol / L.

[0011] Preferably, the mass ratio of deionized water, intercalated nanosheets, sodium phytate, and ε-polylysine hydrochloride in B2 is 500-550:50-52:25:5.

[0012] Preferably, the mass ratio of anhydrous ethanol, deionized water, co-intercalated nanosheets, and cerium nitrate solution in B3 is 300:200:50:300-320; The cerium nitrate solution described in B3 is obtained by mixing anhydrous ethanol and cerium nitrate hexahydrate in a mass ratio of 300-320:12.

[0013] Preferably, the ratio of xylene, heterostructure filler, deionized water, and γ-glycidyl etheroxypropyltrimethoxysilane in B4 is 250-260 mL: 50-52 g: 0.5 g: 4.5 g.

[0014] The preparation method of anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe includes the following steps: The enhanced microspheres, modified fillers, nano-fumed silica, and anhydrous ethanol are mixed and stirred for 10-20 minutes. Then, maleic anhydride-grafted polyethylene is added and stirred for 6-8 minutes. Next, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, antioxidants, polyethylene wax, and black masterbatch are added and mixed at 40-50℃ for 18-20 minutes. Subsequently, the mixture is fed into a parallel twin-screw extruder for melt blending treatment at a feeding section of 140-150℃, a compression section of 165-175℃, a metering section of 175-180℃, a die head of 180-185℃, a screw speed of 100-110 r / min, and a material residence time in the barrel of 1.5-2 minutes. The extruded molten strip is water-cooled, pelletized, and finally cryogenically pulverized and sieved to obtain a modified polyethylene coating with a particle size of 100-200 μm.

[0015] The beneficial effects of this invention are: This invention provides a corrosion-resistant modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipes and its preparation method. This invention simultaneously improves the wear resistance, corrosion resistance, scale resistance, and heat resistance of the corrosion-resistant modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipes through the following method.

[0016] (1) The enhanced microspheres of this invention are made of polyasparagine-based crosslinked microgel (prepared by ring-opening crosslinking reaction of polysuccinimide with asymmetric monoaminopropyl-terminated polydimethylsiloxane and ethylenediamine) as the core, polycaprolactone-polydimethylsiloxane polyurethane-urea block as the shell, and the surface is modified by N-(-aminoethyl)-3-aminopropyltrimethoxysilane; the enhanced microspheres have active amino groups, amide bonds and migratable low surface energy siloxane segments. The active amino groups on the surface of the microspheres can be ring-opened covalently bonded with the anhydride groups of maleic anhydride-grafted polyethylene, and at the same time form hydrogen bonds with the hydroxyl groups on the surface of phosphated steel plate and coordinate bonds with metal ions on the surface of steel plate, solving the core problem of weak interfacial bonding between nonpolar polyethylene and metal substrate, significantly improving the adhesion of coating-substrate interface and inhibiting peeling failure. The polyasparagine-based cross-linked microgel core within the microspheres enhances the coating's toughness, while the polyurethane-urea shell effectively disperses frictional stress and reduces plowing and shedding. The uniformly dispersed microspheres prevent stress concentration, reduce mass loss during friction, and further improve wear resistance. The low surface energy polydimethylsiloxane segments in the microspheres slow the penetration rate of corrosive media such as water and chloride ions, while the cross-linked core structure fills the coating's micropores, reducing the channels for corrosive media transport and extending the coating's corrosion resistance life. The polydimethylsiloxane segments in the microspheres spontaneously migrate and accumulate on the coating surface during film formation, creating a hydrophobic slip interface that reduces the adhesion of calcium and magnesium scale to the coating. Simultaneously, the polar groups interfere with the formation and growth of calcium and magnesium scale nuclei, significantly reducing the amount of scale buildup per unit area. The active amino groups, secondary amine groups, and active hydrogen atoms on urea / urethane bonds in the microspheres can capture thermo-oxidative aging free radicals, inhibiting high-temperature thermo-oxidative chain scission of polyethylene molecular chains. The cross-linked polyamide network can maintain the structural stability of the microspheres at high temperatures. The covalent bonding between the microspheres and the matrix can alleviate the rapid decay of interfacial adhesion at high temperatures, improving the adhesion retention rate of the coating after thermal aging. The surface enrichment effect of low surface energy polydimethylsiloxane segments in the microspheres can significantly reduce the surface energy of the coating, reduce surface polar sites, and improve the static water contact angle of the coating.

[0017] (2) The modified filler of this invention is prepared by stepwise intercalation of sodium phytate-ε-polylysine hydrochloride to obtain magnesium aluminum hydrotalcite as the matrix, first loading nano-cerium oxide, and then modifying the surface with γ-glycidyl etheroxypropyltrimethoxysilane; the modified filler is a two-dimensional sheet organic-inorganic heterostructure. The epoxy silane on the surface of the modified filler can improve the interfacial compatibility with the polyethylene matrix, and the epoxy groups can react with the active amino and hydroxyl groups of the system to avoid interfacial defects caused by filler agglomeration and help maintain the overall adhesion between the coating and the substrate. The two-dimensional sheet hydrotalcite and hard nano-cerium oxide can form a reinforcing skeleton in the coating, improve the coating hardness and anti-plowing ability; the sheet structure can disperse frictional stress, and nano-cerium oxide plays a micro-bearing lubrication role, greatly reducing frictional mass loss, and is the core regulating component of the coating wear resistance performance. Two-dimensional lamellar structures can create a "maze effect" in coatings, significantly extending the penetration path of corrosive media. Intercalated sodium phytate and polylysine can capture chloride ions and release corrosion-inhibiting groups, forming a passivation film on the metal surface. Nano-cerium oxide can capture free radicals generated during corrosion and aging processes, and help improve the coating's density and electrochemical stability. Synergistically with organic intercalating agents, it constructs a multi-layered anti-corrosion system of "barrier-corrosion inhibition-passivation," effectively improving the coating's long-term anti-corrosion capability. The slowly released polylysine between filler layers can interfere with the formation and growth of calcium and magnesium scale nuclei, inhibiting hard scale deposition. Lamellar fillers can increase coating density, reduce scale adhesion anchor points, and help reduce scale buildup. Two-dimensional lamellar structures can block the diffusion of oxygen and thermally decomposed small molecules, inhibiting the thermo-oxidative aging of polyethylene. Nano-cerium oxide can efficiently capture thermo-oxidative aging free radicals, terminating the chain aging reaction. Silane modification can improve the compatibility and dispersion uniformity of the filler and the polyethylene matrix, preventing filler agglomeration at high temperatures and significantly improving the coating's heat aging resistance and adhesion retention. Silane modification optimizes the dispersion of fillers in the matrix. Uniformly dispersed two-dimensional lamellar fillers can form a dense barrier structure in the coating, reducing surface defects. The low surface energy components of the synergistic microspheres jointly improve the static water contact angle of the coating, enhancing its hydrophobic properties. The synergistic microspheres solve the bottleneck of interfacial bonding between non-polar polyethylene and metal substrates, while improving the dispersion of modified fillers in the matrix. The modified fillers enhance the bulk strength, barrier properties, and thermal stability of the coating. The two components complement each other without performance antagonism, achieving simultaneous improvement in the coating's interfacial properties, bulk properties, surface properties, and long-term protective performance.

[0018] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention: The following products were purchased: asymmetric monoaminopropyl-terminated polydimethylsiloxane (PDM) from Shanghai Maclean Biochemical Technology Co., Ltd. (item number: A708844); polycaprolactone diol from Shanghai Aladdin Biochemical Technology Co., Ltd. (item number: P303566); aminopropyl di-terminated PDM from Shanghai Maclean Biochemical Technology Co., Ltd. (item number: A850310); nano-fumed silica from Guangzhou Shenna Trading Co., Ltd. (model: SR380); maleic anhydride-grafted polyethylene (brand name: Arkema OREVAC 18302N); medium-density polyethylene (brand name: Qilu Petrochemical QHM22F); and high-density polyethylene (brand name: Borpure). TM MB6561; Linear low-density polyethylene, grade: Sinopec DFDA-7042; Polyethylene wax, grade: Honeywell AC 6A.

[0021] Example 1: The preparation method of anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe is as follows: S1: Add 50g of polysuccinimide to 200g of N,N-dimethylformamide and stir for 20min. Then add 25g of asymmetric monoaminopropyl-terminated polydimethylsiloxane and 5g of ethylenediamine and stir for 5h at 65℃ under nitrogen atmosphere. Then add 1500g of deionized water and let stand for 30min. Then centrifuge and wash 5 times with a mixture of deionized water and anhydrous ethanol. Finally freeze-dry at -40℃ for 24h to obtain cross-linked microgel powder. S2: Under anhydrous and oxygen-free conditions, 8g of polycaprolactone diol, 2.4g of isophorone diisocyanate, and 0.05g of stannous octoate were added to 900mL of anhydrous tetrahydrofuran and stirred for 3h under a nitrogen atmosphere at 60℃. After cooling to 30℃, 5g of aminopropyl double-terminated polydimethylsiloxane was added and stirred for 1h. Then, 50g of cross-linked microgel powder was added and ultrasonically dispersed for 30min. Then, the mixture was stirred for 2h under a nitrogen atmosphere at 60℃. Subsequently, the solvent was removed by vacuum distillation, centrifugation was performed, and the precipitate was washed three times with anhydrous ethanol. Finally, the precipitate was vacuum dried at 50℃ for 12h to obtain core-shell microspheres. S3: Add 50g of core-shell microspheres to 250g of toluene and disperse by ultrasonication for 30min. Then add 2g of N-(-aminoethyl)-3-aminopropyltrimethoxysilane and 0.5g of deionized water and stir for 3h under nitrogen atmosphere at 80℃. Then centrifuge and wash the precipitate three times with anhydrous toluene. Finally, vacuum dry at 60℃ for 12h to obtain the enhanced microspheres. S4: Under a nitrogen atmosphere, 51.2 g of magnesium nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate were added to 200 g of deionized water. Then, at 60 °C, they were simultaneously and dropwise added to a reaction vessel along with 400 g of 1.5 mol / L sodium hydroxide aqueous solution (the pH of the system was controlled at 9.9-10.1, the addition time was 1 h, and the mixture was stirred while adding). The mixture was stirred for 1 h, then transferred to a polytetrafluoroethylene hydrothermal reactor and crystallized at 110 °C for 12 h. After that, the mixture was centrifuged and washed with degassed deionized water until neutral. Finally, it was vacuum dried at 60 °C for 12 h to obtain intercalated nanosheets. S5: Under a nitrogen atmosphere, 50g of intercalated nanosheets were added to 500mL of degassed deionized water and ultrasonically dispersed for 30min. Then, 25g of sodium phytate was added and the pH was adjusted to 9.0 with sodium hydroxide aqueous solution. The mixture was stirred at 70℃ for 6h. Subsequently, 5g of ε-polylysine hydrochloride was added and stirred for 2h. The mixture was then centrifuged and washed three times with degassed deionized water. Finally, it was vacuum dried at 55℃ for 12h to obtain co-intercalated modified nanosheets. S6: Add 12g of cerium nitrate hexahydrate to 300g of anhydrous ethanol and stir for 30min to obtain a cerium nitrate solution; S7: Under a nitrogen atmosphere, 200g of deionized water was added to 300g of anhydrous ethanol and stirred for 10min. Then, 50g of co-intercalated nanosheets were added and ultrasonically exfoliated for 30min. The temperature was then raised to 60℃ and 300g of cerium nitrate solution was added dropwise at 5g / min while stirring. The pH was then adjusted to 9.5 with ammonia and stirred for 30min. The mixture was then transferred to a microwave hydrothermal reactor and microwaved at 140℃ for 30min at a power of 500W. After cooling to room temperature, the mixture was centrifuged and the precipitate was washed three times with anhydrous ethanol. Finally, the mixture was calcined at 300℃ under a nitrogen atmosphere for 2h and cooled to obtain the heterostructured filler. S8: Add 50g of heterostructured filler to 250mL xylene and ultrasonically disperse for 30min. Then add 0.5g of degassed deionized water and adjust the pH to 4.0 with glacial acetic acid. Stir for 10min, then add 4.5g of γ-glycidoxypropyltrimethoxysilane and stir at 60℃ under nitrogen atmosphere for 1.5h. Then heat to 140℃ and reflux with water under nitrogen atmosphere for 4h (a water separator is installed to separate the methanol and excess water generated in the reaction). After cooling to 60℃, centrifuge and wash the precipitate three times with anhydrous xylene at 60℃. Finally, vacuum dry at 105℃ for 10h to obtain the modified filler. S9: Mix 45g of enhanced microspheres, 30g of modified filler, 10g of nano-fumed silica, and 1.5g of anhydrous ethanol and stir for 10 minutes. Then add 50g of maleic anhydride-grafted polyethylene and stir for 6 minutes. Next, add 700g of medium-density polyethylene, 200g of high-density polyethylene, 100g of linear low-density polyethylene, 4g of antioxidant 1010, 3g of antioxidant 168, 20g of polyethylene wax, and 15g of black masterbatch (40% carbon black content) and heat at 40℃. The mixture was mixed at 1800 r / min for 18 min, and then fed into a parallel twin-screw extruder for melt blending at 140°C in the feeding section, 165°C in the compression section, 175°C in the metering section, 180°C in the die head, 100 r / min in the screw speed, and a residence time of 1.5 min in the barrel. The extruded molten strip was cooled in a 20°C circulating cooling water bath and then pelletized. Finally, it was cryogenically pulverized and sieved to obtain modified polyethylene coating with a particle size of 100-200 μm.

[0022] Example 2: The preparation method of anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe is as follows: S1: Add 50g of polysuccinimide to 210g of N,N-dimethylformamide and stir for 25min. Then add 25g of asymmetric monoaminopropyl-terminated polydimethylsiloxane and 5g of ethylenediamine and stir for 5h under nitrogen atmosphere at 65℃. Then add 1500g of deionized water and let stand for 45min. Then centrifuge and wash 6 times with deionized water-anhydrous ethanol mixture. Finally freeze-dry at -40℃ for 24h to obtain cross-linked microgel powder. S2: Under anhydrous and oxygen-free conditions, 8g of polycaprolactone diol, 2.4g of isophorone diisocyanate, and 0.05g of stannous octoate were added to 930mL of anhydrous tetrahydrofuran and stirred for 3h at 60℃ under a nitrogen atmosphere. After cooling to 30℃, 5g of aminopropyl double-terminated polydimethylsiloxane was added and stirred for 1h. Then, 51g of cross-linked microgel powder was added and ultrasonically dispersed for 30min. Then, the mixture was stirred for 2h at 60℃ under a nitrogen atmosphere. Subsequently, the solvent was removed by vacuum distillation, centrifugation was performed, and the precipitate was washed four times with anhydrous ethanol. Finally, the precipitate was vacuum dried at 50℃ for 12h to obtain core-shell microspheres. S3: Add 51g of core-shell microspheres to 255g of toluene and ultrasonically disperse for 30min. Then add 2g of N-(-aminoethyl)-3-aminopropyltrimethoxysilane and 0.5g of deionized water and stir for 3h under nitrogen atmosphere at 80℃. Then centrifuge and wash the precipitate 4 times with anhydrous toluene. Finally, vacuum dry at 60℃ for 12h to obtain the enhanced microspheres. S4: Under a nitrogen atmosphere, 51.2 g of magnesium nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate were added to 220 g of deionized water. Then, at 60 °C, they were simultaneously and dropwise added to a reaction vessel along with 400 g of 1.5 mol / L sodium hydroxide aqueous solution (the pH of the system was controlled at 9.9-10.1, the addition time was 1 h, and the mixture was stirred while adding). The mixture was stirred for 1 h and then transferred to a polytetrafluoroethylene hydrothermal reactor for crystallization at 110 °C for 12 h. After that, the mixture was centrifuged and washed with degassed deionized water until neutral. Finally, it was vacuum dried at 60 °C for 12 h to obtain intercalated nanosheets. S5: Under a nitrogen atmosphere, 51g of intercalated nanosheets were added to 530mL of degassed deionized water and ultrasonically dispersed for 30min. Then, 25g of sodium phytate was added and the pH was adjusted to 9.0 with sodium hydroxide aqueous solution. The mixture was stirred at 70℃ for 6h, followed by the addition of 5g of ε-polylysine hydrochloride and stirring for 2h. The mixture was then centrifuged and washed 4 times with degassed deionized water. Finally, it was vacuum dried at 55℃ for 12h to obtain co-intercalated modified nanosheets. S6: Add 12g of cerium nitrate hexahydrate to 310g of anhydrous ethanol and stir for 35min to obtain a cerium nitrate solution; S7: Under a nitrogen atmosphere, 200g of deionized water was added to 300g of anhydrous ethanol and stirred for 15min. Then, 50g of co-intercalated nanosheets were added and ultrasonically exfoliated for 30min. The temperature was then raised to 60℃ and 310g of cerium nitrate solution was added dropwise at 5g / min while stirring. The pH was then adjusted to 9.5 with ammonia and stirred for 30min. The mixture was then transferred to a microwave hydrothermal reactor and microwaved at 140℃ for 30min at a power of 500W. After cooling to room temperature, the mixture was centrifuged and the precipitate was washed four times with anhydrous ethanol. Finally, the mixture was calcined at 300℃ under a nitrogen atmosphere for 2h and cooled to obtain the heterostructured filler. S8: Add 51g of heterostructured filler to 255mL xylene and ultrasonically disperse for 30min. Then add 0.5g of degassed deionized water and adjust the pH to 4.3 with glacial acetic acid. Stir for 10min and then add 4.5g of γ-glycidoxypropyltrimethoxysilane. Stir at 60℃ under nitrogen atmosphere for 1.5h. Then heat to 140℃ and reflux with water under nitrogen atmosphere for 4h (with a water separator installed to separate the methanol and excess water generated in the reaction). After cooling to 60℃, centrifuge and wash the precipitate 4 times with anhydrous xylene at 60℃. Finally, vacuum dry at 105℃ for 11h to obtain the modified filler. S9: Mix 48g of enhanced microspheres, 31g of modified filler, 13g of nano-fumed silica, and 1.8g of anhydrous ethanol for 15 minutes. Then add 55g of maleic anhydride-grafted polyethylene and stir for 7 minutes. Next, add 750g of medium-density polyethylene, 220g of high-density polyethylene, 110g of linear low-density polyethylene, 4.3g of antioxidant 1010, 3.3g of antioxidant 168, 23g of polyethylene wax, and 18g of black masterbatch (40% carbon black content). The mixture was mixed at 1800 r / min for 19 min at 45℃, and then fed into a parallel twin-screw extruder for melt blending at 145℃ in the feeding section, 170℃ in the compression section, 178℃ in the metering section, 183℃ in the die head, 105 r / min in the screw speed, and 2 min in the residence time of the material in the barrel. The extruded molten strip was cooled in a 25℃ circulating cooling water tank and then pelletized. Finally, it was cryogenically pulverized and sieved to obtain a modified polyethylene coating with a particle size of 100-200 μm.

[0023] Example 3: The preparation method of anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe is as follows: S1: Add 50g of polysuccinimide to 220g of N,N-dimethylformamide and stir for 30min. Then add 25g of asymmetric monoaminopropyl-terminated polydimethylsiloxane and 5g of ethylenediamine and stir for 5h under nitrogen atmosphere at 65℃. Then add 1500g of deionized water and let stand for 60min. Then centrifuge and wash 7 times with deionized water-anhydrous ethanol mixture. Finally freeze-dry at -40℃ for 24h to obtain cross-linked microgel powder. S2: Under anhydrous and oxygen-free conditions, 8g of polycaprolactone diol, 2.4g of isophorone diisocyanate, and 0.05g of stannous octoate were added to 950mL of anhydrous tetrahydrofuran and stirred for 3h under a nitrogen atmosphere at 60℃. After cooling to 30℃, 5g of aminopropyl double-terminated polydimethylsiloxane was added and stirred for 1h. Then, 52g of cross-linked microgel powder was added and ultrasonically dispersed for 30min. Then, it was stirred for 2h under a nitrogen atmosphere at 60℃. Subsequently, the solvent was removed by vacuum distillation, centrifugation was performed, and the precipitate was washed 5 times with anhydrous ethanol. Finally, it was vacuum dried at 50℃ for 12h to obtain core-shell microspheres. S3: Add 52g of core-shell microspheres to 260g of toluene and ultrasonically disperse for 30min. Then add 2g of N-(-aminoethyl)-3-aminopropyltrimethoxysilane and 0.5g of deionized water and stir for 3h under nitrogen atmosphere at 80℃. Then centrifuge and wash the precipitate 5 times with anhydrous toluene. Finally, vacuum dry at 60℃ for 12h to obtain the enhanced microspheres. S4: Under a nitrogen atmosphere, 51.2 g of magnesium nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate were added to 240 g of deionized water. Then, at 60 °C, they were simultaneously and dropwise added to a reaction vessel along with 400 g of 1.5 mol / L sodium hydroxide aqueous solution (the pH of the system was controlled at 9.9-10.1, the addition time was 1 h, and the mixture was stirred while adding). The mixture was stirred for 1 h, then transferred to a polytetrafluoroethylene hydrothermal reactor and crystallized at 110 °C for 12 h. After that, the mixture was centrifuged and washed with degassed deionized water until neutral. Finally, it was vacuum dried at 60 °C for 12 h to obtain intercalated nanosheets. S5: Under a nitrogen atmosphere, 52g of intercalated nanosheets were added to 550mL of degassed deionized water and ultrasonically dispersed for 30min. Then, 25g of sodium phytate was added and the pH was adjusted to 9.0 with sodium hydroxide aqueous solution. The mixture was stirred at 70℃ for 6h, followed by the addition of 5g of ε-polylysine hydrochloride and stirring for 2h. The mixture was then centrifuged and washed 5 times with degassed deionized water. Finally, it was vacuum dried at 55℃ for 12h to obtain co-intercalated modified nanosheets. S6: Add 12g of cerium nitrate hexahydrate to 320g of anhydrous ethanol and stir for 40min to obtain a cerium nitrate solution; S7: Under a nitrogen atmosphere, 200g of deionized water was added to 300g of anhydrous ethanol and stirred for 20min. Then, 50g of co-intercalated nanosheets were added and ultrasonically exfoliated for 30min. The temperature was then raised to 60℃ and 320g of cerium nitrate solution was added dropwise at 5g / min while stirring. The pH was then adjusted to 9.5 with ammonia and stirred for 30min. The mixture was then transferred to a microwave hydrothermal reactor and microwaved at 140℃ for 30min at a power of 500W. After cooling to room temperature, the mixture was centrifuged and the precipitate was washed 5 times with anhydrous ethanol. Finally, the mixture was calcined at 300℃ under a nitrogen atmosphere for 2h and cooled to obtain the heterostructured filler. S8: Add 52g of heterostructured filler to 260mL xylene and ultrasonically disperse for 30min. Then add 0.5g of degassed deionized water and adjust the pH to 4.5 with glacial acetic acid. Stir for 10min and then add 4.5g of γ-glycidoxypropyltrimethoxysilane. Stir at 60℃ under nitrogen atmosphere for 1.5h. Then heat to 140℃ and reflux with water under nitrogen atmosphere for 4h (with a water separator installed to separate the methanol and excess water generated in the reaction). After cooling to 60℃, centrifuge and wash the precipitate 5 times with anhydrous xylene at 60℃. Finally, vacuum dry at 105℃ for 12h to obtain the modified filler. S9: Mix 50g of enhanced microspheres, 32g of modified filler, 15g of nano-fumed silica, and 2g of anhydrous ethanol for 20 minutes. Then add 60g of maleic anhydride-grafted polyethylene and stir for 8 minutes. Next, add 800g of medium-density polyethylene, 240g of high-density polyethylene, 120g of linear low-density polyethylene, 4.5g of antioxidant 1010, 3.5g of antioxidant 168, 25g of polyethylene wax, and 20g of black masterbatch (40% carbon black content) and stir for 5 minutes. The mixture was mixed at 1800 r / min for 20 min at 0℃, and then fed into a parallel twin-screw extruder for melt blending at 150℃ in the feeding section, 175℃ in the compression section, 180℃ in the metering section, 185℃ in the die head, 110 r / min in the screw speed, and 2 min in the residence time of the material in the barrel. The extruded molten strip was cooled in a 30℃ circulating cooling water tank and then pelletized. Finally, it was cryogenically pulverized and sieved to obtain modified polyethylene coating with a particle size of 100-200 μm.

[0024] Comparative Example 1: Compared with Example 1, this comparative example only did not add "enhancing microspheres" in the preparation process of S9. All other steps and parameters were the same, and will not be repeated here. The final result was an anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe.

[0025] Comparative Example 2: Compared with Example 1, this comparative example only replaces the "heterogeneous structure filler" added in the preparation process of S8 with the "intercalated nanosheets" prepared in S4. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe is obtained.

[0026] Comparative Example 3: Compared with Example 1, this comparative example only did not add "modified filler" in the preparation process of S9. All other steps and parameters were the same, and will not be repeated here. The final result is an anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe.

[0027] Comparative Example 4: Compared with Example 1, this comparative example only omits the addition of "enhancing microspheres and modified fillers" during the preparation process of S9. All other steps and parameters are the same, and will not be repeated here. The final result is an anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe.

[0028] Performance testing: A 5mm thick, oil-free, rust-free steel plate is immersed in a phosphating solution (prepared from deionized water, phosphoric acid, zinc nitrate, zinc dihydrogen phosphate, citric acid monohydrate, sodium fluoride, and sodium nitrite; temperature 55℃, total acidity 20-22 points, free acidity 1.0-1.2 points) for 6 minutes (forming a dense phosphating film of 1-5μm on the steel plate surface). Afterward, it is removed and dried with hot air at 110℃ for 20 minutes, preheated to 250℃ and held for 15 minutes, and then immersed in a fluidized bed (fluidized bed...) The N-HAP hot-dip plastic-coated steel pipe surface anti-corrosion modified polyethylene coating prepared in Examples 1-3 and Comparative Examples 1-4 of this invention was fully fluidized and in a uniform boiling state in a fluidized bed, and was rotated at a constant speed for 10s with dry and filtered compressed air (pressure 0.05MPa, dew point ≤ -20℃). Then it was transferred to a curing oven and cured at 190℃ for 10min. After air cooling to room temperature, a specimen with a coating thickness of 350-450μm was obtained.

[0029] Adhesion determination: Referring to GB / T 5210-2006 standard, the adhesion strength (MPa) of specimens made of anti-corrosion modified polyethylene coating on the surface of N-HAP hot-dip plastic-coated steel pipes prepared by Examples 1-3 and Comparative Examples 1-4 of this invention was measured under tensile conditions with a constant loading rate of 1 MPa / s. The test results are shown in Table 1.

[0030] Abrasion resistance testing: Referring to GB / T 1768-2006 standard, the mass loss (mg) of specimens made of anti-corrosion modified polyethylene coating on the surface of N-HAP hot-dip plastic-coated steel pipes prepared by Examples 1-3 and Comparative Examples 1-4 of this invention was measured. A CS-10 rubber grinding wheel was used to apply a load of 1000g and the test was conducted at a rotation speed of 60r / min for 1000 revolutions. The results are shown in Table 1.

[0031] Determination of corrosion resistance: Referring to GB / T1771-2024 standard, the treatment time (h) for the first occurrence of blistering, rusting, peeling, and cracking of the coating on the surface of N-HAP hot-dip plastic-coated steel pipes prepared by Examples 1-3 and Comparative Examples 1-4 of this invention, after edge sealing treatment, was determined by continuously spraying the coating with a sodium chloride aqueous solution with a mass fraction of 5% and a pH of 6.5-7 at 35°C. Samples were taken and observed every 100h. The test results are shown in Table 1.

[0032] Determination of anti-scaling properties: The specimens made of anti-corrosion modified polyethylene coating on the surface of N-HAP hot-dip plastic-coated steel pipes prepared in Examples 1-3 and Comparative Examples 1-4 of this invention were immersed in 60°C hard water (preparation method: 0.74g anhydrous calcium chloride, 0.678g magnesium chloride hexahydrate, and 0.420g sodium bicarbonate were added to 800mL deionized water and stirred to dissolve. Then, the pH was adjusted to 7.5 with 1mol / L hydrochloric acid aqueous solution and sodium hydroxide aqueous solution, and then transferred to a 1L volumetric flask and diluted to volume with deionized water) for 72h. After static soaking, the surface scale was rinsed with deionized water, and then vacuum dried at 60°C to constant weight. The scale content per unit area (mg / cm²) was then calculated. 2 The measurement results are shown in Table 1.

[0033] Determination of heat resistance: Referring to GB / T 1735-2009 standard, the adhesion retention rate (%) of specimens made of anti-corrosion modified polyethylene coating on the surface of N-HAP hot-dip plastic-coated steel pipes prepared by Examples 1-3 and Comparative Examples 1-4 of this invention was determined after being treated at a constant temperature of 100℃ for 90 days. The results are shown in Table 1.

[0034] Determination of hydrophobicity: The static water contact angle (°) of the coating surface of the N-HAP hot-dip plastic-coated steel pipe prepared by Examples 1-3 and Comparative Examples 1-4 of this invention was measured in an environment of 23°C and 50% relative humidity. The results are shown in Table 1.

[0035] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-4

[0036] Data Analysis: As can be seen from Table 1, the anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe prepared in the embodiments of the present invention has excellent adhesion, wear resistance, corrosion resistance, anti-scaling properties, heat resistance and hydrophobicity.

[0037] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. An anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe, characterized in that, The composition by weight includes: 45-50 parts of a polyisocyanate-terminated polyurethane prepolymer prepared by reacting polycaprolactone diol and isophorone diisocyanate under stannous octoate catalysis, which is first chain-extended with aminopropyl double-terminated polydimethylsiloxane, then reacted with cross-linked microgel powder to form core-shell microspheres, and then modified with N-(-aminoethyl)-3-aminopropyltrimethoxysilane to form synergistic microspheres; and intercalated nanosheets which are first stepwise intercalated with sodium phytate and ε-polylysine hydrochloride, then ultrasonically exfoliated, and then reacted with cerium nitrate to introduce a cerium source, and then subjected to the original... The modified filler, prepared by precipitation, microwave hydrothermal crystallization, calcination at 300℃ in a nitrogen atmosphere, and finally modified with γ-glycidyl etheroxypropyltrimethoxysilane, consists of 30-32 parts; nano-fumed silica, 10-15 parts; anhydrous ethanol, 1.5-2 parts; maleic anhydride-grafted polyethylene, 50-60 parts; high-density polyethylene, 200-240 parts; linear low-density polyethylene, 100-120 parts; antioxidant, 7-8 parts; polyethylene wax, 20-25 parts; black masterbatch, 15-20 parts; and medium-density polyethylene, 700-800 parts.

2. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 1, characterized in that, The mass ratio of polycaprolactone diol, isophorone diisocyanate, stannous octoate, aminopropyl double-terminated polydimethylsiloxane, and crosslinked microgel powder is 8:2.4:0.05:5:50-52.

3. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 1, characterized in that, The mass ratio of the core-shell microspheres to N-(-aminoethyl)-3-aminopropyltrimethoxysilane is 50-52:

2.

4. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 1, characterized in that, The cross-linked microgel powder is polysuccinimide dissolved in N,N-dimethylformamide, which is first reacted with asymmetric monoaminopropyl-terminated polydimethylsiloxane and ethylenediamine, and then obtained through subsequent processing. The mass ratio of N,N-dimethylformamide, polysuccinimide, asymmetric monoaminopropyl-terminated polydimethylsiloxane, ethylenediamine, and deionized water is 200-220:50:25:5:1500.

5. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 1, characterized in that, The mass ratio of the intercalated nanosheets, sodium phytate, and ε-polylysine hydrochloride is 50-52:25:

5.

6. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 1, characterized in that, The intercalated nanosheets are magnesium nitrate hexahydrate and aluminum nitrate nonahydrate dispersed in deionized water. They are first co-precipitated with sodium hydroxide aqueous solution at 60°C and pH 9.9-10.1, and then hydrothermally crystallized at 110°C and post-treated.

7. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 6, characterized in that, The mass ratio of the deionized water, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and sodium hydroxide aqueous solution is 200-240:51.2:37.5:400; The concentration of the sodium hydroxide aqueous solution is 1.5 mol / L.

8. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 1, characterized in that, The mass ratio of the heterostructure filler and γ-glycidyl etheroxypropyltrimethoxysilane is 50-52:4.

5.

9. The anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to claim 5, characterized in that, The mass ratio of the co-intercalated nanosheets to the cerium nitrate solution is 50:300-320; The cerium nitrate solution is obtained by mixing anhydrous ethanol and cerium nitrate hexahydrate in a mass ratio of 300-320:

12.

10. The method for preparing the anti-corrosion modified polyethylene coating for the surface of N-HAP hot-dip plastic-coated steel pipe according to any one of claims 1-9, characterized in that, Includes the following steps: The enhanced microspheres, modified fillers, nano-fumed silica, and anhydrous ethanol are mixed evenly. Then, maleic anhydride-grafted polyethylene is added and stirred for 6-8 minutes. Next, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, antioxidants, polyethylene wax, and black masterbatch are added and mixed at 40-50℃ for 18-20 minutes. Then, melt blending is performed. The extruded melt strips are post-treated to obtain modified polyethylene coating.

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