Anti-corrosion and heat preservation layer for oil and gas pipeline and preparation method thereof

Abstract

The application provides an anticorrosion thermal insulation layer for oil and gas pipelines and a preparation method thereof, and belongs to the technical field of coatings.The preparation method comprises the following steps: step S1, preparing an anticorrosion primer; step S2, preparing slurry A and slurry B, then taking the slurry A and the slurry B, mixing them uniformly, spraying the mixture on a base material, and obtaining the base material after surface drying; step S3, preparing a gradient thermal insulation layer; step S4, dissolving polyvinylidene fluoride in a mixed solvent of N,N-dimethylacetamide and methyl ethyl ketone, adding 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and polydimethylsiloxane, fully stirring, then standing and defoaming, spraying the mixture on a base material, and obtaining the anticorrosion thermal insulation layer for oil and gas pipelines after leveling and drying. The anticorrosion thermal insulation layer for oil and gas pipelines can improve the anticorrosion effect and the thermal insulation effect, and the durability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating, in particular to an anti-corrosion and heat preservation layer for oil and gas pipelines and a preparation method thereof. BACKGROUND

[0002] The safety and service life of oil and gas pipelines, as the arteries of energy transportation, are of great importance. The pipelines are usually laid in complex soil, ocean or industrial atmospheric environment, and are subjected to electrochemical corrosion and chemical corrosion of media such as water, oxygen, chloride ions, hydrogen sulfide and sulfate reducing bacteria for a long time, and also need to resist mechanical damage such as soil stress and external force impact.

[0003] In the prior art, three-layer polyethylene, fusion epoxy powder and other coatings are often used for external anti-corrosion of the pipeline, and polyurethane foam is often used for the heat preservation layer. However, the performance bottleneck of the combination is increasingly prominent: first, when the closed cell rate of the polyurethane foam is insufficient or the outer protective tube fails to seal, the polyurethane foam is easy to absorb water and dissolve, resulting in a sharp decrease in heat preservation performance and corrosion of the inner core steel pipe; second, the multi-layer interface of the traditional structure may be peeled off due to thermal expansion and contraction or external force in long-term operation, forming a channel for the infiltration of corrosion media; and finally, it is difficult to maintain high-efficiency heat preservation while ensuring that the anti-corrosion and durability meet the requirements.

[0004] The patent document with publication number CN110564291A discloses an anti-corrosion and heat preservation integrated coating, in which the organosilicon-based glue is hydroxyl-terminated polydimethylsiloxane, the additives are curing agent, plasticizer and dispersant, the fillers are titanium white, mica and talc, and the cross-linking agent is methyltrimethoxysilane, methyltriacetoxysilane or methoxy POSS. The application realizes anti-corrosion and heat preservation integration to a certain extent, but fails to improve the durability.

[0005] Therefore, it is necessary to provide an anti-corrosion and heat preservation layer for oil and gas pipelines and a preparation method thereof to solve the problems existing in the prior art. SUMMARY

[0006] Therefore, the present application provides an anti-corrosion and heat preservation layer for oil and gas pipelines and a preparation method thereof, which can improve the anti-corrosion and heat preservation effects of the anti-corrosion and heat preservation layer for oil and gas pipelines and improve the durability.

[0007] To achieve the above-mentioned purpose, the present application provides a preparation method of an anti-corrosion and heat preservation layer for oil and gas pipelines, comprising the following steps:

[0008] Step S1, uniformly mixing phenolic epoxy resin and 3-aminopropyl triethoxysilane, then adding fillers and stirring uniformly, spraying the pretreated substrate, and drying to obtain an anti-corrosion bottom layer;

[0009] Step S2, the polyurethane prepolymer is heated in a kettle, silica aerogel powder and hollow glass microspheres are added, after mixing, additives are added, mixed and stirred to obtain slurry A; diethyltoluene diamine and 4, 4'-dithiodianiline are mixed to obtain slurry B; slurry A and slurry B are mixed uniformly at a mass ratio of 9:(0.9-1.1), the corrosion-resistant primer obtained in step S1 is sprayed, and the substrate after surface drying is obtained;

[0010] Step S3, hollow glass microspheres and hydroxyl-terminated polydimethylsiloxane are continuously added to the remaining slurry A, and then mixed uniformly with slurry B at a mass ratio of 9:(0.9-1.1), and the substrate after surface drying is sprayed and cured to obtain a gradient thermal insulation layer;

[0011] Step S4, polyvinylidene fluoride is dissolved in a mixed solvent of N,N-dimethylacetamide and methyl ethyl ketone, 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and polydimethylsiloxane are added, and after sufficient stirring, the gradient thermal insulation layer obtained in step S3 is sprayed to obtain an anticorrosive thermal insulation layer for oil and gas pipelines.

[0012] The phenolic epoxy resin can be cured to form a three-dimensional network with high cross-linking density, which can greatly reduce the penetration and diffusion of substances with corrosive properties such as oxygen, water molecules and chloride ions, improve the corrosion resistance of the coating, and promote the improvement of the durability of the coating. 3-aminopropyltriethoxysilane can hydrolyze to form silanol, which can further form Si-O-metal structure on the surface of the substrate, and the silane can condense to form Si-O-Si network, and the -NH2 on the other end can combine with the phenolic epoxy resin through hydrogen bonding, tightly anchoring the corrosion-resistant primer coating and the metal substrate, and promoting the improvement of the adhesion of the coating.

[0013] Through the first spraying, a dense inner layer is obtained after surface drying, and the silica aerogel and hollow glass microspheres jointly form a dense layer with high strength and high thermal resistance on the corrosion-resistant primer, which can improve the mechanical properties of the coating and achieve thermal insulation effect; the second spraying, i.e. the gradient thermal insulation layer, adds hollow glass microspheres and hydroxyl-terminated polydimethylsiloxane to form a hydrophobic outer layer, which has lower density, higher thermal resistance and greatly improved hydrophobicity. In addition, during the second spraying, the groups on the surface of the dense inner layer can still participate in the reaction to form covalent bonds, avoiding the interlayer peeling problem of traditional layered structure, and realizing the smooth transition from the inner layer to the outer layer in the gradient thermal insulation layer. The combination of the dense inner layer and the hydrophobic outer layer in the gradient thermal insulation layer greatly reduces the gas-liquid-solid three-phase thermal conductivity coefficient and weakens the penetration of water vapor, achieving a great improvement in the thermal insulation performance of the coating.

[0014] The 4,4'-dithiodianiline in slurry B is used as an aromatic diamine, and its -NH2 reacts with the -NCO in the prepolymer to form a urea bond to form a hard segment; the disulfide bond contained therein remains in the network, giving the system reversible dynamic covalent bonds, combined with the physical crosslinking of the urea hard segment, which can improve the toughness and stress relief. In addition, the inhibition of thermal and photo-oxidative degradation by aromatic amines and disulfide bonds can promote the maintenance of the mechanical properties of the coating and reduce the risk of coating embrittlement and pulverization.

[0015] The mass ratio of slurry A to slurry B in the two spraying processes is 9:(0.9-1.1), which helps to avoid the phenomenon of water absorption, tackiness and blistering of the coating caused by amino residue, and can improve the shielding performance of the coating; and the slight excess of -NCO can endcap the silanol of silica aerogel, the terminal hydroxyl of polydimethylsiloxane, and the surface hydroxyl of zeolite, avoiding other side reactions caused by them to reduce the interfacial bonding degree of the coating.

[0016] The C-F bond energy of polyvinylidene fluoride in the outermost layer of the corrosion-resistant and heat-insulating layer is much higher than the photon energy of ultraviolet light, and the molecular chain is not easy to break, thereby avoiding the degradation of the polymer, and further improving the durability of the coating; and polyvinylidene fluoride has low surface energy, natural water-repellent and anti-pollution, and is resistant to most acid, alkali and salt spray environments, further improving the durability of the coating. 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole can effectively absorb ultraviolet light, improve the anti-ultraviolet light ability of the coating, avoid the brittle fracture phenomenon of the coating caused by UV penetration, delay the aging of the coating, and improve the durability of the corrosion-resistant and heat-insulating layer.

[0017] Preferably, in the step S1, the filler includes zinc phosphate, flaky mica powder and fumed silica; the stirring speed is 800-1200 rpm, and the stirring time is 8-10 min.

[0018] Zinc phosphate can release phosphate ions in a humid or slightly acidic environment, which can react with Fe 2+ / Zn 2+ An insoluble phosphate passivation film is formed at the defects or scratches of the coating, which further blocks the micropores, improves the charge transfer impedance, slows down the spread of rust after the coating is scratched, and plays a passive protection role. The lamellar of flaky mica powder is parallel to the surface of the substrate, which can make the penetrating molecules detour between the lamellar, prolong the penetration time, and also can share the shrinkage stress to reduce the cracking phenomenon of the coating in dry-wet cycle.

[0019] Preferably, in the step S1, the preparation of the pretreated substrate includes the following steps: cleaning and drying the substrate, sandblasting, and making the surface roughness 50-75 μm to obtain the pretreated substrate.

[0020] By cleaning, removing dirt and rust, and then sandblasting the substrate to increase the surface roughness, the effective contact area of the coating and the metal substrate is greatly increased, thereby improving the adhesion of the coating.

[0021] Preferably, in step S1, after stirring, isophorone diamine and 4,4'-methylene bis(2-methylcyclohexylamine) are also added and mixed uniformly.

[0022] Using isophorone diamine and 4,4'-methylene bis(2-methylcyclohexylamine) as curing agents, isophorone diamine can provide good toughness and curing speed, and 4,4'-methylene bis(2-methylcyclohexylamine) can provide higher hardness and chemical stability. In combination with phenolic epoxy resin, a three-dimensional network with extremely high cross-linking density is formed, and the three-dimensional network has small free volume and difficult molecular chain segment movement, which can greatly hinder the diffusion path of corrosion media such as water, oxygen, and chloride ions, thereby improving the corrosion resistance of the coating.

[0023] Preferably, in step S2, the preparation of the polyurethane prepolymer includes the following steps:

[0024] Polypropylene glycol and propoxylated glycerol are added to a reaction kettle, and under the protection of nitrogen, dehydration is carried out at 80℃ and -0.08~-0.09MPa for 1.0-1.5h, then dimethylbenzene alkyl diisocyanate and dibutyltin dilaurate are added dropwise after the temperature is lowered to 60℃, the temperature is raised to 80℃, and the reaction is carried out for 1.5-2.5h, then degassing is carried out, and the temperature is cooled to 40-50℃ and sealed with nitrogen to obtain the polyurethane prepolymer.

[0025] By using the Lewis acid catalysis of dibutyltin dilaurate, the reaction activation energy can be reduced, the reaction of diisocyanate and polyol to form polyurethane prepolymer can be promoted, and the conversion rate can be improved; dehydration and degassing can remove free water and dissolved gas, avoid side reactions, and reduce porosity.

[0026] Preferably, in step S2, the additives include zeolite powder, hydroxyl-terminated polydimethylsiloxane, dibutyltin dilaurate, and polydimethylsiloxane; the surface drying time is 40-60min.

[0027] Zeolite has regular micropores and strong polar sites, and can adsorb free water and polar trace impurities; hydroxyl-terminated polydimethylsiloxane can react with -NCO in the polyurethane prepolymer to form silane type carbamate bonds, connecting the silicon chain into the polyurethane network, reducing migration, and thereby reducing the surface tension of the coating, improving hydrophobicity and anti-fouling ability; dibutyltin dilaurate can accelerate curing, promote cross-linking, and help reduce the porosity of the coating, improving the durability of the coating; polydimethylsiloxane can reduce surface tension, break emulsions and defoam, promote dispersion, make the coating more flat, and form a smooth and dense coating.

[0028] Preferably, in the step S2, the speed of the mixing and stirring is 600-800 rpm, and the time is 3-5 min.

[0029] Preferably, in the step S3, the time of the standing and curing is 22-26 h.

[0030] In order to achieve the above-mentioned purpose, the application further provides an oil and gas pipeline anticorrosive and thermal insulation layer prepared by the above-mentioned method.

[0031] The oil and gas pipeline anticorrosive and thermal insulation layer prepared by the method has improved anticorrosive and thermal insulation effects and durability.

[0032] Preferably, the components include the following components by weight:

[0033] Polyvinylidene fluoride 12-18 parts, N,N-dimethylacetamide 35-50 g parts, methyl ethyl ketone 12-20 parts, 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole 0.5-0.8 parts, and polydimethylsiloxane 0.1-0.3 parts.

[0034] The above technical solutions of the application at least have the following beneficial effects:

[0035] 1. The phenolic epoxy resin in the anticorrosive primer can be cured to form a three-dimensional network with high cross-linking density, greatly reducing the penetration and diffusion of oxygen, water molecules and chloride ions and other corrosive substances, and improving the anticorrosive property of the coating.

[0036] 2. The gradient thermal insulation layer greatly reduces the gas-liquid-solid three-phase heat transfer coefficient by combining the dense inner layer with the hydrophobic outer layer, and weakens the penetration of water vapor, thereby greatly improving the thermal insulation performance of the coating.

[0037] 3. The outermost layer of the anticorrosive and thermal insulation layer uses polyvinylidene fluoride as the main material of the coating and cooperates with 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole, so that the coating has both environmental stability and ultraviolet resistance, thereby improving the durability of the anticorrosive and thermal insulation layer. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions of the embodiments of the application will be described clearly and completely below in combination with the embodiments of the application. The described embodiments are part of the embodiments of the application, and all other embodiments obtained by those skilled in the art based on the described embodiments of the application belong to the scope of protection of the application.

[0039] The phenolic epoxy resin described in the following examples and comparative examples was purchased from Hunan Sailve New Material Technology Co., Ltd., and the model was SW-280 bisphenol A type phenolic epoxy resin.

[0040] Example 1

[0041] The outer surface of the pipeline substrate was cleaned, dried, sandblasted to Sa2.5, and the surface roughness was 50-75 μm. The substrate was preheated to 30°C.

[0042] 120 g of phenolic epoxy resin and 2 g of 3-aminopropyl triethoxysilane were added to a reaction kettle, mixed uniformly, and then 24 g of zinc phosphate, 10 g of flaky mica powder, and 3 g of fumed silica were added. The mixture was stirred at a speed of 1000 rpm for 9 min. Finally, 56 g of isophorone diamine and 24 g of 4,4'-methylenebis(2-methylcyclohexylamine) were added and mixed uniformly. The substrate was sprayed, and the thickness was 160-180 μm. After drying, the corrosion-resistant primer layer was obtained.

[0043] 700 g of polypropylene glycol and 210 g of propoxylated glycerol were added to a reaction kettle. Under the protection of nitrogen, the mixture was dehydrated at 80°C and -0.08 to -0.09 MPa for 1 h. After being cooled to 60°C, 270 g of xylene alkanediisocyanate and 0.1 g of dibutyltin dilaurate were added dropwise. The temperature was raised to 80°C, and the reaction was carried out for 2.5 h. After degassing, the temperature was cooled to 45°C, and the nitrogen was sealed. A polyurethane prepolymer was obtained.

[0044] 210 g of the polyurethane prepolymer was placed in a planetary stirring kettle and heated to 35-40°C. 140 g of silica aerogel powder (hydrophobic grade) and 210 g of hollow glass microbeads were added in three batches and mixed uniformly. Then, 20 g of zeolite powder, 10 g of hydroxyl-terminated polydimethylsiloxane, 0.6 g of dibutyltin dilaurate, and 0.4 g of polydimethylsiloxane were added. The mixture was stirred at a speed of 700 rpm for 4 min, and then it was left to stand and degas. Slurry A was obtained. 100 g of diethyltoluene diamine and 32 g of 4,4'-dithiodiamine were mixed uniformly to obtain slurry B. 360 g of slurry A and 40 g of slurry B were mixed uniformly, and the corrosion-resistant primer layer was sprayed. The thickness was 10-12 mm, and the surface drying time was 50 min.

[0045] 65 g of hollow glass microbeads and 5 g of hydroxyl-terminated polydimethylsiloxane were added to the remaining slurry A. Then, 240 g of slurry A and 26 g of slurry B were mixed uniformly, and the substrate after surface drying was sprayed. The thickness was 8-10 mm, and the substrate was left to stand and cure for 24 h. A gradient insulation layer was obtained.

[0046] 15 g of polyvinylidene fluoride was dissolved in 40 g of a mixed solvent of N,N-dimethylacetamide and 15 g of methyl ethyl ketone, 0.5 g of 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and 0.3 g of polydimethylsiloxane were added, and after being stirred thoroughly, it was left to stand to be degassed. The gradient heat insulation layer was sprayed to form a film on the surface of the gradient heat insulation layer, and after leveling and drying, an anti-corrosion heat insulation layer for oil and gas pipelines was obtained.

[0047] Example 2

[0048] The outer surface of the pipeline substrate was cleaned, dried, sandblasted to Sa2.5, and the surface roughness was 50-75 μm. The substrate was preheated to 30 °C.

[0049] 120 g of phenolic epoxy resin and 2 g of 3-aminopropyl triethoxysilane were added to a reaction kettle, mixed uniformly, and then 24 g of zinc phosphate, 10 g of flaky mica powder and 3 g of fumed silica were added. After stirring at a speed of 800 rpm for 10 min, 56 g of isophorone diamine and 24 g of 4,4'-methylenebis(2-methylcyclohexylamine) were finally added and mixed uniformly. The substrate was sprayed, the thickness was 160-180 μm, and after drying, an anti-corrosion primer layer was obtained.

[0050] 700 g of polypropylene glycol and 210 g of propoxylated glycerol were added to a reaction kettle. Under the protection of nitrogen, the dehydration was carried out at 80 °C and -0.08 to -0.09 MPa for 1.5 h. After being reduced to 60 °C, 270 g of xylene alkane diisocyanate and 0.1 g of dibutyltin dilaurate were added dropwise. The temperature was raised to 80 °C, and the reaction was carried out for 2 h. After degassing, the temperature was cooled to 50 °C, and the nitrogen was sealed. A polyurethane prepolymer was obtained.

[0051] 200 g of the polyurethane prepolymer was placed in a planetary stirring kettle and heated to 35-40 °C. 150 g of silica aerogel powder (hydrophobic grade) and 210 g of hollow glass microbeads were added in three batches and mixed uniformly. Then 20 g of zeolite powder, 10 g of hydroxyl-terminated polydimethylsiloxane, 0.6 g of dibutyltin dilaurate and 0.4 g of polydimethylsiloxane were added. After stirring at a speed of 600 rpm for 5 min, it was left to stand to be degassed. Slurry A was obtained. 100 g of diethyltoluene diamine and 32 g of 4,4'-dithiodiamine were mixed uniformly to obtain slurry B. 360 g of slurry A and 44 g of slurry B were mixed uniformly, and the anti-corrosion primer layer was sprayed. The thickness was 10-12 mm, and the surface drying time was 60 min.

[0052] 5 g of hydroxyl-terminated polydimethylsiloxane was added to the remaining slurry A. 240 g of slurry A and 29.3 g of slurry B were mixed uniformly, and the substrate after surface drying was sprayed. The thickness was 8-10 mm, and the substrate was left to stand to be cured for 22 h. A gradient heat insulation layer was obtained.

[0053] 18 g of polyvinylidene fluoride was dissolved in a mixed solvent of 35 g of N,N-dimethylacetamide and 20 g of methyl ethyl ketone, 0.5 g of 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and 0.2 g of polydimethylsiloxane were added, and after being stirred thoroughly, it was left to stand to be degassed. The gradient heat insulation layer was sprayed to form a film on the surface of the gradient heat insulation layer, and after leveling and drying, an anti-corrosion heat insulation layer for oil and gas pipelines was obtained.

[0054] Example 3

[0055] The outer surface of the pipeline substrate was cleaned, dried, sandblasted to Sa2.5, and the surface roughness was 50-75 μm. The substrate was preheated to 30 °C.

[0056] 120 g of phenolic epoxy resin and 2 g of 3-aminopropyl triethoxysilane were added to a reaction kettle and mixed uniformly. Then 24 g of zinc phosphate, 10 g of flaky mica powder and 3 g of fumed silica were added, and stirred at a speed of 1200 rpm for 8 min. Finally, 56 g of isophorone diamine and 24 g of 4,4'-methylenebis(2-methylcyclohexylamine) were added and mixed uniformly. The substrate was sprayed, and after drying, an anti-corrosion primer layer was obtained, with a thickness of 160-180 μm.

[0057] 700 g of polypropylene glycol and 210 g of propoxylated glycerol were added to a reaction kettle. Under the protection of nitrogen, the mixture was dehydrated at 80 °C and -0.08 to -0.09 MPa for 1.0 h. After being cooled to 60 °C, 270 g of xylene alkane diisocyanate and 0.1 g of dibutyltin dilaurate were added dropwise. The temperature was raised to 80 °C, and the reaction was carried out for 2.5 h. After degassing, the temperature was cooled to 40 °C, and the nitrogen was sealed. A polyurethane prepolymer was obtained.

[0058] 220 g of polyurethane prepolymer was placed in a planetary stirring kettle and heated to 35-40 °C. 140 g of silica aerogel powder (hydrophobic grade) and 200 g of hollow glass microbeads were added in three batches and mixed uniformly. Then 20 g of zeolite powder, 10 g of hydroxyl-terminated polydimethylsiloxane, 0.6 g of dibutyltin dilaurate and 0.4 g of polydimethylsiloxane were added. The mixture was stirred at a speed of 800 rpm for 3 min, and then left to stand to be degassed. Slurry A was obtained. 100 g of diethyltoluene diamine and 32 g of 4,4'-dithiodiamine were mixed uniformly to obtain slurry B. 360 g of slurry A and 36 g of slurry B were mixed uniformly, and the anti-corrosion primer layer was sprayed. The thickness was 10-12 mm, and the surface was dry in 40 min.

[0059] 5 g of hydroxyl-terminated polydimethylsiloxane was added to the remaining slurry A. 240 g of slurry A and 24 g of slurry B were mixed uniformly, and the substrate after surface drying was sprayed. The thickness was 8-10 mm, and the substrate was left to stand to be cured for 26 h. A gradient heat insulation layer was obtained.

[0060] 12 g of polyvinylidene fluoride was dissolved in 50 g of a mixed solvent of N,N-dimethylacetamide and 12 g of methyl ethyl ketone, 0.8 g of 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and 0.3 g of polydimethylsiloxane were added, and after being stirred thoroughly, the gradient heat insulation layer was sprayed to form a film on the surface of the gradient heat insulation layer, and after leveling, drying, an anti-corrosion heat insulation layer for oil and gas pipelines was obtained.

[0061] Example 4

[0062] The outer surface of the pipeline substrate was cleaned, dried, sandblasted to Sa2.5, and the surface roughness was 50-75 μm. The substrate was preheated to 30 °C.

[0063] 120 g of phenolic epoxy resin and 2 g of 3-aminopropyl triethoxysilane were added to a reaction kettle, mixed uniformly, and then 24 g of zinc phosphate, 10 g of flaky mica powder and 3 g of fumed silica were added. Stirring was carried out at a speed of 900 rpm for 10 min, and finally 56 g of isophorone diamine and 24 g of 4,4'-methylenebis(2-methylcyclohexylamine) were added and mixed uniformly. The substrate was sprayed, the thickness was 160-180 μm, and after drying, an anti-corrosion primer layer was obtained.

[0064] 700 g of polypropylene glycol and 210 g of propoxylated glycerol were added to a reaction kettle, and under the protection of nitrogen, dehydration was carried out at 80 °C and -0.08 to -0.09 MPa for 1.5 h. After being reduced to 60 °C, 270 g of xylene alkane diisocyanate and 0.1 g of dibutyltin dilaurate were added dropwise. The temperature was raised to 80 °C, and the reaction was carried out for 1.5 h. After degassing, the temperature was cooled to 45 °C, and the nitrogen was sealed. A polyurethane prepolymer was obtained.

[0065] 210 g of the polyurethane prepolymer was placed in a planetary stirring kettle and heated to 35-40 °C. 130 g of silica aerogel powder (hydrophobic grade) and 220 g of hollow glass microbeads were added in three batches and mixed uniformly. Then 20 g of zeolite powder, 10 g of hydroxyl-terminated polydimethylsiloxane, 0.6 g of dibutyltin dilaurate and 0.4 g of polydimethylsiloxane were added. Stirring was carried out at a speed of 650 rpm for 5 min, and after standing and degassing, slurry A was obtained. 100 g of diethyltoluene diamine and 32 g of 4,4'-dithiodiamine were mixed uniformly to obtain slurry B. 360 g of slurry A and 40 g of slurry B were mixed uniformly, and the anti-corrosion primer layer was sprayed. The thickness was 10-12 mm, and the surface was dry for 60 min.

[0066] 5 g of hydroxyl-terminated polydimethylsiloxane was added to the remaining slurry A. 240 g of slurry A and 26 g of slurry B were mixed uniformly, and the substrate after surface drying was sprayed. The thickness was 8-10 mm, and the substrate was cured for 25 h to obtain a gradient heat insulation layer.

[0067] Dissolve 16 g of polyvinylidene fluoride in 45 g of a mixed solvent of N,N-dimethylacetamide and 14 g of methyl ethyl ketone, add 0.7 g of 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and 0.2 g of polydimethylsiloxane, fully stir and then stand to degas, spray the gradient heat insulation layer, form a film on the surface of the gradient heat insulation layer, and after leveling and drying, an anti-corrosion heat insulation layer for oil and gas pipelines is obtained.

[0068] Example 5

[0069] Clean the outer surface of the pipeline substrate, dry, sandblast to Sa2.5, surface roughness 50-75 μm, and preheat the substrate to 30°C.

[0070] Add 120 g of phenolic epoxy resin and 2 g of 3-aminopropyl triethoxysilane to a reaction kettle, mix well, then add 24 g of zinc phosphate, 10 g of flaky mica powder, and 3 g of fumed silica, stir at 1100 rpm for 8 min, and finally add 56 g of isophorone diamine and 24 g of 4,4'-methylenebis(2-methylcyclohexylamine), mix well, spray the substrate, thickness 160-180 μm, and after drying, an anti-corrosion primer layer is obtained.

[0071] Add 700 g of polypropylene glycol and 210 g of propoxylated glycerol to a reaction kettle, dehydrate at 80°C, -0.08 to -0.09 MPa, for 1.0 h under nitrogen protection, then drop 270 g of xylene alkane diisocyanate and 0.1 g of dibutyltin dilaurate after reducing to 60°C, warm to 80°C, react for 2 h, degas, cool to 40°C, and seal with nitrogen to obtain a polyurethane prepolymer.

[0072] Put 200 g of the polyurethane prepolymer into a planetary stirring kettle, heat to 35-40°C, add 150 g of silica aerogel powder (hydrophobic grade) and 210 g of hollow glass microbeads in three batches, mix well, then add 20 g of zeolite powder, 10 g of hydroxyl-terminated polydimethylsiloxane, 0.6 g of dibutyltin dilaurate, and 0.4 g of polydimethylsiloxane, stir at 750 rpm for 3 min, stand to degas, and obtain slurry A; mix 100 g of diethyltoluene diamine and 32 g of 4,4'-dithiodiamine to obtain slurry B; mix 360 g of slurry A and 40 g of slurry B well, spray the anti-corrosion primer layer, thickness 10-12 mm, and surface dry for 45 min.

[0073] Add 65 g of hollow glass microbeads and 5 g of hydroxyl-terminated polydimethylsiloxane to the remaining slurry A, then mix 240 g of slurry A and 24 g of slurry B well, spray the substrate after surface drying, thickness 8-10 mm, and stand to cure for 26 h to obtain a gradient heat insulation layer.

[0074] 15 g of polyvinylidene fluoride was dissolved in 40 g of a mixed solvent of N,N-dimethylacetamide and 15 g of methyl ethyl ketone, 0.6 g of 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and 0.3 g of polydimethylsiloxane were added, and after being stirred thoroughly, the gradient heat insulation layer was sprayed to form a film on the surface of the gradient heat insulation layer, and after leveling, drying, an anti-corrosion heat insulation layer for oil and gas pipelines was obtained.

[0075] Example 6

[0076] The outer surface of the pipeline substrate was cleaned, dried, sandblasted to Sa2.5, and the surface roughness was 50-75 μm. The substrate was preheated to 30 °C.

[0077] 120 g of phenolic epoxy resin and 2 g of 3-aminopropyl triethoxysilane were added to a reaction kettle, mixed uniformly, and then 24 g of zinc phosphate, 10 g of flaky mica powder and 3 g of fumed silica were added. Stirring was carried out at a speed of 1100 rpm for 8 min, the substrate was sprayed, the thickness was 160-180 μm, and after drying, an anti-corrosion primer layer was obtained.

[0078] 700 g of polypropylene glycol and 210 g of propoxylated glycerol were added to a reaction kettle, and under the protection of nitrogen, dehydration was carried out at 80 °C and -0.08 to -0.09 MPa for 1.0 h. After being cooled to 60 °C, 270 g of xylene alkane diisocyanate and 0.1 g of dibutyltin dilaurate were added dropwise, and the temperature was raised to 80 °C. Reaction was carried out for 2 h, degassing was carried out, and the temperature was cooled to 40 °C. Nitrogen sealing was carried out to obtain a polyurethane prepolymer.

[0079] 200 g of the polyurethane prepolymer was placed in a planetary stirring kettle, heated to 35-40 °C, and 150 g of silica aerogel powder (hydrophobic grade) and 210 g of hollow glass microbeads were added in three batches. After being mixed uniformly, 20 g of zeolite powder, 10 g of hydroxyl-terminated polydimethylsiloxane, 0.6 g of dibutyltin dilaurate and 0.4 g of polydimethylsiloxane were added. Stirring was carried out at a speed of 750 rpm for 3 min, and after being left to stand and degassed, slurry A was obtained. 100 g of diethyltoluene diamine and 32 g of 4,4'-dithiodianiline were mixed uniformly to obtain slurry B. 360 g of slurry A and 40 g of slurry B were mixed uniformly, and the anti-corrosion primer layer was sprayed. The thickness was 10-12 mm, and the surface drying time was 45 min.

[0080] 5 g of hydroxyl-terminated polydimethylsiloxane was added to the remaining slurry A, and 240 g of slurry A and 24 g of slurry B were mixed uniformly. The substrate after surface drying was sprayed, the thickness was 8-10 mm, and after being left to stand for 26 h, a gradient heat insulation layer was obtained.

[0081] 15 g of polyvinylidene fluoride was dissolved in 40 g of a mixed solvent of N,N-dimethylacetamide and 15 g of methyl ethyl ketone, 0.6 g of 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and 0.3 g of polydimethylsiloxane were added, and after being fully stirred, the gradient heat insulation layer was sprayed, a film was formed on the surface of the gradient heat insulation layer, and after leveling, drying, an anti-corrosion heat insulation layer for oil and gas pipelines was obtained.

[0082] The present application also carries out comparative examples and related tests.

[0083] Comparative Example 1

[0084] Comparative Example 1 and Example 1 only differ in that the mass ratio of slurry A to slurry B in the two spraying times for preparing the gradient heat insulation layer is 1:1, and the other components and preparation methods are the same as those of Example 1, and an anti-corrosion heat insulation layer for oil and gas pipelines is prepared.

[0085] Comparative Example 2

[0086] Comparative Example 2 and Example 1 differ in that 4,4'-dithiodianiline is not used when preparing slurry B, but diethyltoluene diamine is used instead, and the other components and preparation methods are the same as those of Example 1, and an anti-corrosion heat insulation layer for oil and gas pipelines is prepared.

[0087] Comparative Example 3

[0088] Comparative Example 3 and Example 1 differ in that 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole is not used, and the other components and preparation methods are the same as those of Example 1, and an anti-corrosion heat insulation layer for oil and gas pipelines is prepared.

[0089] Performance detection test

[0090] The anti-corrosion performance test was carried out on the anti-corrosion heat insulation layers for oil and gas pipelines prepared in Examples 1-6 and Comparative Examples 1-3, a single scratch with a length of 60 mm was made on the sample, which penetrated to the metal substrate, the test conditions were 5.0±0.1wt% NaCl (pH 6.5-7.2), temperature 35±2℃, and the test lasted for 1000h, and the scratch propagation length was recorded.

[0091] According to GB / T 10295-2008 "Determination of Steady-state Thermal Resistance and Related Properties of Thermal Insulation Materials by Heat Flow Meter Method", the heat insulation performance test was carried out on the anti-corrosion heat insulation layers for oil and gas pipelines prepared in Examples 1-6 and Comparative Examples 1-3, and the thermal conductivity was taken as the test result.

[0092] According to GB / T 17146-2015 "Test Method for Water Vapor Transmission Performance of Building Materials and Their Products (Wet Cup Method B)", the moisture resistance test was carried out on the anti-corrosion heat insulation layers for oil and gas pipelines prepared in Examples 1-6 and Comparative Examples 1-3, and the water vapor transmission rate was taken as the result.

[0093] The adhesion of the anti-corrosion and thermal insulation layers prepared from examples 1-6 and comparative examples 1-3 was tested according to GB / T 5210-2006 "Paint and Varnish Adhesion Test by Pulling-off Method".

[0094] The durability of the anti-corrosion and thermal insulation layers prepared from examples 1-6 and comparative examples 1-3 was tested according to GB / T 23987-2009 "Paint and Varnish Artificial Aging of Coating", and the chalking grade was taken as the result.

[0095] The above test results were integrated, as shown in Table 1.

[0096] Table 1

[0097]

[0098] As can be seen from Table 1, the thermal conductivity and water vapor transmission rate of the anti-corrosion and thermal insulation layer prepared from comparative example 1 increased obviously compared with example 1, indicating that when preparing the gradient thermal insulation layer, the mass ratio of slurry A to slurry B in the two spraying processes was 9: (0.9-1.1), which could promote the combination of the dense inner layer and the hydrophobic outer layer, improve the shielding performance of the overall anti-corrosion and thermal insulation layer, and further improve the thermal insulation and moisture resistance; compared with example 1, the scratch propagation length of the anti-corrosion and thermal insulation layer prepared from comparative example 2 increased obviously, and the adhesion decreased, indicating that 4,4'-dithiodianiline could effectively promote the stress release of the gradient thermal insulation layer, reduce the occurrence and expansion of cracks, and avoid causing the scratch of the coating to be more prone to water, thereby reducing the corrosion resistance and adhesion of the coating; in comparative example 3, 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole was not used, and the chalking grade of the anti-corrosion and thermal insulation layer prepared therefrom had a relatively obvious gap compared with example 1, indicating that 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole could improve the anti-ultraviolet light ability of the coating, avoid the penetration of UV to cause the coating to appear brittle fracture phenomenon, delay the aging of the coating, and improve the durability of the anti-corrosion and thermal insulation layer.

[0099] Example 6 was different from example 5 in that isophorone diamine and 4,4'-methylenebis (2-methylcyclohexylamine) were not used, and as can be seen from the data in Table 1, the performance of the anti-corrosion and thermal insulation layer prepared therefrom had some gap compared with example 5, indicating that using isophorone diamine and 4,4'-methylenebis (2-methylcyclohexylamine) as the curing agent could form a three-dimensional network with high cross-linking density with the phenolic epoxy resin, thereby improving the performance of the anti-corrosion and thermal insulation layer.

[0100] The above is a preferred embodiment of the present application, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing a corrosion and heat protection layer for oil and gas pipelines, characterized in that, It comprises the following steps: Step S1, mix phenolic epoxy resin with 3-aminopropyl triethoxysilane, then add fillers, stir evenly, spray the pretreated substrate, dry, and obtain the corrosion-resistant primer; Step S2, heat the polyurethane prepolymer in the kettle, add silica aerogel powder and hollow glass microspheres, mix evenly, then add additives, mix and stir to obtain slurry A; mix diethyl toluene diamine with 4,4'-dithiodiamine to obtain slurry B; mix slurry A and slurry B in a mass ratio of 9:(0.9-1.1), spray the corrosion-resistant primer obtained in step S1, and obtain the substrate after surface drying; Step S3, continue to add hollow glass microspheres and hydroxyl-terminated polydimethylsiloxane to the remaining slurry A, then mix evenly with slurry B in a mass ratio of 9:(0.9-1.1), spray the substrate after surface drying, and obtain the gradient insulation layer after standing and curing; Step S4, dissolve polyvinylidene fluoride in a mixed solvent of N,N-dimethylacetamide and methyl ethyl ketone, add 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole and polydimethylsiloxane, stir thoroughly, then stand and degas, spray the gradient insulation layer obtained in step S3, and obtain the corrosion-resistant and insulating layer for oil and gas pipelines.

2. A method of preparing a corrosion and heat protection layer for oil and gas pipelines according to claim 1, characterized in that, In step S1, the fillers include zinc phosphate, flaky mica powder and fumed silica; the stirring speed is 800-1200 rpm, and the stirring time is 8-10 min.

3. The method of claim 1, wherein the anticorrosive and thermal insulation layer for an oil and gas pipeline is prepared by applying the anticorrosive and thermal insulation layer to the outer surface of the pipeline, and then applying the coating layer to the anticorrosive and thermal insulation layer. In step S1, the preparation of the pretreated substrate comprises the following steps: clean and dry the substrate, sandblast, and make the surface roughness 50-75 μm to obtain the pretreated substrate.

4. The method for preparing an anti-corrosion and heat-insulating layer for oil and gas pipelines according to claim 1, characterized in that, In step S1, isophorone diamine and 4,4'-methylenebis(2-methylcyclohexylamine) are also added after stirring evenly and mixed evenly.

5. The method of claim 1, wherein the anticorrosive and thermal insulation layer for an oil and gas pipeline is prepared by applying the anticorrosive and thermal insulation layer to the outer surface of the pipeline, and then applying the coating layer to the anticorrosive and thermal insulation layer. In step S2, the preparation of the polyurethane prepolymer comprises the following steps: Put polypropylene glycol and propoxylated glycerol into a reaction kettle, dehydrate at 80℃ under nitrogen protection at -0.08~-0.09 MPa for 1.0-1.5 h, drop in toluene diisocyanate and dibutyltin dilaurate after reducing to 60℃, heat to 80℃, react for 1.5-2.5 h, degas, cool to 40-50℃, and seal with nitrogen to obtain the polyurethane prepolymer.

6. The method of claim 1, wherein the anticorrosive and thermal insulation layer for an oil and gas pipeline is prepared by applying a coating solution to the surface of the pipeline, and then drying and curing the coating solution. In step S2, the additives include zeolite powder, hydroxyl-terminated polydimethylsiloxane, dibutyltin dilaurate and polydimethylsiloxane; the surface drying time is 40-60 min.

7. The method for preparing an anti-corrosion and heat-insulating layer for oil and gas pipelines according to claim 1, characterized in that, In step S2, the mixing and stirring speed is 600-800 rpm, and the mixing and stirring time is 3-5 min.

8. The method for preparing an anti-corrosion and heat-insulating layer for oil and gas pipelines according to claim 1, characterized in that, In step S3, the standing and curing time is 22-26 h.

9. An anticorrosive and heat-insulating layer for an oil and gas pipeline, characterized by A method for preparing a corrosion-resistant and insulating layer for oil and gas pipelines is prepared by the method of any one of claims 1-8.

10. The anticorrosive and heat-insulating layer for oil and gas pipelines according to claim 9, characterized in that, It comprises the following components by weight: Polyvinylidene fluoride 12-18 parts, N,N-dimethylacetamide 35-50 g parts, methyl ethyl ketone 12-20 parts, 2-(2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole 0.5-0.8 parts, and polydimethylsiloxane 0.1-0.3 parts.

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