Application of organic-inorganic modified powder coating on inner wall surface of petroleum drill pipe

Abstract

The application discloses application of powder coating based on organic-inorganic modification to the inner wall surface of an oil drilling rod and relates to the technical field of corrosion prevention treatment of oil drilling rods. The application comprises the following steps: firstly, pretreating the inner wall surface of the oil drilling rod by a gas-phase corrosion inhibitor spraying method, so that the rust on the surface of the oil drilling rod is converted into a black film in a stable form by a corrosion inhibition gas; and then preparing the powder coating based on organic-inorganic modification, wherein the powder coating is prepared from the following raw material components: rust stabilizer 20-30 parts, wetting dispersant 0.5-1.0 parts, inorganic cementing material 30-45 parts, rust conversion agent 25-35 parts and base material wetting agent 0.2-1.0 parts. The powder coating based on organic-inorganic modification is sprayed on the inner wall of the pretreated oil drilling rod by using electrostatic spraying technology after the formula of the powder coating is improved. Through relevant detection, the sprayed coating film has good temperature change resistance, high-pressure resistance, water resistance, wear resistance and impact resistance, thereby prolonging the service life of the oil drilling rod.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion treatment technology for oil drill pipes, specifically to the application of an organic-inorganic modified powder coating on the inner wall surface of an oil drill pipe. Background Technology

[0002] Oil drill pipe is a rod that connects to the drill bit and transmits power during oil drilling. It connects the drilling rig's surface equipment to the drilling equipment or bottom hole assembly located at the bottom of the well, and transports drilling mud to the drill bit. During operation, oil drill pipes must withstand enormous internal and external pressure, torsion, bending, and vibration, thus requiring particularly high mechanical properties. To improve the wear resistance of the inner wall of the oil drill pipe and extend its service life, current technology typically involves coating the inside of the drill pipe with a layer of paint to prevent corrosion and wear.

[0003] With the rapid development of oil and gas exploration and development, the complex geological structure and harsh downhole environment, containing high levels of H2S, CO2, and Cl, have led to this situation. - The emergence of oil and gas fields containing various corrosive media such as hydrates has made the working environment of oil drill pipes increasingly challenging due to safety concerns, corrosion, wax buildup, and scaling. This places higher demands on the high-temperature resistance, high-pressure resistance, and corrosion resistance of the drill pipe's internal coatings. Good surface treatment is crucial for the adhesion and corrosion resistance of the coating. Due to the limited structure and space within the drill pipe's inner wall, ordinary shot blasting and sandblasting are not only difficult to remove rust but also pollute the environment. Most commonly used anti-corrosion coatings for oil drill pipes both domestically and internationally are solvent-based coatings made of epoxy resin and epoxy phenolic resin. These coatings have limited resistance to high temperatures, high pressures, wear, and harsh environments, and also exhibit high VOCs, posing significant environmental and safety hazards. Furthermore, existing epoxy resin coatings applied directly to the inner surface of oil drill pipes suffer from poor adhesion and fail to meet the required protection standards.

[0004] This shows that the existing technology needs further improvement. Summary of the Invention

[0005] The purpose of this invention is to provide an application of organic-inorganic modified powder coating on the inner wall surface of oil drill pipe. The method involves pretreating the inner surface of the oil drill pipe using vapor phase rust prevention technology, and then spraying the powder coating onto the pretreated inner surface of the oil drill pipe using electrostatic spraying technology, which ultimately melts and forms a film. This method achieves a thick film in a single coating application and exhibits excellent high temperature resistance, high pressure resistance, wear resistance, and acid resistance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The application of organic-inorganic modified powder coatings on the inner surface of oil drill pipes includes the following steps:

[0008] Step 1: Pre-treatment of the inner surface of the oil drill pipe

[0009] The vapor phase corrosion inhibitor is sprayed onto the inner wall of the oil drill pipe. The atomized vapor phase corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion inhibitor gas is adsorbed on the exposed surface of the oil drill pipe. The corrosion inhibitor gas converts the rust on the surface of the oil drill pipe into a stable black film.

[0010] Step 2: Preparation of organic-inorganic modified powder coatings

[0011] The powder coating comprises, by weight, the following raw materials: 35-45 parts modified epoxy resin, 8-15 parts PVDF powder, 6-15 parts nylon powder, 2-5 parts curing agent, 1-4 parts organic wear-resistant filler, 5-12 parts inorganic wear-resistant filler, 1-5 parts solid wear-resistant lubricant, 10-30 parts pigments and fillers, 0.2-0.5 parts curing accelerator, and 1.5-4 parts additives;

[0012] Add each raw material to the mixer according to the above weight ratio and mix them.

[0013] The mixed material is added to a screw extruder for melt extrusion of semi-finished product;

[0014] After the semi-finished product from the melt extrusion is cooled and crushed, it is pulverized in an air classifier mill. The pulverized material is then screened through a 100-mesh sieve to obtain the finished product.

[0015] After sieving, the finished product is sampled and sprayed on a plate for inspection. Once it passes the inspection, it is packaged and put into storage.

[0016] Step 3: Using electrostatic spraying technology, the powder coating prepared in Step 2 is sprayed onto the inner wall surface of the oil drill pipe after the pretreatment in Step 1, and melted to form a film.

[0017] In the application of the above-mentioned organic-inorganic modified powder coating on the inner wall surface of oil drill pipe, in step one, the vapor phase corrosion inhibitor includes, by weight parts: 20-30 parts of corrosion stabilizer, 0.5-1.0 parts of wetting and dispersing agent, 30-45 parts of inorganic cementitious material, 25-35 parts of corrosion conversion agent, and 0.2-1.0 parts of substrate wetting agent.

[0018] The above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes includes the following: the corrosion stabilizer is an organic nitrogen-based chromate; the wetting and dispersing agent is one or more of anionic surfactants, high molecular weight carboxylic acid-modified polysiloxanes, and high molecular weight block copolymers; the inorganic cementing material is one or more of sulfoaluminates, fluoroaluminates, phosphates, and composite silicates; the corrosion conversion agent is one or two of tannic acid and phosphoric acid-based corrosion conversion agents; and the substrate wetting agent is one or more of polyether-modified organosiloxanes, polyester-modified organosiloxanes, and fluorinated polyacrylate copolymers.

[0019] In the above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes, step two involves the preparation of modified epoxy resin as follows: 70-80 parts of low molecular weight epoxy resin, 15-20 parts of bisphenol A, 3-5 parts of rare earth chloride, 2-3 parts of triglycidyl isocyanate, 1-2 parts of pyridine, and 3-5 parts of a mercapto-containing compound are added to a reactor equipped with a condenser and a water jacket. Nitrogen gas is introduced, and the mixture is heated to 110-120°C. The reactor temperature is controlled at 170-180°C using cooling water. The reaction is carried out for 45-70 minutes, then cooled and depressurized. The mixture is discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 380-500 g / eq and a softening point of 95-105°C.

[0020] The above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes uses a low molecular weight epoxy resin with an epoxy equivalent of 175-195 g / eq. The liquid epoxy resin is an epoxy resin with the model number E-51, YP-128, Epon828 or DER331. The mercapto-containing compound is one or two of pentaerythritol tetra(3-mercaptobutyrate) and 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-trione.

[0021] The above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes, wherein the PVDF powder is a transparent or semi-transparent crystalline polymer of polyvinylidene fluoride with a fluorine content of 59% and a molecular weight of 250,000 to 1,000,000.

[0022] The nylon powder mentioned above is one or both of nylon-11 and nylon-12; the curing agent is a modified dicyandiamide curing agent, which is synthesized by reacting one of the aromatic diamines such as 4,4'-diaminodiphenylmethylamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, and p-xylylamine with dicyandiamide.

[0023] The organic wear-resistant filler is polytetrafluoroethylene powder and / or polypropylene powder, and the particle size of the organic wear-resistant filler is less than 5 μm.

[0024] The above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes, wherein the inorganic wear-resistant filler is selected from one or more of ceramic powder, tungsten carbide, chromium carbide, zirconium oxide, cerium oxide and boron nitride powder, and the particle size of the inorganic wear-resistant filler is less than 200 nm.

[0025] The solid wear-resistant lubricant is molybdenum disulfide and / or ethylene bis-stearamide, and the particle size of the solid wear-resistant lubricant is 325-1250 mesh.

[0026] The above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes includes pigments and rust-preventive fillers. The pigments include one or more of carbon black, titanium dioxide, iron oxide red, medium chrome yellow, and phthalocyanine blue. The rust-preventive fillers include one or more of aluminum tripolyphosphate, composite zinc phosphate, composite iron-titanium powder, sericite powder, silica powder, talc powder, and precipitated barium sulfate. The particle size of the pigments and fillers is 800-1250 mesh.

[0027] In the above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes, the curing accelerator is selected from one or more of dimethylimidazole, 2-methylimidazole urea, and boron trifluoride ethylamine complex;

[0028] The additives include leveling agents, dispersants, degassing agents, and loosening agents;

[0029] The leveling agent is one or more of the following: acrylate copolymer, organic modified polysiloxane, and fluorocarbon compound;

[0030] The dispersant is a copolymer of butyl acrylate and methyl methacrylate;

[0031] The degassing agent is diphenylethanol ketone;

[0032] The loosening agent includes fumed silica or alumina;

[0033] The above-mentioned application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes includes, by weight, the following additives: 0.8-1.5 parts leveling agent, 0.5-1.0 parts dispersant, 0.3-0.5 parts degassing agent, and 0.1-0.3 parts loosening agent.

[0034] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0035] (1) Vapor phase rust prevention technology is fast and environmentally friendly. Inorganic cementitious materials can generate hydrates when in contact with water, integrating the synergistic effect of rust conversion agent and rust stabilizer, transforming the rust on the substrate into stable and harmless substances that exist on the metal surface, so that they can be firmly attached to the inner wall of the oil drill pipe, and can also play the role of sealing and passivating rust.

[0036] (2) The powder coating prepared by this invention is a solvent-free product, which is safe and environmentally friendly. During use, it is applied by electrostatic spraying technology onto the surface of the protective substrate and finally melts into a film. Compared with traditional solvent-based coating materials, this material can form a thick film in a single application.

[0037] (3) The powder coating prepared by this invention is very stable after being modified with rare earth chloride epoxy resin, and the storage stability of the powder coating is greatly improved. The mechanical properties of the coating after adding rare earth are significantly improved compared with ordinary epoxy resin, the coating film's resistance to media penetration is further improved, and the coating film's water absorption rate, boiling water resistance and organic solvent resistance are further improved. Since rare earth elements generally easily lose 3 electrons, are trivalent, and have extremely high reactivity, they are highly reactive agents participating in the reaction and also their own catalysts; and the compounds obtained after reacting with resin have extremely strong bond energies, thus improving the resin's heat resistance, wear resistance, corrosion resistance and other properties.

[0038] (4) The powder coating of the present invention modifies the epoxy resin by isocyanate triglycidyl ester, pyridine and mercapto-containing compounds, resulting in higher crosslinking density and improved coating film resistance to media penetration, mechanical properties, wear resistance and chemical resistance.

[0039] (5) The powder coating of the present invention improves the temperature resistance, high pressure resistance, water resistance, wear resistance, impact resistance and chemical corrosion resistance of the coating film by introducing PVDF and nylon powder modification.

[0040] (6) The powder coating of the present invention significantly improves the wear resistance of the coating film and extends the service life of oil drill pipe by adding special organic and inorganic wear-resistant materials.

[0041] (7) The surface treatment technology and powder coating products of the present invention can be used not only for protective coating of oil drill pipes, but also for protective coating of other pipelines and equipment in harsh environments such as oil casing and oil pipelines. Detailed Implementation

[0042] This invention proposes the application of organic-inorganic modified powder coatings on the inner wall surface of oil drill pipes. To make the advantages and technical solutions of this invention clearer and more explicit, the invention is further described below with reference to specific embodiments.

[0043] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0044] The main technical concept of this invention is as follows: Addressing the problem of poor corrosion resistance of the inner wall surface of oil drill pipes in existing technologies, this invention proposes an organic-inorganic modified powder coating. Furthermore, any coating must be applied to a substrate with adequate surface treatment to truly realize its design value. This invention pre-treats the inner wall surface of the oil drill pipe using vapor phase corrosion inhibitor technology, and then sprays the powder coating of this invention onto the pre-treated inner wall. The results show that the sprayed coating forms a thick film, exhibits excellent adhesion to the substrate, and demonstrates superior resistance to high temperatures, high pressures, wear, and acids, meeting the protection requirements of oil drill pipes under harsh environments.

[0045] To address the challenges of difficult, ineffective, and environmentally polluting surface treatments for the inner walls of oil drill pipes, this invention provides a fast and environmentally friendly surface treatment method. This method utilizes vapor phase corrosion inhibitors, which are sprayed onto the inner walls of the oil drill pipe. At room temperature, the vapor phase corrosion inhibitor slowly vaporizes, and the released corrosion-inhibiting gas is adsorbed onto the exposed metal surface, converting rust into a stable black film. This protective film then prevents corrosion of the metal by oxygen, moisture, and other factors.

[0046] After pretreatment of the inner wall surface of existing oil drill pipes, the organic-inorganic modified powder coating prepared in this invention is sprayed onto its surface using electrostatic spraying technology, and finally melted into a film.

[0047] The specific steps are as follows:

[0048] Step 1: Apply the vapor phase corrosion inhibitor to the inner wall of the oil drill pipe using air or an airless spray gun. The atomized corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion-inhibiting gas is adsorbed on the exposed metal surface, converting rust into a stable black film and improving the adhesion of subsequent coatings.

[0049] The vapor phase corrosion inhibitor comprises, by weight, the following raw materials: 20-30 parts of corrosion stabilizer, 0.5-1.0 parts of wetting and dispersing agent, 30-45 parts of inorganic cementing material, 25-35 parts of corrosion conversion agent, and 0.2-1.0 parts of substrate wetting agent. The raw materials are stirred and mixed evenly to prepare the inhibitor.

[0050] Preferably, the aforementioned rust stabilizer is an organic nitrogen-based chromate. The coordination complex generated by the hydrolysis of the rust stabilizer reacts with the active rust to form a complex polyacid complex that is difficult to dissolve, thereby sealing and passivating the rust and preventing it from spreading further.

[0051] Preferably, the wetting and dispersing agent mentioned above is one or more of anionic surfactants, high molecular weight carboxylic acid modified polysiloxanes, and high molecular weight block copolymers.

[0052] Preferably, the aforementioned inorganic cementing material includes one or more of sulfoaluminate, fluoroaluminate, phosphate, and composite silicate.

[0053] Preferably, the aforementioned rust conversion agent is one or two of tannic acid and phosphoric acid rust conversion agents. The rust conversion agent converts the rust on the substrate into a stable and harmless substance that exists within the paint film, allowing it to adhere firmly to the steel structure.

[0054] Preferably, the substrate wetting agent mentioned above is one or more of polyether-modified organosiloxane, polyester-modified organosiloxane, and fluorinated polyacrylate copolymer.

[0055] Step 2: Preparation of Organic-Inorganic Modified Powder Coatings

[0056] The raw materials, by weight, include: 35-45 parts modified epoxy resin, 8-15 parts PVDF powder, 6-15 parts nylon powder, 2-5 parts curing agent, 1-4 parts organic wear-resistant filler, 5-12 parts inorganic wear-resistant filler, 1-5 parts solid wear-resistant lubricant, 10-30 parts pigments and fillers, 0.2-0.5 parts curing accelerator, and 1.5-4 parts additives.

[0057] Preferably, the preparation steps of the modified epoxy resin are as follows: 70-80 parts of low molecular weight epoxy resin, 15-20 parts of bisphenol A, 3-5 parts of rare earth chloride, 2-3 parts of triglycidyl isocyanate (TGIC), 1-2 parts of pyridine, and 3-5 parts of mercapto-containing compound (RHS) are added to a reactor equipped with a condenser and a water jacket. Nitrogen gas is introduced, and the mixture is heated to 110-120°C. The reactor temperature is controlled at around 177°C by cooling water, and the reaction is carried out for 45-70 minutes. Then, the mixture is cooled and depressurized, discharged, and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 380-500 g / eq and a softening point of 95-105°C. The modified epoxy resin has a higher crosslinking density, which improves the coating's resistance to media penetration, and significantly enhances the film's abrasion resistance and chemical resistance.

[0058] Preferably, the low molecular weight epoxy resin is a commercially available liquid epoxy resin with an epoxy equivalent of 175-195 g / eq, such as E-51, YP-128, Epon828, or DER331.

[0059] Preferably, the thiol-containing compound (RHS) is one or two of pentaerythritol tetra(3-mercaptobutyrate) and 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-trione, which is more stable and has a lower odor than ordinary thiol compounds. The thiol-modified epoxy resin exhibits increased reactivity and reduced stress during coating curing, thereby improving the coating's chemical resistance and adhesion.

[0060] Preferably, the PVDF powder is a transparent or semi-transparent crystalline polymer of polyvinylidene fluoride with a fluorine content of 59% and a molecular weight of 250,000 to 1,000,000, which can significantly improve the coating's wear resistance, water and oil repellency, pollution resistance, flexibility, temperature change resistance, corrosion resistance, chemical resistance, and resistance to strong corrosion rich in SO2 gas.

[0061] Preferably, the nylon powder is one or both of nylon-11 and nylon-12, which have excellent abrasion resistance and stain resistance, and improve the hardness, boiling water resistance, alkali resistance and impact resistance of the coating.

[0062] Preferably, the curing agent is a modified dicyandiamide curing agent, which is synthesized by reacting one of the aromatic diamines such as 4,4'-diaminodiphenylmethylamine (DDM), 4,4'-diaminodiphenyl ether (DDE), 4,4'-diaminodiphenyl sulfone (DDS), and p-xyleneamine (DMB) with dicyandiamide. The leveling properties of the coating film of the modified curing agent with the introduction of benzene ring are greatly improved.

[0063] Preferably, the organic wear-resistant filler is polytetrafluoroethylene powder and / or polypropylene powder, and more preferably, the particle size of the organic wear-resistant filler is less than 5 μm.

[0064] Preferably, the inorganic wear-resistant filler is selected from one or more of ceramic powder, tungsten carbide, chromium carbide, zirconium oxide, cerium oxide and boron nitride powder, and preferably the particle size of the inorganic wear-resistant filler is less than 200 nm.

[0065] Preferably, the solid wear-resistant lubricant is molybdenum disulfide and / or ethylene bis-stearamide, and the particle size of the solid wear-resistant lubricant is preferably between 325 and 1250 mesh.

[0066] Preferably, the pigments and fillers include coloring pigments and rust-preventive fillers.

[0067] Preferably, the coloring pigment includes one or more of carbon black, titanium dioxide, iron oxide red, medium chrome yellow, and phthalocyanine blue.

[0068] Preferably, the rust-preventive filler includes one or more of aluminum tripolyphosphate, zinc phosphate composite, iron-titanium composite powder, sericite powder, silica powder, talc powder, and precipitated barium sulfate; preferably, the particle size of the pigment or filler is between 800 and 1250 mesh.

[0069] Preferably, the curing accelerator is selected from one or more of dimethylimidazole, 2-methylimidazole urea, and boron trifluoride ethylamine complex.

[0070] Preferably, the additives include leveling agents, dispersants, degassing agents, and loosening agents. The leveling agent is one or more of acrylate copolymers, organically modified polysiloxanes, and fluorocarbon compounds. The dispersant is a copolymer of butyl acrylate and methyl methacrylate. The degassing agent is benzoin, i.e., diphenylethanol ketone. The loosening agent includes fumed silica or alumina.

[0071] Preferably, the leveling agent is 0.8 to 1.5 parts, the dispersant is 0.5 to 1.0 parts, the degassing agent is 0.3 to 0.5 parts, and the loosening agent is 0.1 to 0.3 parts.

[0072] The preparation method of organic-inorganic modified powder coatings includes the following specific steps:

[0073] (1) Weigh each component according to the mass percentage and add it to the mixer to mix;

[0074] (2) Add the mixed materials to a screw extruder to melt and extrude the semi-finished product;

[0075] (3) After the semi-finished product from the melt extrusion is cooled and crushed, it is then pulverized in an air classifier mill. The pulverized material is then screened through a 100-mesh sieve to obtain the finished product.

[0076] (4) After sieving, the finished product is sampled and sprayed for inspection. If it passes the inspection, it is packaged and put into storage.

[0077] Step 3: Using electrostatic spraying technology, the organic-inorganic modified powder coating prepared in Step 2 is sprayed onto the inner wall of the oil drill pipe and melted to form a film.

[0078] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0079] In the preparation process of the vapor phase corrosion inhibitor of the present invention, the raw materials include: wetting and dispersing agent, inorganic cementing material, corrosion conversion agent, and substrate wetting agent. Depending on the different selection of raw materials, multiple different combinations can be formed.

[0080] Here are some examples:

[0081] The composition includes 20-30 parts of rust stabilizer, 0.5-1.0 parts of high molecular weight carboxylic acid modified polysiloxane, 30-45 parts of sulfoaluminate, 25-35 parts of tannic acid, and 0.2-1.0 parts of polyether modified organosiloxane.

[0082] The composition includes 20-30 parts of rust stabilizer, 0.5-1.0 parts of high molecular weight block copolymer, 30-45 parts of fluoroaluminate, 25-35 parts of phosphoric acid rust converter, and 0.2-1.0 parts of polyester modified organosiloxane.

[0083] The composition includes 20-30 parts of rust stabilizer, 0.5-1.0 parts of high molecular weight carboxylic acid modified polysiloxane, 30-45 parts of sulfoaluminate, 25-35 parts of tannic acid, and 0.2-1.0 parts of polyether modified organosiloxane.

[0084] The composition includes 20-30 parts of rust stabilizer, 0.5-1.0 parts of high molecular weight carboxylic acid modified polysiloxane, 30-45 parts of phosphate, 25-35 parts of phosphate rust converter, and 0.2-1.0 parts of fluorine modified polyacrylate copolymer.

[0085] Guided by the above combinations, other combinations can be readily derived by those skilled in the art, which will not be elaborated upon here.

[0086] In the preparation process of the organic-inorganic powder coating of this invention, the raw materials used include modified epoxy resin, PVDF powder, nylon powder, curing agent, organic wear-resistant filler, inorganic wear-resistant filler, solid wear-resistant lubricant, pigments and fillers, curing accelerator, and additives. Depending on the selection of different raw materials, multiple different combinations can be formed.

[0087] Here are some examples:

[0088] The mixture comprises 35-45 parts modified epoxy resin, 8-15 parts PVDF powder, 6-15 parts nylon-11, 2-5 parts aromatic diamine such as 4,4'-diaminodiphenylmethane (DDM), 1-4 parts polytetrafluoroethylene powder, 5-12 parts ceramic powder, 1-5 parts molybdenum disulfide, 10-30 parts carbon black, 0.2-0.5 parts dimethylimidazole, and 1.5-4 parts additives.

[0089] The mixture comprises 35-45 parts modified epoxy resin, 8-15 parts PVDF powder, 6-15 parts nylon-12, 2-5 parts 4,4'-diaminodiphenyl ether (DDE), 1-4 parts polypropylene powder, 5-12 parts tungsten carbide, 1-5 parts ethylene bis-stearamide, 10-30 parts iron oxide red, 0.2-0.5 parts boron trifluoride ethylamine complex, and 1.5-4 parts additives.

[0090] Guided by the above combinations, other combinations can be readily derived by those skilled in the art, which will not be elaborated upon here.

[0091] Example 1:

[0092] The application of organic-inorganic modified powder coatings on the inner surface of oil drill pipes includes the following steps:

[0093] Step 1: Preparation of vapor phase corrosion inhibitor, which is made by the following steps:

[0094] 30 parts of diphenylguanidine chromate, 0.5 parts of wetting and dispersing agent FA196, 20 parts of fluoroaluminate, 18 parts of composite silicate, 3 parts of tannic acid, 28 parts of phosphate ester and 0.5 parts of substrate wetting agent Levelol 837 are stirred and mixed evenly.

[0095] The vapor phase corrosion inhibitor is sprayed onto the inner wall of the oil drill pipe using air or an airless spray gun. The atomized corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion-inhibiting gas is adsorbed on the exposed metal surface, which converts rust into a stable black film and improves the adhesion of subsequent coatings.

[0096] Step 2: Preparation of powder coating

[0097] Preparation of modified epoxy resin: 76 parts of E-51 epoxy resin, 15 parts of bisphenol A, 3 parts of rare earth chloride, 2 parts of triglycidyl isocyanate (TGIC), 1 part of pyridine, and 3 parts of pentaerythritol tetra(3-mercaptobutyrate) were added to a reactor equipped with a condenser and a cooling water jacket. Nitrogen gas was introduced and the mixture was heated to 110°C. The reactor temperature was controlled at around 177°C by cooling water. The reaction was carried out for 50 minutes, and then the temperature was lowered and the pressure was reduced. The mixture was discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 410 g / eq and a softening point of 98°C.

[0098] 35 parts modified epoxy resin, 8 parts PVDF720 powder, 7.8 parts nylon-11 powder, and modified dicyandiamide curing agent HT-2883 were mixed. 2 parts of polytetrafluoroethylene micro powder, 1.5 parts of ceramic powder (particle size 10nm, Mohs hardness 9), 2.5 parts of tungsten carbide, 1.8 parts of chromium carbide, 2.2 parts of zirconium oxide, 4 parts of molybdenum disulfide, 2 parts of MA-100 carbon black, 5 parts of aluminum tripolyphosphate, 4 parts of silica micro powder, 9 parts of talc powder, 6 parts of precipitated barium sulfate, 3 parts of sericite powder, 0.3 parts of dimethylimidazole, 1.5 parts of PLA-1 acrylate leveling agent, 1.0 part of LD-2180 dispersant, 0.3 parts of benzoin, and 0.1 parts of fumed silica; these are added to a mixer and mixed; the mixed materials are added to a screw extruder for melt extrusion of semi-finished products; the melt-extruded semi-finished products are cooled, crushed, and then pulverized in an air classifier mill; the pulverized materials are screened through a 100-mesh sieve to obtain the finished product; samples of the sieved finished product are sprayed onto a plate for inspection, and those that pass the inspection are obtained as powder coating.

[0099] Step 3: Using electrostatic spraying technology, the organic-inorganic modified powder coating prepared in Step 2 is sprayed onto the inner wall of the oil drill pipe and melted to form a film.

[0100] Example 2:

[0101] The application of organic-inorganic modified powder coatings on the inner surface of oil drill pipes includes the following steps:

[0102] Step 1: Preparation of vapor phase corrosion inhibitor, which is made by the following steps:

[0103] 27 parts of diphenylguanidine chromate, 0.5 parts of wetting and dispersing agent TEGO685, 25 parts of sulfoaluminate, 14.5 parts of composite silicate, 2.5 parts of tannic acid, 30 parts of phosphate ester and 0.5 parts of substrate wetting agent AD01 are stirred and mixed evenly.

[0104] The vapor phase corrosion inhibitor is sprayed onto the inner wall of the oil drill pipe using air or an airless spray gun. The atomized corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion-inhibiting gas is adsorbed on the exposed metal surface, which converts rust into a stable black film and improves the adhesion of subsequent coatings.

[0105] Step 2: Preparation of powder coating

[0106] 75 parts of Epon828 epoxy resin, 15 parts of bisphenol A, 3 parts of rare earth chloride, 2 parts of triglycidyl isocyanate (TGIC), 1.5 parts of pyridine, and 3.5 parts of 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-trione) were added to a reactor equipped with a condenser and a water jacket. Nitrogen gas was introduced, and the mixture was heated to 120°C. The reactor temperature was controlled at around 177°C by cooling water. The reaction was carried out for 60 minutes, then cooled and depressurized. The mixture was discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 420 g / eq and a softening point of 100°C.

[0107] The following ingredients were added: 45 parts modified epoxy resin, 8 parts PVDF720 powder, 6 parts nylon-11 powder, 43 parts modified dicyandiamide curing agent HT-288, 2.5 parts polytetrafluoroethylene micro powder, 2 parts ceramic powder (particle size 10nm, Mohs hardness 9), 3 parts zirconium oxide, 2 parts cerium oxide, 1 part boron nitride, 1.5 parts molybdenum disulfide, 2.5 parts ethylene bis-stearamide wax, 5 parts 237 titanium dioxide, 0.5 parts MA-100 carbon black, 4 parts composite zinc phosphate, 4.5 parts silica micro powder, and precipitated sulfuric acid. 5 parts barium, 2 parts sericite powder, 0.3 parts 2-methylimidazolium urea, 0.8 parts DC75 polysiloxane leveling agent, 0.8 parts LD-2180 dispersant, 0.4 parts benzoin, and 0.2 parts fumed silica are added to a mixer and mixed. The mixed material is then added to a screw extruder to melt and extrude a semi-finished product. The melt-extruded semi-finished product is cooled, crushed, and then pulverized in an air classifier mill. The pulverized material is then screened through a 100-mesh sieve to obtain the finished product. A sample of the sieved finished product is sprayed onto a plate for inspection. If it passes the inspection, the powder coating is obtained.

[0108] Step 3: Using electrostatic spraying technology, the organic-inorganic modified powder coating prepared in Step 2 is sprayed onto the inner wall of the oil drill pipe and melted to form a film.

[0109] Example 3:

[0110] The application of organic-inorganic modified powder coatings on the inner surface of oil drill pipes includes the following steps:

[0111] Step 1: Preparation of vapor phase corrosion inhibitor, which is made by the following steps:

[0112] 27 parts of diphenylguanidine chromate, 0.5 parts of wetting and dispersing agent TEGO685, 25 parts of sulfoaluminate, 14.5 parts of composite silicate, 2.5 parts of tannic acid, 30 parts of phosphate ester and 0.5 parts of substrate wetting agent AD01 are stirred and mixed evenly.

[0113] The vapor phase corrosion inhibitor is sprayed onto the inner wall of the oil drill pipe using air or an airless spray gun. The atomized corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion-inhibiting gas is adsorbed on the exposed metal surface, which converts rust into a stable black film and improves the adhesion of subsequent coatings.

[0114] Step 2: Preparation of powder coating

[0115] 70 parts of DER331 epoxy resin, 18 parts of bisphenol A, 3 parts of rare earth chloride, 2 parts of triglycidyl isocyanate (TGIC), 2 parts of pyridine, 2 parts of pentaerythritol tetra(3-mercaptobutyrate), and 3 parts of 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-trione were added to a reactor equipped with a condenser and a water jacket. Nitrogen gas was introduced, and the mixture was heated to 120°C. The reactor temperature was controlled at around 177°C by cooling water. The reaction was carried out for 70 minutes, and then the temperature was lowered and the pressure reduced. The mixture was discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 480 g / eq and a softening point of 105°C.

[0116] The following ingredients were added: 40 parts modified epoxy resin, 10 parts PVDF5120 powder, 8 parts nylon-12 powder, 3 parts modified dicyandiamide curing agent AEHD-610, 3.5 parts polypropylene micro powder, 2 parts tungsten carbide, 1 part chromium carbide, 3 parts zirconium oxide, 1.5 parts cerium oxide, 3 parts molybdenum disulfide, 8 parts 190 iron oxide red, 5 parts composite iron-titanium powder, 7.4 parts precipitated barium sulfate, 2 parts sericite powder, 0.4 parts 2-methylimidazolidinyl urea, 0.8 parts BYK-366P polyacrylate leveling agent, 0.8 parts LD-2180 dispersant, 0.3 parts benzoin, and 0.3 parts alumina (particle size 30nm, Mohs hardness 9). Add the materials to the mixer and mix; add the mixed materials to the screw extruder to melt and extrude the semi-finished product; cool and crush the melt-extruded semi-finished product and then put it into the air classifier mill for grinding; the ground material is screened through a 100-mesh sieve to obtain the finished product; the finished product after sieving is sampled and sprayed on a plate for inspection, and if it passes the inspection, the powder coating is obtained.

[0117] Step 3: Using electrostatic spraying technology, the organic-inorganic modified powder coating prepared in Step 2 is sprayed onto the inner wall of the oil drill pipe and melted to form a film.

[0118] Example 4:

[0119] The application of organic-inorganic modified powder coatings on the inner surface of oil drill pipes includes the following steps:

[0120] Step 1: Preparation of vapor phase corrosion inhibitor, which is made by the following steps:

[0121] 27 parts of diphenylguanidine chromate, 0.5 parts of wetting and dispersing agent TEGO685, 25 parts of sulfoaluminate, 14.5 parts of composite silicate, 2.5 parts of tannic acid, 30 parts of phosphate ester and 0.5 parts of substrate wetting agent AD01 are stirred and mixed evenly.

[0122] The vapor phase corrosion inhibitor is sprayed onto the inner wall of the oil drill pipe using air or an airless spray gun. The atomized corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion-inhibiting gas is adsorbed on the exposed metal surface, which converts rust into a stable black film and improves the adhesion of subsequent coatings.

[0123] Step 2: Preparation of powder coating

[0124] 70 parts of DER331 epoxy resin, 18 parts of bisphenol A, 3 parts of rare earth chloride, 2 parts of triglycidyl isocyanate (TGIC), 2 parts of pyridine, 2 parts of pentaerythritol tetra(3-mercaptobutyrate), and 3 parts of 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-trione were added to a reactor equipped with a condenser and a water jacket. Nitrogen gas was introduced, and the mixture was heated to 120°C. The reactor temperature was controlled at around 177°C by cooling water. The reaction was carried out for 70 minutes, and then the temperature was lowered and the pressure reduced. The mixture was discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 480 g / eq and a softening point of 105°C.

[0125] The following ingredients were added: modified epoxy resin 35, PVDF460 powder (10 parts), nylon-12 powder (12 parts), modified dicyandiamide curing agent EH-5031S (3.5 parts), polytetrafluoroethylene micro powder (3 parts), chromium carbide (2 parts), zirconium oxide (3 parts), cerium oxide (2.5 parts), boron nitride (1 part), ethylene bis-stearamide wax (2.3 parts), chrome yellow 303 (4.5 parts), phthalocyanine blue 15:3 (0.5 parts), composite zinc phosphate (4 parts), silica micro powder (5 parts), talc powder (3 parts), precipitated barium sulfate (5 parts), boron trifluoride ethylamine complex (0.5 parts), and MODAFLOW. 1.2 parts of Powder6000 modified leveling agent, 1.2 parts of LD-2180 dispersant, 0.5 parts of benzoin, and 0.3 parts of alumina (particle size 30nm, Mohs hardness 9) are added to a mixer and mixed. The mixed material is then added to a screw extruder to melt and extrude a semi-finished product. The melt-extruded semi-finished product is cooled, crushed, and then pulverized in an air classifier mill. The pulverized material is then screened through a 100-mesh sieve to obtain the finished product. A sample of the sieved finished product is sprayed onto a plate for inspection. If it passes the inspection, the powder coating is obtained.

[0126] Step 3: Using electrostatic spraying technology, the organic-inorganic modified powder coating prepared in Step 2 is sprayed onto the inner wall of the oil drill pipe and melted to form a film.

[0127] Comparative Example 1:

[0128] The application of organic-inorganic modified powder coatings on the inner surface of oil drill pipes includes the following steps:

[0129] Step 1: Perform mechanical degreasing and rust removal on the inner wall of the oil drill pipe;

[0130] Step 2: Preparation of powder coating

[0131] Preparation of modified epoxy resin: 76 parts of E-51 epoxy resin, 15 parts of bisphenol A, 3 parts of rare earth chloride, 2 parts of triglycidyl isocyanate (TGIC), 1 part of pyridine, and 3 parts of pentaerythritol tetra(3-mercaptobutyrate) were added to a reactor equipped with a condenser and a cooling water jacket. Nitrogen gas was introduced and the mixture was heated to 110°C. The reactor temperature was controlled at around 177°C by cooling water. The reaction was carried out for 50 minutes, and then the temperature was lowered and the pressure was reduced. The mixture was discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 410 g / eq and a softening point of 98°C.

[0132] 35 parts modified epoxy resin, 8 parts PVDF720 powder, 7.8 parts nylon-11 powder, and modified dicyandiamide curing agent HT-2883 were mixed. 2 parts of polytetrafluoroethylene micro powder, 1.5 parts of ceramic powder (particle size 10nm, Mohs hardness 9), 2.5 parts of tungsten carbide, 1.8 parts of chromium carbide, 2.2 parts of zirconium oxide, 4 parts of molybdenum disulfide, 2 parts of MA-100 carbon black, 5 parts of aluminum tripolyphosphate, 4 parts of silica micro powder, 9 parts of talc powder, 6 parts of precipitated barium sulfate, 3 parts of sericite powder, 0.3 parts of dimethylimidazole, 1.5 parts of PLA-1 acrylate leveling agent, 1.0 part of LD-2180 dispersant, 0.3 parts of benzoin, and 0.1 parts of fumed silica; these are added to a mixer and mixed; the mixed materials are added to a screw extruder for melt extrusion of semi-finished products; the melt-extruded semi-finished products are cooled, crushed, and then pulverized in an air classifier mill; the pulverized materials are screened through a 100-mesh sieve to obtain the finished product; samples of the sieved finished product are sprayed onto a plate for inspection, and those that pass the inspection are obtained as powder coating.

[0133] Step 3: Using electrostatic spraying technology, the organic-inorganic modified powder coating prepared in Step 2 is sprayed onto the inner wall of the untreated oil drill pipe and melted to form a film.

[0134] The performance indicators of the powder coatings of Examples 1-4 and Comparative Example 1 are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138]

[0139] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. Use of an organomineral modified powder coating on the inner wall surface of an oil drill pipe, characterized in that, Includes the following steps: Step 1: Pre-treatment of the inner surface of the oil drill pipe The vapor phase corrosion inhibitor is sprayed onto the inner wall of the oil drill pipe. The atomized vapor phase corrosion inhibitor continues to slowly vaporize on the inner wall of the oil drill pipe. The volatilized corrosion inhibitor gas is adsorbed on the exposed surface of the oil drill pipe. The corrosion inhibitor gas converts the rust on the surface of the oil drill pipe into a stable black film. Step 2: Preparation of organic-inorganic modified powder coatings The powder coating comprises, by weight, the following raw materials: 35-45 parts modified epoxy resin, 8-15 parts PVDF powder, 6-15 parts nylon powder, 2-5 parts curing agent, 1-4 parts organic wear-resistant filler, 5-12 parts inorganic wear-resistant filler, 1-5 parts solid wear-resistant lubricant, 10-30 parts pigments and fillers, 0.2-0.5 parts curing accelerator, and 1.5-4 parts additives; Add each raw material to the mixer according to the above weight ratio and mix them. The mixed material is added to a screw extruder for melt extrusion of semi-finished product; After the semi-finished product from the melt extrusion is cooled and crushed, it is pulverized in an air classifier mill. The pulverized material is then screened through a 100-mesh sieve to obtain the finished product. After sieving, the finished product is sampled and sprayed on a plate for inspection. Once it passes the inspection, it is packaged and put into storage. Step 3: Using electrostatic spraying technology, the powder coating prepared in Step 2 is sprayed onto the inner wall surface of the oil drill pipe after the pretreatment in Step 1, and melted into a film. In step two, the modified epoxy resin is prepared as follows: 70-80 parts of low molecular weight epoxy resin, 15-20 parts of bisphenol A, 3-5 parts of rare earth chloride, 2-3 parts of triglycidyl isocyanate, 1-2 parts of pyridine, and 3-5 parts of mercapto-containing compound are added to a reactor equipped with a condenser and a cooling water jacket. Nitrogen gas is introduced, and the mixture is heated to 110-120°C. The reactor temperature is controlled at 170-180°C by cooling water. The reaction is carried out for 45-70 minutes, then cooled and depressurized. The mixture is discharged and cooled to obtain a solid modified epoxy resin with an epoxy equivalent of 380-500 g / eq and a softening point of 95-105°C.

2. The application of the organic-inorganic modified powder coating according to claim 1 on the inner wall surface of oil drill pipe, characterized in that: In step one, the vapor phase corrosion inhibitor comprises, by weight parts: 20-30 parts of corrosion stabilizer, 0.5-1.0 parts of wetting and dispersing agent, 30-45 parts of inorganic cementing material, 25-35 parts of corrosion conversion agent, and 0.2-1.0 parts of substrate wetting agent.

3. The application of the organic-inorganic modified powder coating according to claim 2 on the inner wall surface of oil drill pipe, characterized in that: The corrosion stabilizer is an organic nitrogen-based chromate; the wetting and dispersing agent is one or more of anionic surfactants, high molecular weight carboxylic acid-modified polysiloxanes, and high molecular weight block copolymers; the inorganic cementing material is one or more of sulfoaluminate, fluoroaluminate, phosphate, and composite silicate; the corrosion conversion agent is one or two of tannic acid and phosphoric acid-based corrosion conversion agents; and the substrate wetting agent is one or more of polyether-modified organosiloxanes, polyester-modified organosiloxanes, and fluorinated polyacrylate copolymers.

4. The application of the organic-inorganic modified powder coating according to claim 1 on the inner wall surface of oil drill pipe, characterized in that: The low molecular weight epoxy resin is a liquid epoxy resin with an epoxy equivalent of 175-195 g / eq. The liquid epoxy resin is an epoxy resin with the model number E-51, YP-128, Epon828 or DER331. The mercapto-containing compound is one or two of pentaerythritol tetra(3-mercaptobutyrate) and 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-trione.

5. The application of the organic-inorganic modified powder coating according to claim 1 on the inner wall surface of oil drill pipe, characterized in that: The PVDF powder is a transparent or semi-transparent crystalline polymer of polyvinylidene fluoride with a fluorine content of 59% and a molecular weight of 250,000 to 1,000,000. The nylon powder is one or both of nylon-11 and nylon-12; the curing agent is a modified dicyandiamide curing agent, which is an aromatic diamine such as 4,4'-diaminodiphenylmethylamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, or p-xylylamine, synthesized by reacting with dicyandiamide. The organic wear-resistant filler is polytetrafluoroethylene powder and / or polypropylene powder, and the particle size of the organic wear-resistant filler is less than 5 μm.

6. The application of the organic-inorganic modified powder coating according to claim 1 on the inner wall surface of oil drill pipe, characterized in that: The inorganic wear-resistant filler is selected from one or more of ceramic powder, tungsten carbide, chromium carbide, zirconium oxide, cerium oxide and boron nitride powder, and the particle size of the inorganic wear-resistant filler is less than 200 nm. The solid wear-resistant lubricant is molybdenum disulfide and / or ethylene bis-stearamide, and the particle size of the solid wear-resistant lubricant is 325-1250 mesh.

7. The application of the organic-inorganic modified powder coating according to claim 1 on the inner wall surface of oil drill pipe, characterized in that: The pigments and fillers include coloring pigments and rust-preventive fillers; the coloring pigments include one or more of carbon black, titanium dioxide, iron oxide red, medium chrome yellow, and phthalocyanine blue; the rust-preventive fillers include one or more of aluminum tripolyphosphate, composite zinc phosphate, composite iron-titanium powder, sericite powder, silica powder, talc powder, and precipitated barium sulfate; the particle size of the pigments and fillers is 800-1250 mesh.

8. The application of the organic-inorganic modified powder coating according to claim 1 on the inner wall surface of oil drill pipe, characterized in that: The curing accelerator is selected from one or more of dimethylimidazole, 2-methylimidazole urea, and boron trifluoride ethylamine complex; The additives include leveling agents, dispersants, degassing agents, and loosening agents; The leveling agent is one or more of the following: acrylate copolymer, organic modified polysiloxane, and fluorocarbon compound; The dispersant is a copolymer of butyl acrylate and methyl methacrylate; The degassing agent is diphenylethanol ketone; The loosening agent includes fumed silica or alumina; 9. The application of the organic-inorganic modified powder coating according to claim 8 on the inner wall surface of oil drill pipe, characterized in that: The additives, by weight, include: 0.8-1.5 parts leveling agent, 0.5-1.0 parts dispersant, 0.3-0.5 parts degassing agent, and 0.1-0.3 parts loosening agent.

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