A 3PE outer and epoxy resin inner anticorrosion pipeline and a production process thereof

Abstract

The present application belongs to the technical field of anticorrosion pipeline, and particularly relates to an outer 3PE and inner epoxy resin anticorrosion pipeline and a production process thereof, which comprises the following steps: online inspection; intermediate frequency preheating; inner and outer shot blasting rust removal; silanization nano-particle suspension treatment; inner anticorrosion; and epoxy powder coating is sprayed on the outer surface of the steel pipe by using electrostatic spraying technology to form an anticorrosion primer layer, and adhesive and polyethylene are coated on the outer surface of the steel pipe to form an adhesive layer and a polyethylene layer. In the present application, a low-molecular-weight bisphenol A epoxy resin is selected, the viscosity of the molten epoxy powder coating is relatively low, the epoxy powder coating can be fully infiltrated to the anchor pattern bottom of the steel pipe surface, the flow leveling effect is improved, the flow leveling time is shortened, and the epoxy resin coating is more uniform; meanwhile, under the promotion of the imidazole group, the acid anhydride is quickly crosslinked and solidified with the bisphenol A epoxy resin to form a gel, the viscosity of the epoxy powder coating is rapidly increased, and sagging is prevented.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion pipeline technology, specifically relating to an external 3PE internal epoxy resin anti-corrosion pipeline and its production process. Background Technology

[0002] In recent years, with the development of oil and gas resources, 3PE anti-corrosion technology has been widely used in buried pipelines. However, during service, phenomena such as anti-corrosion layer peeling failure and pipeline perforation have occurred, and even caused oil and gas leaks and explosions, resulting in huge economic losses and safety accidents.

[0003] The main methods of 3PE anti-corrosion technology for pipelines are as follows: First, the steel pipe is preheated and then its surface is pretreated; then, the steel pipe is heated to a suitable coating temperature, and epoxy powder coating is evenly applied to the surface of the steel pipe; during the curing process of the epoxy powder coating, adhesive is applied and polyethylene is coated. The core of 3PE anti-corrosion technology is the cross-linking and curing of the epoxy powder coating. The epoxy powder coating is sprayed onto the surface of the steel pipe using a high-pressure electrostatic spray gun, and after coalescence, leveling, melt cross-linking, and finally curing into a film.

[0004] Cathodic disbondment resistance is an important indicator for evaluating 3PE anti-corrosion coatings and has become a key indicator for measuring the quality of anti-corrosion coatings. In existing epoxy powder coatings, the leveling performance of the epoxy powder is poor during the application process. During melting, it does not fully flow to the bottom of the anchor pattern on the steel pipe surface, creating voids between the bottom of the anchor pattern and the anti-corrosion layer. This directly causes false adhesion between the anti-corrosion layer and the anchor pattern on the steel pipe surface, reducing the anti-cathodic disbondment resistance of the anti-corrosion layer. Summary of the Invention

[0005] The purpose of this invention is to provide an external 3PE and internal epoxy resin anti-corrosion pipe and its manufacturing process to solve the above-mentioned technical problems.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0007] A manufacturing process for an external 3PE and internal epoxy resin anti-corrosion pipe includes the following steps:

[0008] S1. Online inspection;

[0009] The surface of the steel pipe was inspected and found to be free of mechanical damage, dents, peeling, scarring, and oil contamination.

[0010] S2, Medium-frequency preheating;

[0011] Preheat the steel pipe to 40~60℃;

[0012] S3. Internal and external shot blasting for rust removal;

[0013] Shot blasting abrasive is used to propel the steel pipe onto its inner and outer surfaces at high speed through a rotating shot blasting head, so that the steel pipe surface rust removal grade reaches Sa2.5 and the surface roughness is 65~75μm. Then, clean and dry compressed air is used to blow the inner and outer surfaces of the steel pipe.

[0014] S4, silanized nanoparticle suspension treatment;

[0015] The silanized nano-ionic suspension was sprayed onto the inner and outer surfaces of the steel pipe and then dried at 105~110℃ for 2~2.5h.

[0016] S5, Internal corrosion protection;

[0017] The steel pipe is heated to 200~210℃, and epoxy powder coating is sprayed on the inner surface of the steel pipe using electrostatic spraying technology. After cooling, an inner anti-corrosion layer is formed. The coating line speed is 1.8~2m / min.

[0018] S6. External corrosion protection;

[0019] The steel pipe is heated to 200~210℃, and an epoxy powder coating is sprayed onto the outer surface of the steel pipe using electrostatic spraying technology to form an anti-corrosion base layer. The coating speed is 1.8~2m / min. Adhesive and polyethylene are then coated onto the outer surface of the steel pipe to form an adhesive layer and a polyethylene layer. The coated steel pipe is then cooled to below 60℃ by water cooling to obtain an outer 3PE and inner epoxy resin anti-corrosion pipe.

[0020] As a further improvement, the method for preparing the epoxy powder coating includes the following steps:

[0021] S11. Propyl maleic anhydride, pyridine, sulfoxide and N,N-dimethylformamide are added to solvent 1,2-dichloroethane and refluxed at 60~65℃ for 1~1.2h. After the reaction is completed, a reaction solution is obtained. An equal volume of n-hexane is added to the reaction solution and distilled at 60℃. The remaining product is dried to obtain propyl maleic anhydride acyl chloride.

[0022] S12. Add propyl maleic anhydride chloride to tetrahydrofuran and stir thoroughly in an ice bath to dissolve it, thus obtaining reaction solution A;

[0023] 2-Methylimidazole was added to tetrahydrofuran and stirred thoroughly to dissolve it. Then, triethylamine was added to the solution and mixed evenly to obtain reaction solution B.

[0024] Add reaction solution B dropwise to reaction solution A, seal the container, and stir the mixture at 40-45°C for 4-4.5 hours. After the reaction is complete, filter the mixture, collect the solid by rotary evaporation of the filtrate, wash it with water, and dry it to obtain 2-methylimidazolium-propylmaleic anhydride.

[0025] S13. Weigh out bisphenol A type epoxy resin, 2-methylimidazolium-propylmaleic anhydride, filler, leveling agent, pigment, and benzoin, mix them thoroughly, and feed them into an extruder. The screw diameter of the extruder is 53 mm, and the length-to-diameter ratio is 16:1. After melt extrusion, the material is cooled, pulverized, and passed through an 80-mesh sieve to obtain an epoxy powder coating. The epoxy value of the bisphenol A type epoxy resin is 0.2~0.25 eq / 100g.

[0026] As a further improvement, in step S11, the preparation method of the propylmaleic anhydride is as follows: gasoline and rosin are mixed and heated to dissolve and clarify. Cyclohexylamine oil solution is slowly added to it and the reaction is kept at 40°C for 1 hour. After the reaction is completed, the temperature is lowered to 0~5°C in an ice-water bath and kept for 30 minutes. The filter cake obtained after filtration is washed three times with gasoline at 0~5°C and then dried to obtain a solid.

[0027] The solid was ground into powder and mixed with diethyl ether to obtain a suspension. Hydrochloric acid solution was added to the suspension and stirred until the powder dissolved. After stirring for 30 minutes, the mixture was allowed to stand to remove the aqueous phase. The organic phase was washed with distilled water until the pH of the aqueous phase was 6. The diethyl ether in the organic phase was removed by atmospheric distillation and the resin acid was obtained by vacuum drying.

[0028] Resin acid, 3-propylfuran-2,5-dione, p-toluenesulfonic acid and glacial acetic acid were mixed and heated under a nitrogen atmosphere until the materials melted. Then, the mixture was stirred and heated to 180-185℃ for 4-5 hours. After the reaction was completed, the temperature was lowered to 110℃. Then, 100 mL of glacial acetic acid was added to the reaction system and stirred evenly. After cooling to room temperature, the mixture was cooled to 0-5℃ and filtered to obtain a white solid. The white solid was recrystallized with glacial acetic acid and then dried under vacuum to obtain propylmaleic anhydride.

[0029] As a further improvement, the molar ratio of resin acid, 3-propylfuran-2,5-dione and p-toluenesulfonic acid is 1.8~2:1:0.1, and the mass-volume ratio of 3-propylfuran-2,5-dione to glacial acetic acid is 1g:2~2.5mL.

[0030] As a further improvement, in step S11, the molar ratio of propylmaleic anhydride, pyridine, sulfoxide and N,N-dimethylformamide is 1:1:3:0.01;

[0031] In step S12, 1 mmol of propylmaleic anhydride chloride is added to every 1 mL of tetrahydrofuran in reaction solution A; 1 mmol of 2-methylimidazole is added to every 1 mL of tetrahydrofuran in reaction solution B, and the molar ratio of 2-methylimidazole to triethylamine is 1:1; the volume ratio of reaction solution A to reaction solution B is 1:1.

[0032] In step S13, the extruder temperature is: 50~55℃ in zone 1, 90~95℃ in zone 2, and 70~75℃ in zone 3.

[0033] As a further improvement, in step S13, the components of the epoxy powder coating, by weight percentage, are as follows: 55-65% bisphenol A type epoxy resin, 1-5% 2-methylimidazolium-propylmaleic anhydride, 30-38% filler, 1-1.5% leveling agent, 1-2% pigment, and 0.5-1% benzoin.

[0034] As a further improvement, the preparation method of the silanized nanoparticle suspension is as follows: dodecyltrimethoxysiloxane is added to an ethanol-water mixture with a mass ratio of 9:1, and the mixture is stirred at 2000 r / min for 20-30 min at room temperature. Then, nano-alumina particles are added to the mixture, and the mixture is stirred for another 10-15 min to obtain a suspension. The suspension is then ultrasonically dispersed for 20 min to obtain the silanized nanoparticle suspension.

[0035] As a further improvement, the mass ratio of the nano-alumina particles to dodecyltrimethoxysiloxane is 1:1.2, and the mass ratio of the dodecyltrimethoxysiloxane to the ethanol-water mixture is 1:50.

[0036] The present invention also provides an external 3PE and internal epoxy resin anti-corrosion pipe.

[0037] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0038] This invention provides an external 3PE and internal epoxy resin anti-corrosion pipe and its production process. It uses low molecular weight bisphenol A epoxy resin, resulting in a relatively low viscosity of the molten epoxy powder coating. This allows for thorough wetting of the anchor pattern bottom on the steel pipe surface, improving leveling effect, shortening leveling time, and making the epoxy resin coating more uniform. Simultaneously, 2-methylimidazolium-propylmaleic anhydride is used as a curing agent. Under the promotion of the imidazole group, the anhydride rapidly crosslinks and cures with the bisphenol A epoxy resin to form a gel, causing the viscosity of the epoxy powder coating to increase rapidly and preventing sagging.

[0039] In this invention, the epoxy powder coating forms more hydroxyl groups in a shorter time under the promotion of imidazole groups, thereby improving its adhesion to the steel pipe substrate.

[0040] In this invention, the rigid structure of the hydrogen phenanthrene ring in the 2-methylimidazolium-propylmaleic anhydride curing agent can increase the surface tension of the epoxy resin before it reaches gelation, preventing the surface tension from decreasing too quickly and excessively during the curing process, which would destroy the initial good wetting state or even cause shrinkage, affecting the final adhesion between the epoxy resin and the steel pipe.

[0041] In this invention, after the epoxy powder coating is cured, the octyl long chain in the 2-methylimidazolium-propylmaleic anhydride curing agent extends away from the outer wall of the steel pipe, improving the compatibility with the polypropylene adhesive and increasing the strength of the anti-corrosion layer. At the same time, due to the treatment of the steel pipe surface with silanized nano-ionic suspension, a silanized film is formed on the steel pipe surface. The dodecyl long chain in the silanized film interweaves with the octyl long chain in the epoxy powder coating, further improving the adhesion between the epoxy powder coating and the outer wall of the steel pipe. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0043] In this invention, the leveling agent and pigment are specific components of leveling agents and pigments that can be used in epoxy powder coatings in the prior art. For example, the leveling agent can be an acrylate polymer or polysiloxane, and the pigment can be titanium dioxide or carbon black. This invention does not make specific limitations, and the specific components of the leveling agent and filler will not affect the various performance characteristics of the anti-corrosion pipe of this invention.

[0044] Example 1: A manufacturing process for an external 3PE and internal epoxy resin anti-corrosion pipe, comprising the following steps:

[0045] S1. Online inspection: The surface of the steel pipe is inspected to ensure that there is no mechanical damage, pits, peeling, scarring, or oil contamination.

[0046] S2. Medium frequency preheating; preheat the steel pipe to 40℃;

[0047] S3. Internal and external shot blasting: Shot blasting abrasive is used to propel the steel pipe to the inner and outer surfaces of the steel pipe through a high-speed rotating shot blasting head, so that the steel pipe surface rust removal grade reaches Sa2.5 and the surface roughness is 65μm. Then, clean and dry compressed air is used to blow the inner and outer surfaces of the steel pipe.

[0048] S4. Treatment with silanized nanoparticle suspension: The silanized nanoparticle suspension is sprayed onto the inner and outer surfaces of the steel pipe and then dried at 105℃ for 2.5h.

[0049] S5. Internal corrosion protection: The steel pipe is heated to 200℃, and epoxy powder coating is sprayed on the inner surface of the steel pipe using electrostatic spraying technology. After cooling, an internal anti-corrosion layer is formed. The coating line speed is 1.8m / min.

[0050] S6. External corrosion protection: The steel pipe is heated to 200℃, and an epoxy powder coating is sprayed onto the outer surface of the steel pipe using electrostatic spraying technology to form an anti-corrosion base layer. The coating speed is 1.8m / min. Adhesive and polyethylene are then coated onto the outer surface of the steel pipe to form an adhesive layer and a polyethylene layer. The coated steel pipe is then cooled to below 60℃ by water cooling to obtain an external 3PE and internal epoxy resin anti-corrosion pipe.

[0051] In this embodiment, the silanized nanoparticle suspension treatment, the epoxy powder coating used, and the coating line speed of the epoxy powder coating in the production process of the anti-corrosion steel pipe are different from the production process of anti-corrosion steel pipe in the prior art; the other steps are all prior art.

[0052] In this embodiment, a conventional DN200 steel pipe is used.

[0053] In this embodiment, the preparation method of the silanized nanoparticle suspension is as follows: 20g of dodecyltrimethoxysiloxane is added to 1000g of ethanol-water mixture with a mass ratio of 9:1, and the mixture is stirred at 2000r / min for 20min at room temperature. Then, 16.67g of nano-alumina particles are added, and the mixture is stirred for another 10min to obtain a suspension. The suspension is then ultrasonically dispersed for 20min to obtain the silanized nanoparticle suspension.

[0054] In this embodiment, the preparation method of epoxy powder coating includes the following steps:

[0055] S11. Preparation of propylmaleic anhydride;

[0056] Mix 600L of gasoline and 200kg of rosin, heat to 40℃ to dissolve and clarify, slowly add 100L of cyclohexylamine oil solution (3kg / 25L), forming a large amount of white precipitate, then keep the mixture at 40℃ for 1 hour. After the reaction is complete, cool to 0℃ in an ice-water bath and keep for 30 minutes. After filtration, the filter cake is washed three times with 50L of gasoline at 0℃ and then vacuum dried at 40℃ to obtain a solid.

[0057] Cyclohexylamine oil solution is obtained by dissolving 3 kg of cyclohexylamine in 25 L of gasoline;

[0058] The solid was ground into powder and mixed with 150L of diethyl ether to obtain a suspension. 150L of 3mol / L hydrochloric acid solution was added to the suspension and stirred until the powder was dissolved. After stirring for 30 minutes, the mixture was allowed to stand to remove the aqueous phase. The organic phase was washed with distilled water until the pH of the aqueous phase was 6. The diethyl ether in the organic phase was removed by atmospheric distillation and dried under vacuum at 40°C to obtain the resin acid.

[0059] Resin acid, 3-propylfuran-2,5-dione, p-toluenesulfonic acid, and glacial acetic acid were mixed in a molar ratio of 1.8:1:0.1 and a mass-to-volume ratio of 3-propylfuran-2,5-dione to glacial acetic acid of 1 kg:2 L. The mixture was heated under a nitrogen atmosphere until the materials melted, then stirred and heated to 180 °C for 5 h. After the reaction was completed, the temperature was lowered to 110 °C, and 100 L of glacial acetic acid was added to the reaction system. The mixture was stirred until homogeneous, cooled to room temperature, and then cooled to 0 °C with ice water and filtered to obtain a white solid. The white solid was recrystallized with glacial acetic acid and dried under vacuum at 60 °C to obtain propylmaleic anhydride.

[0060] The reaction equation is as follows:

[0061] ;

[0062] S12, Preparation of propyl maleic anhydride acyl chloride;

[0063] Propyl maleic anhydride, pyridine, sulfoxide and N,N-dimethylformamide (DMF) were added to solvent 1,2-dichloroethane in a molar ratio of 1:1:3:0.01 and refluxed at 60°C for 1 h. After the reaction was completed, a reaction solution was obtained. An equal volume of n-hexane was added to the reaction solution, and the mixture was distilled at 60°C. The remaining product was dried under vacuum at 40°C for 1 h to obtain propyl maleic anhydride acyl chloride.

[0064] The reaction equation is as follows:

[0065] ;

[0066] S13, Preparation of 2-methylimidazolium-propylmaleic anhydride;

[0067] Propyl maleopsidic anhydride chloride was added to tetrahydrofuran and stirred thoroughly in an ice bath to dissolve it, thus obtaining reaction solution A (a tetrahydrofuran solution of propyl maleopsidic anhydride chloride); 1 mol of propyl maleopsidic anhydride chloride was added to every 1 L of tetrahydrofuran in reaction solution A.

[0068] 2-Methylimidazole was added to tetrahydrofuran and stirred thoroughly to dissolve. Then, triethylamine was added to the solution and mixed evenly to obtain reaction solution B. Reaction solution B was added dropwise to reaction solution A. The solution was sealed and stirred at 40°C for 4 hours. After the reaction was completed, the solution was filtered, and the solid was collected by rotary evaporation of the filtrate. After washing with water, the solid was dried at 50°C for 12 hours to obtain 2-methylimidazole-propylmaleic anhydride.

[0069] In reaction solution B, 1 mol of 2-methylimidazole is added to every 1 L of tetrahydrofuran. The molar ratio of 2-methylimidazole to triethylamine is 1:1. The volume ratio of reaction solution A to reaction solution B is 1:1.

[0070] The reaction equation is:

[0071] ;

[0072] S14. Weigh out 60% bisphenol A epoxy resin, 1.5% 2-methylimidazolium-propylmaleic anhydride, 35% calcium carbonate filler, 1.2% leveling agent, 1.5% pigment, and 0.8% benzoin by weight percentage, mix thoroughly, and feed into an extruder. The screw diameter of the extruder is 53mm, and the length-to-diameter ratio is 16:1. After melting and extruding, the material is cooled, pulverized, and passed through an 80-mesh sieve to obtain epoxy powder coating. The extruder temperature is: 50℃ in zone 1, 90℃ in zone 2, and 70℃ in zone 3.

[0073] The epoxy value of bisphenol A epoxy resin is 0.2 eq / 100g.

[0074] Example 2: A manufacturing process for an external 3PE and internal epoxy resin anti-corrosion pipe, comprising the following steps:

[0075] S1. Online inspection: The surface of the steel pipe is inspected to ensure that there is no mechanical damage, pits, peeling, scarring, or oil contamination.

[0076] S2. Medium frequency preheating; preheat the steel pipe to 60℃;

[0077] S3. Internal and external shot blasting: Shot blasting abrasive is used to propel the steel pipe to the inner and outer surfaces of the steel pipe through a high-speed rotating shot blasting head, so that the steel pipe surface rust removal grade reaches Sa2.5 and the surface roughness is 75μm. Then, clean and dry compressed air is used to blow the inner and outer surfaces of the steel pipe.

[0078] S4. Treatment with silanized nanoparticle suspension: The silanized nanoparticle suspension is sprayed onto the inner and outer surfaces of the steel pipe and then dried at 110℃ for 2 hours.

[0079] S5. Internal corrosion protection: The steel pipe is heated to 210℃, and epoxy powder coating is sprayed on the inner surface of the steel pipe using electrostatic spraying technology. After cooling, an internal anti-corrosion layer is formed. The coating line speed is 2m / min.

[0080] S6. External corrosion protection: The steel pipe is heated to 210℃, and an epoxy powder coating is sprayed on the outer surface of the steel pipe using electrostatic spraying technology to form an anti-corrosion base layer. The coating speed is 2m / min. Adhesive and polyethylene are then coated on the outer surface of the steel pipe to form an adhesive layer and a polyethylene layer. The coated steel pipe is then cooled to below 60℃ by water cooling to obtain an external 3PE and internal epoxy resin anti-corrosion pipe.

[0081] In this embodiment, the silanized nanoparticle suspension treatment, the epoxy powder coating used, and the coating line speed of the epoxy powder coating in the production process of the anti-corrosion steel pipe are different from the production process of anti-corrosion steel pipe in the prior art; the other steps are all prior art.

[0082] In this embodiment, a conventional DN1000 steel pipe is used.

[0083] In this embodiment, the preparation method of the silanized nanoparticle suspension is as follows: 20g of dodecyltrimethoxysiloxane is added to 1000g of ethanol-water mixture with a mass ratio of 9:1, and the mixture is stirred at 2000r / min for 30min at room temperature. Then, 16.67g of nano-alumina particles are added, and the mixture is stirred for another 15min to obtain a suspension. The suspension is then ultrasonically dispersed for 20min to obtain the silanized nanoparticle suspension.

[0084] In this embodiment, the preparation method of epoxy powder coating includes the following steps:

[0085] S11. Preparation of propylmaleic anhydride;

[0086] Mix 600L of gasoline and 200kg of rosin, heat to 40℃ to dissolve and clarify, slowly add 100L of cyclohexylamine oil solution (3kg / 25L), forming a large amount of white precipitate, then keep the reaction at 40℃ for 1 hour, after the reaction is complete, cool to 5℃ in an ice-water bath and keep for 30 minutes, filter the obtained filter cake and wash it three times with 50L of gasoline at 5℃, then vacuum dry at 40℃ to obtain a solid.

[0087] Cyclohexylamine oil solution is obtained by dissolving 3 kg of cyclohexylamine in 25 L of gasoline;

[0088] The solid was ground into powder and mixed with 150L of diethyl ether to obtain a suspension. 150L of 3mol / L hydrochloric acid solution was added to the suspension and stirred until the powder was dissolved. After stirring for 30 minutes, the mixture was allowed to stand to remove the aqueous phase. The organic phase was washed with distilled water until the pH of the aqueous phase was 6. The diethyl ether in the organic phase was removed by atmospheric distillation and dried under vacuum at 40°C to obtain the resin acid.

[0089] Resin acid, 3-propylfuran-2,5-dione, p-toluenesulfonic acid, and glacial acetic acid were mixed in a molar ratio of 2:1:0.1, and the mass-to-volume ratio of 3-propylfuran-2,5-dione to glacial acetic acid was 1 kg:2.5 L. The mixture was heated under a nitrogen atmosphere until the materials melted, then stirred and heated to 185 °C for 4 h. After the reaction was completed, the temperature was lowered to 110 °C, and then 100 L of glacial acetic acid was added to the reaction system. The mixture was stirred until homogeneous, cooled to room temperature, and then cooled to 5 °C with ice water and filtered to obtain a white solid. The white solid was recrystallized with glacial acetic acid and dried under vacuum at 60 °C to obtain propylmaleic anhydride.

[0090] S12, Preparation of propyl maleic anhydride acyl chloride;

[0091] Propyl maleic anhydride, pyridine, sulfoxide, and N,N-dimethylformamide (DMF) were added to 1,2-dichloroethane in a molar ratio of 1:1:3:0.01 and refluxed at 65°C for 1.2 h. After the reaction was completed, a reaction solution was obtained. An equal volume of n-hexane was added to the reaction solution, and the mixture was distilled at 60°C. The remaining product was dried under vacuum at 40°C for 1 h to obtain propyl maleic anhydride acyl chloride.

[0092] S13, Preparation of 2-methylimidazolium-propylmaleic anhydride;

[0093] Propyl maleopsidic anhydride chloride was added to tetrahydrofuran and stirred thoroughly in an ice bath to dissolve it, thus obtaining reaction solution A (a tetrahydrofuran solution of propyl maleopsidic anhydride chloride); 1 mol of propyl maleopsidic anhydride chloride was added to every 1 L of tetrahydrofuran in reaction solution A.

[0094] 2-Methylimidazole was added to tetrahydrofuran and stirred thoroughly to dissolve. Then, triethylamine was added to the solution and mixed evenly to obtain reaction solution B. Reaction solution B was added dropwise to reaction solution A. The mixture was sealed and stirred at 45°C for 4.5 h. After the reaction was completed, the mixture was filtered, and the solid was collected by rotary evaporation of the filtrate. After washing with water, the solid was dried at 50°C for 12 h to obtain 2-methylimidazole-propylmaleic anhydride.

[0095] In reaction solution B, 1 mol of 2-methylimidazole is added to every 1 L of tetrahydrofuran. The molar ratio of 2-methylimidazole to triethylamine is 1:1. The volume ratio of reaction solution A to reaction solution B is 1:1.

[0096] S14. Weigh out 55% bisphenol A epoxy resin, 2.5% 2-methylimidazolium-propylmaleic anhydride, 38% calcium carbonate filler, 1.5% leveling agent, 2% pigment, and 1% benzoin by weight percentage, mix thoroughly, and feed into an extruder. The screw diameter of the extruder is 53mm, and the length-to-diameter ratio is 16:1. After melting and extruding, the material is cooled, pulverized, and passed through an 80-mesh sieve to obtain epoxy powder coating. The extruder temperature is: 55℃ in zone 1, 95℃ in zone 2, and 75℃ in zone 3.

[0097] The epoxy value of bisphenol A epoxy resin is 0.25 eq / 100g.

[0098] Example 3: A manufacturing process for an external 3PE and internal epoxy resin anti-corrosion pipe, comprising the following steps:

[0099] S1. Online inspection: The surface of the steel pipe is inspected to ensure that there is no mechanical damage, pits, peeling, scarring, or oil contamination.

[0100] S2. Medium frequency preheating; preheat the steel pipe to 50℃;

[0101] S3. Internal and external shot blasting: Shot blasting abrasive is used to propel the steel pipe to the inner and outer surfaces of the steel pipe through a high-speed rotating shot blasting head, so that the steel pipe surface rust removal grade reaches Sa2.5 and the surface roughness is 70μm. Then, clean and dry compressed air is used to blow the inner and outer surfaces of the steel pipe.

[0102] S4. Treatment with silanized nanoparticle suspension: The silanized nanoparticle suspension is sprayed onto the inner and outer surfaces of the steel pipe and then dried at 108℃ for 2.3h.

[0103] S5. Internal corrosion protection: The steel pipe is heated to 205℃, and epoxy powder coating is sprayed on the inner surface of the steel pipe using electrostatic spraying technology. After cooling, an internal anti-corrosion layer is formed. The coating line speed is 1.9m / min.

[0104] S6. External corrosion protection: The steel pipe is heated to 205℃, and an epoxy powder coating is sprayed onto the outer surface of the steel pipe using electrostatic spraying technology to form an anti-corrosion base layer. The coating speed is 1.9m / min. Adhesive and polyethylene are then coated onto the outer surface of the steel pipe to form an adhesive layer and a polyethylene layer. The coated steel pipe is then cooled to below 60℃ by water cooling to obtain an external 3PE and internal epoxy resin anti-corrosion pipe.

[0105] In this embodiment, the silanized nanoparticle suspension treatment, the epoxy powder coating used, and the coating line speed of the epoxy powder coating in the production process of the anti-corrosion steel pipe are different from the production process of anti-corrosion steel pipe in the prior art; the other steps are all prior art.

[0106] In this embodiment, a conventional DN500 steel pipe is used.

[0107] In this embodiment, the preparation method of the silanized nanoparticle suspension is as follows: 20g of dodecyltrimethoxysiloxane is added to 1000g of ethanol-water mixture with a mass ratio of 9:1, and the mixture is stirred at 2000r / min for 25min at room temperature. Then, 16.67g of nano-alumina particles are added, and the mixture is stirred for another 13min to obtain a suspension. The suspension is then ultrasonically dispersed for 20min to obtain the silanized nanoparticle suspension.

[0108] In this embodiment, the preparation method of epoxy powder coating includes the following steps:

[0109] S11. Preparation of propylmaleic anhydride;

[0110] Mix 600L of gasoline and 200kg of rosin, heat to 40℃ to dissolve and clarify, slowly add 100L of cyclohexylamine oil solution (3kg / 25L) to form a large amount of white precipitate, then keep the mixture at 40℃ for 1 hour. After the reaction is complete, cool to 3℃ in an ice-water bath and keep for 30 minutes. After filtration, the filter cake is washed three times with 50L of gasoline at 3℃ and then vacuum dried at 40℃ to obtain a solid.

[0111] Cyclohexylamine oil solution is obtained by dissolving 3 kg of cyclohexylamine in 25 L of gasoline;

[0112] The solid was ground into powder and mixed with 150L of diethyl ether to obtain a suspension. 150L of 3mol / L hydrochloric acid solution was added to the suspension and stirred until the powder was dissolved. After stirring for 30 minutes, the mixture was allowed to stand to remove the aqueous phase. The organic phase was washed with distilled water until the pH of the aqueous phase was 6. The diethyl ether in the organic phase was removed by atmospheric distillation and dried under vacuum at 40°C to obtain the resin acid.

[0113] Resin acid, 3-propylfuran-2,5-dione, p-toluenesulfonic acid, and glacial acetic acid were mixed in a molar ratio of 1.9:1:0.1, and the mass-to-volume ratio of 3-propylfuran-2,5-dione to glacial acetic acid was 1 kg:2.3 L. The mixture was heated under a nitrogen atmosphere until the materials melted, then stirred and heated to 183 °C for 4.5 h. After the reaction was completed, the temperature was lowered to 110 °C, and then 100 L of glacial acetic acid was added to the reaction system. The mixture was stirred until homogeneous, cooled to room temperature, and then cooled to 3 °C with ice water and filtered to obtain a white solid. The white solid was recrystallized with glacial acetic acid and dried under vacuum at 60 °C to obtain propylmaleic anhydride.

[0114] S12, Preparation of propyl maleic anhydride acyl chloride;

[0115] Propyl maleic anhydride, pyridine, sulfoxide and N,N-dimethylformamide (DMF) were added to solvent 1,2-dichloroethane in a molar ratio of 1:1:3:0.01 and refluxed at 63°C for 1.1 h. After the reaction was completed, a reaction solution was obtained. An equal volume of n-hexane was added to the reaction solution, and the mixture was distilled at 60°C. The remaining product was dried under vacuum at 40°C for 1 h to obtain propyl maleic anhydride acyl chloride.

[0116] S13, Preparation of 2-methylimidazolium-propylmaleic anhydride;

[0117] Propyl maleopsidic anhydride chloride was added to tetrahydrofuran and stirred thoroughly in an ice bath to dissolve it, thus obtaining reaction solution A (a tetrahydrofuran solution of propyl maleopsidic anhydride chloride); 1 mol of propyl maleopsidic anhydride chloride was added to every 1 L of tetrahydrofuran in reaction solution A.

[0118] 2-Methylimidazole was added to tetrahydrofuran and stirred thoroughly to dissolve. Then, triethylamine was added to the solution and mixed evenly to obtain reaction solution B. Reaction solution B was added dropwise to reaction solution A. The mixture was sealed and stirred at 43°C for 4.3 h. After the reaction was completed, the mixture was filtered, and the solid was collected by rotary evaporation of the filtrate. After washing with water, the solid was dried at 50°C for 12 h to obtain 2-methylimidazole-propylmaleic anhydride.

[0119] In reaction solution B, 1 mol of 2-methylimidazole is added to every 1 L of tetrahydrofuran. The molar ratio of 2-methylimidazole to triethylamine is 1:1. The volume ratio of reaction solution A to reaction solution B is 1:1.

[0120] S14. Weigh out 65% bisphenol A epoxy resin, 1% 2-methylimidazolium-propylmaleic anhydride, 30% calcium carbonate filler, 1% leveling agent, 2% pigment, and 1% benzoin by weight percentage, mix thoroughly, and feed into an extruder. The screw diameter of the extruder is 53mm and the length-to-diameter ratio is 16:1. After melting and extruding, the material is cooled, pulverized, and passed through an 80-mesh sieve to obtain epoxy powder coating. The extruder temperature is: 53℃ in zone 1, 93℃ in zone 2, and 73℃ in zone 3.

[0121] The epoxy value of bisphenol A epoxy resin is 0.23 eq / 100g.

[0122] Example 4: A manufacturing process for an external 3PE and internal epoxy resin anti-corrosion pipe, comprising the following steps:

[0123] S1. Online inspection: The surface of the steel pipe is inspected to ensure that there is no mechanical damage, pits, peeling, scarring, or oil contamination.

[0124] S2. Medium frequency preheating; preheat the steel pipe to 45℃;

[0125] S3. Internal and external shot blasting: Shot blasting abrasive is used to propel the steel pipe to the inner and outer surfaces of the steel pipe through a high-speed rotating shot blasting head, so that the steel pipe surface rust removal grade reaches Sa2.5 and the surface roughness is 68μm. Then, clean and dry compressed air is used to blow the inner and outer surfaces of the steel pipe.

[0126] S4. Treatment with silanized nanoparticle suspension: The silanized nanoparticle suspension is sprayed onto the inner and outer surfaces of the steel pipe and then dried at 106℃ for 2.2h.

[0127] S5. Internal corrosion protection: The steel pipe is heated to 200℃, and epoxy powder coating is sprayed on the inner surface of the steel pipe using electrostatic spraying technology. After cooling, an internal anti-corrosion layer is formed. The coating line speed is 1.8m / min.

[0128] S6. External corrosion protection: The steel pipe is heated to 210℃, and an epoxy powder coating is sprayed on the outer surface of the steel pipe using electrostatic spraying technology to form an anti-corrosion base layer. The coating speed is 2m / min. Adhesive and polyethylene are then coated on the outer surface of the steel pipe to form an adhesive layer and a polyethylene layer. The coated steel pipe is then cooled to below 60℃ by water cooling to obtain an external 3PE and internal epoxy resin anti-corrosion pipe.

[0129] In this embodiment, the silanized nanoparticle suspension treatment, the epoxy powder coating used, and the coating line speed of the epoxy powder coating in the production process of the anti-corrosion steel pipe are different from the production process of anti-corrosion steel pipe in the prior art; the other steps are all prior art.

[0130] In this embodiment, a conventional DN800 steel pipe is used.

[0131] In this embodiment, the preparation method of the silanized nanoparticle suspension is as follows: 20g of dodecyltrimethoxysiloxane is added to 1000g of ethanol-water mixture with a mass ratio of 9:1, and the mixture is stirred at 2000r / min for 28min at room temperature. Then, 16.67g of nano-alumina particles are added, and the mixture is stirred for another 14min to obtain a suspension. The suspension is then ultrasonically dispersed for 20min to obtain the silanized nanoparticle suspension.

[0132] In this embodiment, the preparation method of epoxy powder coating includes the following steps:

[0133] S11. Preparation of propylmaleic anhydride;

[0134] Mix 600L of gasoline and 200kg of rosin, heat to 40℃ to dissolve and clarify, slowly add 100L of cyclohexylamine oil solution (3kg / 25L) to form a large amount of white precipitate, then keep the mixture at 40℃ for 1 hour. After the reaction is complete, cool to 2℃ in an ice-water bath and keep for 30 minutes. After filtration, the filter cake is washed three times with 50L of gasoline at 2℃ and then vacuum dried at 40℃ to obtain a solid.

[0135] Cyclohexylamine oil solution is obtained by dissolving 3 kg of cyclohexylamine in 25 L of gasoline;

[0136] The solid was ground into powder and mixed with 150L of diethyl ether to obtain a suspension. 150L of 3mol / L hydrochloric acid solution was added to the suspension and stirred until the powder was dissolved. After stirring for 30 minutes, the mixture was allowed to stand to remove the aqueous phase. The organic phase was washed with distilled water until the pH of the aqueous phase was 6. The diethyl ether in the organic phase was removed by atmospheric distillation and dried under vacuum at 40°C to obtain the resin acid.

[0137] Resin acid, 3-propylfuran-2,5-dione, p-toluenesulfonic acid, and glacial acetic acid were mixed in a molar ratio of 1.8:1:0.1, and the mass-to-volume ratio of 3-propylfuran-2,5-dione to glacial acetic acid was 1 kg:2 L. The mixture was heated under a nitrogen atmosphere until the materials melted, then stirred and heated to 182 °C for 4.2 h. After the reaction was completed, the temperature was lowered to 110 °C, and then 100 L of glacial acetic acid was added to the reaction system. The mixture was stirred until homogeneous, cooled to room temperature, and then cooled to 2 °C with ice water and filtered to obtain a white solid. The white solid was recrystallized with glacial acetic acid and dried under vacuum at 60 °C to obtain propylmaleic anhydride.

[0138] S12, Preparation of propyl maleic anhydride acyl chloride;

[0139] Propyl maleic anhydride, pyridine, sulfoxide and N,N-dimethylformamide (DMF) were added to solvent 1,2-dichloroethane in a molar ratio of 1:1:3:0.01 and refluxed at 62°C for 1.05 h. After the reaction was completed, a reaction solution was obtained. An equal volume of n-hexane was added to the reaction solution, and the mixture was distilled at 60°C. The remaining product was dried under vacuum at 40°C for 1 h to obtain propyl maleic anhydride acyl chloride.

[0140] S13, Preparation of 2-methylimidazolium-propylmaleic anhydride;

[0141] Propyl maleopsidic anhydride chloride was added to tetrahydrofuran and stirred thoroughly in an ice bath to dissolve it, thus obtaining reaction solution A (a tetrahydrofuran solution of propyl maleopsidic anhydride chloride); 1 mol of propyl maleopsidic anhydride chloride was added to every 1 L of tetrahydrofuran in reaction solution A.

[0142] 2-Methylimidazole was added to tetrahydrofuran and stirred thoroughly to dissolve. Then, triethylamine was added to the solution and mixed evenly to obtain reaction solution B. Reaction solution B was added dropwise to reaction solution A. The mixture was sealed and stirred at 42°C for 4.2 h. After the reaction was completed, the mixture was filtered, and the solid was collected by rotary evaporation of the filtrate. After washing with water, the solid was dried at 50°C for 12 h to obtain 2-methylimidazole-propylmaleic anhydride.

[0143] In reaction solution B, 1 mol of 2-methylimidazole is added to every 1 L of tetrahydrofuran. The molar ratio of 2-methylimidazole to triethylamine is 1:1. The volume ratio of reaction solution A to reaction solution B is 1:1.

[0144] S14. Weigh out 55% bisphenol A epoxy resin, 5% 2-methylimidazolium-propylmaleic anhydride, 37% calcium carbonate filler, 1.5% leveling agent, 1% pigment, and 0.5% benzoin by weight percentage, mix thoroughly, and feed into an extruder. The screw diameter of the extruder is 53mm, and the length-to-diameter ratio is 16:1. After melting and extruding, the material is cooled, pulverized, and passed through an 80-mesh sieve to obtain epoxy powder coating. The extruder temperature is: 52℃ in zone 1, 92℃ in zone 2, and 72℃ in zone 3.

[0145] The epoxy value of bisphenol A epoxy resin is 0.3 eq / 100g.

[0146] Comparative Example 1 This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as in Example 1. The difference is that in this comparative example, silanized nanoparticle suspension treatment is not performed after internal and external shot blasting and rust removal.

[0147] Comparative Example 2: This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as in Example 1, except that the preparation method of the epoxy powder coating is different from that in Example 1. The specific preparation method of the epoxy powder coating is as follows:

[0148] By weight percentage, 60% bisphenol A epoxy resin, 1.1% dicyandiamide, 0.4% 2-methylimidazole, 35% calcium carbonate filler, 1.2% leveling agent, 1.5% pigment, and 0.8% benzoin were weighed and thoroughly mixed before being fed into an extruder with a screw diameter of 53 mm and a length-to-diameter ratio of 16:1. After melt extrusion, the material was cooled, pulverized, and passed through an 80-mesh sieve to obtain epoxy powder coating. The extruder temperatures were: 50℃ in zone 1, 90℃ in zone 2, and 70℃ in zone 3.

[0149] The epoxy value of bisphenol A epoxy resin is 0.2 eq / 100g.

[0150] Comparative Example 3 This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as those in Comparative Example 2. The difference is that in this comparative example, the coating speed of the epoxy powder coating on the inner and outer surfaces of the steel pipe is set to 1.6 m / min.

[0151] Comparative Example 4 This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as those in Comparative Example 2. The difference is that in this comparative example, the coating speed of the epoxy powder coating on the inner and outer surfaces of the steel pipe is set to 1.4 m / min.

[0152] Comparative Example 5: This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as in Example 1, except that the preparation method of the epoxy powder coating is different from that in Example 1. The specific preparation method of the epoxy powder coating is as follows:

[0153] S11. Preparation of maleic pine anhydride;

[0154] Mix 600L of gasoline and 200kg of rosin, heat to 40℃ to dissolve and clarify, slowly add 100L of cyclohexylamine oil solution (3kg / 25L), forming a large amount of white precipitate, then keep the mixture at 40℃ for 1 hour. After the reaction is complete, cool to 0℃ in an ice-water bath and keep for 30 minutes. After filtration, the filter cake is washed three times with 50L of gasoline at 0℃ and then vacuum dried at 40℃ to obtain a solid.

[0155] Cyclohexylamine oil solution is obtained by dissolving 3 kg of cyclohexylamine in 25 L of gasoline;

[0156] The solid was ground into powder and mixed with 150L of diethyl ether to obtain a suspension. 150L of 3mol / L hydrochloric acid solution was added to the suspension and stirred until the powder was dissolved. After stirring for 30 minutes, the mixture was allowed to stand to remove the aqueous phase. The organic phase was washed with distilled water until the pH of the aqueous phase was 6. The diethyl ether in the organic phase was removed by atmospheric distillation and dried under vacuum at 40°C to obtain the resin acid.

[0157] Resin acid, maleic anhydride, p-toluenesulfonic acid, and glacial acetic acid were mixed in a molar ratio of 1.8:1:0.1 and a mass-to-volume ratio of maleic anhydride to glacial acetic acid of 1 kg:2 L. The mixture was heated under a nitrogen atmosphere until the materials melted, then stirred and heated to 180 °C for 5 h. After the reaction was completed, the temperature was lowered to 110 °C, and 100 L of glacial acetic acid was added to the reaction system. The mixture was stirred until homogeneous, cooled to room temperature, and then cooled to 0 °C with ice water and filtered to obtain a white solid. The white solid was recrystallized with glacial acetic acid and dried under vacuum at 60 °C to obtain maleic anhydride.

[0158] S12, Preparation of maleic anhydride acyl chloride;

[0159] Maleic anhydride, pyridine, sulfoxide and N,N-dimethylformamide (DMF) were added to solvent 1,2-dichloroethane in a molar ratio of 1:1:3:0.01 and refluxed at 60°C for 1 h. After the reaction was completed, a reaction solution was obtained. An equal volume of n-hexane was added to the reaction solution, and the mixture was distilled at 60°C. The remaining product was dried under vacuum at 40°C for 1 h to obtain maleic anhydride acyl chloride.

[0160] S13, Preparation of 2-methylimidazole-maleic anhydride;

[0161] Maleic anhydride chloride was added to tetrahydrofuran and stirred thoroughly in an ice bath to dissolve it, thus obtaining reaction solution A (a tetrahydrofuran solution of maleic anhydride chloride); 1 mol of maleic anhydride chloride was added to every 1 L of tetrahydrofuran in reaction solution A.

[0162] 2-Methylimidazole was added to tetrahydrofuran and stirred thoroughly to dissolve. Then, triethylamine was added to the solution and mixed evenly to obtain reaction solution B. Reaction solution B was added dropwise to reaction solution A. The solution was sealed and stirred at 40°C for 4 hours. After the reaction was completed, the solution was filtered, and the solid was collected by rotary evaporation of the filtrate. After washing with water, the solid was dried at 50°C for 12 hours to obtain 2-methylimidazole-maleic anhydride.

[0163] In reaction solution B, 1 mol of 2-methylimidazole is added to every 1 L of tetrahydrofuran. The molar ratio of 2-methylimidazole to triethylamine is 1:1. The volume ratio of reaction solution A to reaction solution B is 1:1.

[0164] S14. Weigh out 60% bisphenol A epoxy resin, 1.5% 2-methylimidazolium-maleic anhydride, 35% calcium carbonate filler, 1.2% leveling agent, 1.5% pigment, and 0.8% benzoin by weight percentage, mix thoroughly, and feed into an extruder. The screw diameter of the extruder is 53mm, and the length-to-diameter ratio is 16:1. After melting and extruding, the material is cooled, pulverized, and passed through an 80-mesh sieve to obtain epoxy powder coating. The extruder temperature is: 50℃ in zone 1, 90℃ in zone 2, and 70℃ in zone 3.

[0165] Comparative Example 6: This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as in Example 1, except that the preparation method of the silanized nanoparticle suspension is different from that in Example 1. The specific steps are as follows:

[0166] 20g of ethyltrimethoxysilane was added to 1000g of an ethanol-water mixture with a mass ratio of 9:1. The mixture was stirred at 2000r / min for 20min at room temperature. Then, 16.67g of nano-alumina particles were added and the mixture was stirred for another 10min to obtain a suspension. The suspension was then ultrasonically dispersed for 20min to obtain a silanized nanoparticle suspension.

[0167] Comparative Example 7 This comparative example provides a production process for an external 3PE and internal epoxy resin anti-corrosion pipe. The specific steps are the same as those in Example 4. The difference is that this comparative example does not perform silanized nanoparticle suspension treatment after internal and external shot blasting and rust removal.

[0168] The cathodic stripping performance of the anti-corrosion pipes obtained in Example 1 and Comparative Examples 1-7 was tested, and the specific method is as follows:

[0169] 100mm × 100mm samples were cut from the anti-corrosion steel pipes obtained in Example 1 and Comparative Examples 1-7, respectively. Leakage was first checked using a 25kV spark leak detector. After confirming no leaks, a 6.4mm diameter hole was drilled in the center of the sample, penetrating the anti-corrosion layer to expose the metal. A 75mm outer diameter plastic cylinder was placed on the sample, aligned with the drilled hole. The contact area between the plastic cylinder and the sample was sealed with sealant to form a test groove. After the sealant cured, 10mL of a 3% sodium chloride solution was added to the plastic cylinder. The platinum electrode was connected to the positive terminal of a DC power supply, and the metal part of the sample was connected to the negative terminal. The entire apparatus was placed in a 65℃ electrically insulated chamber and a -1.5V DC voltage was applied.

[0170] Thirty days later, the plastic cylinder was removed, the sample was taken out, and cooled to room temperature. Using a knife, a cross-shaped pattern was drawn outwards from the center of the hole, penetrating to the metal substrate. The drawing distance was at least 20 mm. A sharp knife was inserted under the anti-corrosion layer from the drilled hole, and the coating was pried horizontally along the drawn lines until the anti-corrosion layer showed significant resistance to prying. Starting from the edge of the drilled hole, the prying distance was measured at each point; this is the cathodic disbondment distance of the sample. The cathodic disbondment distance results for the anti-corrosion steel pipes of Example 1 and Comparative Examples 1-7 are shown in Table 1.

[0171] Table 1. Cathodic stripping distance of anti-corrosion steel pipes in Example 1 and Comparative Examples 1-7

[0172] ;

[0173] As shown in Table 1, Example 1 exhibits the best resistance to cathodic disbondment. Compared to Example 1, Comparative Examples 1, 5, and 6 show lower resistance to cathodic disbondment. This is because the treatment of the steel pipe surface with a silanized nanoparticle suspension forms a silanized film, which improves the adhesion between the steel pipe and the epoxy powder coating. Furthermore, the use of dodecyltrimethoxysiloxane to prepare the silanized nanoparticle suspension results in the dodecyl long chains in the silanized film interpenetrating with the octyl long chains in the epoxy powder coating, further enhancing the adhesion between the epoxy powder coating and the outer wall of the steel pipe, thereby improving the resistance to cathodic disbondment. In Comparative Examples 5 and 6, the interpenetration of long chains is not achieved, resulting in a decrease in their resistance to cathodic disbondment.

[0174] Compared with Example 1, Comparative Examples 2-4 and 7 showed lower resistance to cathodic disbondment than Example 1. Furthermore, the resistance to cathodic disbondment of Comparative Examples 2-4 gradually increased. This is because the bisphenol A epoxy resin in the epoxy powder coating has a lower molecular weight, and the higher coating line speed in Comparative Example 2 resulted in incomplete curing of the epoxy powder coating, which in turn reduced the resistance to cathodic disbondment.

[0175] To verify the low degree of curing of the epoxy powder coating in Comparative Example 2, differential scanning calorimetry (DSC) was performed. The specific test method is as follows:

[0176] Take 10 mg of epoxy powder coating from Comparative Example 2, place it in a pre-weighed sample dish, cover it with a sealed cap, seal it, and weigh it. Perform an exothermic scan on the epoxy powder coating, heating it from 25℃ to 70℃ under programmed temperature control, and finally cooling it to room temperature. Then heat the sample from 25℃ to 285℃, then rapidly cool the sample to 25℃, and then heat the sample from 25℃ to 150℃. After the process is complete, the Tg2 and ∆H of the epoxy powder can be obtained.

[0177] Take 10 mg of the anti-corrosion base layer from Comparative Example 2 as the anti-corrosion layer sample, place it in a pre-weighed sample dish, cover it with a sealing cap, seal it and weigh it; under programmed temperature control, heat it from 25℃ to 110℃, hold it at 110℃ for 1.5 min, then rapidly cool the sample to 25℃, then heat the sample from 25℃ to 285℃, then rapidly cool the sample to 25℃, then heat the sample from 25℃ to 150℃, and after the process is complete, the Tg4 and ∆H1 of the epoxy powder can be obtained.

[0178] The absolute value of ∆Tg, |∆Tg|, is used as an indicator to evaluate the degree of curing of epoxy powder.

[0179] The above method was used to measure the absolute values ​​of ∆Tg| for Example 1, Comparative Example 3 and Comparative Example 4. The results are shown in Table 2.

[0180] Table 2 |∆Tg| results for Example 1 and Comparative Examples 2-4

[0181] ;

[0182] As can be seen from Table 2, the |∆Tg| values ​​of Comparative Examples 2-4 gradually decrease, indicating that the epoxy powder coating formulation in Comparative Example 2 requires more curing time to fully cure.

[0183] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A process for the production of an anticorrosive pipe with outer 3PE and inner epoxy resin, characterized in that, The method comprises the following steps: S1, online inspection; Detecting the surface of the steel pipe without mechanical damage, pits, peeling, scarring and oil pollution phenomena; S2, medium frequency preheating; Preheating the temperature of the steel pipe to 40-60 DEG C; S3, inner and outer shot blasting derusting; Adopting the shot blasting abrasive to be projected to the inner and outer surfaces of the steel pipe by the high-speed rotation of the shot head, so that the derusting grade of the surface of the steel pipe reaches Sa2.5, and the surface roughness is 65-75 mu m, then the inner and outer surfaces of the steel pipe are blown by clean and dry compressed air; S4, silanization nano particle suspension treatment; The silanization nano particle suspension is sprayed to the inner and outer surfaces of the steel pipe, and then dried at 105-110 DEG C for 2-2.5 h; S5, inner corrosion prevention; The steel pipe is heated to 200-210 DEG C, and the inner surface of the steel pipe is sprayed with epoxy powder coating by using electrostatic spraying technology, so that the inner corrosion layer is formed after cooling, and the coating line speed is 1.8-2 m / min; S6, outer corrosion prevention; The steel pipe is heated to 200-210 DEG C, and the outer surface of the steel pipe is sprayed with epoxy powder coating by using electrostatic spraying technology to form the corrosion prevention bottom layer, and the coating line speed is 1.8-2 m / min, the adhesive layer and the polyethylene layer are formed by the adhesive and polyethylene coating forming on the outer surface of the steel pipe, and the coated steel pipe is cooled to below 60 DEG C by water cooling to obtain the outer 3PE inner epoxy resin corrosion prevention pipe; The preparation method of the epoxy powder coating comprises the following steps: S11, propyl maleic pine acid anhydride, pyridine, dichloro sulfoxide and N, N-dimethyl formamide are added into solvent 1, 2-dichloroethane, and refluxed at 60-65 DEG C for 1-1.2 h, and then the reaction liquid is obtained, and the same volume of n-hexane is added into the reaction liquid, and distilled at 60 DEG C, and the remaining product is dried to obtain propyl maleic pine acid anhydride acyl chloride; The preparation method of the propyl maleic pine acid anhydride is as follows: gasoline and rosin are mixed, heated to dissolve and clarify, and then cyclohexylamine oil solution is slowly added, and the reaction is carried out at 40 DEG C for 1 h, and then the temperature is reduced to 0-5 DEG C in an ice water bath for 30 min, and the filter cake obtained after filtration is washed with gasoline at 0-5 DEG C for 3 times, and then dried to obtain solid material; The solid material is ground into powder and mixed with diethyl ether to obtain a suspension, hydrochloric acid solution is added into the suspension, and stirred until the powder is dissolved, and then stirred for 30 min, and then placed, and the water phase is removed, and the organic phase is washed with distilled water until the pH of the water phase is 6, and then the organic phase is removed by atmospheric distillation, and then vacuum dried to obtain resin acid; The resin acid, 3-propyl furan-2, 5-dione, p-methyl benzene sulfonic acid and glacial acetic acid are mixed, heated to melt the materials under nitrogen atmosphere, and then stirred and heated to 180-185 DEG C for 4-5 h, and then the temperature is reduced to 110 DEG C, and then 100 mL of glacial acetic acid is added into the reaction system and stirred uniformly, and then cooled to room temperature, and then cooled to 0-5 DEG C for filtration, and then white solid is obtained, and then the white solid is recrystallized with glacial acetic acid and vacuum dried to obtain propyl maleic pine acid anhydride; S12, propyl maleic pine acid anhydride acyl chloride is added into tetrahydrofuran, and then stirred and dissolved under ice bath to obtain reaction liquid A; 2-methylimidazole was added into tetrahydrofuran, stirred and dissolved, then triethylamine was added and mixed to obtain reaction liquid B; Reaction liquid B was added dropwise into reaction liquid A, sealed and stirred at 40-45℃ for 4-4.5h, then filtered, the filtrate was collected by rotary evaporation, washed with water and dried to obtain 2-methylimidazole-propyl male pimaric anhydride; In step S13, the temperature of the extruder was: 50-55℃ in the first zone, 90-95℃ in the second zone and 70-75℃ in the third zone.

2. The process for producing a 3PE outer and epoxy inner anticorrosive pipe according to claim 1, characterized in that, In step S13, the components of the epoxy powder coating were as follows: bisphenol A type epoxy resin 55-65%, 2-methylimidazole-propyl male pimaric anhydride 1-5%, filler 30-38%, leveling agent 1-1.5%, pigment 1-2% and benzoin 0.5-1% by weight percentage.

3. The process for producing the outer 3PE inner epoxy resin anticorrosion pipeline according to claim 1, characterized in that, The preparation method of the silanized nanoparticle suspension was as follows: dodecyltrimethoxysilane was added into an ethanol-water mixture with a mass ratio of 9:1, stirred at 2000r / min for 20-30min at room temperature, then nano-aluminum oxide particles were added and stirred for another 10-15min to obtain a suspension, and the suspension was ultrasonically dispersed for 20min to obtain the silanized nanoparticle suspension. The mass ratio of the nano-aluminum oxide particles to dodecyltrimethoxysilane was 1:1.2, and the mass ratio of the dodecyltrimethoxysilane to the ethanol-water mixture was 1:

50.

7. The anticorrosion pipeline prepared by the production process of the outer 3PE and inner epoxy resin anticorrosion pipeline according to claim 1.

4. The process for producing a 3PE outer and epoxy inner anticorrosive pipe according to claim 1, characterized in that, ​ 5. The process for producing a 3PE outer and epoxy inner anticorrosive pipe according to claim 1, characterized in that, ​ 6. The process for producing a 3PE outer and epoxy inner anticorrosive pipe according to claim 1, characterized in that, ​ ​