A hydrophobic and oleophobic drag-reducing film and a preparation process thereof

Abstract

The application discloses a kind of hydrophobic oleophobic drag-reducing film and preparation process thereof, and relates to the technical field of drag-reducing film.The specific steps include the following steps:S1: polyurethane batch is fused and injected into mold by injection molding machine, cooling and demolding, to obtain a basic drag-reducing film with drag-reducing shape;S2: the basic drag-reducing film is immersed in dopamine modified solution, stirred and reacted, washed, dried, to form a polydopamine layer, to obtain a basic drag-reducing film A;S3: nano-silicon dioxide is dispersed in ethanol aqueous solution, 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane is added, and stirred and reacted;after adjusting pH and heating, the basic drag-reducing film A is immersed multiple times and taken out for drying in the solution, to form a hydrophobic and oleophobic layer, to obtain a hydrophobic and oleophobic drag-reducing film.The hydrophobic and oleophobic drag-reducing film prepared by the application has excellent and long-acting drag-reducing performance.

Description

Technical Field

[0001] This invention relates to the field of drag-reducing membrane technology, specifically a hydrophobic and oleophobic drag-reducing membrane and its preparation process. Background Technology

[0002] With the rapid development of shipping and underwater navigation, effectively reducing fluid resistance to improve speed and energy efficiency has become a key technological issue. Fluid friction resistance increases the power required by equipment and leads to higher electricity consumption; therefore, developing efficient drag reduction technologies is imperative.

[0003] Currently, inspired by the superhydrophobicity and self-cleaning properties of natural biological surfaces such as lotus leaves and shark skin, functional membrane materials based on special wettability have attracted widespread attention. Ideal drag-reducing surfaces typically need to be superhydrophobic to trap air and form an air cushion layer, thereby reducing the solid-liquid contact area and achieving drag reduction. However, real-world aquatic environments are complex and often contain pollutants such as oils. Simply superhydrophobic surfaces are prone to failure due to oil adhesion. Therefore, developing drag-reducing membrane materials that combine hydrophobic and oleophobic properties has become an important research direction.

[0004] In summary, solving the above problems and preparing a hydrophobic and oleophobic drag-reducing membrane is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrophobic and oleophobic drag-reducing membrane and its preparation process to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A process for preparing a hydrophobic and oleophobic drag-reducing film includes the following steps:

[0008] S1: The polyurethane masterbatch is melted and injected into the mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape;

[0009] S2: Immerse the basic drag-reducing membrane in a dopamine-modified solution, stir to react, wash, and dry to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A;

[0010] S3: Disperse nano-silica in an aqueous ethanol solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, stir and react; adjust the pH, heat and repeatedly immerse the basic drag-reducing membrane A in it and take it out and dry it to form a hydrophobic and oleophobic layer, thus obtaining a hydrophobic and oleophobic drag-reducing membrane.

[0011] Preferably, the drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the spacing between the center points of the pits being twice the maximum diameter of the pits; the maximum diameter of the pits is 1~1.2mm.

[0012] Preferredly, the preparation method of the polyurethane masterbatch includes the following steps: under a nitrogen atmosphere, polyester diol is heated at 120~125℃ to remove water, then cooled to 60~70℃, 4,4'-methylenebis(phenyl isocyanate) and dibutyltin dilaurate are added, and the mixture is stirred and reacted for 2~3 hours. Then, N,N-dimethylformamide and N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine are added, and the mixture is stirred and reacted at 40~50℃ for 1~1.5 hours. The mixture is then vacuum dried at 100~105℃ and pulverized to obtain the polyurethane masterbatch.

[0013] Preferably, the polyurethane masterbatch comprises the following raw materials in parts by weight: 38-42 parts polyester diol, 9.5-10.5 parts 4,4'-methylenebis(phenyl isocyanate), 0.02-0.03 parts dibutyltin dilaurate, 80-100 parts N,N-dimethylformamide, and 7-8 parts N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine.

[0014] Preferably, during the injection molding process, the melt temperature is 170~180℃, the injection speed is 50~55mm / s, the holding pressure is 8~10MPa, and the holding time is 10~15s.

[0015] More preferably, in step S3, the specific process is as follows: nano-silica is dispersed in an ethanol aqueous solution, 1H,1H,2H,2H-perfluorodecyltriethoxysilane is added, and the mixture is stirred at 40~45℃ for 1~2h; the pH is adjusted to 4~5, the temperature is raised to 55~60℃, the basic drag-reducing membrane A is repeatedly immersed in it and then taken out and dried to obtain a hydrophobic and oleophobic drag-reducing membrane.

[0016] Preferably, the raw materials of the hydrophobic and oleophobic drag-reducing membrane include nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and an aqueous ethanol solution in a mass ratio of 2~3:1:80~100; the particle size of the nano-silica is 50~100 nm; and the volume fraction of ethanol in the aqueous ethanol solution is 80~90%.

[0017] Preferably, during the process of multiple immersions and drying, the immersion time is 10-15 minutes, the drying temperature is 60-70°C, the drying time is 30-50 minutes, and the process is repeated 3-5 times; after the process, the product needs to be kept at 60-70°C for 2-3 hours.

[0018] Preferably, in step S2, the dopamine-modified solution comprises the following raw materials: 0.05~0.1 mol / L dopamine, 0.2~0.3 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, and 0.1 mol / L Tris, with deionized water as the solvent and a pH of 8~9;

[0019] The stirring reaction is carried out at a temperature of 25-30°C for 20-24 hours; the drying temperature is 60-70°C.

[0020] Preferably, the hydrophobic and oleophobic drag-reducing membrane consists of, from top to bottom, a hydrophobic and oleophobic layer, a polydopamine layer, and a base drag-reducing membrane with a drag-reducing shape.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention uses N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine as a polyurethane chain extender to prepare a polyurethane masterbatch for injection molding to prepare a basic drag-reducing film with a rectangular array of conical pits as a micro-drag-reducing structure. On this basis, a polydopamine layer and a hydrophobic and oleophobic layer are prepared sequentially as a nano-drag-reducing structure to form a micro-nano composite structure. The prepared hydrophobic and oleophobic drag-reducing film has excellent and long-lasting drag-reducing performance.

[0022] The flexible drag-reducing layer has a rectangular array of conical pits. Its central symmetry allows it to maintain a certain drag-reducing effect when facing water flow from different directions, effectively reducing friction. The conical structure is also easier to process and demold, facilitating mass production.

[0023] The polyurethane masterbatch is prepared by reacting polyester diol and 4,4'-methylenebis(phenyl isocyanate) under the catalysis of dibutyltin dilaurate to obtain polyurethane, and then preparing the polyurethane masterbatch with N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine chain extender. In this polyurethane, the diamine group in N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine acts as a hindered amine and reacts with the polyurethane to generate reversible dynamic urea bonds, thereby endowing the drag-reducing layer with self-healing properties when damaged, thus maintaining long-term drag reduction. Moreover, siloxane can enhance the fluidity of chain segments through its polarity, weaken the hydrogen bonding between chain ends to a certain extent, prevent the material rigidity from being too high and reducing flexibility, improve processing performance, make the drag-reducing pattern less prone to deviation, improve uniformity, and enhance the drag reduction effect.

[0024] The preparation method of the polydopamine layer involves immersing the base drag-reducing membrane in a dopamine-modified solution. Dopamine undergoes oxidative self-polymerization on its surface. Simultaneously, during this self-polymerization process, the primary free radicals generated by dopamine can form monomeric free radicals with 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, thereby undergoing chain growth and chain termination reactions to form polyhydroxy branched chain ends, resulting in a dense polyhydroxy dopamine layer. This layer, acting as an intermediate layer, improves the bonding and tightness between the base drag-reducing membrane and the hydrophobic and oleophobic layers. Furthermore, the siloxane groups on the surface of the base drag-reducing layer can undergo certain hydrolysis, forming active sites for dopamine polymerization and promoting the uniform formation of the polydopamine layer. The barrier effect of the polydopamine layer also prevents the entry of ethanol during the subsequent preparation of the hydrophobic and oleophobic coating using fluorosiloxane hydrolysis, reducing the risk of ethanol swelling causing deformation of the drag-reducing shape and deteriorating the drag-reducing effect.

[0025] The preparation method of the hydrophobic and oleophobic layer is as follows: 1H,1H,2H,2H-perfluorodecyltriethoxysilane is hydrolyzed in an ethanol-water solution and reacted with nano-silica to form a fluorosilicone sol. This sol is then repeatedly impregnated and dried to obtain the hydrophobic and oleophobic layer. On the one hand, the nano-silica exhibits a certain degree of agglomeration and stacking during the repeated impregnation and drying process, forming nanostructured pores that increase air penetration and significantly reduce droplet-material contact. On the other hand, the fluorosiloxane has extremely low surface energy, giving the drag-reducing film surface excellent hydrophobic and oleophobic properties, thus comprehensively improving the drag-reducing effect of the film. It is important to note that the impregnation time and number of impregnations need to be limited. Excessive or prolonged impregnation can lead to severe silica agglomeration, forming large agglomerates that may even block the nanopores and result in poor stability. Furthermore, the film is prone to peeling off when deformed, reducing drag-reducing performance. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the following quantities are by weight. There are no special restrictions on the suppliers of any of the raw materials involved in this invention. Exemplary examples include: polyester diol: polycaprolactone diol, model PCL2000, provided by Hubei Jusheng Technology Co., Ltd.; 4,4'-methylenebis(phenyl isocyanate) CAS No.: 101-68-8; dibutyltin dilaurate CAS No.: 77-58-7; N,N-dimethylformamide CAS No.: 68-12-2; N,N'-bis[ CAS No. 3-(trimethoxysilyl)propyl]ethylenediamine: 68845-16-9; CAS No. 51-61-6; CAS No. 77-86-1 for Tris: Tris(hydroxymethyl)aminomethane; CAS No. 50-100nm for nano-silica; CAS No. 1H,1H,2H,2H-perfluorodecyltriethoxysilane: 101947-16-4; CAS No. 5919-74-4 for 2-methyl-2-acrylate-2,3-dihydroxypropyl ester.

[0028] In the following examples, parts refer to parts by weight, and all raw materials mentioned above and others not mentioned are commercially available.

[0029] Example 1: A process for preparing a hydrophobic and oleophobic drag-reducing film includes the following steps:

[0030] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0031] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0032] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0033] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0034] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 15min, and dry at 70℃ for 40min, repeat 4 times, and finally keep at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0035] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0036] Example 2: A process for preparing a hydrophobic and oleophobic drag-reducing film includes the following steps:

[0037] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0038] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0039] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0040] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0041] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 10min, and dry at 70℃ for 40min, repeat 5 times, and finally keep at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0042] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0043] Example 3: A process for preparing a hydrophobic and oleophobic drag-reducing film includes the following steps:

[0044] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0045] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0046] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0047] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0048] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 15min, and dry at 70℃ for 40min, repeat 3 times, and finally keep at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0049] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1.2 mm.

[0050] Comparative Example 1: Based on Example 1, N,N'-diisopropylethylenediamine (CAS No.: 4013-94-9) was used to replace N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine, while the rest of the process remained unchanged, as follows:

[0051] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 2.9 parts of N,N'-diisopropylethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0052] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0053] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0054] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0055] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 15min, and dry at 70℃ for 40min, repeat 4 times, and finally keep at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0056] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0057] Comparative Example 2: Based on Example 1, the number of impregnation and drying cycles was increased, while the rest of the process remained unchanged, as follows:

[0058] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0059] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0060] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0061] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0062] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 15min, and dry at 70℃ for 40min, repeat 8 times, and finally keep at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0063] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0064] Comparative Example 3: Based on Example 1, without the addition of nano-silica, the remaining processes remain unchanged, as follows:

[0065] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0066] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0067] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0068] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0069] S3: Add 1H,1H,2H,2H-perfluorodecyltriethoxysilane to a 90% ethanol aqueous solution and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃ and immerse the basic drag-reducing membrane A in it for 15min, and dry it at 70℃ for 40min. Repeat this process several times, and finally keep it at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane and ethanol aqueous solution is 2.5:1:100;

[0070] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0071] Comparative Example 4: Based on Example 1, 2-methyl-2-acrylate-2,3-dihydroxypropyl ester was not added during the preparation of the polydopamine layer, while the rest of the process remained unchanged, as follows:

[0072] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0073] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0074] S1: Polyurethane masterbatch is melted and injected into a mold through an injection molding machine, cooled and demolded to obtain a basic drag-reducing film with a drag-reducing shape; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0075] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.1 mol / L Tris, deionized water as solvent, and pH 8.5±0.1;

[0076] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 15min, and dry at 70℃ for 40min. Repeat this process several times, and finally keep it at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0077] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0078] Comparative Example 5: Based on Example 1, the basic drag-reducing membrane is planar in shape, and the remaining processes remain unchanged, as follows:

[0079] Step 1: Preparation of polyurethane masterbatch: Under a nitrogen atmosphere, 40 parts of polyester diol were heated at 120°C to remove water, then cooled to 60°C. 10 parts of 4,4'-methylenebis(phenyl isocyanate) and 0.02~0.03 parts of dibutyltin dilaurate were added, and the mixture was stirred and reacted for 2.5 h. Then, 100 parts of N,N-dimethylformamide and 7.7 parts of N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine were added, and the mixture was stirred and reacted at 45°C for 1 h. The mixture was then vacuum dried at 100°C and pulverized to obtain the polyurethane masterbatch.

[0080] Step 2: Preparation of hydrophobic and oleophobic drag-reducing membranes:

[0081] S1: Polyurethane masterbatch is melted and injected into a mold using an injection molding machine, cooled and demolded to obtain a planar basic drag-reducing film; wherein, during the injection molding process, the melt temperature is 180℃, the injection speed is 55mm / s, the holding pressure is 8MPa, and the holding time is 12s.

[0082] S2: The basic drag-reducing membrane is immersed in a dopamine-modified solution, stirred at 25°C for 24 hours, washed, and dried at 60°C to form a polydopamine layer, thus obtaining the basic drag-reducing membrane A; wherein the dopamine-modified solution includes the following raw materials: 0.1 mol / L dopamine, 0.25 mol / L 2-methyl-2-acrylate-2,3-dihydroxypropyl ester, 0.1 mol / L Tris, the solvent is deionized water, and the pH is 8.5±0.1;

[0083] S3: Disperse nano-silica in a 90% ethanol aqueous solution, add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stir at 45℃ for 1.5h; adjust the pH to 4.5±0.1, raise the temperature to 60℃, immerse the basic drag-reducing membrane A in it for 15min, and dry at 70℃ for 40min. Repeat this process several times, and finally keep it at 70℃ for 3h to obtain a hydrophobic and oleophobic drag-reducing membrane; wherein the mass ratio of nano-silica, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and ethanol aqueous solution is 2.5:1:100;

[0084] The drag-reducing shape is a rectangular array of conical pits, with the angle between the pit sidewall and the central axis being 45°, and the pit spacing being twice the maximum pit diameter; the maximum pit diameter is 1 mm.

[0085] Performance Test 1: (1) The drag reduction rate of the samples prepared in each embodiment and comparative example was tested using a rotational viscometer: the sample was attached to the rotor with a diameter of 15 mm and a height of 100 mm, and completely immersed in a water tank with a height of 250 mm. The torque was tested at a rotation speed of 200 r / min, and the drag reduction rate was calculated; (2) The samples of each embodiment were ultrasonically treated in water at 25°C with a power of 200 W for 30 min, taken out, washed and dried, attached to the rotor with a diameter of 15 mm and a height of 100 mm, and completely immersed in a water tank with a height of 250 mm. The torque was tested at a rotation speed of 200 r / min, and the drag reduction rate was calculated; the experimental data are shown in Table 1.

[0086] Table 1

[0087]

[0088] Conclusions: As shown in Table 1, in Comparative Example 1, replacing N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine with N,N'-diisopropylethylenediamine resulted in reduced uniformity and binding of the polydopamine layer due to the lack of siloxane groups on the surface for hydrolysis, leading to decreased drag reduction performance and stability. In Comparative Example 2, increasing the number of impregnation and drying cycles resulted in severe agglomeration of silica, forming larger agglomerates, which reduced air content, decreased drag reduction performance, and caused structural instability and significantly decreased stability. In Comparative Example 3, the absence of nano-silica resulted in the lack of nanoparticle-based drag reduction structures, leading to decreased drag reduction performance. In Comparative Example 4, the absence of 2-methyl-2-acrylate-2,3-dihydroxypropyl ester reduced the density of the polydopamine layer, limiting its ability to inhibit ethanol swelling, and also reduced binding, resulting in decreased drag reduction rate and stability. In Comparative Example 5, the basic drag reduction film was planar in shape, lacking microscopic drag reduction structures, resulting in significantly reduced drag reduction performance.

[0089] Performance Test 2: The water contact angle and oil contact angle of the samples in Examples 1-3 were measured using a water contact angle meter; the oil contact angle was measured using glycerol.

[0090] Table 2

[0091]

[0092] As shown in Table 2, the drag-reducing membrane prepared by this invention has excellent hydrophobic and oleophobic properties.

[0093] In summary, this invention utilizes N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine as a polyurethane chain extender to prepare a polyurethane masterbatch for injection molding, which is used to prepare a basic drag-reducing film with a rectangular array of conical pits as a micron drag-reducing structure. Based on this, a polydopamine layer and a hydrophobic and oleophobic layer are sequentially prepared as nano drag-reducing structures to form a micro-nano composite structure. The prepared hydrophobic and oleophobic drag-reducing film has excellent and long-lasting drag-reducing performance.

[0094] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the preparation of a hydrophobic and oleophobic drag reducing membrane, characterized in that: The method comprises the following steps: S1: melt injection of polyurethane material into a mold through an injection molding machine, cooling and demolding to obtain a base drag reduction film with a drag reduction shape; S2: immersing the base drag reduction film into a dopamine modified solution, stirring and reacting, washing, drying, forming a polydopamine layer, and obtaining a base drag reduction film A; S3: dispersing nano-silicon dioxide in an ethanol aqueous solution, adding 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane, stirring and reacting, adjusting pH, and after warming, immersing the base drag reduction film A in the solution for multiple times and taking out for drying to form a hydrophobic and oleophobic layer, and obtaining a hydrophobic and oleophobic drag reduction film. The preparation method of the polyurethane material comprises the following steps: under a nitrogen atmosphere, heating and dehydrating polyester diol at 120-125 DEG C, cooling to 60-70 DEG C, adding 4, 4 '-methylene bis (isocyanate phenyl) and dibutyl tin dilaurate, stirring and reacting for 2-3 h, adding N, N-dimethylformamide and N, N '-bis [3- (trimethoxysilyl) propyl] ethylenediamine, stirring and reacting at 40-50 DEG C for 1-1.5 h, vacuum drying at 100-105 DEG C, and crushing to obtain the polyurethane material. In step S2, the dopamine modified solution comprises the following raw materials: 0.05-0.1 mol / L dopamine, 0.2-0.3 mol / L 2-methyl-2-propenoic acid-2, 3-dihydroxypropyl ester, 0.1 mol / L Tris, deionized water as solvent, and pH of 8-9. In step S3, the specific process is as follows: dispersing nano-silicon dioxide in an ethanol aqueous solution, adding 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane, stirring at 40-45 DEG C for 1-2 h, adjusting pH to 4-5, warming to 55-60 DEG C, immersing the base drag reduction film A in the solution for multiple times and taking out for drying to obtain the hydrophobic and oleophobic drag reduction film. In the process of multiple immersions and drying, the immersion time is 10-15 min, the drying temperature is 60-70 DEG C, the time is 30-50 min, and the number of repetitions is 3-5 times; after the end, it needs to be kept warm at 60-70 DEG C for 2-3 h.

2. The process for preparing a hydrophobic and oleophobic drag-reducing film according to claim 1, characterized in that: The drag reduction shape is a conical pit rectangular array, the included angle between the pit side wall and the central axis is 45 DEG, and the pit center point spacing is 2 times the maximum diameter of the pit; the maximum diameter of the pit is 1-1.2 mm.

3. The process for preparing a hydrophobic and oleophobic drag-reducing film according to claim 1, characterized in that: The polyurethane material comprises the following raw materials in parts by mass: 38-42 parts of polyester diol, 9.5-10.5 parts of 4, 4 '-methylene bis (isocyanate phenyl), 0.02-0.03 parts of dibutyl tin dilaurate, 80-100 parts of N, N-dimethylformamide, and 7-8 parts of N, N '-bis [3- (trimethoxysilyl) propyl] ethylenediamine.

4. The process for preparing a hydrophobic and oleophobic drag-reducing film according to claim 1, characterized in that: In the process of melt injection of the injection molding machine, the melt temperature is 170-180 DEG C, the injection speed is 50-55 mm / s, the holding pressure is 8-10 MPa, and the holding time is 10-15 s.

5. The process for preparing a hydrophobic and oleophobic drag-reducing film according to claim 1, characterized in that: The raw material of the hydrophobic and oleophobic drag reduction film comprises nanometer silicon dioxide, 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane and ethanol aqueous solution in a mass ratio of 2-3:1:80-100; the particle size of the nanometer silicon dioxide is 50-100 nm; the volume fraction content of ethanol in the ethanol aqueous solution is 80-90%. The temperature of the stirring reaction is 25-30 DEG C, and the time is 20-24 h; the drying temperature is 60-70 DEG C.

6. The hydrophobic and oleophobic drag-reducing film prepared by the process according to any one of claims 1-5, characterized in that: The hydrophobic and oleophobic drag reduction film comprises a hydrophobic and oleophobic layer, a polydopamine layer and a basic drag reduction film with a drag reduction shape from top to bottom.

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