Method for manufacturing super-hydrophobic PVC (polyvinyl chloride) pipe based on phase separation pore-forming technology

Abstract

The invention relates to a method for manufacturing a super-hydrophobic PVC (polyvinyl chloride) pipe based on a phase separation pore-forming technology. According to the method, graded pores are constructed through compounding of a pore-forming agent system, water solubility and oil solubility in a synergistic manner; then ensuring that the pore-forming agent accurately positions the inner wall by utilizing an extrusion directional enrichment technology; a toxic solvent is replaced by aqueous medium phase separation; and finally, the coating is prevented from falling off through in-situ hydrophobization. A solution with high performance, low cost and zero pollution is provided for the super-hydrophobic pipe.

Description

Technical Field

[0001] This invention belongs to the field of plastic pipe additives. Specifically, it relates to the preparation and application of a superhydrophobic surface obtained by creating pores in the inner wall of a PVC hose through a phase separation pore-forming technique. Background Technology

[0002] In modern industrial and civil infrastructure sectors, polyvinyl chloride (PVC) pipes have become a core material for fluid transportation and pipeline protection due to their significant comprehensive performance advantages. Specifically, these advantages include: outstanding cost-effectiveness; excellent processing adaptability, enabling continuous production through extrusion molding; superior chemical corrosion resistance; and reliable physical stability. Based on these characteristics, PVC pipes dominate three major areas: water supply and drainage systems, gas transmission, and electrical cable conduits. In municipal water supply and drainage, and chemical transportation, PVC pipes hold a dominant market position due to their low cost and corrosion resistance. However, their high internal surface energy (approximately 38-42 mN / m) makes them prone to adsorbing calcium and magnesium ions, microorganisms, and organic impurities from the water. According to a report by the US EPA, after 18 months of operation, scaling in water pipelines leads to an average pipe diameter shrinkage rate of 7.3%, and an increase in fluid resistance of over 25%. More seriously, biofilm growth (such as Pseudomonas aeruginosa and Legionella) not only pollutes water quality but also causes localized corrosion of the pipe walls.

[0003] To reduce adhesion to pipe walls, superhydrophobic surface technology has been introduced into the pipe industry in recent years. Patent CN 119823511A proposes using polyvinyl chloride resin as the main raw material, adding hydrophobic titanium dioxide particles and hydrophobic reinforcing agents to achieve a superhydrophobic surface design and self-cleaning function. However, this technology suffers from adhesion defects; the coating is physically bonded to the PVC substrate, and under fluid shear force (>0.8MPa), the peeling rate reaches 65% within 30 days. Patent CN 111303705A mixes modified nano-cobalt oxide, modified kaolin, polyacrylic acid, polypropylene, and polyvinyl chloride, adds trifluorotrichloroethane as a solvent, and heats and stirs at 20-30℃. The mixture is then rolled at room temperature and dried at 80-90℃ to obtain a superhydrophobic porous resin coating. However, this process is complex: it requires an additional spray-curing production line, increasing energy consumption by 40%, and the nano-dust poses a health hazard to operators.

[0004] Phase separation pore formation, as a cutting-edge technology for constructing micro and nanostructures, has matured in the field of membrane science. Its principle involves phase separation in a thermodynamically unstable system (such as polymer-solvent-nonsolvent), followed by solidification to form a porous structure. Based on the pore-forming mechanism, it can be divided into: non-solvent-induced phase separation (NIPS) and thermally induced phase separation (TIPS). However, the application of this technology in the pipe industry has long been stagnant. This is because traditional NIPS requires the use of toxic solvents such as DMF and NMP to dissolve the polymer, which conflicts with the "solvent-free" trend in PVC processing; the pore-forming agent fails to be properly positioned: in conventional extrusion processes, the pore-forming agent is randomly distributed, leading to simultaneous pore formation on the inner and outer walls of the pipe, resulting in a decrease in mechanical strength of more than 50%. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings in the performance of current PVC pipes by providing a method for manufacturing superhydrophobic PVC pipes based on phase separation pore-forming technology. This method involves adding different types of pore-forming agents to the PVC pipe and using a non-solvent phase separation pore-forming technology to modify the inner wall surface of the PVC pipe to be superhydrophobic. The PVC melt is heated to 160°C, and a uniformly dispersed pore-forming agent is added. At this point, the system is a molecular-level mixture (lowest free energy). Immersion in a water bath: water molecules diffuse into the melt, reducing the PVC solubility parameter. The pore-forming agent initiates phase separation through dual diffusion: forward diffusion: water penetrates into the PVC phase (non-solvent); reverse diffusion: the pore-forming agent dissolves into the water (solvent loss). The system composition crosses the binodal lines, resulting in spinolysis and the formation of a bicontinuous phase: PVC-rich phase (skeleton): solidifies into a polymer network; pore-forming agent / water-depleted phase (pores): after being replaced by water, pore structure = volume occupied by the depleted phase + space for pore-forming agent dissolution; hierarchical structure construction: micron-sized pores (10-50 μm). The addition of the pore-forming agent in this invention significantly improves the superhydrophobic properties of PVC pipes; and the water-soluble pore-forming agents polyethylene glycol and polyvinylpyrrolidone are industrial-grade chemicals with ample market supply and low procurement costs; the oil-soluble pore-forming aid zinc stearate is also a commonly used additive in the plastics processing field, and is inexpensive and readily available.

[0006] The technical solution of this invention is as follows:

[0007] A method for manufacturing superhydrophobic PVC pipes based on phase separation pore-forming technology, the method comprising the following steps:

[0008] (1) After mixing the pore-forming agent, heat stabilizer, antioxidant and polyvinyl chloride, knead it for 1-3 hours at a speed of 60-100 r / min and room temperature to obtain the kneaded material; then add the kneaded material to the twin-screw extruder at a speed of 6-12 kg / h. The twin screw is divided into six temperature control sections: the first section is 110-120℃, the second section is 140-150℃, the third section is 160-170℃, the fourth section is 180-190℃, the fifth section is 200-210℃, the die temperature is 200-225℃, the screw speed is 130-150 r / min, after the die extrudes the pipe, cool it to room temperature to obtain the pre-crosslinked polyvinyl chloride pipe, named PVC-pore-forming agent;

[0009] The mass ratio of pore-forming agent, heat stabilizer, antioxidant, and polyethylene is 1-2: 0.01-0.05: 0.01-0.05: 8-9.

[0010] The antioxidant is 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]); the heat stabilizer is dibutyltin dilaurate.

[0011] The pore-forming agent is a composite system of water-soluble pore-forming agent and oil-soluble pore-forming aid, with a mass ratio of 1:0.01 to 0.10; the water-soluble pore-forming agent is polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP); the oil-soluble pore-forming aid is zinc stearate.

[0012] The PEG is PEG-2000, 4000, or 6000;

[0013] (2) Immerse the pre-crosslinked PVC pipe obtained in the previous step in a phase-separated aqueous medium at 40-60℃ for 10-60 minutes to obtain superhydrophobic PVC pipe.

[0014] The phase separation aqueous medium is a low surface energy fluorosilane solution with a mass concentration of 0.1-1%.

[0015] The low surface energy fluorosilanes mentioned are specifically tridecafluorooctyltriethoxysilane or heptadecafluorodecyltrimethoxysilane.

[0016] The essential features of this invention are:

[0017] This invention creatively proposes: ① a compound pore-forming agent system → water-soluble + oil-soluble synergistic construction of hierarchical pores; ② extrusion directional enrichment technology → precise positioning of the pore-forming agent on the inner wall; ③ aqueous phase separation → replacing toxic solvents; ④ in-situ hydrophobication → preventing coating peeling. This technical route perfectly fills the industry gap, providing an ultimate solution for superhydrophobic pipes that combines high performance, low cost, and zero pollution.

[0018] This invention achieves superhydrophobic modification of the inner wall of PVC pipes based on the non-solvent-induced phase separation (NIPS) mechanism. First, water-soluble pore-forming agent PEG and oil-soluble pore-forming agent zinc stearate are uniformly dispersed in molten PVC to form a homogeneous system with molecular-level mixing. Then, the pipe is immersed in a water bath. Water molecules, acting as a non-solvent, diffuse forward into the PVC phase, while the pore-forming agent undergoes reverse diffusion. PEG dissolves in water, and zinc stearate softens and melts. When the system composition crosses the thermodynamic double nodal line, cyclohexane decomposition occurs, separating into two continuous phases. The PVC-enriched phase solidifies into a polymer framework network, while the pore-forming agent / water-depleted phase is replaced by water to form a multi-level pore structure. The final constructed three-level micro / nano structure includes: ① micron-sized pores (10-50 μm, originating from PEG dissolution); ② nano-sized pits (200-500 nm, left over from zinc stearate melting); ③ surface papillae (protrusions formed by microcapsule paraffin pore creation). Meanwhile, low surface energy fluorosilanes are present in the phase separation liquid, which are then modified in situ to achieve superhydrophobicity. This process simultaneously modifies the pore walls, resulting in a superhydrophobic property with a contact angle greater than 150°. Furthermore, because the pore structure is integrally formed with the substrate, the risk of coating peeling is completely avoided.

[0019] The beneficial effects of this invention are:

[0020] This invention aims to overcome the shortcomings of current PVC pipes in terms of drainage and fouling performance, and thus provides a method for preparing a phase-separation pore-forming agent that can modify the hydrophobic properties of the inner wall of PVC pipes, as well as its application. Various pore-forming agents are provided, including polyethylene glycol (PEG, M). w =2000, 4000, 6000), polyvinylpyrrolidone (PVP), zinc stearate. Compared with the application of traditional superhydrophobic coating technology for PVC pipes, spraying silica nanoparticles / fluororesin composite slurry has disadvantages such as adhesion defects, easy collapse of nano-protrusion structure under micro-particle impact, complex process, need to set up an additional spraying-curing production line, and increased energy consumption by 40%. This NIPS in-situ pore-forming superhydrophobic technology, the PVC matrix grows in-situ in phase separation, the pore structure is chemically bonded to the matrix, and there are no weak interfacial areas; shear strength ≥3.2MPa, withstands high flow velocity fluid impact (>5m / s); life cycle is greater than 15 years, the same life as the pipe; failure occurs in the gradual collapse of micropores, without causing sudden blockage. The pore-forming agent is added to the PVC pipe as an additive. With the unique non-solvent phase separation pore-forming technology, it can interact on the inner wall of the polymer matrix to form a multi-level pore structure on the inner wall surface.

[0021] This invention incorporates pore-forming agents, such as PEG, PVP, and composite systems of water-soluble PEG and oil-soluble zinc stearate, into the formulation of PVC plastic pipes by varying the proportions of these agents. The pore-forming agent is enriched on the inner wall of the pipe through a twin-screw extruder design. Due to the characteristics of the pore-forming agent, after extrusion of the PVC pipe, it accumulates on the inner wall and is uniformly mixed with the polymer on the inner wall surface. After extrusion, the PVC pipe undergoes a phase separation process by immersing it in an aqueous medium at 40-60°C (for 10-60 minutes). This process dissolves and melts the pore-forming agent, resulting in non-solvent-induced phase separation (NIPS) to form a micron-nano hierarchical porous structure (pore size 0.5-50 μm). Subsequently, a superhydrophobic treatment is performed for in-situ modification: a low surface energy substance (such as 0.1-1% fluorosilane) is added to the phase separation solution to simultaneously modify the pore walls. The contact angle of PVC pipes with added pore-forming agents is >150°, compared to 90° for untreated PVC. The micro-nano porous surface increases the contact angle by 150°, effectively improving superhydrophobic properties and transforming the pipe from "static hydrophobicity" to "dynamic anti-adhesion." Therefore, the addition of the pore-forming agent in this invention significantly improves the superhydrophobic properties of PVC pipes. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the inner wall of the PVC pipe with added PEG-2000 obtained in Example 2.

[0023] Figure 2 This is a scanning electron microscope image of the inner wall of the PVC pipe with added PEG-4000 obtained in Example 5.

[0024] Figure 3 This is a scanning electron microscope image of the inner wall of the PVC pipe with added PEG-6000 obtained in Example 8.

[0025] Figure 4 This is a scanning electron microscope image of the inner wall of the PVC pipe with added PVP obtained in Example 11.

[0026] Figure 5 This is the contact angle of the PVC pipe with added PEG-2000 obtained in Example 2.

[0027] Figure 6 It is the contact angle of the PVC pipe with added PEG-4000 obtained in Example 5.

[0028] Figure 7 It is the contact angle of the PVC pipe with added PEG-6000 obtained in Example 8.

[0029] Figure 8It is the contact angle of the PVC pipe with added PEG-PVP obtained in Example 11.

[0030] Figure 9 This is the contact angle of the PVC pipe obtained in Comparative Example 1. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] In conventional extrusion processes, the pore-forming agent is uniformly dispersed during fluid flow, resulting in full-section pore formation upon cooling. This leads to a decrease in the compressive strength of the PVC pipe and insufficient hydrophobicity of the inner wall. This invention employs a special double-layer co-extrusion die design: two extruders are used to deliver different melts. Extruder 1 delivers the outer melt (without pore-forming agent), while extruder 2 delivers the inner melt (containing 100% pore-forming agent). After entering the die, the outer and inner melts are guided by a flow divider cone within the die and flow within an annular channel. The thickness of the inner channel is set to 20% of the pipe wall thickness to ensure that the pore-forming agent-containing inner melt is concentrated on the inner side of the pipe, forming a pore-forming agent enrichment zone, ultimately achieving double-layer co-extrusion molding of the pipe.

[0033] The pore-forming agent additive of the present invention, which enhances the superhydrophobic properties of PVC pipes through phase separation pore formation, is applied to PVC pipes. Examples 1-12 illustrate its application in the preparation of superhydrophobic PVC pipes.

[0034] Example 1

[0035] The preparation and application of the superhydrophobic PVC pipe are characterized by the following steps:

[0036] (1) Preparation of PVC-10%PEG2000 pipe: PEG-2000, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride were added to a kneading pot at a mass ratio of 1:0.05:0.01:0.01:9. The mixture was kneaded for 3 hours at 60 r / min and room temperature to obtain a kneaded material. The kneaded material was added to a twin-screw extruder at a rate of 6 kg / h. The twin-screw extruder was temperature-controlled in six sections: 110℃ for the first section, 150℃ for the second section, 160℃ for the third section, 180℃ for the fourth section, and 200℃ for the fifth section. The die temperature was 225℃, and the screw speed was 130 r / min. After the pipe was extruded from the die, it was cooled to room temperature to obtain a pre-crosslinked polyvinyl chloride pipe, named PVC-10%PEG2000.

[0037] (2) The pore-forming agent is enriched on the inner wall by the design of the twin-screw extruder. After the PVC pipe is extruded, the phase separation process is carried out by immersing the pipe in a phase separation aqueous medium at 60℃ (time: 60min). The pore-forming agent dissolves and non-solvent-induced phase separation (NIPS) occurs to form a micron-nano hierarchical porous structure.

[0038] The phase separation aqueous medium is a 0.1% (w / w) aqueous solution of tridecafluorooctyltriethoxysilane. In the warm phase separation medium, it hydrolyzes into silanol, which diffuses into the forming porous structure and adsorbs onto the highly active fresh pore walls. Through condensation reactions, it forms a network and may bond to the substrate or be strongly adsorbed and fixed, self-assembling into a single / multilayer membrane with outwardly aligned fluorocarbon chains. This process occurs simultaneously with NIPS pore formation. The main component of this membrane is the outwardly aligned fluorocarbon chains (Rf), which have extremely low surface energy. The chemical modification of the inner wall surface of the pipe simultaneously achieves pore wall modification.

[0039] As shown in Table 1, the contact angle of the PVC pipe with 10% PEG-2000 pore-forming agent is 148°, while the contact angle of the PVC pipe without pore-forming agent is 89.6°. After 30 days of water flow, the contact angle was slightly smaller, and there was less scaling on the surface compared to the pipe without pore-forming agent.

[0040] Example 2-Example 3

[0041] The other steps are the same as in Example 1, except that in step (1), the amounts of PEG-2000 and polyvinyl chloride are changed. The mass ratios of PEG-2000, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride are changed to 1.5:0.05:0.01:0.01:8.5 and 2:0.05:0.01:0.01:8, respectively, and are named PVC-15%PEG2000 (Example 2) and PVC-20%PEG2000 (Example 3).

[0042] The polyvinyl chloride is in powder form with a powder diameter of 20 μm.

[0043] like Figure 1 Scanning electron microscope (SEM) images of the inner wall of PVC pipes with 15% PEG-2000 are shown, revealing a micron-sized finger-like hierarchical porous structure (pore size 0.5-50 μm).

[0044] like Figure 5 The contact angle of PVC pipes with 15% PEG-2000 added is shown. The contact angle of the pipe with PEG-2000 pore-forming agent is 154.9°, while the contact angle of the pipe without pore-forming agent is 86.9°. After 30 days of water flow, the contact angle was tested again and found to be slightly smaller. Compared with the pipe without pore-forming agent, there is less scaling on the surface.

[0045] Table 1 shows that the contact angle of PVC pipes with 20% PEG-2000 pore-forming agent added is >150°, while the contact angle of PVC pipes without pore-forming agent added is 89.6°. After 30 days of water flow, the contact angle was slightly reduced, indicating less surface scaling compared to pipes without pore-forming agent added.

[0046] Example 4

[0047] (1) Preparation of PVC-10%PEG4000 pipe: PEG-4000, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride were added to a kneading pot at a mass ratio of 1:0.05:0.01:0.01:9. The mixture was kneaded for 3 hours at 60 r / min and room temperature to obtain a kneaded material. The kneaded material was added to a twin-screw extruder at a rate of 6 kg / h. The twin-screw extruder was temperature-controlled in six sections: 110℃ for the first section, 150℃ for the second section, 160℃ for the third section, 180℃ for the fourth section, and 200℃ for the fifth section. The die temperature was 225℃, and the screw speed was 130 r / min. After the pipe was extruded from the die, it was cooled to room temperature to obtain a pre-crosslinked polyvinyl chloride pipe, named PVC-10%PEG4000.

[0048] (2) The pore-forming agent is enriched on the inner wall by the design of the twin-screw extruder. After the PVC pipe is extruded, the phase separation process involves immersing the pipe in 60°C warm water (time: 60min). The pore-forming agent dissolves and melts, and non-solvent-induced phase separation (NIPS) occurs to form a micron-nano hierarchical porous structure (pore size 0.5-50μm). The pipe is then subjected to superhydrophobic treatment for in-situ modification. Low surface energy substances are added to the phase separation medium to simultaneously modify the pore walls.

[0049] Examples 5-6

[0050] The other steps are the same as in Example 4, except that in step (1), the amounts of PEG-4000 and polyvinyl chloride are changed. The mass ratios of PEG-4000, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride are changed to 1.5:0.05:0.01:0.01:8.5 and 2:0.05:0.01:0.01:8, respectively, and are named PVC-15%PEG4000 (Example 5) and PVC-20%PEG4000 (Example 6).

[0051] The polyvinyl chloride is in powder form with a powder diameter of 20 μm.

[0052] like Figure 2The scanning electron microscope image of the inner wall of PVC pipe with 15% PEG-4000 is shown. The inner wall has a micron finger-like hierarchical porous structure (pore size 0.5-50 μm).

[0053] like Figure 6 The contact angle of PVC pipes with 15% PEG-4000 is shown. The contact angle of the pipe with PEG-4000 pore-forming agent is 157.8°, while the contact angle of the pipe without pore-forming agent is 86.9°. After 30 days of water flow, the contact angle was tested and found to be slightly smaller. Compared with the pipe without pore-forming agent, there is less scaling on the surface.

[0054] Example 7

[0055] (1) Preparation of PVC-10%PEG6000 pipe: PEG-6000, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride were added to a kneading pot at a mass ratio of 1:0.05:0.01:0.01:9. The mixture was kneaded for 3 hours at 60 r / min and room temperature to obtain a kneaded material. The kneaded material was added to a twin-screw extruder at a rate of 6 kg / h. The twin-screw extruder was temperature-controlled in six sections: 110℃ for the first section, 150℃ for the second section, 160℃ for the third section, 180℃ for the fourth section, and 200℃ for the fifth section. The die temperature was 225℃, and the screw speed was 130 r / min. After the pipe was extruded from the die, it was cooled to room temperature to obtain a pre-crosslinked polyvinyl chloride pipe, named PVC-10%PEG6000.

[0056] (2) The pore-forming agent is enriched on the inner wall by the design of the twin-screw extruder. After the PVC pipe is extruded, the phase separation process involves immersing the pipe in 60℃ warm water (time: 60min). The pore-forming agent dissolves and melts, and non-solvent-induced phase separation (NIPS) occurs to form a micron-level porous structure (pore size 0.5-50μm). Superhydrophobic treatment is then performed for in-situ modification, and low surface energy substances are added to the phase separation medium (water) to simultaneously modify the pore walls.

[0057] Examples 8-9

[0058] The other steps are the same as in Example 7, except that in step (1), the amounts of PEG-6000 and polyvinyl chloride are changed. The mass ratios of PEG-2000, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride are changed to 1.5:0.05:0.01:0.01:8.5 and 2:0.05:0.01:0.01:8, respectively, and are named PVC-15%PEG6000 (Example 8) and PVC-20%PEG6000 (Example 9).

[0059] The polyvinyl chloride is in powder form with a powder diameter of 20 μm.

[0060] like Figure 3 The scanning electron microscope image of the inner wall of PVC pipe with 15% PEG-6000 is shown. The inner wall has a micron-level porous structure (pore size 0.5-50 μm).

[0061] like Figure 7 The contact angle of PVC pipes with 15% PEG-6000 is shown. The contact angle of the pipe with PEG-6000 pore-forming agent is >150°, while the contact angle of the pipe without pore-forming agent is 90°. After 30 days of water flow, the contact angle was tested and found to be slightly smaller. Compared with the pipe without pore-forming agent, there is less scaling on the surface.

[0062] Example 10

[0063] (1) Preparation of PVC-10%PVP pipe: Polyvinylpyrrolidone (PVP), zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride were added to a kneading pot at a mass ratio of 1:0.05:0.01:0.01:9. The mixture was kneaded for 3 hours at 60 r / min and room temperature to obtain a kneaded material. The kneaded material was added to a twin-screw extruder at a rate of 6 kg / h. The twin-screw extruder was temperature-controlled in six sections: 110℃ for the first section, 150℃ for the second section, 160℃ for the third section, 180℃ for the fourth section, and 200℃ for the fifth section. The die temperature was 225℃, and the screw speed was 130 r / min. After the pipe was extruded from the die, it was cooled to room temperature to obtain a pre-crosslinked polyvinyl chloride pipe, named PVC-10%PVP.

[0064] (2) The pore-forming agent is enriched on the inner wall by the design of the twin-screw extruder. After the PVC pipe is extruded, the phase separation process is carried out by immersing the pipe in 40℃ warm water (time: 40min). The pore-forming agent dissolves and melts, and non-solvent-induced phase separation (NIPS) occurs to form a micron-level porous structure (pore size 0.5-50μm). The pipe is then subjected to superhydrophobic treatment for in-situ modification. Low surface energy substances are added to the phase separation medium water to simultaneously achieve pore wall modification.

[0065] Examples 11-12

[0066] The other steps are the same as in Example 10, except that in step (1), the amounts of polyvinylpyrrolidone (PVP) and polyvinyl chloride are changed, and the mass ratios of PVP, zinc stearate, dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride are changed to 1.5:0.05:0.01:0.01:8.5 and 2:0.05:0.01:0.01:8, respectively, and are named PVC-15%PVP (Example 11) and PVC-20%PVP (Example 12).

[0067] like Figure 4The scanning electron microscope image of the inner wall of a PVC pipe with 15% PVP added is shown in Example 11. The inner wall has a micron-level porous structure (pore size 0.5-50 μm).

[0068] like Figure 8 The contact angle of PVC pipes with 15% PVP is shown. The contact angle of the pipe with PVP pore-forming agent is >150°, while the contact angle of the pipe without pore-forming agent is 89.6°. After 30 days of water flow, the contact angle was tested and found to be slightly smaller. Compared with the pipe without pore-forming agent, there is less scaling on the surface.

[0069] Comparative Example 1

[0070] The preparation and application of the PVC pipe are characterized by comprising the following steps:

[0071] Preparation of PVC pipes: Heat stabilizer dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride are poured into a kneading pot and kneaded for 3 hours at 60 r / min and room temperature to obtain a kneaded material. The kneaded material is added to a twin-screw extruder at a rate of 6 kg / h. The twin-screw extruder has six temperature control sections: the first section is 110℃, the second section is 150℃, the third section is 160℃, the fourth section is 180℃, and the fifth section is 200℃. The die temperature is 225℃, and the screw speed is 130 r / min. After the pipe is extruded from the die, it is cooled to room temperature to obtain pre-crosslinked polyvinyl chloride pipes.

[0072] The mass ratio of dibutyltin dilaurate, antioxidant 1010, and polyvinyl chloride is 0.01:0.01:10, and it is named PVC.

[0073] The polyvinyl chloride is in powder form with a powder diameter of 20 μm.

[0074] like Figure 9 The contact angle of the PVC pipe obtained in Comparative Example 1 is 89.6°.

[0075] To verify the properties of the materials obtained in Examples 1 to 12 and Comparative Example 1, relevant characterization and performance tests were conducted on them below.

[0076] (I) Scanning Electron Microscope

[0077] The inner walls of the prepared PVC-PEG2000, PVC-PEG4000, PVC-PEG6000, and PVC-PVP pipes were tested using scanning electron microscopy. Figures 1-4 It can be clearly observed that after immersion in a non-solvent aqueous medium, the pore-forming agent on the inner wall undergoes phase separation, producing a micron-sized finger-shaped porous structure.

[0078] (II) Contact Angle Test

[0079] Water droplets were drawn with a syringe and placed on the inner wall of the prepared PVC, PVC-PEG2000, PVC-PEG4000, PVC-PEG6000, and PVC-PVP pipes. After taking a picture, the contact angle between the inner wall and the water was calculated by computer.

[0080] (III) Tensile Strength

[0081] The tensile strength of the plastic pipes prepared in Examples 1-12 and Comparative Example 1 was tested according to the method specified in GB / T1040.2-2006.

[0082] (iv) Water scouring aging test

[0083] The obtained PVC-PEG2000, PVC-PEG4000, PVC-PEG6000, and PVC-PVP pipes are passed through a circulation pump (flow rate 5 m / s). -1 100mg / L of quartz sand -1 After 30 days, the contact angle was measured and the contact angle decay rate was calculated.

[0084] Table 1. Testing of the PEG pore-forming agent of the present invention on the inner wall of modified PVC plastic pipes.

[0085]

[0086] Compared with PVC pipes without PEG pore-forming agent doping, the present invention exhibits optimal performance when the doping ratio of PEG-2000, PEG-4000 and PEG-6000 is 15%, with contact angles increased by 72.8%, 76.1% and 72.7% respectively compared with PVC, while the tensile strength remains essentially unchanged.

[0087] Table 2. Testing of the PVP pore-forming agent of the present invention on the inner wall of modified PVC plastic pipes.

[0088]

[0089] Compared with PVC pipes without PVP pore-forming agent doping, the present invention exhibits optimal performance with a PVC-PVP doping ratio of 15%, with a contact angle increased by 68.7% compared to PVC, while the tensile strength remains essentially unchanged.

[0090] The above descriptions are merely several preferred embodiments of the present invention, but the present invention is not limited to the specific implementation methods described above. The specific implementation methods described above are illustrative and not restrictive. Researchers in the art, under the guidance of the present invention and in accordance with the spirit and principles of the present invention, can make improvements and modifications, all of which fall within the protection scope of the present invention.

[0091] Matters not covered in this invention are common knowledge.

Claims

1. A method for manufacturing superhydrophobic PVC pipes based on phase separation pore-forming technology, characterized in that, The method includes the following steps: (1) After mixing the pore-forming agent, heat stabilizer, antioxidant and polyvinyl chloride, knead it for 1-3 hours at a speed of 60-100 rpm / min and room temperature to obtain the kneaded material; then add the kneaded material to the twin-screw extruder at a speed of 6-12 kg / h, extrude the pipe through the die head, and cool it to room temperature to obtain the pre-crosslinked polyvinyl chloride pipe. The mass ratio of pore-forming agent, heat stabilizer, antioxidant, and polyvinyl chloride is 1-2: 0.01-0.05: 0.01-0.05: 8-9. The pore-forming agent is a water-soluble pore-forming agent and an oil-soluble pore-forming aid, with a mass ratio of 1:0.01 to 0.10; the water-soluble pore-forming agent is polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP); the oil-soluble pore-forming aid is zinc stearate. (2) Immerse the pre-crosslinked PVC pipe obtained in the previous step in a phase-separated aqueous medium at 40-60℃ for 10-60 min to obtain superhydrophobic PVC pipe. The phase separation aqueous medium is a low surface energy fluorosilane solution with a mass concentration of 0.1-1%.

2. The manufacturing method of superhydrophobic PVC pipe based on phase separation pore-forming technology as described in claim 1, characterized in that, The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the heat stabilizer is dibutyltin dilaurate.

3. The manufacturing method of superhydrophobic PVC pipe based on phase separation pore-forming technology as described in claim 1, characterized in that, The PEG is PEG-2000, 4000 or 6000.

4. The manufacturing method of superhydrophobic PVC pipe based on phase separation pore-forming technology as described in claim 1, characterized in that, The low surface energy fluorosilanes mentioned are specifically tridecafluorooctyltriethoxysilane or heptadecafluorodecyltrimethoxysilane.

5. The manufacturing method of superhydrophobic PVC pipe based on phase separation pore-forming technology as described in claim 1, characterized in that, The twin-screw extruder has six temperature control sections: the first section is 110-120℃, the second section is 140-150℃, the third section is 160-170℃, the fourth section is 180-190℃, the fifth section is 200-210℃, the die temperature is 200-225℃, and the screw speed is 130-150 r / min.

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