High-corrosion-resistance PVC (polyvinyl chloride) pipe and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses a high-corrosion-resistance PVC pipe and a preparation method thereof. The high-corrosion-resistance PVC pipe is prepared from the following raw materials in parts by weight: 80 to 120 parts of PVC resin, 5 to 7 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 3 to 5 parts of compatilizer, 7 to 10 parts of composite filler and 2 to 3 parts of processing aid, the composite filler comprises mesoporous silica, a corrosion inhibitor and Mg-Al hydrotalcite. The high-corrosion-resistance PVC pipe has excellent corrosion resistance, and can maintain long-term corrosion and aging resistance under a high-corrosion working condition while maintaining long-term mechanical properties.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and more specifically, to a highly corrosion-resistant PVC pipe and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC) pipes have become the mainstream pipe material in the fields of building water supply and drainage, agricultural irrigation, power communication sheathing, municipal engineering, etc. due to their light weight, high strength, low cost, easy processing and resistance to general chemical corrosion.

[0003] However, traditional PVC pipes exhibit significant performance deficiencies when subjected to long-term service in extremely corrosive environments such as those found in marine engineering, chemical wastewater treatment, and electroplating industries, where strong acids (such as sulfuric acid or hydrochloric acid with a concentration greater than 50%), strong bases (such as sodium hydroxide solutions with a pH greater than 12), or high-salt environments. These conditions can lead to molecular chain breakage and surface corrosion, accelerating material aging and causing structural embrittlement or even rupture. The penetration of corrosive media causes molecular chain breakage and structural damage within PVC pipes, significantly reducing mechanical properties such as tensile strength and impact toughness, making them unable to meet dynamic load requirements.

[0004] In recent years, with the rapid development of chemical, pharmaceutical, marine engineering and infrastructure construction in coastal areas, pipes need to be exposed to extreme corrosion conditions such as strong acid (such as industrial wastewater), strong alkali (such as detergent environment), high-concentration salt spray (such as seawater desalination system) for a long time. Especially in application scenarios that require stronger corrosion resistance and impact resistance, higher requirements are placed on the corrosion resistance and aging performance and mechanical properties of the material.

[0005] Most of the methods used in the industry to improve the corrosion and aging resistance of PVC pipes are to add stabilizers (such as nano-silica or montmorillonite) or to blend and modify (such as compound fluororubber). In response to the above-mentioned related technologies, the inventors found that although the addition of nano-silica / montmorillonite can improve the mechanical properties of the material to a certain extent, the compatibility between the interface of these inorganic fillers and the PVC matrix will deteriorate rapidly in a highly corrosive environment, causing a stress concentration effect and accelerating the cracking of the pipe. The use of highly corrosion-resistant materials such as fluororesins for blending and modification can improve the corrosion resistance of the pipe to a certain extent. However, as a polymer material, fluororesins are generally poorly dispersible in the PVC matrix, and the amount of addition is limited. Excessive addition will further reduce the mechanical properties of the pipe, making it impossible to strike a balance between high corrosion resistance and high mechanical strength. Summary of the Invention

[0006] In order to improve the corrosion and aging resistance of PVC pipes and maintain the long-term mechanical properties under corrosive conditions, thereby extending the service life of PVC pipes, the present application provides a highly corrosion-resistant PVC pipe and a preparation method thereof.

[0007] In the first aspect, the present application provides a highly corrosion-resistant PVC pipe, which adopts the following technical solution: A highly corrosion-resistant PVC pipe, comprising, by weight, 80-120 parts of PVC resin, 5-7 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 3-5 parts of a compatibilizer, 7-10 parts of a composite filler, and 2-3 parts of a processing aid. The composite filler comprises mesoporous silica, a corrosion inhibitor and Mg-Al hydrotalcite.

[0008] By adopting the above technical solution, polyvinylidene fluoride-hexafluoropropylene copolymer and composite filler are used as functional components. On the one hand, fluorine element is introduced, and the fluorine-carbon chain can form a dense barrier in the PVC matrix, effectively blocking the erosion and penetration of strong acid and high-salt media, and forming a corrosion-resistant barrier on the surface of the pipe. On the other hand, the use of mesoporous silica-loaded corrosion inhibitor can enhance the resistance of the pipe to corrosive media in a strong corrosive environment. The layered structure of Mg-Al hydrotalcite can effectively extend the diffusion path of the corrosive medium and inhibit the diffusion of the corrosive medium. Through the dual-effect protection of chemical corrosion inhibition and physical barrier effect, the corrosion resistance and aging performance of the PVC pipe and the durability of the mechanical properties under corrosive conditions are effectively improved, thereby extending the service life of the PVC pipe.

[0009] Optionally, the method for preparing the composite filler comprises the following steps: S1: adding mesoporous silica to an ethanol solution containing a corrosion inhibitor, adding 0.3-0.8 wt% sodium dodecyl sulfate, ultrasonicating at 30-50°C, centrifuging, washing, and drying to obtain silica microspheres loaded with the corrosion inhibitor; S2: dissolving Mg(NO3)2 and Al(NO3)3 in water to form a mixed salt solution, wherein the molar ratio of Mg(NO3)2 and Al(NO3)3 is (2-3):1, and the total concentration of the mixed salt solution is 0.1-0.2 mol / L, dispersing silica microspheres in the mixed salt solution, and heating and stirring to form a mixed solution; S3: The mixed solution is added dropwise to a mixed alkaline solution containing sodium hydroxide and sodium carbonate, the pH is adjusted to (9.5±0.1), the mixture is stirred and aged, filtered, washed, dried, and then calcined at 100-120°C to form a Mg-Al hydrotalcite layer on the surface of the silica microspheres, which is the composite filler.

[0010] By adopting the above technical solution, the composite filler formed in the present application has mesoporous silica as the core, and forms a lamellar Mg-Al hydrotalcite layer after in-situ vertical growth on the surface of the mesoporous silica, with the overall microparticle structure being sea urchin-shaped.

[0011] First, mesoporous silica is fully loaded in a solution containing anionic surfactants and corrosion inhibitors, promoting the effective loading of the corrosion inhibitor into the mesoporous silica pores. The Mg-Al hydrotalcite formed on the surface then takes on a radial pattern. When added to a PVC matrix, composite filler particles with this structure can form a strong mechanical interlocking effect with the organic matrix, reducing the possibility of inorganic filler agglomeration. This improves the uniformity of the inorganic filler dispersion in the PVC matrix, effectively reducing the deterioration of the interfacial compatibility between the inorganic filler and the organic matrix in highly corrosive environments, and reducing the stress concentration caused by the addition of inorganic fillers, thereby maintaining the durability of the mechanical properties of the PVC pipe.

[0012] In addition, the radial lamellar structure formed by the Mg-Al hydrotalcite layer increases the resistance to the inward penetration of corrosive medium ions inside the PVC matrix, further enhancing the barrier penetration effect of the PVC pipe to the corrosive medium and improving the corrosion resistance and durability of the PVC pipe.

[0013] Optionally, the silica microspheres are pretreated as follows before being dispersed in the mixed salt solution: The silica microspheres are dispersed in a 1-2% silane coupling agent solution, subjected to ultrasonic dispersion for 6-8 minutes, reacted at 40-50° C., washed by centrifugation and dried to obtain pretreated silica microspheres.

[0014] By adopting the above technical solution, -NH2 is introduced on the surface of silica particles, and the lone pair electrons of the nitrogen atom in -NH2 interact with Mg 2+ / Al 3+ The formation of coordination bonds effectively guides the vertical growth of Mg-Al hydrotalcite. Compared with the Mg-Al hydrotalcite layer formed by physical adsorption of silica microspheres without the introduction of -NH2, it has a stronger interfacial bonding force and helps to form a uniform radial Mg-Al hydrotalcite layer.

[0015] Optionally, the silane coupling agent is an aminosilane coupling agent selected from KH-550.

[0016] Optionally, the composite filler is subjected to the following post-processing: Optionally, the corrosion inhibitor is selected from any one of 2-mercapto-5-methylbenzimidazole and 5-methoxy-2-mercaptobenzimidazole.

[0017] By adopting this technical solution, in highly corrosive environments, the corrosion inhibitor within the pores of the mesoporous silica continuously seeps out due to concentration gradients and ion exchange between the hydrotalcite layers. Compared to traditional benzimidazole corrosion inhibitors, the use of a mercapto group-containing corrosion inhibitor is more compatible with the PVC matrix. The mercapto group can react with free radicals in the PVC molecular chain, terminating oxidative induction.

[0018] In an acidic environment, sulfhydryl protonation can neutralize the penetrating H + In an alkaline environment, the thiol group ionizes to -S- and reacts with OH- to maintain the pH stability of the microenvironment inside the PVC pipe. 3+ 、Cu 2+ When in contact with corrosive media, it can form stable chelates with metal ions, effectively inhibiting their catalytic degradation of PVC. In addition, the conjugated structure of the benzimidazole ring forms a π-π stacking with the PVC molecular chain, which also strengthens the intermolecular force and improves thermal stability.

[0019] Optionally, the compatibilizer is chlorinated polyethylene.

[0020] Optionally, the processing aid includes a lubricant, and the lubricant is PE wax and magnesium stearate in a mass ratio of 1:(1-3).

[0021] In a second aspect, the present application provides a method for preparing a highly corrosion-resistant PVC pipe, which adopts the following technical solution: A method for preparing a highly corrosion-resistant PVC pipe comprises the following steps: PVC resin, polyvinylidene fluoride-hexafluoropropylene copolymer, compatibilizer, composite filler and processing aid are weighed and mixed according to the raw material ratio, hot-mixed in a hot mixer at 110-120°C, and then cold-mixed in a cold mixer at 30-40°C to obtain a blend; the blend is sent to a screw extruder for extrusion molding, and after extrusion through a mold, vacuum cooling is performed to determine the size to obtain the product.

[0022] By adopting the above technical solution, cold mixing is performed first and then fillers are added for hot mixing, which effectively reduces the destructive effect of the Mg-Al hydrotalcite layer on the surface of the composite filler under the shear force of high-temperature premixing. The composite filler and processing aid are added during cold mixing, which helps to evenly disperse the composite filler inside the PVC matrix, enhance the compatibility between the filler and the organic matrix, reduce the phase separation of the PVC pipe, and significantly improve the corrosion resistance and long-term retention of the mechanical properties of the PVC pipe in a highly corrosive environment.

[0023] In summary, this application has the following beneficial effects: 1. The present application obtains a sea urchin-shaped composite filler by forming a lamellar Mg-Al hydrotalcite layer by radioactive in-situ vertical growth on the surface of mesoporous silica loaded with a corrosion inhibitor. The composite filler has excellent corrosion resistance and uniform dispersion in an organic matrix, which can not only inhibit the penetration of corrosive media, but also form a strong mechanical interlocking effect with the organic matrix when added to the PVC matrix, and is anchored inside the PVC matrix, effectively preventing the deterioration of the interface compatibility between the inorganic filler and the organic matrix in a strong corrosive environment from causing stress concentration, leading to rupture of the PVC pipe, and significantly enhancing the mechanical performance stability of the PVC pipe in a strong corrosive environment.

[0024] 2. Under the formula ratio of this application, the chemical barrier formed by polyvinylidene fluoride-hexafluoropropylene copolymer and the physical path blocking barrier formed by the composite filler can form a stable corrosion-resistant barrier in the PVC pipe, inhibit the penetration and diffusion of corrosive media, and significantly improve the service life of PVC pipes in strong corrosive environments.

[0025] 3. This application preferably uses a benzimidazole corrosion inhibitor containing a thiol group. The introduction of the thiol group can inhibit the free radical reaction of the PVC molecular chain in a strong corrosive environment, terminate the oxidation-induced reaction, maintain the pH stability inside the PVC pipe, and at the same time form a stable chelate with the metal corrosion ions, effectively inhibiting its catalytic degradation effect, and enhancing the corrosion resistance of the PVC pipe in a strong corrosive environment. DETAILED DESCRIPTION

[0026] The present application is further described in detail below with reference to examples and comparative examples.

[0027] raw material Unless otherwise specified, the raw materials used in the examples and comparative examples of this application are all commercially available products, specifically: PVC resin, selected from Shanxi Ruiheng Chemical Co., Ltd., SG-5; Polyvinylidene fluoride-hexafluoropropylene copolymer, selected from Guangzhou Wengjiang Biotechnology Co., Ltd., PA14975; Chlorinated polyethylene, selected from Dongguan Shanyi Plastics Co., Ltd., CPE135A; Mesoporous silica, selected from Zhejiang Manli Nanotechnology Co., Ltd., ML-SiO2-ZW01; KH-550, selected from Shandong Maofa Chemical Co., Ltd., KH-550; Antioxidant 1010, selected from Dongguan Baineng New Materials Co., Ltd., antioxidant 1010; PE wax, selected from Honeywell, AC-6A; Magnesium stearate, selected from Zhongshan Yuanda New Materials Co., Ltd., magnesium octadecanoate.

[0028] Preparation example of composite filler Preparation Example 1 The preparation method of the composite filler comprises the following steps: S1: 2-mercapto-5-methylbenzimidazole was dissolved in 80% ethanol solution to form a corrosion inhibitor solution, the concentration of 2-mercapto-5-methylbenzimidazole was 0.01 mol / L, 10 g of mesoporous silica was added to 50 mL of the corrosion inhibitor solution, 0.3 wt % of sodium dodecyl sulfate was added, and the solution was ultrasonicated at 30° C. and 300 W for 2 h. After centrifugation and alcohol washing, the solution was vacuum dried at 60° C. for 8 h to obtain silica microspheres loaded with corrosion inhibitor; S2: KH-550 was dissolved in 80% ethanol solution to form a 1 wt% coupling agent solution, and silica microspheres were dispersed in the coupling agent solution at a material-liquid ratio of 1:12. After ultrasonic dispersion at 300W for 6 minutes, the mixture was reacted at 50°C for 4 hours, washed by centrifugation, and vacuum dried at 60°C for 10 hours to obtain pretreated silica microspheres; S3: dissolving Mg(NO3)2 and Al(NO3)3 in a molar ratio of 2:1 in water to form a mixed salt solution with a total concentration of 0.2 mol / L. Dispersing the pretreated silica microspheres obtained in step S2 in the mixed salt solution at a material-liquid ratio of 1:10. Heat to 60℃ and stir evenly to form a mixed solution; S4: Sodium hydroxide and sodium carbonate are dissolved in water to form an alkaline solution. Under stirring, the mixed solution obtained in step S3 is added dropwise to an equal volume of alkaline solution at a dropping rate of 0.5 mL / min, and the pH is adjusted to (9.5±0.1). After continuing to stir the reaction for 0.5 h, the mixture is hydrothermally aged at 100° C. for 10 h. After filtering, washing, drying, and low-temperature calcination at 120° C., a Mg-Al hydrotalcite layer is formed on the surface of the silica microspheres, which is a composite filler.

[0029] Preparation Example 2 The preparation method of the composite filler comprises the following steps: S1: 5-methoxy-2-mercaptobenzimidazole was dissolved in 80% ethanol solution to form a corrosion inhibitor solution, the concentration of 5-methoxy-2-mercaptobenzimidazole was 0.01 mol / L, 10 g of mesoporous silica was added to 50 mL of the corrosion inhibitor solution, 0.5 wt % of sodium dodecyl sulfate was added, and the solution was ultrasonicated at 50° C. and 300 W for 1.5 h. After centrifugation and alcohol washing, the solution was vacuum dried at 60° C. for 8 h to obtain silica microspheres loaded with corrosion inhibitor; S2: KH-550 was dissolved in 80% ethanol solution to form a 1.7 wt% coupling agent solution, and silica microspheres were dispersed in the coupling agent solution at a material-liquid ratio of 1:12. After ultrasonic dispersion at 300W for 8 minutes, the mixture was reacted at 50°C for 5 hours, centrifuged and washed, and vacuum dried at 60°C for 10 hours to obtain pretreated silica microspheres; S3: dissolving Mg(NO3)2 and Al(NO3)3 in a molar ratio of 3:1 in water to form a mixed salt solution with a total concentration of 0.2 mol / L, dispersing the pretreated silica microspheres obtained in step S2 in the mixed salt solution at a material-liquid ratio of 1:8, heating to 60°C and stirring uniformly to form a mixed solution; S4: Sodium hydroxide and sodium carbonate are dissolved in water to form an alkaline solution. Under stirring, the mixed solution obtained in step S3 is added dropwise to an equal volume of alkaline solution at a dropping rate of 0.5 mL / min, and the pH is adjusted to (9.5±0.1). After continuing to stir the reaction for 1 hour, the mixture is hydrothermally aged at 100° C. for 8 hours. After filtering, washing, drying, and low-temperature calcination at 100° C., a Mg-Al hydrotalcite layer is formed on the surface of the silica microspheres, which is a composite filler.

[0030] Preparation Example 3 The preparation method of the composite filler comprises the following steps: S1: 5-methoxy-2-mercaptobenzimidazole was dissolved in 80% ethanol solution to form a corrosion inhibitor solution, the concentration of 5-methoxy-2-mercaptobenzimidazole was 0.01 mol / L, 10 g of mesoporous silica was added to 50 mL of the corrosion inhibitor solution, 0.8 wt % of sodium dodecyl sulfate was added, and the solution was ultrasonicated at 40° C. and 300 W for 2 h. After centrifugation and alcohol washing, the solution was vacuum dried at 60° C. for 8 h to obtain silica microspheres loaded with corrosion inhibitor; S2: KH-550 was dissolved in 80% ethanol solution to form a 1.2 wt% coupling agent solution, and silica microspheres were dispersed in the coupling agent solution at a material-liquid ratio of 1:12. After ultrasonic dispersion at 300W for 7 minutes, the mixture was reacted at 45°C for 4 hours, washed by centrifugation, and vacuum dried at 60°C for 10 hours to obtain pretreated silica microspheres; S3: dissolving Mg(NO3)2 and Al(NO3)3 in a molar ratio of 2:1 in water to form a mixed salt solution with a total concentration of 0.1 mol / L, dispersing the pretreated silica microspheres obtained in step S2 in the mixed salt solution at a material-liquid ratio of 1:8, heating to 60°C and stirring uniformly to form a mixed solution; S4: Sodium hydroxide and sodium carbonate are dissolved in water to form an alkaline solution. Under stirring, the mixed solution obtained in step S3 is added dropwise to an equal volume of alkaline solution at a dropping rate of 0.5 mL / min, and the pH is adjusted to (9.5±0.1). After continuing to stir the reaction for 1 hour, the mixture is hydrothermally aged at 100° C. for 9 hours. After filtering, washing, drying, and low-temperature calcination at 110° C., a Mg-Al hydrotalcite layer is formed on the surface of the silica microspheres, which is a composite filler.

[0031] Preparation Example 4 The preparation method of the composite filler comprises the following steps: S1: 2-mercapto-5-methylbenzimidazole was dissolved in 80% ethanol solution to form a corrosion inhibitor solution, the concentration of 2-mercapto-5-methylbenzimidazole was 0.01 mol / L, 10 g of mesoporous silica was added to 50 mL of the corrosion inhibitor solution, 0.6 wt % of sodium dodecyl sulfate was added, and the solution was ultrasonicated at 30° C. and 300 W for 1.5 h. After centrifugation and alcohol washing, the solution was vacuum dried at 60° C. for 8 h to obtain silica microspheres loaded with corrosion inhibitor; S2: KH-550 was dissolved in 80% ethanol solution to form a 2 wt% coupling agent solution, and silica microspheres were dispersed in the coupling agent solution at a material-liquid ratio of 1:12. After ultrasonic dispersion at 300W for 8 minutes, the mixture was reacted at 40°C for 6 hours, washed by centrifugation, and vacuum dried at 60°C for 10 hours to obtain pretreated silica microspheres; S3: dissolving Mg(NO3)2 and Al(NO3)3 in a molar ratio of 2.5:1 in water to form a mixed salt solution with a total concentration of 0.15 mol / L, dispersing the pretreated silica microspheres obtained in step S2 in the mixed salt solution at a material-liquid ratio of 1:10, heating to 60°C and stirring uniformly to form a mixed solution; S4: Sodium hydroxide and sodium carbonate are dissolved in water to form an alkaline solution. Under stirring, the mixed solution obtained in step S3 is added dropwise to an equal volume of alkaline solution at a dropping rate of 0.5 mL / min, and the pH is adjusted to (9.5±0.1). After continuing to stir the reaction for 1 hour, the mixture is hydrothermally aged at 100° C. for 8 hours. After filtering, washing, drying, and low-temperature calcination at 100° C., a Mg-Al hydrotalcite layer is formed on the surface of the silica microspheres, which is a composite filler.

[0032] Preparation Example 5 The composite filler differs from Preparation Example 1 in that the preparation method does not perform the coupling agent pretreatment in step S2, and the other steps are the same as those in Preparation Example 1.

[0033] Preparation Example 6 The composite filler is different from the one in Preparation Example 1 in that its preparation method includes the following steps: S: KH-550 was dissolved in 80% ethanol solution to form a 1 wt% coupling agent solution, and mesoporous silica was dispersed in the coupling agent solution at a material-liquid ratio of 1:12. After ultrasonic dispersion at 300W for 6 minutes, the mixture was reacted at 50°C for 4 hours, centrifuged and washed, and vacuum dried at 60°C for 10 hours to obtain pretreated silica; S2: dissolving Mg(NO3)2 and Al(NO3)3 in a molar ratio of 2:1 in water to form a mixed salt solution, wherein the total concentration of the mixed salt solution is 0.2 mol / L, and dispersing the pretreated silica microspheres obtained in step S2 in the mixed salt solution at a material-liquid ratio of 1:10, heating to 60°C and stirring uniformly to form a mixed solution; S3: Sodium hydroxide and sodium carbonate are dissolved in water to form an alkaline solution. Under stirring, the mixed solution obtained in step S3 is added dropwise to an equal volume of alkaline solution at a dropping rate of 0.5 mL / min, and the pH is adjusted to (9.5±0.1). After continuing to stir the reaction for 0.5 h, the mixture is hydrothermally aged at 100° C. for 10 h. After filtering, washing, and drying, it is low-temperature calcined at 120° C. to form a Mg-Al hydrotalcite layer on the surface of the silica microspheres, which is a composite filler.

[0034] Preparation Example 7 The composite filler is different from the one in Preparation Example 1 in that its preparation method includes the following steps: S1: 2-mercapto-5-methylbenzimidazole was dissolved in 80% ethanol solution to form a corrosion inhibitor solution, the concentration of 2-mercapto-5-methylbenzimidazole was 0.01 mol / L, 10 g of mesoporous silica was added to 50 mL of the corrosion inhibitor solution, 0.3 wt % of sodium dodecyl sulfate was added, and the solution was ultrasonicated at 30° C. and 300 W for 2 h. After centrifugation and alcohol washing, the solution was vacuum dried at 60° C. for 8 h to obtain silica microspheres loaded with corrosion inhibitor; S2: KH-550 was dissolved in 80% ethanol solution to form a 1 wt% coupling agent solution, and silica microspheres were dispersed in the coupling agent solution at a material-liquid ratio of 1:12. After ultrasonic dispersion at 300W for 6 minutes, the mixture was reacted at 50°C for 4 hours. After centrifugal washing, the mixture was vacuum dried at 60°C for 10 hours to obtain a composite filler. Example

[0035] Example 1 A highly corrosion-resistant PVC pipe, the raw materials and amounts of which are shown in Table 1, wherein the compatibilizer is chlorinated polyethylene, the composite filler is prepared according to Preparation Example 1, the lubricant is PE wax and magnesium stearate in a mass ratio of 1:2, and the antioxidant is antioxidant 1010.

[0036] Table 1 The method for preparing the above-mentioned highly corrosion-resistant PVC pipe comprises the following steps: S1: PVC resin, polyvinylidene fluoride-hexafluoropropylene copolymer, compatibilizer, composite filler and processing aid were weighed according to the raw material ratio, added into a high-speed mixer at 1200 rpm and mixed for 10 min, then hot-mixed in a hot mixer at 110° C., and then cold-mixed in a cold mixer at 30° C. to obtain a blend; S2: The blend is fed into a screw extruder for extrusion molding, with the feed screw speed set at 50 r / min, the main screw speed at 500 r / min, the temperature of zones 1 to 3 at 190°C, the temperature of zones 4 to 6 at 210°C, and the temperature of zones 7 to 9 at 200°C. After extrusion through a mold, the blend is vacuum cooled and sized to obtain a highly corrosion-resistant PVC pipe with an outer diameter of (102 ± 0.1) mm and a wall thickness of (5.5 ± 0.1) mm.

[0037] Example 2 A highly corrosion-resistant PVC pipe, which differs from Example 1 in that the raw materials and amounts are as shown in Table 1, wherein the composite filler is prepared according to Preparation Example 2, and the lubricant is PE wax and magnesium stearate in a mass ratio of 1:1; The method for preparing the above-mentioned highly corrosion-resistant PVC pipe comprises the following steps: S1: PVC resin, polyvinylidene fluoride-hexafluoropropylene copolymer, compatibilizer, composite filler and processing aid were weighed according to the raw material ratio, added into a high-speed mixer and mixed at 1200 rpm for 10 min, then hot-mixed in a hot mixer at 120° C., and then cold-mixed in a cold mixer at 40° C. to obtain a blend; S2: The blend is fed into a screw extruder for extrusion molding, with the feed screw speed set at 50 r / min, the main screw speed at 500 r / min, the temperature of zones 1 to 3 at 190°C, the temperature of zones 4 to 6 at 210°C, and the temperature of zones 7 to 9 at 200°C. After extrusion through a mold, the blend is vacuum cooled and sized to obtain a highly corrosion-resistant PVC pipe with an outer diameter of (102 ± 0.1) mm and a wall thickness of (5.5 ± 0.1) mm.

[0038] Example 3 A highly corrosion-resistant PVC pipe, which differs from Example 1 in that the raw materials and amounts are as shown in Table 1, wherein the composite filler is prepared according to Preparation Example 3, and the lubricant is PE wax and magnesium stearate in a mass ratio of 1:3; The method for preparing the above-mentioned highly corrosion-resistant PVC pipe comprises the following steps: S1: PVC resin, polyvinylidene fluoride-hexafluoropropylene copolymer, compatibilizer, composite filler and processing aid were weighed according to the raw material ratio, added into a high-speed mixer and mixed at 1200 rpm for 10 min, then hot-mixed in a hot mixer at 110° C., and then cold-mixed in a cold mixer at 35° C. to obtain a blend; S2: The blend is fed into a screw extruder for extrusion molding, with the feed screw speed set at 50 r / min, the main screw speed at 500 r / min, the temperature of zones 1 to 3 at 190°C, the temperature of zones 4 to 6 at 210°C, and the temperature of zones 7 to 9 at 200°C. After extrusion through a mold, the blend is vacuum cooled and sized to obtain a highly corrosion-resistant PVC pipe with an outer diameter of (102 ± 0.1) mm and a wall thickness of (5.5 ± 0.1) mm.

[0039] Example 4 A highly corrosion-resistant PVC pipe, which differs from Example 1 in that the raw materials and amounts are as shown in Table 1, wherein the composite filler is prepared according to Preparation Example 4, and the lubricant is PE wax and magnesium stearate in a mass ratio of 1:2.5; The method for preparing the above-mentioned highly corrosion-resistant PVC pipe comprises the following steps: S1: PVC resin, polyvinylidene fluoride-hexafluoropropylene copolymer, compatibilizer, composite filler and processing aid were weighed according to the raw material ratio, added into a high-speed mixer at 1200 rpm and mixed for 10 min, then hot-mixed in a hot mixer at 115° C., and then cold-mixed in a cold mixer at 40° C. to obtain a blend; S2: The blend is fed into a screw extruder for extrusion molding, with the feed screw speed set at 50 r / min, the main screw speed at 500 r / min, the temperature of zones 1 to 3 at 190°C, the temperature of zones 4 to 6 at 210°C, and the temperature of zones 7 to 9 at 200°C. After extrusion through a mold, the blend is vacuum cooled and sized to obtain a highly corrosion-resistant PVC pipe with an outer diameter of (102 ± 0.1) mm and a wall thickness of (5.5 ± 0.1) mm.

[0040] Example 5 A highly corrosion-resistant PVC pipe is different from Example 1 in that the composite filler in the raw material is prepared by Preparation Example 5, and the other steps are the same as Example 1.

[0041] Example 6 A highly corrosion-resistant PVC pipe is different from Example 1 in that the lubricant in the raw material is only PE wax, and the other steps are the same as Example 1.

[0042] Example 7 A highly corrosion-resistant PVC pipe is different from Example 1 in that the lubricant in the raw material is only magnesium stearate, and the other steps are the same as Example 1.

[0043] Comparative Example Comparative Example 1 A highly corrosion-resistant PVC pipe is different from Example 1 in that the original composite filler is prepared by Preparation Example 6, and the other steps are the same as Example 1.

[0044] Comparative Example 2 A highly corrosion-resistant PVC pipe is different from Example 1 in that the composite filler in the raw material is prepared by Preparation Example 7, and the other steps are the same as Example 1.

[0045] Comparative Example 3 A highly corrosion-resistant PVC pipe is different from Example 1 in that no composite filler is added, and the composite filler in the raw material is replaced with PVC resin of equal mass. Other steps are the same as Example 1.

[0046] Comparative Example 4 A highly corrosion-resistant PVC pipe is different from Example 1 in that no polyvinylidene fluoride-hexafluoropropylene copolymer is added, and the polyvinylidene fluoride-hexafluoropropylene copolymer in the raw material is replaced with PVC resin of equal mass. Other steps are the same as Example 1.

[0047] Performance testing The following relevant performance test tests were performed on a high corrosion-resistant PVC pipe prepared in Examples 1-7 and Comparative Examples 1-4. Each test was performed 3 times, and the average value of the 3 test results was taken as the final result and the final result was recorded in Table 2-3.

[0048] 1. Impact resistance: Refer to the relevant provisions of GB / T 4219.1-2008 "Industrial Unplasticized Polyvinyl Chloride (PVC-U) Piping Systems Part 1: Pipes" and use A-notch to test the notched impact strength of the specimens. Perform a hydraulic test at 20°C and 40 MPa for 1 hour to observe whether the specimens have cracks or leakage. 2. Corrosion resistance durability test: Prepare 50wt% NaCl solution, 10wt% sulfuric acid solution, and 40wt% sodium hydroxide solution as corrosive media, immerse the specimens in each of the corrosive media for corrosion treatment, place them in a 60°C constant temperature oven for 200 hours, rinse with water, and dry with hot air. The mass and tensile properties of the specimens before and after corrosion treatment are tested. The tensile properties were tested using a universal testing machine. Referencing the relevant provisions of GB / T 1040-2022, the tensile strength test was carried out at a test temperature of 25°C and a tensile rate of 50 mm / min. The tensile strength loss rate of each group of specimens was used to characterize the degree of corrosion of the specimens in the medium. Tensile strength loss rate = (initial tensile strength - tensile strength after corrosion) / initial tensile strength × 100%; Mass loss rate = (initial sample mass - post-corrosion sample mass) / initial sample mass × 100%.

[0049] Table 2 Table 3 According to the performance test results of Examples 1-4 in Table 2 and Table 3, it can be seen that the notched impact strength of the high corrosion-resistant PVC pipe of the present application reaches 5.1-5.7 KJ / m 2 At 20°C and 40MPa hydraulic pressure for 1h, it can maintain structural stability, maintain high corrosion resistance in strong acid, strong alkali and high-concentration salt water systems, and maintain long-term stability of structure and mechanical properties.

[0050] According to the performance results of Example 1 and Comparative Examples 1-3, it can be seen that the present application obtains a composite filler with a sea urchin shape by forming a lamellar Mg-Al hydrotalcite layer in a radioactive in-situ vertical growth on the surface of the mesoporous silica loaded with a corrosion inhibitor. It can not only significantly improve the impact resistance of the PVC pipe, but also effectively suppress the penetration of the corrosive medium, significantly improve the corrosion resistance of the PVC pipe in highly corrosive media. The addition of the corrosion inhibitor further improves the corrosion resistance of the composite filler in the PVC pipe. This is because the composite filler of this special structure can form a strong mechanical interlocking effect with the organic matrix, reduce the possibility of agglomeration of the inorganic filler, so that the dispersion uniformity of the inorganic filler in the PVC matrix is ​​improved, effectively reduce the deterioration of the interface compatibility between the inorganic filler and the organic matrix under a strong corrosive environment, significantly reduce the stress concentration caused by the addition of the inorganic filler, and can maintain the mechanical properties durability of the PVC pipe under a highly corrosive environment.

[0051] In Example 5, the mesoporous silica surface was not modified with an aminosilane coupling agent. The growth of Mg-Al hydrotalcite on the surface of the silica microspheres mainly relied on physical adsorption. The surface of the silica microspheres introduced with -NH2 could connect with the Mg-Al hydrotalcite through covalent bonds, attracting denser Mg-Al hydrotalcite to grow vertically in situ on the silica surface in a radioactive manner, resulting in stronger interfacial bonding and more significant effects.

[0052] Comparative Example 4 does not add polyvinylidene fluoride-hexafluoropropylene copolymer. It can be seen that its corrosion resistance and mechanical property stability in a highly corrosive environment are significantly affected. This is because the chemical barrier formed by the polyvinylidene fluoride-hexafluoropropylene copolymer and the physical path barrier formed by the composite filler work together to form a stable corrosion-resistant barrier in the PVC pipe, inhibiting the penetration and diffusion of the corrosive medium, thereby improving the service life of the PVC pipe in a highly corrosive environment.

[0053] According to the performance test results of Examples 1 and 6-7, it can be seen that when PE wax and magnesium stearate are mixed as lubricants, the lubrication effect is better, which can better promote the uniform dispersion of the composite filler in the PVC matrix, so that the various raw material components can better cooperate with each other, and improve the application effect of PVC pipes in application scenarios requiring stronger corrosion resistance and impact resistance.

[0054] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A highly corrosion-resistant PVC pipe, characterized in that: The raw materials include 80-120 parts by weight of PVC resin, 5-7 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 3-5 parts of compatibilizer, 7-10 parts of composite filler and 2-3 parts of processing aid; The composite filler comprises mesoporous silica, a corrosion inhibitor and Mg-Al hydrotalcite.

2. The highly corrosion-resistant PVC pipe according to claim 1, characterized in that: The preparation method of the composite filler comprises the following steps: S1: adding mesoporous silica to an ethanol solution containing a corrosion inhibitor, adding 0.3-0.8 wt% sodium dodecyl sulfate, ultrasonicating at 30-50°C, centrifuging, washing, and drying to obtain silica microspheres loaded with the corrosion inhibitor; S2: dissolving Mg(NO3)2 and Al(NO3)3 in water to form a mixed salt solution, wherein the molar ratio of Mg(NO3)2 and Al(NO3)3 is (2-3):1, and the total concentration of the mixed salt solution is 0.1-0.2 mol / L, dispersing silica microspheres in the mixed salt solution, and heating and stirring to form a mixed solution; S3: The mixed solution is added dropwise to a mixed alkaline solution containing sodium hydroxide and sodium carbonate, the pH is adjusted to (9.5±0.1), the mixture is stirred and aged, filtered, washed, dried, and then calcined at 100-120°C to form a Mg-Al hydrotalcite layer on the surface of the silica microspheres, which is the composite filler.

3. The highly corrosion-resistant PVC pipe according to claim 2, characterized in that: The silica microspheres are pretreated as follows before being dispersed in the mixed salt solution: The silica microspheres are dispersed in a 1-2% silane coupling agent solution, subjected to ultrasonic dispersion for 6-8 minutes, reacted at 40-50° C., centrifuged, washed, and dried to obtain pretreated silica microspheres.

4. The highly corrosion-resistant PVC pipe according to claim 3, characterized in that: The silane coupling agent is an aminosilane coupling agent selected from KH-550.

5. The highly corrosion-resistant PVC pipe according to claim 1, characterized in that: The corrosion inhibitor is selected from any one of 2-mercapto-5-methylbenzimidazole and 5-methoxy-2-mercaptobenzimidazole.

6. The highly corrosion-resistant PVC pipe according to claim 1, characterized in that: The compatibilizer is chlorinated polyethylene.

7. The highly corrosion-resistant PVC pipe according to claim 1, characterized in that: The processing aid includes a lubricant, and the lubricant is PE wax and magnesium stearate in a mass ratio of 1:(1-3).

8. The method for preparing a highly corrosion-resistant PVC pipe according to any one of claims 1 to 7, characterized in that: The following steps are involved: PVC resin, polyvinylidene fluoride-hexafluoropropylene copolymer, compatibilizer, composite filler and processing aid are weighed and mixed according to the raw material ratio, hot-mixed in a hot mixer at 110-120°C, and then cold-mixed in a cold mixer at 30-40°C to obtain a blend; the blend is sent to a screw extruder for extrusion molding, and after extrusion through a mold, vacuum cooling is performed to determine the size to obtain the product.

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