Polyvinyl chloride double-walled corrugated pipe and method for producing the same

Abstract

The application discloses a polyvinyl chloride double-wall corrugated pipe and a preparation method thereof, and relates to the field of PVC pipes.The polyvinyl chloride double-wall corrugated pipe comprises an integrally-formed inner layer and an outer layer, and the inner layer and the outer layer comprise the following raw materials in parts by weight: 100 parts of polyvinyl chloride, 4-8 parts of chlorinated polyethylene, 4.5-8.5 parts of an acrylate core-shell toughening agent, 0.3-1.0 parts of a lubricant, 3.8-7.0 parts of a heat stabilizer, and 20-30 parts of a filler; the acrylate core-shell toughening agent comprises a core layer and a shell layer coated on the core layer, and the preparation raw materials of the core layer comprise butyl acrylate, isooctyl acrylate, a crosslinking agent, silane-modified nano silicon dioxide, acrylamide and a first initiator. Through the synergistic effect of the chlorinated polyethylene and the acrylate core-shell toughening agent, a multi-scale toughening network is formed in the PVC matrix, and the impact resistance of the pipe in a normal temperature and low-temperature environment is significantly improved.

Description

Technical Field

[0001] This application relates to the field of PVC materials, and in particular to a double-walled corrugated pipe of polyvinyl chloride and its preparation method. Background Technology

[0002] Double-wall corrugated pipe is a new type of pipe with a ring-shaped outer wall and a smooth inner wall. Due to the high ring stiffness provided by the corrugated outer wall and the low fluid resistance resulting from the smooth inner wall, it has been widely used in municipal drainage, telecommunications engineering, power conduits, and building sewage systems. Currently, the main base materials of double-wall corrugated pipes include two main categories: high-density polyethylene (HDPE) and polyvinyl chloride (PVC).

[0003] Polyvinyl chloride (PVC) double-wall corrugated pipes play an important role in municipal drainage and communication engineering due to their advantages such as light weight, corrosion resistance, good flame retardancy, excellent electrical insulation, convenient installation, and relatively low cost. However, PVC material itself has a significant inherent defect—high brittleness, especially at low temperatures. The glass transition temperature (Tg) of PVC is approximately 70-85℃, much higher than room temperature. This means that PVC is in a glassy state at room temperature, with restricted molecular chain movement, resulting in obvious brittleness. When the ambient temperature decreases further, the brittleness of PVC intensifies. When the pipes are subjected to external impacts (such as falling rocks during construction, collisions during transportation, and uneven foundation settlement during use), they are extremely prone to breakage or cracking, seriously affecting the service life of the pipes and the safety of the project.

[0004] To improve the toughness of PVC materials, existing technologies typically employ the addition of impact modifiers. Commonly used impact modifiers include acrylic processing aids (ACRs). Ordinary ACRs primarily promote PVC plasticization, improve melt flow, and increase melt strength, significantly improving the processing performance of PVC pipes. However, the toughening effect of commercially available ordinary ACRs is limited, especially at low temperatures. Their improvement in the impact resistance of pipes is insufficient to meet the requirements for high impact resistance, thus restricting their application scenarios.

[0005] Therefore, how to develop a method that can significantly improve the low-temperature impact resistance of PVC double-wall corrugated pipes is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The main purpose of this application is to propose a polyvinyl chloride double-wall corrugated pipe and its preparation method, which aims to solve the problem of poor low-temperature impact resistance of existing PVC double-wall corrugated pipes.

[0007] In a first aspect, this application provides a polyvinyl chloride double-wall corrugated pipe, comprising an integrally formed inner layer and an outer layer, wherein the inner layer and the outer layer comprise the following raw materials in parts by weight: 100 parts of polyvinyl chloride, 4-8 parts of chlorinated polyethylene, 4.5-8.5 parts of acrylate core-shell toughening agent, 0.3-1.0 parts of lubricant, 3.8-7.0 parts of heat stabilizer, and 20-30 parts of filler; The acrylate core-shell toughening agent includes a core layer and a shell layer covering the core layer. The raw materials for preparing the core layer include butyl acrylate, isooctyl acrylate, crosslinking agent, silane-modified nano-silica, acrylamide, and a first initiator. The raw materials for preparing the shell include water, a second initiator, and methyl methacrylate.

[0008] In this invention, polyvinyl chloride (PVC) is used as the matrix, and chlorinated polyethylene and acrylate core-shell toughening agents are introduced for synergistic toughening modification to improve the impact resistance of the pipe at low temperatures. Chlorinated polyethylene and PVC blends to form an interpenetrating polymer network. When subjected to external force, this interpenetrating network structure deforms and releases a large amount of energy. The shell layer of the acrylate core-shell toughening agent has good compatibility with the PVC matrix resin, ensuring the dispersibility of the acrylate core-shell toughening agent. Impact energy is absorbed through the shear yield deformation of the core layer rubber elastomer. Chlorinated polyethylene and acrylate core-shell toughening agents form a synergistic toughening network to improve the impact resistance of the pipe at low temperatures.

[0009] The core layer of this acrylate-based core-shell toughening agent uses butyl acrylate and isooctyl acrylate as comonomers, both of which have low glass transition temperatures (Tg). The resulting core layer exhibits excellent low-temperature rubber elasticity. Silane-modified nano-silica is dispersed within the core layer. A silane coupling agent grafts organic functional groups onto the surface of the nano-silica, achieving uniform dispersion and strong interfacial bonding of the nanoparticles within the core layer. The nano-silica acts as a nano-reinforcing agent within the core layer's rubber matrix. Acrylamide is also introduced into the core layer; its amide groups enhance the interaction and interfacial bonding between the core and shell layers. The shell layer uses methyl methacrylate (PMMA), which exhibits good thermodynamic compatibility with PVC, ensuring uniform dispersion of the toughening agent and efficient stress transfer within the PVC.

[0010] Optionally, the weight ratio of the chlorinated polyethylene to the acrylate core-shell toughening agent is (6~7):(5.5~6.5).

[0011] By adopting the above technical solution, chlorinated polyethylene and acrylate core-shell toughening agents can achieve a better synergistic toughening effect. Chlorinated polyethylene provides a large-scale silvering toughening mechanism, while acrylate core-shell toughening agents provide a small-scale shear yield toughening mechanism. The two work together to achieve multi-scale toughening, so as to effectively improve the impact resistance of pipes at low temperatures.

[0012] Optionally, the preparation method of the acrylate core-shell toughening agent includes the following steps: S1. Mix water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent and silane-modified nano silica dispersion, ultrasonically disperse, stir under nitrogen protection atmosphere, control temperature at 60~75℃, add first initiator, stir for 2~3h, add acrylamide, stir for 0.5~1.0h to obtain core layer latex; S2. Mix water, the second initiator and the core latex obtained in step S1, stir under a nitrogen protective atmosphere, add methyl methacrylate dropwise, control the temperature at 70~80℃, stir the reaction, cool down to 60~65℃, demulsify with an inorganic salt aqueous solution, filter, wash and dry to obtain the acrylate core-shell toughening agent.

[0013] By adopting the above technical solution, step S1 uses emulsion polymerization to first polymerize butyl acrylate and isooctyl acrylate under the action of a crosslinking agent to form a crosslinked elastomer core layer. Silane-modified nano-silica is dispersed in the monomer emulsion. Acrylamide is added only after the main polymerization reaction of the core layer is basically completed, so it will not interfere with the formation of the elastomer network inside the core layer, and at the same time provides a better interfacial bonding point for subsequent shell coating. Step S2 uses seed emulsion polymerization, using the core layer latex as a seed, to initiate the polymerization of methyl methacrylate on its surface to form a complete PMMA shell coating.

[0014] Optionally, the preparation method of the acrylate core-shell toughening agent includes the following steps: S11. Disperse silane-modified nano-silica in water to obtain a silane-modified nano-silica dispersion. Divide the silane-modified nano-silica dispersion into three parts to obtain the first part of the silane-modified nano-silica dispersion, the second part of the silane-modified nano-silica dispersion, and the third part of the silane-modified nano-silica dispersion. S12. Mix water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent and the first part of silane-modified nano silica dispersion, ultrasonically disperse, stir under nitrogen protection atmosphere, control the temperature at 60~75℃, add the first initiator, stir for 2~3h, add acrylamide and the second part of silane-modified nano silica dispersion, stir for 0.5~1.0h to obtain core layer latex; S2. Mix water, the second initiator and the core layer latex obtained in step S12, stir under a nitrogen protective atmosphere, add methyl methacrylate dropwise, add the third part of silane-modified nano silica dispersion, control the temperature at 70~80℃, stir the reaction, cool down to 60~65℃, use an inorganic salt aqueous solution to break the emulsion, filter, wash and dry to obtain the acrylate core-shell toughening agent.

[0015] By employing the above technical solution, silane-modified nano-silica is divided into three parts and added stepwise at different stages of the core-shell toughening agent preparation process. This allows the nano-silica to achieve a gradient distribution in different regions of the core-shell structure, thereby further improving the toughening efficiency. The first part of nano-silica is added during the bulk polymerization stage of the core layer, dispersing in the core region of the core layer and playing a role in energy dissipation. The second part is added during the acrylamide grafting stage in the outer region of the core layer, synergistically improving the core-shell interface with the acrylamide segments. The third part is added along with methyl methacrylate during the shell polymerization stage, being encapsulated in the PMMA shell, improving the hardness and wear resistance of the shell, while simultaneously enhancing the interfacial strength between the shell and the PVC matrix.

[0016] Optionally, in step S11, the weight ratio of the first silane-modified nano silica dispersion, the second silane-modified nano silica dispersion, and the third silane-modified nano silica dispersion is (4~6):(2~4):(1~3).

[0017] Preferably, in step S11, the weight ratio of the first silane-modified nano-silica dispersion, the second silane-modified nano-silica dispersion, and the third silane-modified nano-silica dispersion is 5:3:2.

[0018] By adopting the above technical solution and controlling the ratio of the three parts of silane-modified nano-silica, the nano-silica can be gradient-distributed in different regions of the core-shell structure, thereby further improving the toughening efficiency.

[0019] Optionally, in step S1, styrene is added along with acrylamide, and the weight ratio of acrylamide to styrene is (3.5~4.5):1.

[0020] Preferably, in step S1, styrene is added along with acrylamide, and the weight ratio of acrylamide to styrene is 4:1.

[0021] By adopting the above technical solution, after styrene and acrylamide form copolymer segments on the outer surface of the core layer, a transition layer with intermediate stiffness can be established between the elastic matrix of the core layer and the rigid PMMA of the shell layer, forming a three-layer stiffness gradient structure of "soft core-semi-rigid transition layer-hard shell". This gradient structure allows stress to be gradually dispersed and buffered when external impact force is transmitted from the hard shell layer to the flexible core layer, avoiding stress concentration and interface debonding caused by abrupt changes in stiffness at the soft-hard interface, thereby further improving the toughening efficiency of the core-shell toughening agent. Controlling the weight ratio of acrylamide to styrene ensures that the transition layer is dominated by acrylamide and supplemented by styrene, maintaining good polar interaction between the transition layer and the shell layer while providing an appropriate stiffness gradient.

[0022] Optionally, in step S1, the weight ratio of water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent, silane-modified nano-silica dispersion, first initiator, and acrylamide is (65~75):(0.5~1.5):(0.5~0.8):(55~65):(35~45):(0.5~1.5):(25~35):(0.4~0.6):(2.5~3.5); In step S2, the weight ratio of water, the second initiator, the core layer latex, and methyl methacrylate is 100:(0.2~0.4):(105~125):(25~35).

[0023] Preferably, in step S1, the weight ratio of water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent, silane-modified nano-silica dispersion, first initiator, acrylamide, and the mixture in step S2 is 70:1:0.6:60:40:1:30:0.5:3; wherein, in the silane-modified nano-silica dispersion, the mass percentage of silane-modified nano-silica is 15~17wt%.

[0024] In step S2, the weight ratio of water, the second initiator, and methyl methacrylate is 100:0.3:30.

[0025] By adopting the above technical solution and controlling the ratio of raw materials used in the core layer and shell layer, it is ensured that the core layer has sufficient rubber elastomer to provide efficient toughening, and the shell layer has a moderate thickness, which can fully cover the core layer to achieve good interfacial compatibility, and will not reduce the toughening effect of the core layer due to excessive shell layer thickness.

[0026] Optionally, in step S1, the emulsifier is sodium dodecyl sulfate, the alkalinity regulator is sodium bicarbonate, the crosslinking agent is ethylene glycol dimethacrylate, and the first initiator is potassium persulfate.

[0027] In step S2, the second initiator is potassium persulfate. Optionally, the lubricant comprises paraffin and stearic acid, and the filler comprises light calcium carbonate.

[0028] By adopting the above technical solutions, paraffin wax can reduce the friction between the PVC melt and the processing equipment, preventing sticking to the mold; stearic acid can reduce the internal friction between PVC molecular chains, promoting melt flow. The combined use of paraffin wax and stearic acid improves processing fluidity, reduces processing torque and energy consumption, and ensures the quality of the pipes.

[0029] Optionally, the heat stabilizer includes lead salt composite stabilizer, tribasic lead sulfate, and calcium stearate.

[0030] By adopting the above technical solution, the lead salt composite stabilizer, as the main stabilizer, can effectively inhibit the thermal degradation and discoloration of PVC during high-temperature processing. Tribasic lead sulfate, as an auxiliary stabilizer, forms a multi-element stabilizing system with the lead salt composite stabilizer, enhancing thermal stability and extending the thermal stability time during pipe processing. Calcium stearate has both auxiliary stabilizing and lubricating functions. The three components work synergistically to form a highly efficient composite thermal stabilizing system, ensuring the quality and performance of the pipes.

[0031] Secondly, this application provides a method for preparing a polyvinyl chloride double-wall corrugated pipe as described in any of the above claims, comprising the following steps: Step 1: Mix the raw materials corresponding to the inner and outer layers separately, stir at high speed, control the temperature ≤55℃, stir at low speed to obtain the outer layer premix and the inner layer premix; Step 2: Add the outer layer premix and the inner layer premix to the corresponding screw extruders for melting and extrusion, and form them into an integral tube blank with inner and outer layers through a mold. Vacuum sizing, cooling and shaping of the tube blank, and cutting are then performed to obtain the polyvinyl chloride double-wall corrugated pipe.

[0032] By adopting the above technical solution, in step one, the PVC resin particles are first subjected to high-speed shearing and frictional heat to fully absorb plasticizers and various additives, achieving uniform dispersion and initial gelation of each component. Subsequently, low-speed stirring is used for cooling to prevent pre-decomposition or agglomeration of the material due to high temperature, ensuring the fluidity and uniformity of the premix and facilitating subsequent metering and feeding. In step two, the inner and outer premixes are melted and plasticized separately through their respective screw extruders, and then combined in a co-extrusion die to form an integral pipe blank, achieving integrated molding of the inner and outer layers. The pipe blank undergoes vacuum sizing and cooling, adhering tightly to the inner wall of the sizing sleeve under vacuum negative pressure to ensure the dimensional accuracy and roundness of the pipe. Simultaneously, cooling water rapidly solidifies and shapes the pipe, maintaining its integrity.

[0033] In summary, this application includes at least one of the following beneficial technical effects: (1) This application forms a multi-scale toughening network in the PVC matrix through the synergistic effect of chlorinated polyethylene and acrylate core-shell toughening agents, which significantly improves the impact resistance of the pipe in normal and low temperature environments.

[0034] (2) Silane-modified nano-silica was introduced into the core layer of the core-shell toughening agent. The nanoparticles played a nano-reinforcing role in the core layer of the rubber elastomer. Acrylamide was also introduced into the core layer, and its amide groups enhanced the interaction and interfacial bonding between the core layer and the shell layer. While the toughness of the pipe was greatly improved, the ring stiffness could still meet the requirements, achieving a good balance between rigidity and toughness. Detailed Implementation

[0035] The present application will be further described in detail below with reference to embodiments. All raw materials involved in this application are commercially available, wherein... Nano-silica, Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., specific surface area 145~160m² 2 / g; Polyvinyl chloride, Anhui Huasheng Co., Ltd., SG-5 type; Chlorinated polyethylene, Weifang Yaxing Chemical Co., Ltd., brand name WEIPREN@RESIN 6000; Paraffin wax, Xintuo Chemical (Tianjin) Co., Ltd., molecular formula C 21 H 27 NO3; Lead salt composite stabilizer, Hangzhou Lin'an Huali Plastics Co., Ltd., product model SCD-318; Calcium stearate, Zhongshan Huamingtai Technology Co., Ltd., model BS-3818; Light calcium carbonate, Hubei Guangao Biotechnology Co., Ltd., purity 99wt%. Preparation Example 1

[0036] A method for preparing an acrylate core-shell toughening agent includes the following steps: S1. Mix 70 parts by weight of deionized water, 1 part by weight of sodium dodecyl sulfate, 0.6 parts by weight of sodium bicarbonate, 60 parts by weight of butyl acrylate, 40 parts by weight of isooctyl acrylate, 1 part by weight of ethylene glycol dimethacrylate, and 30 parts by weight of silane-modified nano silica dispersion (5 parts by weight of silane-modified nano silica were added to 25 parts by weight of deionized water and ultrasonically dispersed for 20 min). Ultrasonically disperse for 30 min. Under a nitrogen protective atmosphere, stir at 300 rpm and heat to 65°C. Add 0.5 parts by weight of potassium persulfate (first initiator) and continue stirring at 300 rpm for 2.5 h. Then add 3 parts by weight of acrylamide and continue stirring at 300 rpm for 0.6 h to obtain the core layer latex. S2. Add 100 parts by weight of deionized water and 0.3 parts by weight of potassium persulfate (second initiator) to the core latex obtained in step S1. Under a nitrogen protective atmosphere, stir at 300 rpm and add 30 parts by weight of methyl methacrylate dropwise, controlling the dropping rate to about 0.5 parts by weight / min. Control the temperature at 75℃ and stir at 300 rpm for 3 hours. Cool down to 65℃ and add 5% calcium chloride aqueous solution dropwise to demulsify. When the supernatant becomes clear and the solid-liquid separation is obvious after standing, the demulsification is complete. Stop adding 5% calcium chloride aqueous solution, filter, and wash the obtained filter cake with deionized water 3 times. Filter the resulting suspension again, wash the obtained filter cake with deionized water 3 times, filter, and dry the obtained filter cake under vacuum at 70℃ to constant weight to obtain an acrylate core-shell toughening agent.

[0037] In step S1, the preparation method of silane-modified nano-silica includes the following steps: (1) Prepare materials by mixing silane coupling agent KH-570, deionized water, anhydrous ethanol and nano silica in a mass ratio of 1:5:40:25; mix deionized water and anhydrous ethanol and stir at 200 rpm for 10 min to obtain an ethanol solution; add silane coupling agent KH-570 to the ethanol solution and stir at 200 rpm for 10 min to obtain a modified solution; (2) Dry the nano-silica at 100℃ for 1.5h, add the dried nano-silica to the modified liquid obtained in step (1), disperse ultrasonically for 30min, control the temperature at 80℃, stir at 200rpm for 10h, filter, and dry the obtained reaction product under vacuum at 70℃ for 8h to obtain silane modified nano-silica. Preparation Example 2

[0038] A method for preparing an acrylate core-shell toughening agent includes the following steps: S11. Silane-modified nano-silica was prepared according to the preparation method of silane-modified nano-silica in Preparation Example 1. 5 parts by weight of silane-modified nano-silica were added to 25 parts by weight of deionized water and ultrasonically dispersed for 20 min to obtain a silane-modified nano-silica dispersion. The silane-modified nano-silica dispersion was dispersed into three parts by weight ratio of 5:3:2 to obtain the first silane-modified nano-silica dispersion (15 parts by weight), the second silane-modified nano-silica dispersion (9 parts by weight), and the third silane-modified nano-silica dispersion (6 parts by weight). S12. Mix 70 parts by weight of deionized water, 1 part by weight of sodium dodecyl sulfate, 0.6 parts by weight of sodium bicarbonate, 60 parts by weight of butyl acrylate, 40 parts by weight of isooctyl acrylate, 1 part by weight of ethylene glycol dimethacrylate, and 15 parts by weight of the first silane-modified nano silica dispersion. Sonicate the mixture for 30 min. Stir at 300 rpm under a nitrogen atmosphere and heat to 65°C. Add 0.5 parts by weight of potassium persulfate (first initiator) and continue stirring at 300 rpm for 2.5 h. Add 3 parts by weight of acrylamide and 9 parts by weight of the second silane-modified nano silica dispersion and continue stirring at 300 rpm for 0.6 h to obtain the core layer latex. S2. Add 100 parts by weight of deionized water and 0.3 parts by weight of potassium persulfate (second initiator) to the core latex obtained in step S1. Under a nitrogen protective atmosphere, stir at 300 rpm, add 30 parts by weight of methyl methacrylate (controlling the dropping rate to about 0.5 parts by weight / min), and add 6 parts by weight of the third silane-modified nano silica dispersion. Control the temperature at 75℃, stir at 300 rpm for 3 hours, cool down to 65℃, and add 5% calcium chloride aqueous solution to break the emulsion. When the supernatant becomes clear and the solid-liquid separation is obvious after standing, the emulsion is completely broken. Stop adding 5% calcium chloride aqueous solution, filter, and wash the obtained filter cake with deionized water 3 times. Filter the obtained suspension again, wash the obtained filter cake with deionized water 3 times, filter, and dry the obtained filter cake under vacuum at 70℃ to constant weight to obtain an acrylate core-shell toughening agent. Preparation Example 3

[0039] This preparation example is based on Preparation Example 2, except that step S12 includes the addition of 0.75 parts by weight of styrene; all other steps remain the same as in Preparation Example 2. Specifically, step S12 of this preparation example is as follows: S12. Mix 70 parts by weight of deionized water, 1 part by weight of sodium dodecyl sulfate, 0.6 parts by weight of sodium bicarbonate, 60 parts by weight of butyl acrylate, 40 parts by weight of isooctyl acrylate, 1 part by weight of ethylene glycol dimethacrylate, and 15 parts by weight of the first silane-modified nano silica dispersion. Sonicate the mixture for 30 min. Stir at 300 rpm under a nitrogen atmosphere and heat to 65°C. Add 0.5 parts by weight of potassium persulfate (first initiator) and continue stirring at 300 rpm for 2.5 h. Then add 3 parts by weight of acrylamide, 0.75 parts by weight of styrene, and 9 parts by weight of the second silane-modified nano silica dispersion. Continue stirring at 300 rpm for 0.6 h to obtain the core layer latex. Preparation of Comparative Example 1

[0040] This comparative preparation example is based on Preparation Example 1, except that in step S1, silane-modified nano-silica and acrylamide are not added; the other steps remain the same as in Preparation Example 1. Specifically, step S1 of this comparative preparation example is as follows: S1. Mix 70 parts by weight of deionized water, 1 part by weight of sodium dodecyl sulfate, 0.6 parts by weight of sodium bicarbonate, 60 parts by weight of butyl acrylate, 40 parts by weight of isooctyl acrylate and 1 part by weight of ethylene glycol dimethacrylate, and ultrasonically disperse for 30 min. Under a nitrogen protective atmosphere, stir at 300 rpm, heat to 65°C, add 0.5 parts by weight of potassium persulfate (first initiator), and continue stirring at 300 rpm for 2.5 h to obtain core layer latex. Preparation of Comparative Example 2

[0041] This comparative preparation example is based on Preparation Example 1, except that in step S1, silane-modified nano-silica is not added; all other steps remain the same as in Preparation Example 1. Specifically, step S1 of this comparative preparation example is as follows: S1. Mix 70 parts by weight of deionized water, 1 part by weight of sodium dodecyl sulfate, 0.6 parts by weight of sodium bicarbonate, 60 parts by weight of butyl acrylate, 40 parts by weight of isooctyl acrylate and 1 part by weight of ethylene glycol dimethacrylate, and ultrasonically disperse for 30 min. Under a nitrogen protective atmosphere, stir at 300 rpm and heat to 65°C. Add 0.5 parts by weight of potassium persulfate (first initiator) and continue stirring at 300 rpm for 2.5 h. Then add 3 parts by weight of acrylamide and continue stirring at 300 rpm for 0.6 h to obtain the core layer latex. Preparation of Comparative Example 3

[0042] This comparative example is based on Preparation Example 1, except that acrylamide is not added in step S1, while the other steps remain the same as in Preparation Example 1. Specifically, step S1 of this comparative example is as follows: S1. Mix 70 parts by weight of deionized water, 1 part by weight of sodium dodecyl sulfate, 0.6 parts by weight of sodium bicarbonate, 60 parts by weight of butyl acrylate, 40 parts by weight of isooctyl acrylate, 1 part by weight of ethylene glycol dimethacrylate, and 30 parts by weight of silane-modified nano silica dispersion (5 parts by weight of silane-modified nano silica were added to 25 parts by weight of deionized water and ultrasonically dispersed for 20 min). Ultrasonically disperse for 30 min. Under a nitrogen protective atmosphere, stir at 300 rpm and heat to 65°C. Add 0.5 parts by weight of potassium persulfate (the first initiator) and continue stirring at 300 rpm for 2.5 h to obtain the core layer latex. Example 1

[0043] This embodiment provides a polyvinyl chloride double-wall corrugated pipe and its preparation method. The polyvinyl chloride double-wall corrugated pipe includes an inner layer and an outer layer integrally formed with the inner layer.

[0044] The outer layer raw materials and their proportions (parts by weight) are: 100 parts polyvinyl chloride, 6 parts chlorinated polyethylene, 6.5 parts acrylate core-shell toughening agent prepared in Example 1, 0.3 parts paraffin wax, 0.3 parts stearic acid, 3.5 parts lead salt composite stabilizer, 1.5 parts tribasic lead sulfate, 0.3 parts calcium stearate, and 25 parts light calcium carbonate. The inner layer raw materials and their proportions (parts by weight) are the same as those of the outer layer raw materials.

[0045] The preparation method of polyvinyl chloride double-wall corrugated pipe includes the following steps: Step 1: Add all the raw materials of the outer layer formula to a high-speed mixer and stir at high speed (1000 rpm) for 10 minutes at 120±5℃. Then transfer to a cooling mixer and stir at low speed (50 rpm) until the temperature drops to 50℃. Stop stirring to obtain the outer layer premix. Prepare the inner layer premix in the same way.

[0046] Step 2: Add the outer layer premix and the inner layer premix to the corresponding twin-screw extruders respectively. Set the feeding section temperature to 165℃, the compression section temperature to 175℃, the metering section temperature to 180℃, the die temperature to 188℃, and the screw speed to 25 rpm for melt extrusion. The tube blank with inner and outer layers is formed by co-extrusion die. The tube blank is then vacuum sizing (vacuum pressure 0.06MPa), cooled and shaped, and cut to obtain a PVC double-wall corrugated pipe with an inner diameter of 90mm, an inner wall thickness of 0.8mm, and an outer wall thickness of 1.0mm. Examples 2-4

[0047] Examples 2-4 are based on Example 1, the difference being that the total weight of chlorinated polyethylene and the acrylate core-shell toughening agent obtained in Preparation Example 1 remains unchanged at 12.5 parts in both the outer and inner layer raw materials, while the ratio of their amounts is adjusted; other steps remain the same as in Example 1. Specifically, In Example 2, the weight percentage of chlorinated polyethylene was 4 parts, and the weight percentage of acrylate core-shell toughening agent was 8.5 parts.

[0048] In Example 3, the weight of chlorinated polyethylene was 7 parts and the weight of acrylate core-shell toughening agent was 5.5 parts.

[0049] In Example 4, the weight of chlorinated polyethylene was 8 parts, and the weight of acrylate core-shell toughening agent was 4.5 parts. Examples 5-6

[0050] Examples 5 and 6 are based on Example 3, the difference being that: in both the outer and inner layers, the proportions of polyvinyl chloride (PVC) 100 parts by weight, chlorinated polyethylene (CPE) 7 parts by weight, and acrylate core-shell toughening agent (acrylate) 5.5 parts by weight remain unchanged, while the amounts of other raw materials are adjusted; the other steps are the same as in Example 3. Specifically, In Example 5, the raw materials and their weight parts for the preparation of the outer and inner layers are as follows: 100 parts of polyvinyl chloride, 7 parts of chlorinated polyethylene, 5.5 parts of the acrylate core-shell toughening agent obtained in Preparation Example 1, 0.1 parts of paraffin wax, 0.2 parts of stearic acid, 2.8 parts of lead salt composite stabilizer, 1 part of tribasic lead sulfate, 0.1 parts of calcium stearate, and 20 parts of light calcium carbonate.

[0051] In Example 6, the raw materials and their weight parts for preparing the outer and inner layers are as follows: 100 parts of polyvinyl chloride, 7 parts of chlorinated polyethylene, 5.5 parts of the acrylate core-shell toughening agent obtained in Preparation Example 1, 0.5 parts of paraffin wax, 0.5 parts of stearic acid, 4.5 parts of lead salt composite stabilizer, 2 parts of tribasic lead sulfate, 0.5 parts of calcium stearate, and 30 parts of light calcium carbonate. Examples 7-8

[0052] Examples 7 and 8 are based on Example 3, the difference being that the source of the acrylate core-shell toughening agent is different, while the other steps remain the same as in Example 3. Specifically, In Example 7, an acrylate core-shell toughening agent prepared in Preparation Example 2 was used in equal parts by weight to replace the acrylate core-shell toughening agent prepared in Preparation Example 1.

[0053] In Example 8, the acrylate core-shell toughening agent prepared in Preparation Example 3 was replaced with an equal part by weight of the acrylate core-shell toughening agent prepared in Preparation Example 1. Comparative Example 1

[0054] This comparative example is based on Example 1, except that: in both the outer and inner layers, 6 parts by weight of the acrylate core-shell toughening agent prepared in Preparation Example 1 are used to replace 6 parts by weight of chlorinated polyethylene, and the other steps are the same as in Example 1. Comparative Example 2

[0055] This comparative example is based on Example 1, except that 6.5 parts by weight of chlorinated polyethylene is used to replace 6.5 parts by weight of the acrylate core-shell toughening agent prepared in Preparation Example 1 in both the outer and inner layers. Other steps are the same as in Example 1. Comparative Examples 3-5

[0056] Comparative Examples 3-5 are based on Example 1, except that the source of the acrylate core-shell toughening agent is different; the other steps are the same as in Example 1. Specifically, In Comparative Example 3, the acrylate core-shell toughening agent prepared in Comparative Example 1 was replaced with an equal part by weight of the acrylate core-shell toughening agent prepared in Preparation Example 1.

[0057] In Comparative Example 4, the acrylate core-shell toughening agent prepared in Comparative Example 2 was used in equal parts by weight to replace the acrylate core-shell toughening agent prepared in Preparation Example 1.

[0058] In Comparative Example 5, the acrylate core-shell toughening agent prepared in Comparative Example 3 was used in equal parts by weight to replace the acrylate core-shell toughening agent prepared in Preparation Example 1. Performance test

[0059] The polyvinyl chloride double-wall corrugated pipes obtained in Examples 1-8 and Comparative Examples 1-5 were subjected to drop hammer impact tests and ring stiffness tests. The test results are shown in Table 1 below.

[0060] Drop hammer impact test: Referring to standard B / T 14152-2001, the specimens were conditioned for 60 minutes in air baths at room temperature (23±2℃) and low temperature (-15±2℃). Specimens treated in the room temperature air bath were subjected to a room temperature drop hammer impact test at 23±2℃, and specimens treated in the low temperature air bath were subjected to a low temperature drop hammer impact test at -15±2℃. Each group of tests used 100 specimens. The drop hammer mass was 1.0 kg, and the impact height was 2 m. The true impact rate (TIR) ​​of the specimens was measured, and the average value of the test results was taken. Wherein, TIR = (total number of impact failures / total number of impacts) × 100%.

[0061] Ring stiffness: The ring stiffness (kN / m) of the pipe was measured with reference to GB / T 9647-2003 standard under a 3% deformation. 2 Each group of tests had 10 samples, and the average value of the test results was taken.

[0062] Table 1 Results of impact test and ring stiffness test

[0063] As shown in Table 1, the test results demonstrate that this application achieves a multi-scale toughening network within the PVC matrix through the synergistic effect of chlorinated polyethylene and acrylate-based core-shell toughening agents. Silane-modified nano-silica is introduced into the core layer of the core-shell toughening agent, and these nanoparticles provide nano-reinforcement within the rubber elastomer core layer. Acrylamide is also introduced into the core layer, and its amide groups enhance the interaction and interfacial bonding between the core and shell layers. While significantly improving the pipe's toughness, the ring stiffness still meets requirements, achieving a good balance between rigidity and toughness.

[0064] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the principles of this application should be covered within the scope of protection of this application.

Claims

1. A double-walled corrugated pipe of polyvinyl chloride, characterized in that, It includes an integrally molded inner layer and an outer layer, wherein the inner layer and the outer layer comprise the following raw materials in parts by weight: 100 parts of polyvinyl chloride, 4-8 parts of chlorinated polyethylene, 4.5-8.5 parts of acrylate core-shell toughening agent, 0.3-1.0 parts of lubricant, 3.8-7.0 parts of heat stabilizer, and 20-30 parts of filler; The acrylate core-shell toughening agent includes a core layer and a shell layer covering the core layer. The raw materials for preparing the core layer include butyl acrylate, isooctyl acrylate, crosslinking agent, silane-modified nano-silica, acrylamide, and a first initiator. The raw materials for preparing the shell include a second initiator and methyl methacrylate.

2. The polyvinyl chloride double-wall corrugated pipe according to claim 1, characterized in that, The weight ratio of the chlorinated polyethylene to the acrylate core-shell toughening agent is (6~7):(5.5~6.5).

3. The polyvinyl chloride double-wall corrugated pipe according to claim 1, characterized in that, The preparation method of the acrylate core-shell toughening agent includes the following steps: S1. Mix water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent and silane-modified nano silica dispersion, ultrasonically disperse, stir under nitrogen protection atmosphere, control temperature at 60~75℃, add first initiator, stir for 2~3h, add acrylamide, stir for 0.5~1.0h to obtain core layer latex; S2. Mix water, the second initiator and the core latex obtained in step S1, stir under a nitrogen protective atmosphere, add methyl methacrylate dropwise, control the temperature at 70~80℃, stir the reaction, cool down to 60~65℃, demulsify with an inorganic salt aqueous solution, filter, wash and dry to obtain the acrylate core-shell toughening agent.

4. The polyvinyl chloride double-wall corrugated pipe according to claim 3, characterized in that, In step S1, the weight ratio of water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent, silane-modified nano-silica dispersion, first initiator, and acrylamide is (65~75):(0.5~1.5):(0.5~0.8):(55~65):(35~45):(0.5~1.5):(25~35):(0.4~0.6):(2.5~3.5); wherein, the mass percentage of silane-modified nano-silica in the silane-modified nano-silica dispersion is 15~17%. In step S2, the weight ratio of water, the second initiator, and methyl methacrylate is 100:(0.2~0.4):(25~35).

5. The polyvinyl chloride double-wall corrugated pipe according to claim 1, characterized in that, The preparation method of the acrylate core-shell toughening agent includes the following steps: S11. Disperse silane-modified nano-silica in water to obtain a silane-modified nano-silica dispersion. Divide the silane-modified nano-silica dispersion into three parts to obtain the first part of the silane-modified nano-silica dispersion, the second part of the silane-modified nano-silica dispersion, and the third part of the silane-modified nano-silica dispersion. S12. Mix water, emulsifier, alkalinity regulator, butyl acrylate, isooctyl acrylate, crosslinking agent and the first part of silane-modified nano silica dispersion, ultrasonically disperse, stir under nitrogen protection atmosphere, control the temperature at 60~75℃, add the first initiator, stir for 2~3h, add acrylamide and the second part of silane-modified nano silica dispersion, stir for 0.5~1.0h to obtain core layer latex; S2. Mix water, the second initiator and the core layer latex obtained in step S12, stir under a nitrogen protective atmosphere, add methyl methacrylate dropwise, add the third part of silane-modified nano silica dispersion, control the temperature at 70~80℃, stir the reaction, cool down to 60~65℃, use an inorganic salt aqueous solution to break the emulsion, filter, wash and dry to obtain the acrylate core-shell toughening agent.

6. The polyvinyl chloride double-wall corrugated pipe according to claim 5, characterized in that, In step S11, the weight ratio of the first silane-modified nano silica dispersion, the second silane-modified nano silica dispersion, and the third silane-modified nano silica dispersion is (4~6):(2~4):(1~3).

7. The polyvinyl chloride double-wall corrugated pipe according to claim 3 or 5, characterized in that, Acrylamide is added along with styrene, and the weight ratio of acrylamide to styrene is (3.5~4.5):

1.

8. The polyvinyl chloride double-wall corrugated pipe according to claim 1, characterized in that, The lubricant comprises paraffin wax and stearic acid, and the filler comprises light calcium carbonate.

9. The polyvinyl chloride double-wall corrugated pipe according to claim 1, characterized in that, The heat stabilizer includes lead salt composite stabilizer, tribasic lead sulfate, and calcium stearate.

10. A method for preparing a polyvinyl chloride double-wall corrugated pipe as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1: Mix the raw materials corresponding to the inner and outer layers separately, using high-speed stirring and low-speed stirring, while controlling the temperature to ≤55℃, to obtain the outer layer premix and the inner layer premix. Step 2: Add the outer layer premix and the inner layer premix to the corresponding screw extruders for melting and extrusion, and form them into an integral tube blank with inner and outer layers through a mold. Vacuum sizing, cooling and shaping of the tube blank, and cutting are then performed to obtain the polyvinyl chloride double-wall corrugated pipe.

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