Hyperdispersant, preparation method thereof and PVC-U double-wall corrugated pipe

Abstract

The invention discloses a hyperdispersant, a preparation method thereof and a PVC-U double-wall corrugated pipe, and belongs to the technical field of high polymer materials. A preparation method of the hyperdispersant comprises the following steps: adding an oxidizing agent into an isobutenol polyoxyethylene ether aqueous solution, and carrying out polymerization reaction with a monomer mixed solution, a chain transfer agent and a reducing agent to obtain the hyperdispersant, wherein the monomer mixed solution is a mixed solution of acrylic acid, styrene and glycidyl methacrylate. The hyperdispersant disclosed by the invention is prepared by a polymerization reaction between a mixed solution of acrylic acid, styrene and glycidyl methacrylate and an aqueous solution of isobutylene alcohol polyoxyethylene ether, so that the dispersion uniformity of calcium carbonate in a polyvinyl chloride resin matrix is remarkably improved, and the effects of reinforcing and toughening a polyvinyl chloride material are achieved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a superdispersant and its preparation method, and a PVC-U double-wall corrugated pipe. Background Technology

[0002] PVC-U double-wall corrugated pipe is a special type of pipe made primarily from rigid polyvinyl chloride (PVC). It features a smooth inner wall, a corrugated outer wall, and hollow inner and outer walls. Due to its unique manufacturing process, this pipe possesses excellent properties such as light weight, high flow capacity, high mechanical strength, chemical corrosion resistance, and cost savings. Therefore, it is widely used in municipal engineering, building construction, and electrical and telecommunications engineering, including but not limited to urban drainage pipes, sewage pipes, building rainwater pipes, ventilation pipes, and protective conduits for various power cables.

[0003] PVC-U double-wall corrugated pipes, with their superior performance, have gained high market acceptance and are gradually replacing cement pipes, flat-wall pipes, and other traditional pipe materials. In the plastic pipe industry, PVC-U double-wall corrugated pipes mainly use calcium carbonate particles as filler. However, calcium carbonate particles are hydrophilic, non-polar compounds with a large number of hydroxyl groups on their surface. They have poor affinity with organic polymers and other base materials, easily agglomerating and dispersing unevenly within PVC products. This results in interface defects in the PVC products, reducing product performance and limiting their wider application in engineering. The main problems include insufficient toughness, low impact strength, and high brittleness. Under impact, they are prone to brittle fracture, leading to rapid pipe cracking and posing significant risks to pipe lifespan and engineering safety. Therefore, there is an urgent need to develop a PVC-U pipe with high impact strength, high toughness, high rigidity, and high heat resistance.

[0004] To improve the dispersion performance of calcium carbonate in PVC resin, the existing technology "Preparation and Performance Study of a Calcium Carbonate Superdispersant for PVC Products" discloses a calcium carbonate polymeric dispersant that is added together with calcium carbonate and other additives during PVC product processing to improve the dispersibility of calcium carbonate, prevent agglomeration, and increase the affinity between calcium carbonate and PVC. This calcium carbonate polymeric dispersant is prepared by redox-initiated polymerization of isobutylene alcohol polyoxyethylene ether (HPEG), hydrophilic monomer acrylic acid, and lipophilic monomer styrene.

[0005] However, the dispersing effect of this superdispersant on calcium carbonate needs to be further improved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing calcium carbonate superdispersants used for PVC products, which still have room for improvement in dispersing effect on calcium carbonate in PVC, and to provide a superdispersant that can further improve the dispersion effect of calcium carbonate in PVC.

[0007] Another object of the present invention is to provide a PVC composition.

[0008] Another object of the present invention is to provide a method for preparing a PVC composition.

[0009] Another object of the present invention is to provide a PVC-U double-wall corrugated pipe.

[0010] The above-mentioned objective of this invention is achieved through the following technical solution: A superdispersant is prepared by the following method: adding an oxidant to an aqueous solution of isobutylene alcohol polyoxyethylene ether, and then polymerizing it with a monomer mixture, a chain transfer agent and a reducing agent to obtain the superdispersant; The monomer mixture is a mixed solution of acrylic acid, styrene, and glycidyl methacrylate; The weight ratio of acrylic acid, styrene, and glycidyl methacrylate is (0.5~4):(0.5~3):1; The weight ratio of isobutylene alcohol polyoxyethylene ether to glycidyl methacrylate is (60~120):1; The polymerization temperature is 50~70℃, and the polymerization time is 3~6h; The weight-average molecular weight of the superdispersant is 40,000 to 43,000 g / mol, and the molecular weight distribution index of the superdispersant is 1.8 to 2.3.

[0011] This invention utilizes a redox initiation system, where an oxidant initiates free radical polymerization at 50-70°C to prepare a superdispersant for dispersing calcium carbonate filler in PVC materials. The invention employs isobutylene glycol polyoxyethylene ether (HPEG) as an anchoring group, with the long polyether chain acting as a solvating chain ("teeth"), anchoring to the surface of calcium carbonate and calcium carbonate whiskers through hydrophobic interactions. This is combined with monomers such as acrylic acid (AA), styrene (St), and glycidyl methacrylate (GMA) for free radical copolymerization. A chain transfer agent (mercaptopropionic acid) controls the molecular weight, ensuring uniform branch density and forming a superdispersant with excellent dispersibility and stability. The carboxyl groups (-COOH) in acrylic acid enhance the compatibility of the superdispersant with PVC and fillers. Styrene provides rigid chain segments, improving the molecular rigidity and thermal stability of the superdispersant. During melt blending, the epoxy groups on the glycidyl methacrylate (GMA) molecular chain chemically bond with the chlorine atoms on the PVC molecular chain and the hydroxyl groups (-OH) on the surface of calcium carbonate particles, forming stable ether covalent bonds (-CH2-O-PVC). This anchors the dispersant more firmly to the PVC matrix, further improving dispersion stability and interfacial strength, effectively inhibiting calcium carbonate agglomeration, forming a rigid-flexible interpenetrating network, directly improving matrix toughness, and enhancing the mechanical properties of PVC composites.

[0012] The superdispersant of this invention possesses excellent surface wettability, dispersibility, anchoring groups, and solvation chains, effectively optimizing the interfacial compatibility between PVC-U double-wall corrugated pipe material and calcium carbonate. Compared with traditional dispersants, the superdispersant of this invention has the following characteristics: rapid and thorough wetting of particles; significantly increased solid particle content in the polymer matrix, reducing costs; uniform dispersion and good stability, thereby significantly improving the final performance of the dispersion system; strong adhesion, resistance to desorption, and good heat resistance.

[0013] When the reaction temperature is below 50℃, the redox initiation efficiency is insufficient, resulting in low monomer conversion and a wide molecular weight distribution. Above 70℃, the ring-opening side reaction of glycidyl methacrylate (GMA) epoxy groups is triggered, destroying its chemical bonding ability with PVC and causing the toughening effect to be lost. If the reaction time is less than 3 hours, the superdispersant will be unevenly dispersed and prone to agglomeration. If the reaction time is more than 6 hours, the solvent solvation chain will be shortened and the molecular chain will break.

[0014] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the superdispersant were determined by gel permeation chromatography (GPC) using polyethylene glycol (PEG) as the standard, N,N-dimethylformamide (DMF) as the mobile phase, a flow rate of 1.0 mL / min, and a column temperature of 35℃.

[0015] The molecular weight distribution index (PDI) is calculated as: weight-average molecular weight (Mw) / number-average molecular weight (Mn).

[0016] Preferably, the oxidant can be hydrogen peroxide.

[0017] Preferably, the reducing agent can be ascorbic acid.

[0018] Preferably, the chain transfer agent can be mercaptopropionic acid.

[0019] Preferably, the superdispersant is prepared by the following method: an oxidant is added to an aqueous solution of isobutylene alcohol polyoxyethylene ether; a chain transfer agent is added to a monomer mixture. The monomer mixture containing the chain transfer agent is slowly added dropwise to the isobutylene alcohol polyoxyethylene ether aqueous solution using a peristaltic pump. Simultaneously, a reducing agent is added dropwise to the isobutylene alcohol polyoxyethylene ether aqueous solution using another peristaltic pump. After the addition is complete, the temperature is raised to 50-70°C until the reaction is complete. The pH is adjusted to 6-7, the solution is cooled, and the polycarboxylate superdispersant solution is prepared into a powdered product, the polycarboxylate superdispersant, using a centrifugal spray drying method.

[0020] Preferably, the weight ratio of acrylic acid, styrene, and glycidyl methacrylate is (1~2):(1~2):1.

[0021] Preferably, the number average molecular weight of isobutylene alcohol polyoxyethylene ether is 1500~2500.

[0022] This invention also protects a PVC composition comprising, by weight fraction, the following components: 100 portions of PVC; 15-20 parts of filler; 1-10 parts of dispersant; Stabilizer 3-6 parts; 5-10 parts titanium dioxide; 1-5 parts of whitening agent; The dispersant is any of the superdispersants described above; The filler is calcium carbonate particles and calcium carbonate whiskers; the mass ratio of calcium carbonate whiskers to calcium carbonate particles is (0.5~2):1.

[0023] Calcium carbonate whiskers are a type of single-crystal fiber, a green and environmentally friendly material. Their mechanical strength is close to the theoretical strength of interatomic valence bonds. They possess excellent mechanical properties such as high strength and high elastic modulus. When added to a PVC polymer matrix, they act as a skeleton, which not only reduces shrinkage and internal stress in the product and increases mechanical strength, but also enhances the matrix's ability to absorb energy and prevents crack growth, thereby achieving a strengthening and toughening effect.

[0024] This invention uses calcium carbonate particles and calcium carbonate whiskers as composite fillers, and achieves both performance and cost optimization through the synergistic effect of dual interfaces, resulting in better reinforcement and toughening effects.

[0025] The superdispersant of this invention has excellent dispersion performance for both calcium carbonate particles and calcium carbonate whiskers in PVC-U materials, improving the compatibility of the calcium carbonate particle and calcium carbonate whisker composite filler dispersion system with PVC-U. Under the action of the superdispersant, the calcium carbonate whiskers are directionally dispersed and absorb impact energy through microcrack deflection and stress transfer, thereby achieving the effect of strengthening and toughening.

[0026] Preferably, the aspect ratio of the calcium carbonate whiskers is (20~30):1.

[0027] Calcium carbonate whiskers with an aspect ratio of (20~30):1 have a high specific surface area and a reinforcing effect, which can effectively transfer stress and prevent crack propagation. Good dispersibility ensures uniform distribution of whiskers and enhances the overall performance of PVC matrix.

[0028] Preferably, the stabilizer is a calcium-zinc composite stabilizer.

[0029] Preferably, the whitening agent is a fluorescent whitening agent.

[0030] The present invention also protects a method for preparing the PVC composition described in any of the above claims, comprising the following steps: mixing the components evenly, heating and stirring to obtain a premix, melting and plasticizing in a twin-screw extruder at an extrusion temperature of 180~210℃, extruding, and granulating to obtain the PVC composition.

[0031] Preferably, a pretreatment step is included before mixing: the superdispersant is dissolved in water, and the filler and zirconium beads are added in sequence with stirring. After thorough stirring, the zirconium beads are removed.

[0032] The present invention also protects a PVC-U double-wall corrugated pipe prepared from any of the PVC compositions described above.

[0033] In a specific embodiment, the PVC composition can be plasticized and molded on an injection molding machine to prepare a PVC-U double-wall corrugated pipe.

[0034] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a superdispersant, which is prepared by polymerization reaction of a mixed solution of acrylic acid, styrene, and glycidyl methacrylate with an aqueous solution of isobutylene alcohol polyoxyethylene ether. This carboxylic acid type superdispersant significantly improves the dispersion uniformity of calcium carbonate in polyvinyl chloride resin matrix, thereby achieving the effect of reinforcing and toughening polyvinyl chloride materials. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0036] Isobutylene alcohol polyoxyethylene ether, manufactured by Zhejiang Huangma Technology, brand name HM-IPEG-2000, molecular weight 2000.

[0037] The PVC, manufactured by Sinopec Qilu Branch, is grade S-1000 and has a molecular weight of 75,000~85,000 g / mol.

[0038] The calcium carbonate particles have an average particle size of 1.5 μm.

[0039] Calcium carbonate whisker 1, manufactured by Shanxi Tianyi Nanomaterials Co., Ltd., grade TY-20, aspect ratio 20:1, average diameter 0.8μm.

[0040] Calcium carbonate whiskers 2, manufactured by Shanxi Tianyi Nanomaterials Co., Ltd., grade TY-30, aspect ratio 30:1, average diameter 0.5μm.

[0041] Stabilizer, calcium-zinc composite stabilizer, commercially available, and the same type was used in the parallel examples and comparative examples.

[0042] The whitening agent, a type of fluorescent whitening agent, is commercially available, and the same one was used in the parallel examples and comparative examples.

[0043] Example 1 A superdispersant, the preparation method of which includes the following steps: Add 24g of isobutylene glycol polyoxyethylene ether and 100g of deionized water to a beaker, stir until homogeneous, heat to 60℃, maintain a constant temperature, add 0.5g of hydrogen peroxide (H2O2), stir until homogeneous, and prepare the monomer mixture: mix 0.40g of acrylic acid, 0.40g of styrene, and 0.40g of glycidyl methacrylate (i.e., the weight ratio of acrylic acid, styrene, and glycidyl methacrylate is 1:1:1, and the weight ratio of isobutylene glycol polyoxyethylene ether and glycidyl methacrylate is 60:1), and add 0.12g of mercaptopropionic acid as a chain transfer agent. Slowly add the monomer mixture dropwise using a peristaltic pump, controlling the addition time to 3 hours. Simultaneously, add 1.5g of a 2.5 wt% ascorbic acid (VC) aqueous solution dropwise using another peristaltic pump, controlling the addition time to 3.5 hours. After the addition is complete, heat to 65℃ and continue stirring for 1 hour to ensure complete reaction. After the reaction solution cools down to below 45°C, slowly add 32% sodium hydroxide solution to adjust the pH to 6-7. After cooling to room temperature, use centrifugal spray drying at 300-350°C to prepare the polycarboxylate superdispersant solution into a powder product, which is denoted as polycarboxylate superdispersant 1.

[0044] The weight-average molecular weight (Mw) of superdispersant 1 is 40,700 g / mol, the number-average molecular weight (Mn) is 21,400 g / mol, and the molecular weight distribution index is 1.9.

[0045] Example 2 A superdispersant, the preparation method of which differs from that in Example 1: The monomer mixture consists of 0.60g acrylic acid, 0.30g styrene, and 0.30g glycidyl methacrylate. The weight ratio of acrylic acid, styrene, and glycidyl methacrylate is 2:1:1. The weight ratio of isobutylene alcohol polyoxyethylene ether and glycidyl methacrylate is 80:1.

[0046] The product is designated as polycarboxylate superdispersant 2.

[0047] The rest is the same as in Example 1, and will not be repeated here.

[0048] The weight-average molecular weight (Mw) of the superdispersant 2 is 41,500 g / mol, the number-average molecular weight (Mn) is 20,800 g / mol, and the molecular weight distribution index is 2.0.

[0049] Example 3 A superdispersant, the preparation method of which differs from that in Example 1: The monomer mixture consists of 0.48g acrylic acid, 0.48g styrene, and 0.24g glycidyl methacrylate. The weight ratio of acrylic acid, styrene, and glycidyl methacrylate is 2:2:1. The weight ratio of isobutylene alcohol polyoxyethylene ether and glycidyl methacrylate is 100:1.

[0050] The product is designated as polycarboxylate superdispersant 3.

[0051] The rest is the same as in Example 1, and will not be repeated here.

[0052] The weight-average molecular weight (Mw) of the superdispersant 3 is 41,000 g / mol, the number-average molecular weight (Mn) is 22,000 g / mol, and the molecular weight distribution index is 1.9.

[0053] Example 4 A superdispersant, the preparation method of which differs from that in Example 1: The monomer mixture consists of 0.60g acrylic acid, 0.40g styrene, and 0.20g glycidyl methacrylate. The weight ratio of acrylic acid, styrene, and glycidyl methacrylate is 3:2:1. The weight ratio of isobutylene alcohol polyoxyethylene ether and glycidyl methacrylate is 120:1.

[0054] The product is designated as polycarboxylate superdispersant 4.

[0055] The rest is the same as in Example 1, and will not be repeated here.

[0056] The weight-average molecular weight (Mw) of superdispersant 4 is 42,700 g / mol, the number-average molecular weight (Mn) is 19,400 g / mol, and the molecular weight distribution index is 2.2.

[0057] Examples 5-14 A PVC composition, by weight, comprises the following components: PVC, fillers, dispersants, stabilizers, titanium dioxide, whitening agents; The filler consists of calcium carbonate particles and calcium carbonate whiskers.

[0058] The specific content of each component is shown in Table 1 below.

[0059] Table 1

[0060] The specific method for preparing the above-mentioned PVC composition is as follows: Add a superdispersant to a beaker and dissolve it in water. Use a stirrer to stir the dispersant at 500 rpm to pre-wet it. While stirring, slowly add calcium carbonate and calcium carbonate whisker composite filler. Then add zirconium beads to fully mix the calcium carbonate particles and calcium carbonate whiskers. Continue stirring at 3000 rpm for 30 minutes. Filter out the zirconium beads to obtain a dispersion of calcium carbonate particles and calcium carbonate whiskers.

[0061] Calcium carbonate granules, calcium carbonate whisker dispersion, PVC, stabilizer, titanium dioxide, and whitening agent are mixed evenly and heated and stirred to obtain a premix. The premix is ​​then melt-plasticized, extruded, and granulated in a twin-screw extruder at an extrusion temperature of 180~210℃, and cooled to room temperature to obtain a PVC composition.

[0062] The above PVC composition is plasticized and molded on an injection molding machine to prepare PVC-U double-wall corrugated pipe.

[0063] Comparative Example 1 A polycarboxylate superdispersant, the preparation method of which differs from that in Example 1: The monomer mixture consists of 0.60g acrylic acid and 0.60g styrene. It does not include glycidyl methacrylate.

[0064] The product is designated as polycarboxylate superdispersant 5.

[0065] The rest is the same as in Example 1, and will not be repeated here.

[0066] The weight-average molecular weight (Mw) of the superdispersant 5 is 84,500 g / mol, the number-average molecular weight (Mn) is 28,200 g / mol, and the molecular weight distribution index is 3.0.

[0067] Comparative Examples 2-3 A PVC composition, by weight, comprises the following components: PVC, fillers, dispersants, stabilizers, titanium dioxide, whitening agents; The filler is calcium carbonate particles.

[0068] The specific content of each component is shown in Table 2 below.

[0069] Table 2. Composition of PVC compositions in each comparative example (parts by weight)

[0070] The preparation method of the above PVC composition is the same as that in Example 5, and will not be repeated here.

[0071] The preparation method of the above-mentioned PVC-U double-wall corrugated pipe is the same as that in Example 5, and will not be repeated here.

[0072] Result detection The PVC-U double-wall corrugated pipes of the above embodiments and comparative examples were tested using the following performance test methods: Ring stiffness: According to GB / T 9647-2015 "Determination of ring stiffness of thermoplastic pipes", the unit is KN / m. 2 The higher the ring stiffness, the better the performance.

[0073] Tensile strength: Tested according to GB / T 8804.2-2003 "Determination of Tensile Properties of Thermoplastic Pipes", unit is MPa. The higher the tensile strength, the better the performance.

[0074] Longitudinal shrinkage rate: Tested according to the method in GB / T 6671-2001 "Determination of Longitudinal Shrinkage Rate of Thermoplastic Pipes". The lower the longitudinal shrinkage rate, the better the performance.

[0075] Elongation at break: GB / T 1040.2 The test was conducted according to the method specified in 2022, "Determination of Tensile Properties of Thermoplastic Pipes - Part 2". Higher elongation at break indicates better performance.

[0076] Impact strength: Tested according to GB / T 1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams". Higher impact strength indicates better performance.

[0077] Drop hammer impact test (TIR): GB / T 18477.1-2007 "Rigid Polyvinyl Chloride (PVC-U) Double-Wall Corrugated Pipes for Buried Drainage", test conditions: 0℃. The pipes prepared in each example and comparative example were cut into PVC-U pipes with a length of 200mm, a wall thickness of 5mm, and an outer diameter of 50mm. The hammer head mass was 0.5kg, and the drop hammer height was 1000mm. Twenty PVC-U pipe samples from each example or comparative example were tested for their impact resistance at 0℃. Each sample underwent three impacts (3 lines), for a total of 60 impacts. The test began with the drop hammer impacting line 1. If the sample did not break, line 2 was then impacted until the sample broke or all lines were impacted once, at which point the result was determined. The true impact rate (TIR) ​​is the percentage of total number of impact failures to the total number of impacts. A lower true impact rate indicates better performance.

[0078] The specific test results for each embodiment and comparative example are shown in Table 3 below:

[0079] The results above show that the PVC pipes prepared in Examples 1-14 of this invention have the characteristics of being reinforced and toughened, with a ring stiffness of 8.1-10.8 kN / m. 2 The tensile strength can reach 42.8~45.7 MPa, the longitudinal shrinkage rate can be as low as 2.6~3.3%, the elongation at break can be as high as 139~159%, the drop hammer impact TIR can be as low as 3.3~8.3%, and the cantilever beam impact strength can reach 13.2~16.6 KJ / m. 2 This indicates that the present invention significantly improves the various properties of PVC pipes through the synergistic effect of the super-dispersant molecular design and the calcium carbonate particle / whisker composite filler.

[0080] As can be seen from Comparative Example 2, without the use of a dispersant, the various properties of the PVC pipe are all too poor. This may be due to the poor dispersibility of calcium carbonate particles in the PVC pipe.

[0081] As can be seen from Comparative Example 3, although the performance of polycarboxylate superdispersant 5 is slightly improved compared to Comparative Example 2, it still cannot achieve the effect of the embodiment of the present invention. This may be because the dispersion effect of polycarboxylate superdispersant 5 on fillers is not as good as that of the superdispersant in the embodiment of the present invention.

[0082] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A superdispersant, characterized in that, The superdispersant is prepared by the following method: adding an oxidant to an aqueous solution of isobutylene alcohol polyoxyethylene ether, and then reacting it with a monomer mixture, a chain transfer agent and a reducing agent to obtain the superdispersant; The monomer mixture is a mixed solution of acrylic acid, styrene, and glycidyl methacrylate; The weight ratio of acrylic acid, styrene, and glycidyl methacrylate is (0.5~4):(0.5~3):1; The weight ratio of isobutylene alcohol polyoxyethylene ether to glycidyl methacrylate is (60~120):1; The polymerization temperature is 50~70℃, and the polymerization time is 3~6h; The weight-average molecular weight of the superdispersant is 40,000 to 43,000 g / mol, and the molecular weight distribution index of the superdispersant is 1.8 to 2.

3.

2. The superdispersant as described in claim 1, characterized in that, The weight ratio of acrylic acid, styrene, and glycidyl methacrylate is (1~2):(1~2):

1.

3. The superdispersant as described in claim 1, characterized in that, The number average molecular weight of isobutylene alcohol polyoxyethylene ether is 1500~2500.

4. A PVC composition, characterized in that, By weight fraction, it includes the following components: 100 portions of PVC; 15-20 parts of filler; 1-10 parts of dispersant; Stabilizer 3-6 parts; 5-10 parts titanium dioxide; 1-5 parts of whitening agent; The dispersant is the superdispersant according to any one of claims 1 to 3; The filler is calcium carbonate particles and calcium carbonate whiskers; the mass ratio of calcium carbonate whiskers to calcium carbonate particles is (0.3~2):

1.

5. The PVC composition according to claim 4, characterized in that, The aspect ratio of the calcium carbonate whiskers is (20~30):

1.

6. The PVC composition according to claim 4, characterized in that, The average diameter of the calcium carbonate particles is 1~2 μm.

7. The PVC composition according to claim 4, characterized in that, The stabilizer is a calcium-zinc composite stabilizer.

8. A method for preparing the PVC composition according to any one of claims 4 to 7, characterized in that, The process includes the following steps: mixing the components evenly, heating and stirring to obtain a premix, melting and plasticizing in a twin-screw extruder at an extrusion temperature of 180~210℃, extruding, and granulating to obtain a PVC composition.

9. The method for preparing the PVC composition according to claim 8, characterized in that, The process also includes a pretreatment step before mixing: dissolving the superdispersant in water, stirring and adding the filler and zirconium beads, stirring thoroughly and then removing the zirconium beads.

10. A PVC-U double-wall corrugated pipe, characterized in that, It is prepared from the PVC composition according to any one of claims 4 to 7.

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