Toughened modified PVC pipe and preparation method thereof

Abstract

The invention discloses a toughened modified PVC pipe and a preparation method thereof, and relates to the technical field of PVC pipe materials. The toughened modified PVC pipe at least comprises the following raw materials in parts by mass: 100 parts of polyvinyl chloride resin; 5-10 parts of a vinyl acetate copolymer; 3 to 8 parts of MBS core-shell particles; 0.5 to 1.5 parts of modified lanthanum metal salt; 2-5 parts of a modified composite stabilizer; 0.3 to 0.8 part of an antioxidant; 5-20 parts of a filling agent; 1-3 parts of a lubricant; and 1-2 parts of a processing aid. The vinyl acetate copolymer, the MBS core-shell particles and the modified lanthanum metal salt are added into the polyvinyl chloride resin to form a ternary blending toughening agent, grid toughening and sea island toughening mechanisms are combined, the stability of the interface of the polyvinyl chloride resin is improved by using rare earth, and the obdurability and thermal stability of the modified PVC pipe are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of PVC pipe materials, and in particular to a toughened modified PVC pipe and a preparation method thereof. Background Art

[0002] Currently, polyvinyl chloride (PVC) is one of the five major general-purpose plastics, with an annual production volume second only to polyethylene. It is widely applicable, simple to process and produce, and easily commercialized. It possesses excellent physical properties, such as low density, high strength, good oil resistance, chemical corrosion resistance, high transparency, excellent flame retardancy, and high insulation. It is also inexpensive, making it widely used in various industries and fields, becoming the second most popular general-purpose plastic. Although PVC resin possesses many excellent properties, its development is limited by inherent structural defects. Polyvinyl chloride (PVC) engineering plastic pipes are widely used in building downspouts, urban sewage pipes, and urban pipeline corridor construction due to their high cost-effectiveness. With the development of PVC pipes and the improvement of their application environment, higher performance requirements are being placed on them, especially in terms of resistance to soil displacement and ability to withstand damage in harsh construction environments, which has led to higher requirements for the toughness and impact resistance of the pipes.

[0003] While PVC resin is widely used and possesses numerous advantages, it also suffers from two major drawbacks: poor thermal stability and toughness. The presence of CIC chemical bonds in the PVC matrix creates significant intermolecular forces within the resin, resulting in rigid PVC products with high rigidity but insufficient toughness, making them susceptible to brittle fracture during use. PVC also suffers from poor thermal stability, making it susceptible to degradation and crosslinking reactions when used under heat or prolonged exposure to light, which reduces its mechanical properties and processing performance. Furthermore, PVC resin is prone to thermal decomposition at temperatures exceeding 100°C, releasing HCI, which leads to oxidative decomposition of the PVC, further impacting its performance and service life. These two drawbacks significantly limit the industrial application of PVC resin. However, when PVC resin is blended with a toughening agent to create a tough blend and improve its thermal stability, the application range of PVC can be broadened. Therefore, research and toughening modification of PVC are crucial to developing PVC pipes with excellent toughness and heat resistance. Summary of the Invention

[0004] The purpose of the present invention is to provide a toughened modified PVC pipe and a preparation method thereof to solve the following technical problems:

[0005] Existing PVC pipes have problems such as poor toughness, insufficient thermal stability and short service life.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A toughened modified PVC pipe comprises at least the following raw materials in parts by weight:

[0008] 100 parts of polyvinyl chloride resin; 5-10 parts of vinyl acetate copolymer; 3-8 parts of MBS core-shell particles; 0.5-1.5 parts of modified lanthanum metal salt; 2-5 parts of calcium zinc composite stabilizer; 0.3-0.8 parts of antioxidant; 5-20 parts of filler; 1-3 parts of lubricant; and 1-2 parts of processing aid.

[0009] As a further solution of the present invention: the content of vinyl acetate in the vinyl acetate copolymer is 25-30%, and the content of lanthanum in the modified lanthanum metal salt is 10-15%.

[0010] As a further solution of the present invention: the core of the MBS core-shell particles is polybutadiene latex, and the shell is a copolymer of methyl methacrylate, butyl acrylate and glycidyl methacrylate.

[0011] As a further embodiment of the present invention, the particle size of the MBS core-shell particles is 250-350 nm, the butyl acrylate accounts for 8-12 wt % of the shell layer, and the glycidyl methacrylate accounts for 2-3 wt % of the shell layer.

[0012] As a further embodiment of the present invention, the preparation method of the modified lanthanum metal salt comprises the following steps:

[0013] Mixing maleic acid, dipentaerythritol and p-toluenesulfonic acid, adding cyclohexane and heating under reflux, washing, distilling and drying to obtain dipentaerythritol maleate;

[0014] The dipentaerythritol maleate and lanthanum acetate are mixed, anhydrous ethanol is added, refluxed and heated, washed and dried to obtain a modified lanthanum metal salt.

[0015] As a further embodiment of the present invention, the molar ratio of the maleic acid, the dipentaerythritol and the p-toluenesulfonic acid is 1:2.1-2.3:0.03-0.05.

[0016] As a further embodiment of the present invention, the molar ratio of the dipentaerythritol maleate to the lanthanum acetate is 1:0.45-0.55.

[0017] As a further embodiment of the present invention, the antioxidant includes at least one of antioxidant 1076 or antioxidant 1010, the filler includes at least one of calcium carbonate or talc, the lubricant includes at least one of stearic acid, calcium stearate, polyethylene wax or oxidized polyethylene wax, and the processing aid includes at least one of polymethyl methacrylate, dioctyl phthalate and ACR resin.

[0018] A method for preparing a toughened modified PVC pipe as described in any one of the above items comprises at least the following preparation steps:

[0019] ball-milling the modified lanthanum metal salt and a portion of the calcium-zinc composite stabilizer to obtain a stabilizer slurry;

[0020] The polyvinyl chloride resin, the stabilizer slurry and the filler are mixed in the first stage, the vinyl acetate copolymer, the MBS core-shell particles, the antioxidant and the remaining calcium type composite stabilizer are added for the second stage, and finally the processing aid and the lubricant are added for the third stage to obtain a premix;

[0021] The premix is ​​added into a twin-screw extruder for extrusion, and after cooling and cutting, a toughened modified PVC pipe is obtained.

[0022] Beneficial effects of the present invention:

[0023] The present invention adds vinyl acetate copolymer, MBS core-shell particles and modified lanthanum metal salts to polyvinyl chloride resin to form a ternary blended toughening agent, combines the "grid" toughening of vinyl acetate copolymer with the "island" toughening mechanism of MBS core-shell particles, and uses rare earth to enhance the stability of the polyvinyl chloride resin interface, greatly enhancing the toughness and thermal stability of the modified PVC pipe, thereby enhancing the service life of the PVC pipe. The present invention uses vinyl acetate copolymer and MBS core-shell particles to perform blended toughening modification on PVC, which can form a grid coating-island binary toughening mechanism within the blend matrix, wherein the grid coating generated by the vinyl acetate copolymer can transmit and disperse a large amount of impact energy, and the "sea-island" generated by the MBS core-shell particles generates a large number of shear bands and silver streaks under the impact of external forces to absorb most of the impact energy, thereby greatly enhancing the toughness of PVC relative to a single elastic toughening mechanism. Rare earth is added on the basis of binary toughening, and rare earth has strong adsorption and activity and can be evenly diffused in the PVC matrix. In the body, the interface of vinyl acetate copolymer, MBS core-shell particles and PVC matrix is ​​filled and connected, which increases the interface fusion between the multi-component toughening agents and between the toughening agents and the matrix, thereby improving the interface strength; on the other hand, the rare earth ions can form stable coordination bonds with the chlorine atoms in PVC, thereby enhancing the intermolecular force of PVC, making the ability of PVC to transmit shear force under impact enhanced, thereby improving the matrix toughness of PVC, and finally improving the overall strength, toughness and heat resistance of the PVC ternary blend through the ternary composite of vinyl acetate copolymer-MBS core-shell particles-rare earth.

[0024] The present invention uses styrene-butadiene polybutadiene latex as the seed emulsion and a shell layer composed of a copolymer of methyl methacrylate, butyl acrylate, and glycidyl methacrylate. The introduction of butyl acrylate lowers the glass transition temperature of the shell layer and enhances its flexibility at low temperatures. Furthermore, the introduction of glycidyl methacrylate into the shell layer results in a larger particle size due to the higher activity of glycidyl methacrylate with epoxy groups, which improves the grafting rate and efficiency. The resulting glycidyl methacrylate has a higher modulus, resulting in higher impact strength for the toughened and modified PVC pipe. The epoxy groups bond with lanthanum ions to form a "PVC-rare earth-MBS" bridging network, further enhancing interfacial integration. Furthermore, the MBS core-shell particles are kept within a particle size range of 250-350 nm, enabling them to form an effective "micro-region toughening" structure within the PVC matrix. This avoids stress concentration caused by excessively large particle size while fully utilizing the toughening effect of each particle, maximizing the toughness and impact resistance of the PVC pipe.

[0025] The present invention utilizes dipentaerythritol maleate to modify rare earth lanthanum. The hydroxyl group in dipentaerythritol can chelate metal chlorides, inhibiting the catalytic effect of metal chlorides on the thermal degradation of PVC. It can also absorb HCl generated by the thermal degradation of PVC, thereby improving the service life of PVC pipes. Rare earth ions have a large ionic radius and a large number of coordination numbers, which can coordinate with the oxygen atoms in dipentaerythritol to form stable macromolecular rare earth compounds, thereby reducing the loss of thermal stability caused by the migration of dipentaerythritol in PVC. On the other hand, the rare earth heat stabilizer itself has poor initial coloring properties, but compounding with dipentaerythritol can also improve its initial coloring properties to a certain extent. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Example 1 The preparation method of the modified lanthanum metal salt comprises the following steps:

[0028] 1 mol maleic acid, 2 mol dipentaerythritol, and 0.03 mol p-toluenesulfonic acid were respectively mixed and placed in a three-necked round-bottom flask. 200 mL cyclohexane was added as a water-carrying agent. The mixture was refluxed at 160°C for 2 h. The dehydrated solid sample was washed with ethanol to remove the unreacted raw materials. After vacuum distillation and vacuum drying, dipentaerythritol maleate was obtained.

[0029] Place 1 mol of dipentaerythritol maleate and 0.5 mol of lanthanum acetate in a 500 mL three-necked round-bottom flask, and add 2000 mL of anhydrous ethanol. Heat under reflux at 120°C for 4 hours while stirring continuously with a stirrer to accelerate the reaction. Wait until the reaction is complete, then distill off the anhydrous ethanol to obtain a crude product. Dissolve and filter the crude product in dimethylformamide to remove unreacted raw materials, then dry it in a vacuum drying oven to remove residual anhydrous ethanol, thereby obtaining a modified lanthanum metal salt.

[0030] Example 2 The preparation method of the modified lanthanum metal salt comprises the following steps:

[0031] 1 mol maleic acid, 2.2 mol dipentaerythritol, and 0.04 mol p-toluenesulfonic acid were respectively mixed and placed in a three-necked round-bottom flask. 200 mL cyclohexane was added as a water-carrying agent. The mixture was refluxed at 160°C for 2 h. The dehydrated solid sample was washed with ethanol to remove the unreacted raw materials. After vacuum distillation and vacuum drying, dipentaerythritol maleate was obtained.

[0032] Place 1 mol of dipentaerythritol maleate and 0.55 mol of lanthanum acetate in a 500 mL three-necked round-bottom flask, and add 2000 mL of anhydrous ethanol. Heat under reflux at 120°C for 4 hours while stirring continuously with a stirrer to accelerate the reaction. Wait until the reaction is complete, then distill off the anhydrous ethanol to obtain a crude product. Dissolve and filter the crude product in dimethylformamide to remove unreacted raw materials, then dry it in a vacuum drying oven to remove residual anhydrous ethanol, thereby obtaining a modified lanthanum metal salt.

[0033] The preparation method of MBS core-shell particles in Example 3 comprises the following steps:

[0034] In a 500 ml three-necked flask, 120 g of deionized water, 2 g of emulsifier sodium dodecylbenzenesulfonate, 0.2 g of reducing agent sodium bisulfite and 50 g of polybutadiene latex (solid content 50%) were added, nitrogen was introduced, the stirring speed was adjusted to 250 rpm, and the mixture was heated in a water bath at 65 ° C for 15 minutes. A monomer mixture composed of 25 g of styrene (St), 25 g of methyl methacrylate (MMA), 5 g of butyl acrylate (BA) and 1.5 g of glycidyl methacrylate (GMA) and 0.7 g of The initiator potassium persulfate is used to carry out the emulsion graft polymerization reaction. After the dropwise addition process is completed, the temperature is raised to 70°C, and then 0.3g of the initiator potassium persulfate is added to allow it to react completely. Then, the antioxidant 2,6-di-tert-butyl-p-cresol is added and mixed for 30 minutes. The temperature is lowered to 60°C, and 100g of 8% magnesium sulfate solution by mass is slowly added dropwise until the emulsion is completely flocculated. The solid is separated by filtration, washed with deionized water three times to remove residual salt, and dried in a 60°C forced air drying oven to constant weight to obtain MBS core-shell particles.

[0035] Example 4 A method for preparing a toughened modified PVC pipe comprises the following steps:

[0036] 1 part by mass of the modified lanthanum metal salt prepared in Example 1 and 1.5 parts by mass of a calcium-zinc composite stabilizer were ball-milled to obtain a stabilizer slurry;

[0037] 100 parts by mass of polyvinyl chloride resin (WS800), the above-mentioned stabilizer slurry and 15 parts by mass of filler nano calcium carbonate were mixed at 158° C. for 8 minutes in a primary mixing stage, and then 5 parts by mass of vinyl acetate copolymer (vinyl acetate content is 28 wt%), 6 parts by mass of MBS core-shell particles prepared in Example 3, 0.5 parts by mass of antioxidant 1010 and 2 parts by mass of calcium type composite stabilizer were added and mixed at 135° C. for 5 minutes in a secondary mixing stage, and finally 1 part by mass of processing aid ACR resin and 2 parts by mass of lubricant calcium stearate were added and mixed at 148° C. for 3 minutes in a tertiary mixing stage to obtain a premix;

[0038] The premix was added to a twin-screw extruder for extrusion, and the five-zone temperature of the extruder was set to 160 / 165 / 170 / 165 / 160° C. and the die pressure was 14 MPa. After cooling and cutting, a toughened modified PVC pipe was obtained.

[0039] Example 5 A method for preparing a toughened modified PVC pipe comprises the following steps:

[0040] 1 part by mass of the modified lanthanum metal salt prepared in Example 2 and 1.5 parts by mass of a calcium-zinc composite stabilizer were ball-milled to obtain a stabilizer slurry;

[0041] 100 parts by mass of polyvinyl chloride resin (WS800), the above-mentioned stabilizer slurry and 15 parts by mass of filler nano calcium carbonate were mixed at 158° C. for 8 minutes in a primary mixing stage, and then 5 parts by mass of vinyl acetate copolymer (vinyl acetate content is 28 wt%), 6 parts by mass of MBS core-shell particles prepared in Example 3, 0.5 parts by mass of antioxidant 1010 and 2 parts by mass of calcium type composite stabilizer were added and mixed at 135° C. for 5 minutes in a secondary mixing stage, and finally 1 part by mass of processing aid ACR resin and 2 parts by mass of lubricant calcium stearate were added and mixed at 148° C. for 3 minutes in a tertiary mixing stage to obtain a premix;

[0042] The premix was added to a twin-screw extruder for extrusion, and the five-zone temperature of the extruder was set to 160 / 165 / 170 / 165 / 160° C. and the die pressure was 14 MPa. After cooling and cutting, a toughened modified PVC pipe was obtained.

[0043] Example 6 A method for preparing a toughened modified PVC pipe comprises the following steps:

[0044] 1.2 parts by mass of the modified lanthanum metal salt prepared in Example 1 and 1.5 parts by mass of a calcium-zinc composite stabilizer were ball-milled to obtain a stabilizer slurry;

[0045] 100 parts by mass of polyvinyl chloride resin (WS800), the above-mentioned stabilizer slurry and 15 parts by mass of filler nano calcium carbonate were mixed at 158° C. for 8 minutes in a primary mixing stage, and then 6 parts by mass of vinyl acetate copolymer (vinyl acetate content is 28 wt%), 8 parts by mass of MBS core-shell particles prepared in Example 3, 0.5 parts by mass of antioxidant 1010 and 2.5 parts by mass of calcium type composite stabilizer were added and mixed at 135° C. for 5 minutes in a secondary mixing stage, and finally 1 part by mass of processing aid ACR resin and 2 parts by mass of lubricant calcium stearate were added and mixed at 148° C. for 3 minutes in a tertiary mixing stage to obtain a premix;

[0046] The premix was added to a twin-screw extruder for extrusion, and the five-zone temperature of the extruder was set to 160 / 165 / 170 / 165 / 160° C. and the die pressure was 14 MPa. After cooling and cutting, a toughened modified PVC pipe was obtained.

[0047] Example 7 A method for preparing a toughened modified PVC pipe comprises the following steps:

[0048] 1.2 parts by mass of the modified lanthanum metal salt prepared in Example 2 and 1.5 parts by mass of a calcium-zinc composite stabilizer were ball-milled to obtain a stabilizer slurry;

[0049] 100 parts by mass of polyvinyl chloride resin (WS800), the above-mentioned stabilizer slurry and 15 parts by mass of filler nano calcium carbonate were mixed at 158° C. for 8 minutes in a primary mixing stage, and then 6 parts by mass of vinyl acetate copolymer (vinyl acetate content is 28 wt%), 8 parts by mass of MBS core-shell particles prepared in Example 3, 0.5 parts by mass of antioxidant 1010 and 2.5 parts by mass of calcium type composite stabilizer were added and mixed at 135° C. for 5 minutes in a secondary mixing stage, and finally 1 part by mass of processing aid ACR resin and 2 parts by mass of lubricant calcium stearate were added and mixed at 148° C. for 3 minutes in a tertiary mixing stage to obtain a premix;

[0050] The premix was added to a twin-screw extruder and extruded. The five-zone temperature of the extruder was set to 160 / 165 / 170 / 165 / 160°C and the die pressure was 14 MPa. After cooling and cutting, the toughened modified PVC pipe was obtained.

[0051] Comparative Example 1 The preparation method of core-shell particles comprises the following steps:

[0052] In a 500ml three-necked flask, 120g of deionized water, 2g of emulsifier sodium dodecylbenzenesulfonate, 0.2g of reducing agent sodium bisulfite and 50g of polybutadiene latex (solid content 50%) were added, nitrogen was introduced, the stirring speed was adjusted to 250rpm, and the mixture was heated in a water bath at 65°C for 15 minutes. A monomer mixture composed of 25g of styrene (St), 25g of methyl methacrylate (MMA) and 5g of butyl acrylate (BA) and 0.7g of initiator potassium persulfate were added dropwise using a peristaltic pump to further An emulsion graft polymerization reaction was carried out. After the addition process was completed, the temperature was raised to 70°C, and then 0.3g of initiator potassium persulfate was added to complete the reaction. Then, the antioxidant 2,6-di-tert-butyl-p-cresol was added and mixed for 30 minutes. The temperature was lowered to 60°C, and 100g of 8% magnesium sulfate solution by mass was slowly added dropwise until the emulsion was completely flocculated. The solid was separated by filtration, washed with deionized water three times to remove residual salt, and dried in a 60°C forced air drying oven to constant weight to obtain MBS core-shell particles.

[0053] Compared with Example 4, Comparative Example 2 only replaces the MBS core-shell particles prepared in Example 3 added to Example 4 with the MBS core-shell particles prepared in Comparative Example 1. The other components and preparation methods are exactly the same as those in Example 4.

[0054] Comparative Example 3 is compared with Example 4. In Comparative Example 3, only the mass of the modified lanthanum metal salt prepared in Example 1 added in Example 4 is replaced by lanthanum carbonate, and the other components and preparation methods are exactly the same as those in Example 4.

[0055] Comparative Example 4 is compared with Example 4. In Comparative Example 4, only vinyl acetate copolymer is not added. The remaining components and preparation method are completely consistent with those of Example 4.

[0056] Comparative Example 5 is compared with Example 4. In Comparative Example 5, only MBS core-shell particles are not added. The other components and preparation methods are completely consistent with those of Example 4.

[0057] Compared with Example 4, Comparative Example 6 only does not add the modified lanthanum metal salt, and the other components and preparation methods are completely consistent with Example 4.

[0058] Performance testing

[0059] Tensile performance test: After the tensile specimens were placed at 25°C for 24 hours, they were tested on a universal testing machine. The test standard is GB / T1040-92, the test temperature is 25°C, the tensile rate in the tensile test is 50 mm / min, and each group of specimens was tested 5 times, and the average value was taken. The test results are shown in Table 1.

[0060] Bending performance test: After the tensile specimens were placed at 25°C for 24 hours, they were tested on a universal testing machine. The test standard is GB / T9341-2000, the test temperature is 25°C, the indenter movement speed during the bending test is 2mm / min, and each group of specimens was tested 5 times, and the average value was taken. The test results are shown in Table 1.

[0061] Impact performance test: The specimens were notched with a 2mm gap, left for 24 hours, and then subjected to an impact tester according to GB / T1843-2008. Each pattern was tested five times, and the average value was taken. The test results are shown in Table 1.

[0062] Thermal stability test: The thermal stability time of PVC pipes was tested according to GB / T 2917.1-2002, and the HCl precipitation time was measured in an oil bath at 180°C. The test results are shown in Table 1.

[0063] Low temperature resistance test: The brittle temperature of PVC pipes was tested according to GB5470-2008; the test results are shown in Table 1;

[0064] Table 1: Statistical table of PVC pipe performance test data for Examples 4-7 and Comparative Examples 2-6

[0065]

[0066] As can be seen from Table 1, the toughened PVC pipe prepared by the present invention is added with a ternary composite toughening agent consisting of vinyl acetate copolymer, MBS core-shell particles and modified lanthanum metal salt, which greatly improves the toughness and thermal stability of the PVC pipe and reduces the low-temperature brittle temperature. In Comparative Example 2, the MBS core-shell particles added do not introduce glycidyl methacrylate, the interface bonding is weakened, and the toughening effect of the obtained PVC pipe is reduced. In Comparative Example 3, the rare earth lanthanum added is not modified, and the thermal stability of the obtained PVC pipe is reduced. In Comparative Examples 4-6, only any two toughening agents of vinyl acetate copolymer, MBS core-shell particles and modified lanthanum metal salt are added, and the toughening effect of the toughened PVC pipe obtained is reduced, and the thermal stability of the toughened PVC pipe obtained without the addition of modified lanthanum metal salt is greatly reduced.

[0067] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A toughened modified PVC pipe, characterized in that: At least include the following raw materials by mass: 100 parts of polyvinyl chloride resin; 5-10 parts of vinyl acetate copolymer; 3-8 parts of MBS core-shell particles; 0.5-1.5 parts of modified lanthanum metal salt; 2-5 parts of calcium zinc composite stabilizer; 0.3-0.8 parts of antioxidant; 5-20 parts of filler; 1-3 parts of lubricant; and 1-2 parts of processing aid.

2. The toughened modified PVC pipe according to claim 1, characterized in that: The content of vinyl acetate in the vinyl acetate copolymer is 25-30%, and the content of lanthanum element in the modified lanthanum metal salt is 10-15%.

3. The toughened modified PVC pipe according to claim 1, characterized in that: The core of the MBS core-shell particles is polybutadiene latex, and the shell is a copolymer of methyl methacrylate, butyl acrylate and glycidyl methacrylate.

4. The toughened modified PVC pipe according to claim 3, characterized in that: The particle size of the MBS core-shell particles is 250-350 nm, the butyl acrylate accounts for 8-12 wt % of the shell layer, and the glycidyl methacrylate accounts for 2-3 wt % of the shell layer.

5. The toughened modified PVC pipe according to claim 2, characterized in that: The preparation method of the modified lanthanum metal salt comprises the following steps: Mixing maleic acid, dipentaerythritol and p-toluenesulfonic acid, adding cyclohexane and heating under reflux, washing, distilling and drying to obtain dipentaerythritol maleate; The dipentaerythritol maleate and lanthanum acetate are mixed, anhydrous ethanol is added, refluxed and heated, washed and dried to obtain a modified lanthanum metal salt.

6. The toughened modified PVC pipe according to claim 5, characterized in that: The molar ratio of the maleic acid, the dipentaerythritol and the p-toluenesulfonic acid is 1:2.1-2.3:0.03-0.

05.

7. The toughened modified PVC pipe according to claim 5, characterized in that: The molar ratio of the dipentaerythritol maleate to the lanthanum acetate is 1:0.45-0.

55.

8. The toughened modified PVC pipe according to claim 1, characterized in that: The antioxidant includes at least one of antioxidant 1076 or antioxidant 1010, the filler includes at least one of calcium carbonate or talc, the lubricant includes at least one of stearic acid, calcium stearate, polyethylene wax or oxidized polyethylene wax, and the processing aid includes at least one of polymethyl methacrylate, dioctyl phthalate and ACR resin.

9. A method for preparing a toughened modified PVC pipe according to any one of claims 1 to 8, characterized in that: The method comprises at least the following preparation steps: ball-milling the modified lanthanum metal salt and a portion of the calcium-zinc composite stabilizer to obtain a stabilizer slurry; The polyvinyl chloride resin, the stabilizer slurry and the filler are mixed in the first stage, the vinyl acetate copolymer, the MBS core-shell particles, the antioxidant and the remaining calcium type composite stabilizer are added for the second stage, and finally the processing aid and the lubricant are added for the third stage to obtain a premix; The premix is ​​added into a twin-screw extruder for extrusion, and after cooling and cutting, a toughened modified PVC pipe is obtained.

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