A low-foaming rigid polyvinyl chloride drain pipe and a method for producing the same

Abstract

This invention discloses a low-foaming rigid polyvinyl chloride (PVC) drainage pipe and its preparation method, belonging to the field of drainage pipe technology. The rigid PVC drainage pipe of this invention, through a three-layer co-extrusion structure, possesses multiple advantages including lightweight, high strength, corrosion resistance, and aging resistance. Specifically, the inner layer contains a corrosion-resistant modifier composed of chlorinated polyethylene and acrylate copolymers, which improves the strength of the drainage pipe and the corrosion resistance of the inner wall. The core layer incorporates a foaming agent and a co-foaming agent to form a microporous structure, reducing the material density and overall weight of the pipe. The introduction of modified PVC, crosslinking agents, isocyanates, and acid anhydrides during processing forms an interpenetrating network or crosslinked structure, significantly improving the strength of the core layer material. The outer layer's preparation materials include an anti-aging agent composition consisting of hindered phenolic antioxidants, ultraviolet absorbers, and nano-inorganic anti-aging agents, effectively preventing the pipe from becoming brittle, discolored, and cracked during use, achieving a significant overall aging resistance effect.

Description

Technical Field

[0001] This invention relates to the field of drainage pipe technology, and more specifically, to a low-foaming rigid polyvinyl chloride drainage pipe and its preparation method. Background Technology

[0002] Rigid polyvinyl chloride (UPVC) pipes are widely used in building water supply and drainage, municipal drainage and agricultural irrigation and drainage due to their advantages such as good corrosion resistance, smooth inner wall, light weight and low price.

[0003] To reduce pipe weight while providing sound and heat insulation, low-foaming PVC pipes have been developed. Currently, common low-foaming PVC pipes mainly come in two structures: skin-coated low-foaming pipes and core-foaming pipes. Skin-coated low-foaming pipes incorporate a foaming agent in the formula, causing a dense skin layer to form on the inner and outer walls during extrusion, with a foamed layer in the middle. Core-foaming pipes typically employ a three-layer co-extrusion process, with two rigid PVC layers on the inner and outer sides and a low-foaming layer in the middle. Structurally, they utilize the I-structure principle in materials mechanics, providing energy absorption and sound insulation.

[0004] However, in conventional foaming formulations for preparing low-foaming rigid PVC drainage pipes, the gases generated by the decomposition of the foaming agent in the melt are difficult to control precisely. This can easily lead to excessively large cell diameters, cell wall rupture, or uneven cell distribution. This not only affects the appearance quality of the pipe but also severely reduces its mechanical strength, such as ring stiffness and impact resistance. Moreover, the presence of the foam layer creates numerous voids within the material, resulting in a decrease in the overall pressure-bearing capacity and creep resistance of the pipe, making it difficult to meet the requirements of certain high-standard drainage projects. Furthermore, the outer layer material has limited anti-aging properties and is prone to powdering and discoloration during outdoor use, shortening the pipe's lifespan.

[0005] Therefore, developing a low-foaming drainage pipe that combines excellent mechanical properties, thermal stability, and high weather resistance has significant practical value. Summary of the Invention

[0006] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides a low-foaming rigid polyvinyl chloride drainage pipe and its preparation method, the specific technical solution of which is as follows:

[0007] A low-foaming rigid polyvinyl chloride drainage pipe comprises, from the inside out, an inner layer, a core layer, and an outer layer, wherein, By weight, the inner layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 1-5 parts heat stabilizer, 3-8 parts corrosion resistant modifier, 0.5-2 parts lubricant, and 10-15 parts filler. By weight, the core layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 15-30 parts modified polyvinyl chloride resin, 1-5 parts heat stabilizer, 0.5-2 parts crosslinking agent, 3-7 parts isocyanate, 1-5 parts acid anhydride, 0.5-2 parts foaming agent, 0.1-0.5 parts foaming aid, and 10-20 parts filler; By weight, the outer layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 1-5 parts heat stabilizer, 1-10 parts anti-aging agent composition, 1-2 parts lubricant, 2-5 parts titanium dioxide, and 5-15 parts filler.

[0008] Furthermore, in the inner layer, the corrosion-resistant modifier is obtained by mixing chlorinated polyethylene and acrylate copolymers in a mass ratio of (1~5):(1~2).

[0009] Furthermore, the modified polyvinyl chloride resin is a polyvinyl chloride copolymer grafted with polyurethane prepolymer, and the grafting rate of the polyurethane prepolymer is 5%~8%.

[0010] Furthermore, the crosslinking agent is obtained by mixing an organic peroxide crosslinking agent and a polyfunctional isocyanurate in a mass ratio of (1~2):(1~3).

[0011] Further, the isocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate, and polyphenylmethylene polyisocyanate.

[0012] Furthermore, the acid anhydride is at least one of trimellitic anhydride and pyromellitic dianhydride.

[0013] Furthermore, the foaming agent is azodicarbonamide.

[0014] Furthermore, the foaming agent is at least one of zinc stearate and stearic acid.

[0015] Furthermore, in the outer layer, the anti-aging agent composition includes a hindered phenolic antioxidant, an ultraviolet absorber, and a nano-inorganic anti-aging agent; the nano-inorganic anti-aging agent is obtained by mixing nano-cerium oxide and lignin activated by a titanate coupling agent in a mass ratio of (1~5):(1~3).

[0016] In addition, the present invention also provides a method for preparing a low-foaming rigid polyvinyl chloride drainage pipe, the method comprising the following steps: S1. Add polyvinyl chloride resin, heat stabilizer, corrosion resistant modifier, lubricant and filler to the mixer, stir and mix at 80~100℃ for 10~20min, cool down to below 60℃ and discharge to obtain the inner layer mixture; S2. Add polyvinyl chloride resin, modified polyvinyl chloride resin, heat stabilizer and filler to a mixer, stir and mix at 100~120℃ for 10~20min, cool down to below 60℃, add crosslinking agent, isocyanate, acid anhydride, foaming agent and foaming aid, continue stirring for 5~15min to obtain core layer mixture. S3. Add polyvinyl chloride resin, heat stabilizer, anti-aging agent composition, lubricant, titanium dioxide and filler to a mixer, stir and mix at 100~120℃ for 10~20min, cool down to below 60℃ and discharge to obtain the outer layer mixture; S4. The inner layer mixture, core layer mixture, and outer layer mixture are fed into an extruder and extruded through a three-layer co-extrusion die; the extruder barrel temperature is controlled at 160~210℃ and the die temperature at 170~195℃ to obtain a tube blank; S5. The tube blank is sized, cooled, drawn and cut to obtain a low-foaming rigid polyvinyl chloride drainage pipe.

[0017] Compared with existing technologies, its beneficial effects include: 1. The rigid polyvinyl chloride drainage pipe of the present invention has multiple advantages such as light weight, high strength, corrosion resistance and aging resistance through a three-layer co-extrusion structure, and has excellent comprehensive performance.

[0018] 2. The corrosion-resistant modifier, a composite of chlorinated polyethylene and acrylate copolymer, is added to the raw materials for preparing the inner layer of the present invention. After plasticization, it not only improves the strength of the drainage pipe, but also significantly improves the corrosion resistance of the inner wall and extends the service life of the drainage pipe.

[0019] 3. The core layer of this invention incorporates a foaming agent and a foaming co-foaming agent to form a microporous structure, reducing the material density and overall weight of the pipe. Furthermore, modified polyvinyl chloride (polyurethane prepolymer grafted onto PVC), a crosslinking agent, isocyanate, and acid anhydride are introduced into the core layer. These components undergo chemical reactions during processing to form an interpenetrating network or crosslinked structure, significantly improving the strength of the core layer material and the stability of the cell walls, preventing cell collapse. Isocyanate and acid anhydride act as reactive compatibilizers, enhancing the interfacial bonding between PVC and the modified resin and fillers, resulting in a foam that is not only lightweight but also possesses high strength and rigidity. The foaming aid regulates the foaming process, making the cells finer and more uniform, avoiding stress concentration and strength reduction caused by excessively large or unevenly distributed cells. The addition of nano-sized mica flakes treated with titanate coupling agent not only provides reinforcement but also acts as an excellent nucleating agent, promoting uniform bubble formation and further refining and stabilizing the cell structure.

[0020] 4. This invention introduces an anti-aging agent composition consisting of hindered phenolic antioxidants, ultraviolet absorbers, and nano-inorganic anti-aging agents into the raw materials for the preparation of the outer layer. The antioxidants inhibit thermal oxidative degradation, the ultraviolet absorbers shield or absorb ultraviolet light, and the nano-inorganic anti-aging agents are compounded from lignin activated by nano-cerium oxide and titanate coupling agents. Nano-cerium oxide can efficiently absorb ultraviolet light; lignin itself has anti-ultraviolet properties, and after activation by titanate, its compatibility with the resin matrix and nano-cerium oxide is better. The synergistic effect of the components not only enhances the ultraviolet shielding ability but also captures free radicals, making the anti-aging performance of the outer layer superior to that of a single component. This effectively prevents the pipe from becoming brittle, discolored, and cracked during use, achieving a significant overall anti-aging effect. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] One embodiment of the present invention provides a low-foaming rigid polyvinyl chloride drainage pipe, which, from the inside out, comprises an inner layer, a core layer, and an outer layer, wherein... By weight, the inner layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 1-5 parts heat stabilizer, 3-8 parts corrosion resistant modifier, 0.5-2 parts lubricant, and 10-15 parts filler. By weight, the core layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 15-30 parts modified polyvinyl chloride resin, 1-5 parts heat stabilizer, 0.5-2 parts crosslinking agent, 3-7 parts isocyanate, 1-5 parts acid anhydride, 0.5-2 parts foaming agent, 0.1-0.5 parts foaming aid, and 10-20 parts filler; By weight, the outer layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 1-5 parts heat stabilizer, 1-10 parts anti-aging agent composition, 1-2 parts lubricant, 2-5 parts titanium dioxide, and 5-15 parts filler.

[0024] In one embodiment, the corrosion-resistant modifier in the inner layer is obtained by mixing chlorinated polyethylene and acrylate copolymers in a mass ratio of (1~5):(1~2).

[0025] In one embodiment, the modified polyvinyl chloride resin is a polyurethane prepolymer grafted onto a polyvinyl chloride copolymer, and the polyurethane prepolymer grafting rate is 5% to 8%.

[0026] In one embodiment, the polyurethane prepolymer is at least one of a hydroxyl-terminated polyurethane prepolymer and a carboxyl-terminated polyurethane prepolymer.

[0027] In one embodiment, the crosslinking agent is obtained by mixing an organic peroxide crosslinking agent and a polyfunctional isocyanurate in a mass ratio of (1~2):(1~3).

[0028] In one embodiment, the organic peroxide crosslinking agent is dicumyl peroxide.

[0029] In one embodiment, the polyfunctional isocyanurate is triallyl isocyanurate.

[0030] In one embodiment, the isocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate, and polyphenylmethylene polyisocyanate.

[0031] In one embodiment, the acid anhydride is at least one of trimellitic anhydride and pyromellitic dianhydride.

[0032] In one embodiment, the foaming agent is azodicarbonamide.

[0033] In one embodiment, the foaming agent is at least one of zinc stearate and stearic acid.

[0034] In one embodiment, the outer layer of the anti-aging agent composition includes a hindered phenolic antioxidant, an ultraviolet absorber, and a nano-inorganic anti-aging agent; the nano-inorganic anti-aging agent is obtained by mixing nano-cerium oxide and lignin activated by a titanate coupling agent in a mass ratio of (1~5):(1~3).

[0035] In one embodiment, the hindered phenolic antioxidant is at least one of antioxidant 1010, antioxidant 1076, and antioxidant 245.

[0036] In one embodiment, the ultraviolet absorber is at least one of UV-326, UV-327, and UV-329.

[0037] In one embodiment, the cerium nanoparticles have a particle size of 10-50 nm.

[0038] In one embodiment, the heat stabilizer is at least one of a calcium-zinc composite stabilizer and an organotin stabilizer.

[0039] In one embodiment, the lubricant is at least one of paraffin wax, stearic acid alcohol, and stearamide.

[0040] In one embodiment, the filler in the raw materials for preparing the core layer is mica sheet surface-treated with titanate coupling agent.

[0041] In one embodiment, the mica sheet has a particle size of 10nm to 50nm.

[0042] In one embodiment, the raw materials for preparing the inner layer and the outer layer, and the filler, are at least one of nano-calcium carbonate and nano-talc.

[0043] In one embodiment, the raw materials for preparing the inner layer and the outer layer, and the filler have an average particle size of 50~200nm.

[0044] In addition, the present invention also provides a method for preparing a low-foaming rigid polyvinyl chloride drainage pipe, the method comprising the following steps: S1. Add polyvinyl chloride resin, heat stabilizer, corrosion resistant modifier, lubricant and filler to the mixer, stir and mix at 80~100℃ for 10~20min, cool down to below 60℃ and discharge to obtain the inner layer mixture; S2. Add polyvinyl chloride resin, modified polyvinyl chloride resin, heat stabilizer and filler to a mixer, stir and mix at 100~120℃ for 10~20min, cool down to below 60℃, add crosslinking agent, isocyanate, acid anhydride, foaming agent and foaming aid, continue stirring for 5~15min to obtain core layer mixture. S3. Add polyvinyl chloride resin, heat stabilizer, anti-aging agent composition, lubricant, titanium dioxide and filler to a mixer, stir and mix at 100~120℃ for 10~20min, cool down to below 60℃ and discharge to obtain the outer layer mixture; S4. The inner layer mixture, core layer mixture, and outer layer mixture are fed into an extruder and extruded through a three-layer co-extrusion die; the extruder barrel temperature is controlled at 160~210℃ and the die temperature at 170~195℃ to obtain a tube blank; S5. The tube blank is sized, cooled, drawn and cut to obtain a low-foaming rigid polyvinyl chloride drainage pipe.

[0045] In one embodiment, the inner layer of the low-foaming rigid PVC drain pipe has a thickness of 0.3mm to 0.5mm, the core layer has a thickness of 2.0mm to 3.0mm, and the outer layer has a thickness of 0.3mm to 0.7mm.

[0046] The above-mentioned scheme, by compounding the components of the drainage pipe, produces rigid polyvinyl chloride drainage pipes with superior mechanical properties and aging resistance, thus having greater application value.

[0047] The embodiments of the present invention will be described in detail below with reference to specific examples. The raw materials used in the preparation of the present invention, unless otherwise specified in the following examples, are all commercially available, and the processes not specified are considered conventional techniques and will not be elaborated upon here.

[0048] Example 1: A method for preparing a low-foaming rigid polyvinyl chloride drainage pipe includes the following steps: S1. By weight, add 100 parts of polyvinyl chloride resin, 3 parts of calcium-zinc composite stabilizer, 5 parts of corrosion-resistant modifier, 0.5 parts of stearic acid alcohol and 12 parts of filler to a mixer, stir and mix at 100℃ for 20 minutes, cool to room temperature, and discharge to obtain the inner layer mixture. In the inner layer mixture, the corrosion-resistant modifier is obtained by mixing chlorinated polyethylene and acrylate copolymers in a mass ratio of 3:2; the filler is nano-calcium carbonate with an average particle size of 80nm. S2. By weight, add 100 parts of polyvinyl chloride resin, 18 parts of modified polyvinyl chloride resin, 1 part of calcium-zinc composite stabilizer and 15 parts of filler to a mixer, stir and mix at 120°C for 20 minutes, cool down to 45°C, add 1 part of crosslinking agent, 5 parts of diphenylmethane diisocyanate, 3 parts of trimellitic anhydride, 1 part of azodicarbonamide and 0.2 parts of zinc stearate, and continue stirring for 10 minutes to obtain the core layer mixture; In the core layer mixture, the modified polyvinyl chloride resin is a polyvinyl chloride copolymer grafted with hydroxyl-terminated polyurethane prepolymer, and the grafting rate of the polyurethane prepolymer is 5%. The crosslinking agent is obtained by mixing dicumyl peroxide and triallyl isocyanurate in a mass ratio of 2:3; The filler is mica flakes surface-treated with titanate coupling agent, and the particle size of the mica flakes is 40 nm.

[0049] S3. By weight, add 100 parts of polyvinyl chloride resin, 2 parts of calcium-zinc composite stabilizer, 6 parts of anti-aging agent composition, 1 part of stearic acid alcohol, 3 parts of titanium dioxide and 12 parts of filler into a mixer, stir and mix at 100°C for 20 minutes, cool to room temperature, and discharge to obtain the outer layer mixture. The outer layer mixture comprises an anti-aging agent composition including a hindered phenolic antioxidant (antioxidant 1010), an ultraviolet absorber (UV-326), and a nano-inorganic anti-aging agent; the nano-inorganic anti-aging agent is obtained by mixing 45nm nano-cerium oxide and lignin activated by a titanate coupling agent at a mass ratio of 3:2; the filler is nano-calcium carbonate with an average particle size of 80nm. S4. The inner layer mixture, core layer mixture, and outer layer mixture are fed into an extruder and extruded through a three-layer co-extrusion die; the extruder barrel temperature is controlled at 160~210℃ and the die temperature at 170~195℃ to obtain a tube blank; S5. The tube blank is sized, cooled, drawn and cut to obtain a low-foaming rigid polyvinyl chloride drainage pipe.

[0050] The low-foaming rigid PVC drainage pipe prepared in Example 1 has an inner layer thickness of 0.5 mm, a core layer thickness of 2.0 mm, and an outer layer thickness of 0.5 mm.

[0051] Example 2: A method for preparing a low-foaming rigid polyvinyl chloride drainage pipe includes the following steps: S1. By weight, add 100 parts of polyvinyl chloride resin, 3 parts of calcium-zinc composite stabilizer, 6 parts of corrosion-resistant modifier, 0.6 parts of stearic acid alcohol and 11 parts of filler to a mixer, stir and mix at 100℃ for 20 minutes, cool to room temperature, and discharge to obtain the inner layer mixture. In the inner layer mixture, the corrosion-resistant modifier is obtained by mixing chlorinated polyethylene and acrylate copolymers in a mass ratio of 3:2; the filler is nano-calcium carbonate with an average particle size of 80nm. S2. By weight, add 100 parts of polyvinyl chloride resin, 20 parts of modified polyvinyl chloride resin, 1 part of calcium-zinc composite stabilizer and 12 parts of filler to a mixer, stir and mix at 120°C for 20 minutes, cool down to 45°C, add 1 part of crosslinking agent, 4 parts of diphenylmethane diisocyanate, 4 parts of trimellitic anhydride, 1 part of azodicarbonamide and 0.2 parts of zinc stearate, and continue stirring for 15 minutes to obtain the core layer mixture; In the core layer mixture, the modified polyvinyl chloride resin is a polyvinyl chloride copolymer grafted with hydroxyl-terminated polyurethane prepolymer, and the grafting rate of the polyurethane prepolymer is 6%. The crosslinking agent is obtained by mixing dicumyl peroxide and triallyl isocyanurate in a mass ratio of 2:3; The filler is mica flakes surface-treated with titanate coupling agent, and the particle size of the mica flakes is 40 nm.

[0052] S3. By weight, add 100 parts of polyvinyl chloride resin, 3 parts of calcium-zinc composite stabilizer, 7 parts of anti-aging agent composition, 1 part of stearic acid alcohol, 3 parts of titanium dioxide and 10 parts of filler into a mixer, stir and mix at 120°C for 20 minutes, cool to room temperature, and discharge to obtain the outer layer mixture. The outer layer mixture comprises an anti-aging agent composition including a hindered phenolic antioxidant (antioxidant 1010), an ultraviolet absorber (UV-326), and a nano-inorganic anti-aging agent; the nano-inorganic anti-aging agent is obtained by mixing 45nm nano-cerium oxide and lignin activated by a titanate coupling agent at a mass ratio of 3:2; the filler is nano-calcium carbonate with an average particle size of 80nm. S4. The inner layer mixture, core layer mixture, and outer layer mixture are fed into an extruder and extruded through a three-layer co-extrusion die; the extruder barrel temperature is controlled at 160~210℃ and the die temperature at 170~195℃ to obtain a tube blank; S5. The tube blank is sized, cooled, drawn and cut to obtain a low-foaming rigid polyvinyl chloride drainage pipe.

[0053] The low-foaming rigid PVC drainage pipe prepared in Example 2 has an inner layer thickness of 0.5 mm, a core layer thickness of 2.0 mm, and an outer layer thickness of 0.5 mm.

[0054] Example 3: A method for preparing a low-foaming rigid polyvinyl chloride drainage pipe includes the following steps: S1. By weight, add 100 parts of polyvinyl chloride resin, 3 parts of calcium-zinc composite stabilizer, 5 parts of corrosion-resistant modifier, 0.5 parts of stearic acid alcohol and 13 parts of filler to a mixer, stir and mix at 100℃ for 20 minutes, cool to room temperature, and discharge to obtain the inner layer mixture. In the inner layer mixture, the corrosion-resistant modifier is obtained by mixing chlorinated polyethylene and acrylate copolymers in a mass ratio of 3:2; the filler is nano-calcium carbonate with an average particle size of 80nm. S2. By weight, add 100 parts of polyvinyl chloride resin, 18 parts of modified polyvinyl chloride resin, 2 parts of calcium-zinc composite stabilizer and 15 parts of filler to a mixer, stir and mix at 120°C for 20 minutes, cool down to 45°C, add 0.8 parts of crosslinking agent, 6 parts of diphenylmethane diisocyanate, 5 parts of trimellitic anhydride, 1 part of azodicarbonamide and 0.3 parts of zinc stearate, and continue stirring for 15 minutes to obtain the core layer mixture; In the core layer mixture, the modified polyvinyl chloride resin is a polyvinyl chloride copolymer grafted with hydroxyl-terminated polyurethane prepolymer, and the grafting rate of the polyurethane prepolymer is 8%. The crosslinking agent is obtained by mixing dicumyl peroxide and triallyl isocyanurate in a mass ratio of 2:3; The filler is mica flakes surface-treated with titanate coupling agent, and the particle size of the mica flakes is 40 nm.

[0055] S3. By weight, add 100 parts of polyvinyl chloride resin, 3 parts of calcium-zinc composite stabilizer, 8 parts of anti-aging agent composition, 1 part of stearic acid alcohol, 3 parts of titanium dioxide and 11 parts of filler into the mixer, stir and mix at 120°C for 20 minutes, cool to room temperature, and discharge to obtain the outer layer mixture. The outer layer mixture comprises an anti-aging agent composition including a hindered phenolic antioxidant (antioxidant 1010), an ultraviolet absorber (UV-326), and a nano-inorganic anti-aging agent; the nano-inorganic anti-aging agent is obtained by mixing 45nm nano-cerium oxide and lignin activated by a titanate coupling agent at a mass ratio of 3:2; the filler is nano-calcium carbonate with an average particle size of 80nm. S4. The inner layer mixture, core layer mixture, and outer layer mixture are fed into an extruder and extruded through a three-layer co-extrusion die; the extruder barrel temperature is controlled at 160~210℃ and the die temperature at 170~195℃ to obtain a tube blank; S5. The tube blank is sized, cooled, drawn and cut to obtain a low-foaming rigid polyvinyl chloride drainage pipe.

[0056] The low-foaming rigid PVC drainage pipe prepared in Example 3 has an inner layer thickness of 0.5 mm, a core layer thickness of 2.0 mm, and an outer layer thickness of 0.5 mm.

[0057] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that no corrosion-resistant modifier was added to the inner layer mixture of Comparative Example 1, while the rest is the same as Example 3.

[0058] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that no modified polyvinyl chloride resin was added to the core layer mixture of Comparative Example 2, while the rest is the same as Example 3.

[0059] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that diphenylmethane diisocyanate was not added to the core layer mixture of Comparative Example 3, but otherwise it was the same as Example 3.

[0060] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that trimellitic anhydride was not added to the core layer mixture of Comparative Example 4, but otherwise it was the same as Example 3.

[0061] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that only a single hindered phenolic antioxidant (antioxidant 1010) is added to the outer layer mixture of Comparative Example 5, that is, antioxidant 1010 is used to replace the anti-aging agent composition, and the rest is the same as Example 3.

[0062] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that only a single ultraviolet absorber (UV-326) was added to the outer layer mixture of Comparative Example 6, that is, UV-326 was used to replace the anti-aging agent composition, and the rest was the same as Example 3.

[0063] Comparative Example 7: Compared with Example 3, Comparative Example 7 differs in that only a nano-inorganic anti-aging agent (obtained by mixing nano-cerium oxide with a particle size of 45nm and lignin activated by titanate coupling agent in a mass ratio of 3:2) is added to the outer layer mixture of Comparative Example 7. That is, the nano-inorganic anti-aging agent replaces the anti-aging agent composition, while the rest is the same as Example 3.

[0064] Comparative Example 8: The difference between Comparative Example 8 and Example 3 is that no anti-aging agent composition was added in Comparative Example 8, but otherwise it is the same as Example 3.

[0065] The rigid PVC drainage pipe samples prepared in Examples 1-3 and the rigid PVC drainage pipe samples prepared in Comparative Examples 1-8 were subjected to performance tests, and the results are shown in Table 1 below.

[0066] The corrosion resistance tensile strength test was conducted according to the method in GB / T5836.1-2018 "Rigid Polyvinyl Chloride Pipes for Building Drainage". After that, the samples of Examples 1 to 3 and Comparative Examples 1 to 8 were immersed in a 15% hydrochloric acid solution for 48 hours and then the corrosion resistance tensile strength was tested according to the above tensile strength test method.

[0067] UV resistance and aging resistance tests were conducted using a UVC-LED disinfection lamp (30W, 254nm wavelength) at a vertical distance of 10cm for 40 hours, according to CIE1976L. a b The standard test measures the color difference before and after UVC-LED irradiation; samples are placed in a UV aging chamber at 60℃ and 0.86w / cm². 2 Expose the product to ultraviolet light for 1000 hours and test the difference in the yellow index. The larger the difference, the worse the anti-aging performance.

[0068] Table 1: Performance Test Results

[0069] As shown in Table 1, this invention, by optimizing the raw materials for pipe preparation, can effectively reduce the erosion of corrosive media and exhibit excellent overall mechanical strength. The synergistic effect of the components in the anti-aging agent composition can effectively delay UV-induced degradation and discoloration. Compared with Example 3, Comparative Example 1, without the addition of a corrosion-resistant modifier, showed a significant decrease in tensile strength after corrosion, indicating that the composite of chlorinated polyethylene and acrylate copolymers plays a significant role in the corrosion resistance of the inner layer; Comparative Example 2, without the addition of modified polyvinyl chloride resin, showed performance inferior to Example 3, indicating that the polyurethane prepolymer grafted with modified polyvinyl chloride resin has a certain improving effect on the mechanical properties and interfacial bonding of the core layer; Comparative Example 3, without the addition of cyanate ester, showed lower strength than Example 3, indicating that isocyanate helps to form a cross-linked structure and enhances the stability of the cell walls; Comparative Example 4, without the addition of acid anhydride, showed performance inferior to Example 3, indicating that acid anhydride, as a reactive compatibilizer, helps to improve interfacial bonding and cell uniformity, thereby improving tensile strength; Comparative Example 5, using only antioxidants, showed a large change in the yellow index, indicating that... Antioxidants alone resist UV aging; Comparative Example 6 only has UV absorbers, and its color difference and yellow index are not as good as in Example 3; Comparative Example 7 only has nano-inorganic anti-aging agents, but its aging resistance is not as good as in Example 3, indicating that nano-cerium oxide and activated lignin have certain UV shielding and free radical scavenging capabilities, but lack the synergistic effect of organic antioxidants and UV absorbers, and the effect is significantly worse than in Example 3; Comparative Example 8 did not add an anti-aging agent composition, and its color difference and yellow index changes were significantly worse than in Example 3, indicating that without any anti-aging protection, the material is very easy to age and discolor under UV light, and its performance will significantly decline. This shows that the anti-aging agent composition of the present invention, composed of hindered phenolic antioxidants, UV absorbers and nano-inorganic anti-aging agents, can effectively prevent the pipe from becoming brittle, discolored and cracked during use, and achieves a significant overall aging resistance effect.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-foaming rigid polyvinyl chloride drainage pipe, comprising, from the inside out, an inner layer, a core layer, and an outer layer, characterized in that, By weight, the inner layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 1-5 parts heat stabilizer, 3-8 parts corrosion resistant modifier, 0.5-2 parts lubricant, and 10-15 parts filler. By weight, the core layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 15-30 parts modified polyvinyl chloride resin, 1-5 parts heat stabilizer, 0.5-2 parts crosslinking agent, 3-7 parts isocyanate, 1-5 parts acid anhydride, 0.5-2 parts foaming agent, 0.1-0.5 parts foaming aid, and 10-20 parts filler; By weight, the outer layer comprises the following raw materials: 100 parts polyvinyl chloride resin, 1-5 parts heat stabilizer, 1-10 parts anti-aging agent composition, 1-2 parts lubricant, 2-5 parts titanium dioxide, and 5-15 parts filler.

2. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, In the inner layer, the corrosion-resistant modifier is obtained by mixing chlorinated polyethylene and acrylate copolymers in a mass ratio of (1~5):(1~2).

3. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, The modified polyvinyl chloride resin is a polyvinyl chloride copolymer grafted with polyurethane prepolymer, and the grafting rate of the polyurethane prepolymer is 5%~8%.

4. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, The crosslinking agent is obtained by mixing an organic peroxide crosslinking agent and a polyfunctional isocyanurate in a mass ratio of (1~2):(1~3).

5. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, The isocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate, and polyphenylmethylene polyisocyanate.

6. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, The acid anhydride is at least one of trimellitic anhydride and pyromellitic dianhydride.

7. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, The foaming agent is azodicarbonamide.

8. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, The foaming agent is at least one of zinc stearate and stearic acid.

9. The low-foaming rigid polyvinyl chloride drainage pipe according to claim 1, characterized in that, In the outer layer, the anti-aging agent composition includes hindered phenolic antioxidants, ultraviolet absorbers and nano-inorganic anti-aging agents; the nano-inorganic anti-aging agents are obtained by mixing nano-cerium oxide and lignin activated by titanate coupling agent in a mass ratio of (1~5):(1~3).

10. A method for preparing a low-foaming rigid polyvinyl chloride drainage pipe, characterized in that, The preparation method is used to prepare the low-foaming rigid polyvinyl chloride drainage pipe as described in any one of claims 1 to 9, and the preparation method includes the following steps: S1. Add polyvinyl chloride resin, heat stabilizer, corrosion resistant modifier, lubricant and filler to the mixer, stir and mix at 80~100℃ for 10~20min, cool down to below 60℃ and discharge to obtain the inner layer mixture; S2. Add polyvinyl chloride resin, modified polyvinyl chloride resin, heat stabilizer and filler to a mixer, stir and mix at 100~120℃ for 10~20min, cool down to below 60℃, add crosslinking agent, isocyanate, acid anhydride, foaming agent and foaming aid, continue stirring for 5~15min to obtain core layer mixture. S3. Add polyvinyl chloride resin, heat stabilizer, anti-aging agent composition, lubricant, titanium dioxide and filler to a mixer, stir and mix at 100~120℃ for 10~20min, cool down to below 60℃ and discharge to obtain the outer layer mixture; S4. The inner layer mixture, core layer mixture, and outer layer mixture are fed into an extruder and extruded through a three-layer co-extrusion die; the extruder barrel temperature is controlled at 160~210℃ and the die temperature at 170~195℃ to obtain a tube blank; S5. The tube blank is sized, cooled, drawn and cut to obtain a low-foaming rigid polyvinyl chloride drainage pipe.

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