Composite pipe and preparation method thereof

Abstract

The present invention discloses a composite pipe and its preparation method. The composite pipe comprises 80-120 parts low-density polyethylene, 5-15 parts high-density polyethylene, 20-40 parts ethylene-vinyl alcohol copolymer, 1-10 parts maleic anhydride-grafted polyethylene, 5-10 parts reinforcing agent, 5-20 parts anti-wear agent, and 0.1-1 parts antioxidant. The present invention also provides a preparation method. Compared with existing technologies, the composite pipe prepared by the present invention has advantages such as high barrier capacity, excellent mechanical properties, and good antibacterial properties.

Description

Technical Field

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

[0002] Product packaging materials, including bags, boxes, and packaging hoses, are crucial for preventing leakage and spoilage of product contents. Due to their relatively low cost, packaging hoses have rapidly developed over the past decade and are now widely used in packaging daily necessities, food, and other products. However, packaging hoses are still susceptible to deformation and damage due to repeated external pressure and use, leading to leakage of contents. Alternatively, they can be susceptible to the long-term infiltration of moisture and oxygen in humid environments, compromising the quality of the contents. Therefore, a composite tubing material with excellent barrier properties, the ability to withstand repeated external pressure, and antibacterial properties is highly desirable.

[0003] CN108623915A discloses a modified white graphene composite polypropylene pipe and its preparation method. The pipe is composed of 1-3 parts barium sulfate whiskers, 3-12 parts flame retardant, 10-16 parts antistatic agent, 4-8 parts modified white graphene, 6-12 parts impact modifier, 0.6-1.2 parts antioxidant, 0.6-1.2 parts dispersant, 0.5-1 parts nano-calcium carbonate, 0.7-1.4 parts nano-ceramic powder, 0.2-0.5 parts lubricant, 0.4-0.8 parts surfactant, and 60-120 parts polypropylene. The pipe has improved mechanical properties. However, the addition of many inorganic ingredients in this recipe may result in increased pipe rigidity and poor extrusion resistance during use.

[0004] CN1357702A discloses a plastic composite hose for packaging. The hose comprises a composite aluminum foil inner layer, an adhesive layer, and a plastic outer layer. The composite aluminum foil inner layer is a roll-welded structure, while the adhesive layer and plastic outer layer are co-extruded. The aluminum foil layer in the composite structure serves as a barrier, primarily preventing the permeation of various molecules inside and outside the hose, particularly the permeation between oxygen molecules in the air outside the hose and molecules within the hose. While the aluminum foil layer provides a barrier, this type of aluminum-plastic hose packaging material is opaque, has poor recyclability, is environmentally unfriendly, and exhibits poor extrusion resistance. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the object of the present invention is to provide a composite tube having good antibacterial properties, mechanical properties, and good barrier properties, which can be used for cosmetics and toothpaste packaging.

[0006] One of the purposes of the present invention is to provide a composite pipe, wherein the raw material components include, by weight: 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-10 parts of reinforcing agent, 5-20 parts of anti-wear agent, and 0.1-1 part of antioxidant;

[0007] Or, 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-20 parts of anti-wear agent, and 0.1-1 part of antioxidant.

[0008] Preferably, the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and antioxidant 168.

[0009] Preferably, the preparation method of the enhancer comprises the following steps, calculated by weight:

[0010] Step 1: Dissolve 1-5 parts of tetracycline and 10-20 parts of citric acid in 10-50 parts of water, transfer to an autoclave, and react at 180-220°C for 6-10 hours. After cooling to room temperature, centrifuge at 8000-12000 rpm for 5-15 minutes. Use a 0.22 mm microporous membrane filter to remove larger particles in the supernatant to obtain a carbon dot stock solution.

[0011] Step 2: dissolving 1-5 parts of melamine and 5-15 parts of ammonium chloride in 20-40 parts of water, and then calcining at 500-700°C for 2-4 hours to obtain modified graphite carbon nitride; uniformly mixing 1-5 parts of modified graphite carbon nitride with 10-20 parts of the carbon dot stock solution prepared in step 1 above, transferring the mixture to a reactor, and reacting at 160-200°C for 16-24 hours; after naturally cooling to room temperature, centrifuging at 8000-12000 rpm for 5-15 minutes, removing larger particles in the supernatant with a 0.22 mm microporous membrane filter, and then freeze-drying for 16-36 hours to obtain a composite material of carbon dots supported on graphite carbon nitride;

[0012] Step 3, 5-10 parts of the modifier, 10-20 parts of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 50-100 parts of N,N-dimethylformamide are mixed evenly, and 1-5 parts of the carbon point-loaded graphite carbon nitride composite material prepared in the above step 2 are added, and the mixture is reacted at 40-60 ° C and 1000-2000 rpm for 10-16 hours, and then filtered. The filter residue is washed with water 2-4 times and dried at 40-60 ° C for 4-6 hours to obtain a reinforcing agent.

[0013] More preferably, the modifier in step 3 is at least one of chitosan, polylysine, and N-ethyl-2-nitroaniline.

[0014] Carbon dots are a new type of carbon nanomaterial with a particle size of less than 10 nm. 2 Hybrid or amorphous sp 3 Hybrid carbon cores are polymerized with organic functional groups to form nano-scale particles with a large specific surface area and rich functional groups on the surface, such as carboxyl, carbonyl and hydroxyl groups. These functional groups make them water-soluble and easier to surface modify and couple. Some carbon dots have positive charges on their surfaces and can be adsorbed on the negatively charged bacterial cell membrane surface through electrostatic action, thereby destroying the integrity of the cell membrane, causing the leakage of intracellular substances and leading to bacterial death. Under light or specific conditions, carbon dots can produce reactive oxygen species, such as singlet oxygen, hydroxyl radicals and superoxide anions. These highly oxidizing substances can oxidize bacterial cell walls, cell membranes and intracellular biomacromolecules, thereby inhibiting bacterial growth or directly killing bacteria. They may interact with biomacromolecules such as enzymes and proteins in bacterial cells, interfering with the normal metabolic process of bacteria and affecting bacterial growth and reproduction.

[0015] In the preparation step of the enhancer of the present invention, modified graphite carbon nitride is synthesized by high-temperature calcination of melamine and ammonium chloride. It has a graphite-like layered structure, and is connected by triazines or units through covalent bonds in the plane to form a two-dimensional planar network. These planes are then stacked by van der Waals forces to form a three-dimensional structure. This unique structure gives it higher chemical stability. Compared with the conventional graphite carbon nitride synthesized by calcining with melamine, the present invention can synthesize modified graphite carbon nitride with a higher specific surface area through the combined action of melamine and ammonium chloride, and has better light absorption capacity. Graphite carbon nitride absorbs photon energy under light conditions, and its valence band electrons transition to the conduction band to form photogenerated electrons and holes. The photogenerated electrons react with oxygen adsorbed on the surface of the material to generate superoxide anion radicals, and the holes react with water molecules on the surface to generate hydroxyl radicals. These highly oxidizing active oxygen species can attack the cell wall and cell membrane of bacteria, resulting in increased permeability and leakage of contents, thereby destroying the cell structure of bacteria and killing the bacteria, with excellent antibacterial properties.

[0016] Based on this, the present invention synthesizes a composite material in which carbon dots are loaded on graphite carbon nitride by mixing a carbon dot material and modified graphite carbon nitride, that is, in the process of preparing the enhancer of the present invention, the carbon dot stock solution prepared in step 1 and the modified graphite carbon nitride in step 2 are combined in step 2 to synthesize a composite material in which carbon dots are loaded on graphite carbon nitride. The present invention forms an enhancer with high reaction activity with the matrix by subjecting the composite material in which carbon dots are loaded on graphite carbon nitride to an amide condensation reaction with a modifier to form a stable chemical bond. The enhancer prepared by the present invention has good photocatalytic properties. The overlap of the ultraviolet-visible absorption of the graphite carbon nitride in its structure and the upconversion emission spectrum of the carbon dots produces strong spectral coupling, inducing a broadband photocatalytic response from the ultraviolet to the NIR region, which can further enhance the antibacterial effect. The reinforcing agent prepared by the present invention is introduced into the preparation process of the composite pipe. Since the surface of the carbon dots in the reinforcing agent structure is rich in functional groups such as hydroxyl and carboxyl groups, maleic anhydride can be grafted onto polyethylene to react to form stable chemical bonds, and the reinforcing agent has high reaction activity with the matrix. The carbon dots and modifiers introduced into the reinforcing agent can chemically react or physically cross-link with the polyethylene molecular chains to form a three-dimensional cross-linked network. At the same time, the graphite carbon nitride in the reinforcing agent has good mechanical effects, which can enhance the mechanical effects of the composite material and at the same time increase the dispersibility of the composite material to improve the antibacterial effect.

[0017] Preferably, the step of adding the anti-wear agent comprises the following steps, calculated by parts by mass:

[0018] Dissolve 1-5 parts of γ-aminopropyltriethoxysilane in dichloromethane to obtain a mass fraction of 1-5%, add 20-40 parts of ultra-high molecular weight polyethylene, ultrasonically extract for 5-10 minutes, filter, and dry the filter cake to obtain solid a, dissolve 1-5 parts of solid a in 10-50 parts of white oil, add 1-10 parts of wear-resistant particles, and react at 40-60°C for 2-4 hours to obtain a wear-resistant agent.

[0019] Further preferably, the wear-resistant particles are nano-silicon dioxide.

[0020] As a further illustration of the present invention, in the preparation process of the wear-resistant agent, the present invention ultrasonically extracts γ-aminopropyltriethoxysilane and ultra-high molecular weight polyethylene to obtain solid a. The cavitation effect of ultrasound can accelerate the material exchange between the solvent and the solid. The components in the γ-aminopropyltriethoxysilane solution may interact with the ultra-high molecular weight polyethylene. The amino groups and other functional groups in the molecule may be adsorbed or chemically reacted with the active sites on the surface of the ultra-high molecular weight polyethylene, thereby introducing γ-aminopropyltriethoxysilane into the ultra-high molecular weight polyethylene to obtain an ultra-high molecular weight polyethylene containing amino groups and hydroxyl groups on the surface, i.e., solid a. Afterwards, solid a is mixed with wear-resistant particles. The amino groups on its surface may undergo a condensation reaction with the hydroxyl groups on the surface of the nano-silica or other active sites may undergo adsorption and other interactions, thereby preparing the wear-resistant agent. The wear-resistant agent prepared by the present invention is introduced into the preparation process of the composite pipe. During the melt mixing process, the amino groups, alkoxy groups, silanol groups, etc. on the surface of the wear-resistant agent may chemically react with the oxygen-containing functional groups of the reinforcing agent and the functional groups on the maleic anhydride grafted polyethylene to form a cross-linked network, further increasing the wear resistance and mechanical properties.

[0021] A second object of the present invention is to provide a method for preparing the composite pipe, the method comprising the following steps:

[0022] Step 1: mixing low-density polyethylene, high-density polyethylene, ethylene-vinyl alcohol copolymer, maleic anhydride grafted polyethylene, anti-wear agent, and reinforcing agent (if any) at 140-220° C. for 5-15 minutes to obtain a mixture;

[0023] Step 2: Extruding and granulating the mixture to obtain masterbatch;

[0024] Step 3: Melt the masterbatch and the antioxidant to form a tube to obtain a composite tube.

[0025] Preferably,

[0026] In the step 2, the granulation temperature is 140-220° C., the die head temperature is 140-230° C., and the screw speed is 10-30 r / min.

[0027] Preferably, the tube drawing process parameters in step 3 are as follows: the upper drawing temperature is 120-180°C, the temperature inside the table is 140-180°C, and the temperature outside the table is 165-190°C.

[0028] Beneficial effects of the present invention:

[0029] 1. Compared with existing technologies, the present invention produces composite tubing by rationally proportioning the raw materials, utilizing the interactions between them, and optimizing the preparation process. The composite tubing produced by the present invention not only exhibits excellent barrier properties but also possesses excellent mechanical properties, mechanical effects, and antibacterial properties, making it suitable for packaging of cosmetics, toothpaste, and other products.

[0030] 2. Compared to existing technologies, the present invention enhances mechanical properties and antimicrobial performance by introducing a reinforcing agent and an anti-wear agent into the composite pipe preparation process, further improving barrier properties. During the composite pipe preparation process, the reinforcing agent of the present invention reacts with the anti-wear agent and maleic anhydride-grafted polyethylene to form chemical bonds, which improves the mechanical properties of the composite pipe. Furthermore, the reinforcing agent and anti-wear agent may also produce synergistic effects through electrostatic adsorption, further enhancing antimicrobial efficacy. DETAILED DESCRIPTION

[0031] The parameters and sources of some substances in the examples are as follows:

[0032] Low-density polyethylene, brand 2426K, sourced from Maoming Petrochemical;

[0033] High-density polyethylene, brand: 9007, sourced from Taiwan Plastics;

[0034] Ethylene-vinyl alcohol copolymer, brand: 3201, sourced from Sinopec Sichuan Weifang;

[0035] Maleic anhydride grafted polyethylene, sourced from Nanjing Feiteng New Materials Technology Co., Ltd.;

[0036] Ultra-high molecular weight polyethylene, brand: U-PE350, sourced from Yuyao Jiuding;

[0037] Nano-silica, particle size 50nm;

[0038] Nano calcium carbonate, particle size 40-80nm;

[0039] Nano zinc oxide, particle size 30-80nm;

[0040] Chitosan, deacetylation degree ≥95%, viscosity 150mPa.s.

[0041] Example 1

[0042] A method for preparing a composite pipe comprises the following steps:

[0043] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, 5 g of maleic anhydride-grafted polyethylene, and 15 g of an anti-wear agent at 200° C. for 10 minutes to obtain a mixture;

[0044] Step 2: Extruding and granulating the mixture to obtain masterbatch; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0045] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube. The tube drawing process parameters are: an upper drawing temperature of 160° C., a table temperature of 170° C., and a table temperature of 175° C.

[0046] The preparation method of the anti-wear agent comprises the following steps:

[0047] 3 g of γ-aminopropyltriethoxysilane was dissolved in dichloromethane to obtain a mass fraction of 3%, 30 g of ultra-high molecular weight polyethylene was added, and ultrasonic extraction was performed for 8 min. The solid a was filtered and the filter cake was dried to obtain solid a. 3 g of solid a was dissolved in 30 g of white oil, 5 g of nano-silica was added, and the mixture was reacted at 50°C for 3 h to obtain the wear-resistant agent.

[0048] Example 2

[0049] A method for preparing a composite pipe comprises the following steps:

[0050] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, 5 g of maleic anhydride-grafted polyethylene, 8 g of a reinforcing agent, and 15 g of an anti-wear agent at 200° C. for 10 minutes to obtain a mixture;

[0051] Step 2: Extruding and granulating the mixture to obtain masterbatch; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0052] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube. The tube drawing process parameters are: an upper drawing temperature of 160° C., a table temperature of 170° C., and a table temperature of 175° C.

[0053] The preparation method of the enhancer comprises the following steps:

[0054] Step 1: 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, then transferred to an autoclave and reacted at 200°C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10,000 rpm for 10 min. Large particles in the supernatant were removed using a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution.

[0055] Step 2: 3 g of melamine and 10 g of ammonium chloride were dissolved in 30 g of water, dried, mixed, and then calcined at 600 ° C for 3 h to obtain modified graphite carbon nitride. 3 g of modified graphite carbon nitride was evenly mixed with 15 g of the carbon dot stock solution prepared in step 1 above, transferred to a reactor, reacted at 180 ° C for 20 h, and after naturally cooling to room temperature, centrifuged at 10000 rpm for 10 min. The larger particles in the supernatant were removed with a 0.22 mm microporous membrane filter, and then freeze-dried for 24 h to obtain a composite material of carbon dots supported on graphite carbon nitride;

[0056] Step 3: 8 g of chitosan, 15 g of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 80 g of N,N-dimethylformamide were mixed evenly, and 3 g of the carbon dot-supported graphite carbon nitride composite material prepared in step 2 above was added. The mixture was reacted at 50 ° C and 1500 rpm for 14 h, and then filtered. The filter cake was washed with water three times and dried at 50 ° C for 5 h to obtain a reinforcing agent.

[0057] The preparation method of the anti-wear agent is consistent with that of Example 1.

[0058] Example 3

[0059] A method for preparing a composite pipe, which differs from Example 2 in that the method for preparing the reinforcing agent comprises the following steps:

[0060] Step 1: 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, then transferred to an autoclave and reacted at 200°C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10,000 rpm for 10 min. Large particles in the supernatant were removed using a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution.

[0061] Step 2: 3 g of melamine and 10 g of ammonium chloride were dissolved in 30 g of water and then calcined at 600 ° C for 3 h to obtain modified graphite carbon nitride. 3 g of modified graphite carbon nitride was evenly mixed with 15 g of the carbon dot stock solution prepared in step 1 above, transferred to a reactor, reacted at 180 ° C for 20 h, and after naturally cooling to room temperature, centrifuged at 10000 rpm for 10 min. The larger particles in the supernatant were removed with a 0.22 mm microporous membrane filter, and then freeze-dried for 24 h to obtain a composite material of carbon dots supported on graphite carbon nitride;

[0062] Step 3. Mix 8 g of N-ethyl-2-nitroaniline, 15 g of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 80 g of N,N-dimethylformamide, add 3 g of the carbon dot-supported graphite carbon nitride composite material prepared in step 2 above, react at 50 ° C and 1500 rpm for 14 h, then filter, wash the filter cake three times with water, and dry it at 50 ° C for 5 h to obtain a reinforcer.

[0063] Example 4

[0064] A method for preparing a composite pipe, which differs from Example 2 in that the method for preparing the reinforcing agent comprises the following steps:

[0065] Step 1: 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, then transferred to an autoclave and reacted at 200°C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10,000 rpm for 10 min. Large particles in the supernatant were removed using a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution.

[0066] Step 2: 3 g of melamine and 10 g of ammonium chloride were dissolved in 30 g of water and then calcined at 600 ° C for 3 h to obtain modified graphite carbon nitride. 3 g of modified graphite carbon nitride was evenly mixed with 15 g of the carbon dot stock solution prepared in step 1 above, transferred to a reactor, reacted at 180 ° C for 20 h, and after naturally cooling to room temperature, centrifuged at 10000 rpm for 10 min. The larger particles in the supernatant were removed with a 0.22 mm microporous membrane filter, and then freeze-dried for 24 h to obtain a composite material of carbon dots supported on graphite carbon nitride;

[0067] Step 3. Mix 8 g of polylysine, 15 g of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 80 g of N,N-dimethylformamide, add 3 g of the carbon dot-supported graphite carbon nitride composite material prepared in step 2 above, react at 50 ° C and 1500 rpm for 14 h, then filter, wash the filter cake three times with water, and dry it at 50 ° C for 5 h to obtain a reinforcer.

[0068] Comparative Example 1

[0069] A method for preparing a composite pipe comprises the following steps:

[0070] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, and 5 g of maleic anhydride-grafted polyethylene at 200° C. for 10 minutes to obtain a mixture;

[0071] Step 2: Extruding and granulating the mixture to obtain masterbatch; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0072] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube. The tube drawing process parameters are: an upper drawing temperature of 160° C., a table temperature of 170° C., and a table temperature of 175° C.

[0073] Comparative Example 2

[0074] A method for preparing a composite pipe comprises the following steps:

[0075] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, 5 g of maleic anhydride-grafted polyethylene, and 8 g of a reinforcing agent at 200° C. for 10 minutes to obtain a mixture;

[0076] Step 2: Extruding and granulating the mixture to obtain masterbatch; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0077] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube. The tube drawing process parameters are: an upper drawing temperature of 160° C., a table temperature of 170° C., and a table temperature of 175° C.

[0078] The preparation method of the enhancer is consistent with that of Example 4.

[0079] Comparative Example 3

[0080] A method for preparing a composite pipe, which differs from Example 4 in that the method for preparing the reinforcing agent comprises the following steps:

[0081] 3g of tetracycline and 15g of citric acid were dissolved in 40g of water, then transferred to an autoclave and reacted at 200°C for 8h. After naturally cooling to room temperature, the mixture was centrifuged at 10,000rpm for 10min. The larger particles in the supernatant were removed with a 0.22mm microporous membrane filter to obtain a carbon dot stock solution, which was then freeze-dried for 24h to obtain an enhancer.

[0082] Comparative Example 4

[0083] A method for preparing a composite pipe, which differs from Example 4 in that the method for preparing the wear-resistant agent comprises the following steps:

[0084] 3 g of γ-aminopropyltriethoxysilane was dissolved in dichloromethane to obtain a mass fraction of 3%, 30 g of ultra-high molecular weight polyethylene was added, and ultrasonic extraction was performed for 8 min. The solid a was filtered and the filter cake was dried to obtain solid a. 3 g of solid a was dissolved in 30 g of white oil, 5 g of nano-calcium carbonate was added, and the mixture was reacted at 50°C for 3 h to obtain the wear-resistant agent.

[0085] Comparative Example 5

[0086] A method for preparing a composite pipe, which differs from Example 4 in that the method for preparing the wear-resistant agent comprises the following steps:

[0087] 3 g of γ-aminopropyltriethoxysilane was dissolved in dichloromethane to obtain a mass fraction of 3%, 30 g of ultra-high molecular weight polyethylene was added, and ultrasonic extraction was performed for 8 min. The solid a was filtered and the filter cake was dried to obtain solid a. 3 g of solid a was dissolved in 30 g of white oil, 5 g of nano zinc oxide was added, and the reaction was carried out at 50°C for 3 h to obtain the wear-resistant agent.

[0088] Test Example 1

[0089] Performance Testing

[0090] Performance tests were performed on the composite pipes prepared in Examples 1-4 and Comparative Examples 1-5 of the present invention. The oxygen permeability of each example and comparative example was measured according to GB / T 19789-2021 Plastic Film and Sheeting for Packaging Materials - Oxygen Permeability - Coulometer Method; the water vapor permeability of each example and comparative example was measured according to GB 1037-2021 Plastic Film and Sheeting - Determination of Water Vapor Permeability - Cup Weight Gain and Loss Method; the tensile strength and elongation at break of each example and comparative example were measured according to GB / T 1040.2-2022 Plastics - Determination of Tensile Properties - Part 2: Test Conditions for Molded and Extruded Plastics; and the wear resistance of each example and comparative example was measured according to GB / T 3960-2016 Plastics - Test Method for Sliding Friction and Wear. The wear resistance of each example and comparative example was measured based on the mass loss rate of each specimen before and after the wear test.

[0091] The specific test results are shown in Table 1;

[0092] Table 1 Performance test

[0093]

[0094] By comparing Examples 1-4 with Comparative Examples 1-5, it can be found that the mass loss rate of Example 4 is only 0.15%, and the oxygen permeability is only 0.015 cm 3 / m 2 ·24h·0.1Mpa, water vapor transmission rate is only 0.083g / m 2After 24 hours, the tensile strength reached 41.2 MPa and the elongation at break reached 351%, achieving the best overall performance. This may be due to the simultaneous addition of a reinforcing agent and an anti-wear agent in Example 4. In Example 4, tetracycline and citric acid were reacted to produce a carbon dot stock solution, which was then reacted with melamine and ammonium chloride after calcination. Finally, polylysine was introduced to react with the carbon dot stock solution to form a highly reactive reinforcing agent. This reinforcing agent may form more effective chemical bonds or interactions with substrates such as ethylene-vinyl alcohol copolymer and maleic anhydride-grafted polyethylene, which have excellent barrier properties, to form a cross-linked three-dimensional network, thereby reducing the permeability of water vapor and oxygen. Furthermore, the graphite carbon nitride (GCN) in the reinforcing agent possesses high chemical stability and a unique layered structure. This layered structure acts as a physical barrier to gas and water vapor molecules, potentially interacting with the molecular structure of the ethylene-vinyl alcohol copolymer to further enhance the overall barrier performance. At the same time, the anti-wear agent can form a wear-resistant protective film on the surface of the pipe. When the pipe is subjected to friction or external force, the nano-silica in the anti-wear agent can withstand part of the friction force, reducing the wear of the pipe base material, thereby reducing the mass loss rate. In addition, the anti-wear agent and the reinforcing agent are mixed, and there may be a synergistic effect between the two. The surface functional groups of the carbon dots in the reinforcing agent react with polylysine to form chemical bonds. At the same time, polylysine reacts chemically or physically cross-links with the polyethylene molecular chains to form a three-dimensional cross-linked network structure. During the stretching process, it can limit the slippage of the polymer molecular chains, allowing the molecular chains to synergistically bear force, improving the material's ability to resist tensile deformation, thereby increasing the tensile strength. The cross-linked structure formed can, to a certain extent, cause the material to yield and orient during the stretching process, thereby further increasing the elongation at break.

[0095] By comparing Example 4 with Comparative Examples 4-5, it can be found that Example 4 has the best performance. Analysis shows that the reason may be that the wear-resistant particles added in Comparative Example 4 are nano-calcium carbonate, while the wear-resistant particles added in Example 5 are nano-zinc oxide. Nano-calcium carbonate and nano-zinc oxide have fewer reactive groups on their surfaces and cannot react well to form chemical bonds. Their binding ability is weaker, and their effect is weaker than that of nano-silicon dioxide.

[0096] Test Example 2

[0097] Antibacterial properties

[0098] Examples 2-4 and Comparative Example 3 were tested for their antibacterial properties according to the test method provided in the reference standard "GB / T 31402-2023 Determination of antibacterial activity on the surface of plastics and other non-porous materials"; experimental bacteria: Escherichia coli (commercially available, CGMCC 1.2463), Staphylococcus aureus (commercially available, CGMCC 1.2910); the test results are shown in Table 2.

[0099] Table 2 Antibacterial properties

[0100]

[0101] By comparing Examples 2-4 and Comparative Example 3, it can be found that the antibacterial rates of Examples 2-4 against Escherichia coli and golden glucose bacteria are higher than those of Comparative Example 3, showing excellent antibacterial effects. By comparing Examples 2-4, it can be found that Example 4 has the highest antibacterial rates against Escherichia coli and golden glucose bacteria, with the Escherichia coli inhibition rate reaching 95.3% and the golden glucose inhibition rate reaching 94.9%. Analysis shows that the reason may be that the modifier added during the preparation of the enhancer in Example 4 is polylysine. The polylysine molecular chain carries a large amount of positive charge and can be adsorbed on the negatively charged bacterial cell membrane surface through electrostatic action, producing a sterilization effect. In addition, polylysine can react chemically with matrices such as composite materials in which carbon dots are loaded on graphite carbon nitride and maleic anhydride grafted polyethylene, which can synergistically enhance the antibacterial effect. In addition, the overlap of the ultraviolet-visible absorption of graphite carbon nitride in the enhancer and the upconversion emission spectrum of the carbon dots produces a strong spectral coupling, inducing a broadband photocatalytic response from the ultraviolet to the NIR region, which can further enhance the antibacterial effect.

[0102] By comparing Examples 2-4 and Comparative Example 3, it can be found that Example 4 has the highest antibacterial rate. The reason for this may be that the modifier added during the preparation of the enhancer in Example 2 is chitosan. Although it is similar in structure to the polylysine in Example 4 and also has a certain antibacterial effect, it may be because the positive charge is lower than that of polylysine, which is lower than that of polylysine in promoting the antibacterial effect of the composite material of carbon dots loaded on graphite carbon nitride; the modifier added during the preparation of the enhancer in Example 3 is N-ethyl-2-nitroaniline, which can produce a chemical reaction but has a weaker molecular chain length and reaction activity with the matrix than chitosan and polylysine, and promotes the antibacterial effect of the composite material of carbon dots loaded on graphite carbon nitride. Therefore, the antibacterial effect is lower; the enhancer in Comparative Example 3 is carbon dots. Although carbon dots have an antibacterial effect, they do not have the synergistic effect of modified graphite carbon nitride to promote the antibacterial effect, so the antibacterial rate is lower.

Claims

1. A composite pipe, characterized by: The raw material components include, by mass: 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-10 parts of reinforcing agent, 5-20 parts of anti-wear agent, and 0.1-1 part of antioxidant; The preparation method of the enhancer comprises the following steps, calculated by weight: Step 1: Dissolve 1-5 parts of tetracycline and 10-20 parts of citric acid in 10-50 parts of water, transfer to an autoclave, and react at 180-220°C for 6-10 hours. After cooling to room temperature, centrifuge at 8000-12000 rpm for 5-15 minutes. Use a 0.22 mm microporous membrane filter to remove larger particles in the supernatant to obtain a carbon dot stock solution. Step 2: dissolving 1-5 parts of melamine and 5-15 parts of ammonium chloride in 20-40 parts of water, and then calcining at 500-700°C for 2-4 hours to obtain modified graphite carbon nitride; uniformly mixing 1-5 parts of modified graphite carbon nitride with 10-20 parts of the carbon dot stock solution prepared in step 1 above, transferring the mixture to a reactor, and reacting at 160-200°C for 16-24 hours; after naturally cooling to room temperature, centrifuging at 8000-12000 rpm for 5-15 minutes, removing larger particles in the supernatant with a 0.22 mm microporous membrane filter, and then freeze-drying for 16-36 hours to obtain a composite material of carbon dots supported on graphite carbon nitride; Step 3, 5-10 parts of a modifier, 10-20 parts of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 50-100 parts of N,N-dimethylformamide are mixed evenly, 1-5 parts of the carbon dot-supported graphite carbon nitride composite material prepared in step 2 above are added, and the mixture is reacted at 40-60°C and 1000-2000 rpm for 10-16 hours, and then filtered. The filter residue is washed with water 2-4 times and dried at 40-60°C for 4-6 hours to obtain a reinforcing agent; In step 3, the modifier is selected from at least one of chitosan, polylysine, and N-ethyl-2-nitroaniline; The preparation method of the anti-wear agent comprises the following steps, calculated by mass: Dissolve 1-5 parts of γ-aminopropyltriethoxysilane in 100 parts of dichloromethane, add 20-40 parts of ultra-high molecular weight polyethylene, and ultrasonically extract for 5-10 minutes; filter, and dry the filter cake to obtain solid a; dissolve 1-5 parts of solid a in 10-50 parts of white oil, add 1-10 parts of wear-resistant particles, and react at 40-60°C for 2-4 hours to obtain a wear-resistant agent; The wear-resistant particles are nano-silicon dioxide.

2. The composite pipe according to claim 1, characterized in that: The antioxidant is selected from at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and antioxidant 168.

3. The method for preparing a composite pipe according to any one of claims 1 to 2, characterized in that: The steps include: Step 1: Mix low-density polyethylene, high-density polyethylene, ethylene-vinyl alcohol copolymer, maleic anhydride grafted polyethylene, wear-resistant agent, and reinforcing agent at 140-220° C. for 5-15 minutes to obtain a mixture; Step 2: Extruding and granulating the mixture to obtain masterbatch; Step 3: Melt the masterbatch and the antioxidant to form a tube to obtain a composite tube.

4. The method for preparing a composite pipe according to claim 3, wherein: In the step 2, the granulation temperature is 140-220° C., the die head temperature is 140-230° C., and the screw speed is 10-30 r / min.

5. The method for preparing a composite pipe according to claim 3, wherein: The tube drawing process parameters in step 3 are as follows: the upper drawing temperature is 120-180°C, the temperature inside the table is 140-180°C, and the temperature outside the table is 165-190°C.

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